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Sample records for quadrature laser interferometer

  1. Enhanced ellipse fitting in a two-detector homodyne quadrature laser interferometer

    NASA Astrophysics Data System (ADS)

    Požar, T.; Možina, J.

    2011-08-01

    The choice of fitting methods for elliptically scattered data obtained with displacement-measuring homodyne quadrature laser interferometers significantly influences the accuracy of the interferometer. This is especially important when the data contain a lot of noise or provide only a segment of the ellipse. The ellipse parameters extracted by the fitting are used either to correct the data or the basic arctangent phase-unwrapping function in order to enhance the accuracy of the measured displacement by reducing the common nonlinearities. We propose the use of linear, ellipse-specific, least-squares fitting that is further bias-corrected using a linear algorithm. This stable fitting method provides a good balance between the accuracy of the fit and the computational efficiency, and never returns corrupt, non-ellipse parameters. It is therefore applicable for an online, uniform fringe subdivision when there is a demand for sub-nanometric resolution. An experimental confirmation of the improvement over traditional fitting methods was carried out with a single-pass, two-detector homodyne quadrature laser interferometer. We were able to operate the interferometer with nanometric accuracy, provided the data draw out at least a quarter-arc of an ellipse.

  2. A Homodyne Quadrature Laser Interferometer for Micro-Asperity Deformation Analysis

    PubMed Central

    PogaČnik, Aljaž; Požar, Tomaž; Kalin, Mitjan; Možina, Janez

    2013-01-01

    We report on the successful realization of a contactless, non-perturbing, displacement-measuring system for characterizing the surface roughness of polymer materials used in tribological applications. A single, time-dependent, scalar value, dubbed the collective micro-asperity deformation, is extracted from the normal-displacement measurements of normally loaded polymer samples. The displacement measurements with a sub-nanometer resolution are obtained with a homodyne quadrature laser interferometer. The measured collective micro-asperity deformation is critical for a determination of the real contact area and thus for the realistic contact conditions in tribological applications. The designed measuring system senses both the bulk creep as well as the micro-asperity creep occurring at the roughness peaks. The final results of our experimental measurements are three time-dependent values of the collective micro-asperity deformation for the three selected surface roughnesses. These values can be directly compared to theoretical deformation curves, which can be derived using existing real-contact-area models. PMID:23296328

  3. Quantitative phase imaging using grating-based quadrature phase interferometer

    NASA Astrophysics Data System (ADS)

    Wu, Jigang; Yaqoob, Zahid; Heng, Xin; Cui, Xiquan; Yang, Changhuei

    2007-02-01

    In this paper, we report the use of holographic gratings, which act as the free-space equivalent of the 3x3 fiber-optic coupler, to perform full field phase imaging. By recording two harmonically-related gratings in the same holographic plate, we are able to obtain nontrivial phase shift between different output ports of the gratings-based Mach-Zehnder interferometer. The phase difference can be adjusted by changing the relative phase of the recording beams when recording the hologram. We have built a Mach-Zehnder interferometer using harmonically-related holographic gratings with 600 and 1200 lines/mm spacing. Two CCD cameras at the output ports of the gratings-based Mach-Zehnder interferometer are used to record the full-field quadrature interferograms, which are subsequently processed to reconstruct the phase image. The imaging system has ~12X magnification with ~420μmx315μm field-of-view. To demonstrate the capability of our system, we have successfully performed phase imaging of a pure phase object and a paramecium caudatum.

  4. Calculation method for a quadrature phase-shifting interferometer and its applications.

    PubMed

    Nakadate, Suezou; Sawada, Shinya; Kiire, Tomohiro; Shibuya, Masato; Yatagai, Toyohiko

    2013-01-01

    A calculation method for a quadrature phase-shifting interferometer is presented, and its applications to specular and speckle interferometers and digital holography are described. Two sets of quadrature phase-shifted interferograms are acquired, and the calculation method proposed gives the phase distribution of the interferograms. The principle of the calculation method with error analysis and experimental results for specular and speckle interferometers and digital holography are also given. PMID:23292421

  5. Compensation for the Variable Cyclic Error in Homodyne Laser Interferometers

    PubMed Central

    Hu, Pengcheng; Zhu, Jinghao; Guo, Xuanbiao; Tan, Jiubin

    2015-01-01

    This paper presents a real-time method to compensate for the variable cyclic error in a homodyne laser interferometer. The parameters describing the quadrature signals of the interferometer are estimated using simple peak value detectors. The cyclic error in the homodyne laser interferometer was then corrected through simple arithmetic calculations of the quadrature signals. A field programmable gate array was utilized for the real-time compensation of the cyclic error in a homodyne laser interferometer. The simulation and experimental results indicated that the proposed method could provide a cyclic error that was fixed without compensation down to a value under 0.6 nm in a homodyne laser interferometer. The proposed method could also reduce the time-varying cyclic error to a value under 0.6 nm in a homodyne laser interferometer, in contrast to the equivalent value of 13.3 nm for a conventional elliptical fitting method. PMID:25647739

  6. Laser interferometer calibration station

    NASA Astrophysics Data System (ADS)

    Campolmi, R. W.; Krupski, S. J.

    1981-10-01

    The laser interferometer is a versatile tool, used for calibration over both long and short distances. It is considered traceable to the National Bureau of Standards. The system developed under this project was to be capable of providing for the calibration of many types of small linear measurement devices. The logistics of the original concept of one location for calibration of all mics, calipers, etc. at a large manufacturing facility proved unworkable. The equipment was instead used for the calibration of the large machines used to manufacture cannon tubes.

  7. Instrument Reflections and Scene Amplitude Modulation in a Polychromatic Microwave Quadrature Interferometer

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Jones, Jonathan E.; Chavers, Greg

    2003-01-01

    A polychromatic microwave quadrature interferometer has been characterized using several laboratory plasmas. Reflections between the transmitter and the receiver have been observed, and the effects of including reflection terms in the data reduction equation have been examined. An error analysis which includes the reflections, modulation of the scene beam amplitude by the plasma, and simultaneous measurements at two frequencies has been applied to the empirical database, and the results are summarized. For reflection amplitudes around 1096, the reflection terms were found to reduce the calculated error bars for electron density measurements by about a factor of 2. The impact of amplitude modulation is also quantified. In the complete analysis, the mean error bar for high- density measurements is 7.596, and the mean phase shift error for low-density measurements is 1.2". .

  8. Michelson interferometer for laser wavelength

    NASA Astrophysics Data System (ADS)

    Wang, Liqiang; Ren, Wenjie

    2005-11-01

    A wavemeter based on Michelson interferometer accurately measure static wavelength of a tunable laser. Its operation principle is formulated in details. Double longitudinal-mode He-Ne laser with frequency stabilization is used as the reference optical source of the wavemeter. Voice-coil motor using PID means can realize to move in uniform motion. Phase-locked loop circuit including NE564 and 74LS193 is used to enhance resolution of the wavemeter. Data processing is carried out by the counter unit including two 8254 programmable timer, a MCU, a LCD. The test shows that its measurement accuracy is 1×10 -6 and is higher than those of other wavemeters such as Fizeau interference and Fabry-Perot wavemeter.

  9. Laser interferometer for absolute distance measurement based on a tunable VCSEL laser

    NASA Astrophysics Data System (ADS)

    Cip, Ondrej; Mikel, Bretislav; Lazar, Josef

    2005-02-01

    In the work, we present the absolute distance interferometer with a narrow-linewidth tunable VCSEL laser (Vertical-Cavity Surface-Emitting Laser) working at &lambda ~760 nm. As a detection technique, we use a fast wavelength-scanning interferometry improved by an amplitude division of the interference fringe with using two signals in quadrature. Used VCSEL laser is wide tunable with the mod-hop free tuning range more than 1.2 nm by means of the amplitude modulation of the injection current. We control the stabilization and tuning process of the laser wavelength with using the frequency lock to a Fabry-Perot resonator. We build that resonator as a glass plan-parallel etalon with high-fines. Except the frequency lock, the etalon helps us to measure a wavelength-tuning interval of VCSEL laser during the scanning process. We have stabilized an operating temperature of the VCSEL laser by means of a fast digital temperature controller. The optical set-up of the interferometer begins with a polarizing beam-splitter. It splits the laser beam into the measuring and reference arm of the Michelson interferometer. Two cubic corner cubes reflect beams back to this beam-splitter. It collects reflected beams to the same axis of propagation. Then a detection unit produces the combination of two perpendicularly polarized laser beams with production of two electronic signals that are in the quadrature. A fast analog-to-digital card equipped with the digital signal processor (DSP) samples these signals. DSP also controls the course of the scanning process. After Δλ ~ 1 nm scan of the wavelength of VCSEL laser we obtain a record of passed interference fringes and passed Fabry-Perot resonance modes at the same time. On basis of these measured quantities we are able to calculate with high precision the instantaneous value of the optical path length difference between the measuring and reference arm of the Michelson interferometer. We experimentally compared the developed absolute interferometer with a conventional - incremental Michelson interferometer based on a single frequency He-Ne laser that has the resolution 1.2 nm. We achieved the relative uncertainty and scale linearity below 8 x 10-5 for range of tested distances L ɛ < 78; 118 > mm. The interferometer is able to work as the conventional interferometer too in case the wavelength of the VCSEL laser is locked into the selected resonance mode of the Fabry-Perot resonator.

  10. CO2 laser interferometer array for Big Dee

    NASA Astrophysics Data System (ADS)

    Fairbanks, E. S.

    1984-09-01

    A twelve channel interferometer array is planned for obtaining electron density profiles of Big Dee. Each channel consists of coaxial CO2 and HeNe laser beams. The reference beam is formed by splitting off half of the laser power at each wavelength by using acousto-optic modulators which introduce a 40 MHz frequency shift in the reference beam. The detected interference signals from room temperature visible and IR detectors are mixed with the 40 MHz drive for the acousto-optic cells. The quadrature mixer signals result in phase information due to vibration and phase velocity variation in the plasma. Simultaneous solution of the two equations describing the phase shift at the two wavelengths yields the phase shift due only to the plasma effects. The arithmetic operations are to be performed digitally in real time by a dedicated microprocessor in each channel. Density profiles are derived from chordal line integral density data by computer tomography.

  11. Two color far infrared laser interferometer

    SciTech Connect

    Kawahata, K.; Akiyama, T.; Pavlichenko, R.; Tanaka, K.; Tokuzawa, T.; Ito, Y.; Okajima, S.; Nakayama, K.; Wood, K.

    2006-10-15

    Two color interferometer using a short wavelength far infrared laser has been developed for high performance plasmas on large helical device and for future fusion devices such as ITER. High power laser lines simultaneously oscillating at 57.2 and 47.6 {mu}m were achieved in a CO{sub 2}-laser-pumped CH{sub 3}OD laser. By introducing Ge:Ga photoconductive detectors operating at liquid He temperature, we have successfully detected two color beat signals (0.55 and 1.2 MHz) with excellent signal-to-noise ratio ({approx}40 dB). These beat signals were fed into phase comparators for phase measurement after passing through intermediate frequency bandpass filters. Two color far infraned laser interferometer work was successful in the demonstration of mechanical vibration compensation.

  12. Modeling the Laser Interferometer Space Antenna Optics

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Pedersen, Tracy R.; McNamara, paul

    2005-01-01

    The Laser Interferometer Space Antenna (LISA), shown below, will detect gravitational waves produced by objects such as binary black holes or objects falling into black holes (extreme mass ratio inspirals) over a frequency range of l0(exp -4) to 0.1 Hz. Within the conceptual frame work of Newtonian physics, a gravitational wave produces a strain, (Delta)l/l, with magnitudes of the order of Earth based gravitational wave detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) project, use Michelson interferometers with arm lengths l = 4 km to detect these strains. Earth induced seismic noise limits ground-based instruments detecting gravitational waves with frequencies lower than approx. 1 Hz.

  13. CO2 laser interferometer array for Big Dee

    NASA Astrophysics Data System (ADS)

    Fairbanks, E. S.

    1985-05-01

    A 12 channel interferometer array is planned for obtaining electron density profiles on Big Dee. Each channel consists of coaxial CO2 and HeNe laser beams. The reference beam is formed by splitting off half of the laser power at each wavelength by using acousto-optic modulators which introduce a 40-MHz frequency shift in the reference beam. The detected interference signals from room-temperature visible and IR detectors are mixed with the 40-MHz drive for the acousto-optic cells. The quadrature mixer signals result in phase information due to vibration and phase-velocity variation in the plasma. Simultaneous solution of the two equations describing the phase shift at the two wavelengths yields the phase shift due only to the plasma effects. The arithmetic operations will be performed digitally in real time by a dedicated microprocessor in each channel. The execution speed of the microprocessor is expected to be sufficient for measuring line integral density in the presence of vibrations of 1-mm amplitude at 1 Hz or 10-μm amplitude at 100 Hz. Phase resolution for each channel is 2π/64 and time between samples is 25 μs. Density profiles are derived from chordal line integral density data by computer tomography.

  14. Ultrashort-pulse lasers based on the Sagnac interferometer

    NASA Astrophysics Data System (ADS)

    Bezrodnyi, V. I.; Prokhorenko, V. I.; Tikhonov, E. A.; Shpak, M. T.; Iatskiv, D. Ia.

    Results of experimental studies carried out on passively mode-locked and synchronously pumped ultrashort-pulse lasers with cavities based on the Sagnac interferometer are reported. It is shown that the use of the interferometer makes it possible to substantially improve the principal parameters of the ultrashort-pulse laser, such as repeatability, stability, spatial-angular characteristics, and the frequency tuning range. In particular, results are presented for YAG:Nd(3+) and dye lasers with Sagnac interferometers.

  15. Numerical simulation of an injection-locked sub-Poissonian laser: Quadrature squeezing

    SciTech Connect

    Ivanov, D. A.

    2010-04-15

    The master equation for a regularly pumped laser with coherent injection has been numerically solved using quantum trajectories. The onset of quadrature squeezing of the intracavity light has been observed. The case where the injection is switched well after the pumping has been considered.

  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. Automated calibration system for laser interferometers

    NASA Astrophysics Data System (ADS)

    Tang, Chung-Chi; Cheng, Kai-Yu

    2003-11-01

    For dimensional measurements and positioning, laser interferometers are often used to obtain highly accurate readings. To service their reliability, a system of laser interferometry standards is made available at the National Measurement Laboratory to offer instrument calibration as well as to ensure their traceability to the SI units. Owing much to their great sensitivity, the accuracy of laser interferometers undergoing calibration is strictly influenced by surrounding conditions, especially the correction parameter in the refractive index of air - a complex combination of ambient temperature, humidity, and atmosphere pressure. In order to minimize the deviation, an automated calibration system is constructed by employing a computer-controlled driver stage to perform linear displacement and data acquisition in the absence of operator intervention. A supplementary displacement measurement sub-system was set up to serve as an independent control on the stage. An average of 12 data points were taken at each predefined positions along the 20-m travel to support the comparison between the original system and the automated one. Several test runs from the calibration operation showed a standard deviation of 2.4×10-8 for the automated system and 6.5×10-8 for the previous. In addition to lower operational cost, experimental data also indicated improved calibration reliability benefited from the automation.

  18. 15-m laser-stabilized imaging interferometer

    NASA Astrophysics Data System (ADS)

    Stebbins, Robin T.; Bender, Peter L.; Chen, Che Jen; Page, Norman A.; Meier, D.; Dupree, A. K.

    1995-06-01

    The LAser-Stabilized Imaging Interferometer (LASII) concept is being developed as an astronomical telescope for the next generation of optical resolution beyond Hubble Space Telescope (HST). The essential ingredients are: a rigid and stable structure to minimize mechanical and thermal distortion, active control of the optical geometry by a laser metrology system, a self-deploying structure fitting into a single launch vehicle, and ultraviolet operation. We have modified earlier design concepts to fit the scale of an intermediate sized NASA mission. Our present design calls for 24 0.5 m apertures in a Mills Cross configuration, supported on four trusses. A fifth truss perpendicular to the primary surface would support the secondary mirror and the laser metrology control points. Either separate interferometers or two guide telescopes would track guide stars. This instrument would have about 6 times the resolution of HST in the visible and the same collecting area. The resolution would reach 2.5 mas at 150 nm. The primary trusses would fold along the secondary truss for launch, and automatically deploy on orbit. Possible orbits are sun-synchronous at 900 km altitude, high earth orbit or solar orbit. Infrared capability could be included, if desired.

  19. 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.

  20. Modeling the Laser Interferometer Space Antenna Optics

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Pedersen, Trace R.; McNamara, Paul

    2005-01-01

    Creating an optical model of the Laser Interferometer Space antenna which can be used to predict optical sensitivities and set tolerances sufficiently well such that picometer level displacements can be reliably seen poses certain challenges. In part, because the distances between key optical elements, the proof masses, are constantly changing, at speeds of meters/second, the separation between them is about 5 million kilometers and a contributing factor to optical jitter is the self-gravity of the spacecraft. A discussion of the current state and future approach(s) to the creation of such an optical model will be presented.

  1. Gravitational Wave Detection with Single-Laser Atom Interferometers

    NASA Technical Reports Server (NTRS)

    Yu, Nan; Tinto, Massimo

    2011-01-01

    A new design for a broadband detector of gravitational radiation relies on two atom interferometers separated by a distance L. In this scheme, only one arm and one laser are used for operating the two atom interferometers. The innovation here involves the fact that the atoms in the atom interferometers are not only considered as perfect test masses, but also as highly stable clocks. Atomic coherence is intrinsically stable, and can be many orders of magnitude more stable than a laser.

  2. Compact in-line laser radial shear interferometer

    NASA Technical Reports Server (NTRS)

    Shukla, R. P.; Moghbel, M.; Venkateswarlu, P.

    1992-01-01

    A compact in-line radial shearing interferometer using laser as a light source is presented. The interferometer is made out of a cube-type beam splitter so that the two opposite surfaces are generated with different curvatures while the normal to the entrance and exit surfaces are in the same line. The interferometer is simple to make and easy to align. Aberration analysis of the interferometer is also presented. Some applications of the interferometer for testing lenses and infrared optical systems and for accessing the quality of an emerging wave front from the exit slit of a monochromator are suggested.

  3. Fiber-optic interferometer using frequency-modulated laser diodes

    NASA Technical Reports Server (NTRS)

    Beheim, G.

    1986-01-01

    This paper describes an electrically passive fiber-optic interferometer which uses dual frequency-modulated laser diodes. Experimental results show that this type of interferometer can attain a displacement range of 100 micron with subnanometer resolution. This technique can serve as the basis for a number of high-precision fiber-optic sensors.

  4. Homodyne interferometry with quadrature fringe detection for absolute gravimeter.

    PubMed

    Svitlov, Sergiy; Araya, Akito

    2014-06-01

    An absolute gravimeter is based on interferometric displacement measurement during repeated free falls of a target mirror in a high vacuum. A suitable homodyne quadrature laser interferometer is developed and reported. Standard deviation of the mean absolute gravity value in a typical two-day measurement session is less than 1×10⁻⁸ m/s². Additionally, digital demodulation of the interference signal using a 90° phase-shift filter based on the Hilbert transform is presented. A combination of optical and digital quadrature phase shifts is shown to be helpful to improve accuracy in homodyne interferometers with the accelerated target mirror. PMID:24922433

  5. Passive directional discrimination in laser-Doppler anemometry by the two-wavelength quadrature homodyne technique.

    PubMed

    Büttner, Lars; Czarske, Jürgen

    2003-07-01

    We report a method for passive optical directional discrimination in laser-Doppler anemometers. For this purpose frequency-shift elements such as acousto-optic modulators, which are bulky and difficult to align during assembly, have traditionally been employed. We propose to use a quadrature homodyne technique to achieve directional discrimination of the fluid flow without any frequency-shift elements. It is based on the employment of two laser wavelengths, which generate two interference fringe systems with a phase shift of a quarter of the common fringe spacing. Measurement signal pairs with a direction-dependent phase shift of +/- pi/2 are generated. As a robust signal-processing technique, the cross-correlation technique is used. The principles of quadrature homodyne laser-Doppler anemometry are investigated. A setup that provides a constant phase shift of pi/2 throughout the entire measurement volume was achieved with both single-mode and multimode radiation. The directional discrimination was successfully verified with wind tunnel measurements. The complete passive technique offers the potential of building miniaturized measurement heads that can be integrated, e.g., into wind tunnel models. PMID:12868823

  6. Low-coherence interferometer using a pulsation laser diode

    NASA Astrophysics Data System (ADS)

    Suzuki, Takamasa; Ueno, Yusuke; Choi, Samuel; Sasaki, Osami

    2014-05-01

    A self-pulsation laser diode interferometer based on spectral-domain optical coherence tomography is proposed. A visible multimode laser diode allows easy optical alignment and an economical, configurable system. A cylindrical lens and acousto-optic deflector used in our system enable rapid and stable scanning. Experimental results confirm that full-field measurement is possible without mechanical scanning devices.

  7. Polarization Considerations for the Laser Interferometer Space Antenna (LISA)

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Pedersen, Trace R.; McNamara, Paul

    2005-01-01

    A polarization ray trace model of the Laser Interferometer Space Antenna's (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required picometer level interferometry. All of the computational steps are described in detail. This should eliminate any ambiguities associated with polarization ray trace modeling of interferometers and provide a basis for determining its limitations and serve as a clearly defined starting point for future improvements.

  8. Research of measurement assurance program (MAP) for laser interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Yue; Chen, Lingfeng; Ren, JianRong; Sha, Dingguo

    2003-09-01

    A multi-parameter Measurement Assurance Program (MAP) aim at laser interferometer is discussed detailedly in this paper. Firstly, we summarize the basic implementation process of MAP. After analyzing the measurement parameters of the laser interferometer, we design a set of transfer standard and check standard. Then, the mathematical statistic model of the whole MAP process is presented including the statistic process control and the evaluation of the measurement uncertainty. Lastly, we demonstrate the MAP software we programmed for this process in order to facilitate the implementation. It's clear that our MAP implementation has greatly improved the attending laboratories' confidence for their measurement results.

  9. Performance analysis of a swept-source optical coherence tomography system with a quadrature interferometer and optical amplification

    NASA Astrophysics Data System (ADS)

    Mao, Youxin; Flueraru, Costel; Chang, Shoude; Popescu, Dan P.; Sowa, Michael G.

    2011-05-01

    A performance analysis of signal to noise ratio for an optical coherence tomography system with quadrature detection and a semiconductor optical amplifier in the sample arm is discussed. The results are compared and discussed in relation to a conventional OCT system (without optical amplification). An increase of the signal to noise ratio up to 14 dB at a depth of 0.5 mm is obtained compared to the system without the optical amplifier. Overall, an improvement was demonstrated for signal coming from deeper regions within the samples. Arterial plaque from a myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbit is visualized and characterized using this system. Improvement of signal to noise ratio increases the penetration depth possible for OCT images, from 1 mm to 2 mm within the vessel wall of an artery. Preliminary results show that vulnerable plaque with fibrous cap, macrophage accumulations and calcification in the arterial tissue are measurable with this OCT system.

  10. Arm Locking for the Laser Interferometer Space Antenna

    NASA Technical Reports Server (NTRS)

    Maghami, P. G.; Thorpe, J. I.; Livas, J.

    2009-01-01

    The Laser Interferometer Space Antenna (LISA) mission is a planned gravitational wave detector consisting of three spacecraft in heliocentric orbit. Laser interferometry is used to measure distance fluctuations between test masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Laser frequency fluctuations must be suppressed in order to meet the measurement requirements. Arm-locking, a technique that uses the constellation of spacecraft as a frequency reference, is a proposed method for stabilizing the laser frequency. We consider the problem of arm-locking using classical optimal control theory and find that our designs satisfy the LISA requirements.

  11. Long-term laser frequency stabilization using fiber interferometers

    NASA Astrophysics Data System (ADS)

    Kong, Jia; Lucivero, Vito Giovanni; Jiménez-Martínez, Ricardo; Mitchell, Morgan W.

    2015-07-01

    We report long-term laser frequency stabilization using only the target laser and a pair of 5 m fiber interferometers, one as a frequency reference and the second as a sensitive thermometer to stabilize the frequency reference. When used to stabilize a distributed feedback laser at 795 nm, the frequency Allan deviation at 1000 s drops from 5.6 × 10-8 to 6.9 × 10-10. The performance equals that of an offset lock employing a second, atom-stabilized laser in the temperature control.

  12. Polarization Considerations for the Laser Interferometer Space Antenna

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Pedersen, Tracy R.; McNamara, Paul

    2005-01-01

    A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work.

  13. Dual-frequency laser displacement and angle interferometer

    NASA Astrophysics Data System (ADS)

    Zhao, Shijie; Wei, Haoyun; Li, Yan

    2014-11-01

    Traditional laser angular interferometers based on a Michelson Interferometer or its modifications have the same principle: changing the angle displacement to an optical path difference. However, measuring the angular error of stage travels is a dynamic process. The main trouble is lack of displacement information and need to be solved urgently. A obvious method is using two dual-frequency interferometers to get the displacement and angular. In this paper, a new kind of displacement and angle interferometer (DIAI) is introduced. In this DIAI, displacement and angular are measured simultaneously by special optical path. The DIAI consists of a stabilized orthogonal polarization dualfrequency laser, a monolithic prism and additional optical and electronic components. The dual-frequency laser is divided into reference light and measurement light by a beam-splitting prism. The measurement light spatially separated into horizontal polarized light and vertical polarized light by the polarization splitting prism. Changing by a fixed 45°- tilted reflector, the vertical polarized light is parallel to the horizontal polarized light. These parallel lights reflected by two corner cube retroreflectors at a moving target. Compared with the reference light, the displacement and angular are measured. Different from the traditional method, there is only one reference corner cube retroreflector in this system. Thus, the angular measurement accuracy is better. The accuracy of the DIAI is better than +/-0.25 arcsec in comparison with an autocollimator.

  14. A lunar gravitational wave antenna using a laser interferometer

    SciTech Connect

    Stebbins, R.T.; Bender, P.L. National Institute of Standards and Technology, Boulder, CO )

    1990-03-15

    A moon-based laser interferometer for detecting gravitational radiation could detect signals in the band 10{sup {minus}1} to 10{sup 4} Hz. A preliminary evaluation of the noise budget for an optimistic antenna design is reported here and compared to that for other planned gravitational wave interferometers. Over most of the frequency range, the sensitivity is controlled by the thermal noise in the test mass suspensions. From roughly 3 to a few hundred Hertz, it is about the same as the sensitivity expected in terrestrial antennas of the same construction, which will have been operating for at least a decade. Below 0.3 Hz, a proposed space-based interferometer, designed for operation down to 10{sup {minus}5} Hz, would have better sensitivity. As pointed out by others, the most important role of a lunar antenna would be the improved angular resolution made possible by the long baseline to terrestrial antennas.

  15. 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.

  16. Laser Interferometers, Gravitational waves and Echos from the Universe

    NASA Astrophysics Data System (ADS)

    Cadonati, Laura; LIGO Scientific Collaboration; Virgo Collaboration

    2010-04-01

    The Laser Interferometer Gravitational-wave Observatory (LIGO) and its sister project Virgo aim for the first direct detections of gravitational waves. Such detections will provide not only a test of general relativity, but also a fundamental, new probe into the Universe. To achieve this goal, LIGO and Virgo use laser interferometers to monitor changes in the relative separation of mirrors at the ends of each of two perpendicular arms of km-scale length, in response to the space-time distortions induced by the passage of gravitational waves. This paper gives an overview of the status and the science of LIGO and Virgo, with selected results from the initial detector phase and predictions for the enhanced and advanced detector configurations.

  17. Reference laser source for the IASI interferometer

    NASA Astrophysics Data System (ADS)

    Pujol, Laurence; Lizet, Jacques; Sosnicki, Olivier

    2001-02-01

    12 IASI is a key instrument of the payload on METOP, a European meteorological platform. METOP will provide meteorology with atmosphere emission spectra, allowing to set atmosphere temperature and moisture profiles with high accuracy. In order to achieve these specifications, several new and innovative technologies and technical answers have had to be developed. Among them, the reference laser of IASI presents challenging concepts and widely uses the last commercial developments of telecommunication technologies. The reference laser is frequency locked onto a molecular reference absorption line providing a very stable frequency behavior over the several year duration of the instrument life. The principle is well known for atomic clocks and has been adapted to the commercial availability of reliable telecommunication lasers. Semiconductor laser modules, optical fibers and fibered components are used to achieve a compact and reliable subsystem. The availability of such space compliant frequency stabilized laser sources opens new opportunities in the field of optical metrology such as interferometry and multi- aperture telescope co-phasing.

  18. A simple pendulum laser interferometer for determining the gravitational constant

    PubMed Central

    Parks, Harold V.; Faller, James E.

    2014-01-01

    We present a detailed account of our 2004 experiment to measure the Newtonian constant of gravitation with a suspended laser interferometer. The apparatus consists of two simple pendulums hanging from a common support. Each pendulum has a length of 72 cm and their separation is 34 cm. A mirror is embedded in each pendulum bob, which then in combination form a Fabry–Perot cavity. A laser locked to the cavity measures the change in pendulum separation as the gravitational field is modulated due to the displacement of four 120 kg tungsten masses. PMID:25201994

  19. A compact semiconductor digital interferometer and its applications

    NASA Astrophysics Data System (ADS)

    Britsky, Oleksander I.; Gorbov, Ivan V.; Petrov, Viacheslav V.; Balagura, Iryna V.

    2015-05-01

    The possibility of using semiconductor laser interferometers to measure displacements at the nanometer scale was demonstrated. The creation principles of miniature digital Michelson interferometers based on semiconductor lasers were proposed. The advanced processing algorithm for the interferometer quadrature signals was designed. It enabled to reduce restrictions on speed of measured movements. A miniature semiconductor digital Michelson interferometer was developed. Designing of the precision temperature stability system for miniature low-cost semiconductor laser with 0.01ºС accuracy enabled to use it for creation of compact interferometer rather than a helium-neon one. Proper firmware and software was designed for the interferometer signals real-time processing and conversion in to respective shifts. In the result the relative displacement between 0-500 mm was measured with a resolution of better than 1 nm. Advantages and disadvantages of practical use of the compact semiconductor digital interferometer in seismometers for the measurement of shifts were shown.

  20. Analysis of optical flat flatness measuring method with phase-shifting laser interferometer

    NASA Astrophysics Data System (ADS)

    Yao, Xing-yu

    2015-10-01

    Flatness of the optical flat measurement mainly has two methord: first is laser plane interferometer, second is the Phase-shifting Laser Interferometer. The two methods were compared by analysis. For the detection of high precision optical flat, expounds the principle and method of Phase-shifting Laser Interferometer. Uncertainty analysis was carried out to validate the approach, meet the flat verification regulation. The method is feasible.

  1. A Fiber Optic PD Sensor Using a Balanced Sagnac Interferometer and an EDFA-Based DOP Tunable Fiber Ring Laser

    PubMed Central

    Wang, Lutang; Fang, Nian; Wu, Chunxu; Qin, Haijuan; Huang, Zhaoming

    2014-01-01

    A novel fiber-optic acoustic sensor using an erbium-doped fiber amplifier (EDFA)-based fiber ring laser and a balanced Sagnac interferometer for acoustic sensing of the partial discharge (PD) in power transformers is proposed and demonstrated. As a technical background, an experimental investigation on how the variations of the fiber birefringence affect the sensor performances was carried out, and the results are discussed. The operation principles are described, and the relevant formulas are derived. The analytical results show that an EDFA-based fiber ring laser operating in chaotic mode can provide a degree of polarization (DOP) tunable light beam for effectively suppressing polarization fading noises. The balanced Sagnac interferometer can eliminate command intensity noises and enhance the signal-to-noise ratio (SNR). Furthermore, it inherently operates at the quadrature point of the response curve without any active stabilizations. Several experiments are conducted for evaluating the performances of the sensor system, as well as for investigating the ability of the detection of high-frequency acoustic emission signals. The experimental results demonstrate that the DOP of the laser beam can be continuously tuned from 0.2% to 100%, and the power fluctuation in the whole DOP tuning range is less than 0.05 dBm. A high-frequency response up to 300 kHz is reached, and the high sensing sensitivity for detections of weak corona discharges, as well as partial discharges also is verified. PMID:24824371

  2. A fiber optic PD sensor using a balanced Sagnac interferometer and an EDFA-based DOP tunable fiber ring laser.

    PubMed

    Wang, Lutang; Fang, Nian; Wu, Chunxu; Qin, Haijuan; Huang, Zhaoming

    2014-01-01

    A novel fiber-optic acoustic sensor using an erbium-doped fiber amplifier (EDFA)-based fiber ring laser and a balanced Sagnac interferometer for acoustic sensing of the partial discharge (PD) in power transformers is proposed and demonstrated. As a technical background, an experimental investigation on how the variations of the fiber birefringence affect the sensor performances was carried out, and the results are discussed. The operation principles are described, and the relevant formulas are derived. The analytical results show that an EDFA-based fiber ring laser operating in chaotic mode can provide a degree of polarization (DOP) tunable light beam for effectively suppressing polarization fading noises. The balanced Sagnac interferometer can eliminate command intensity noises and enhance the signal-to-noise ratio (SNR). Furthermore, it inherently operates at the quadrature point of the response curve without any active stabilizations. Several experiments are conducted for evaluating the performances of the sensor system, as well as for investigating the ability of the detection of high-frequency acoustic emission signals. The experimental results demonstrate that the DOP of the laser beam can be continuously tuned from 0.2% to 100%, and the power fluctuation in the whole DOP tuning range is less than 0.05 dBm. A high-frequency response up to 300 kHz is reached, and the high sensing sensitivity for detections of weak corona discharges, as well as partial discharges also is verified. PMID:24824371

  3. Detection of volcanic infrasound with a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Hosman, Ashley R.

    2014-11-01

    Over the last 15 years, large horizontally mounted ring lasers have been used to study numerous geophysical phenomena. This paper provides examples of the sensitivity of large active ring laser interferometers to far field infrasound emissions from explosive volcanic eruptions. Volcanic infrasound is reported from representative eruptions of volcanoes Kelut (Kelud), Klyuchevskaya (Kliuchevskoi), Puyehua, Santa Maria, Sakurajima, and Tungurahua. The detected infrasound frequencies are in basic agreement with the far field air wave frequencies from the 1980 eruption of Mount St. Helens and the 1991 eruption of Mount Pinatubo. Cavities of large horizontally mounted active ring lasers contain two counter-propagating waves that in the presence Earth's rotation become traveling waves of slightly different frequencies. The Sagnac or beat frequency due to the difference in the traveling wave frequencies is modulated by geophysical phenomena, in this case volcanic infrasound. Signatures of the infrasound are found in the frequency modulated side bands.

  4. Data processing for LISA's laser interferometer tracking system (LITS)

    NASA Astrophysics Data System (ADS)

    Hellings, Ronald W.

    2001-10-01

    In this paper, we present results on the subject of data processing for LISA. We present, for the first time, time-domain algorithms for the elimination of clock jitter noise algorithms that avoid the singularities of the previous frequency-domain method. We also discuss how to generate the data averages that each spacecraft will eventually need to telemeter to the ground, thereby inferring what a realistic scientific data rate will be for LISA. Finally, we argue, based partly on these results, that a laser interferometer tracking system (LITS) that employs independent lasers in each spacecraft is preferable, for reasons of simplicity, to one in which the lasers in two of the spacecraft are locked to the incoming beam from the third.

  5. Explosive component acceptance tester using laser interferometer technology

    NASA Technical Reports Server (NTRS)

    Wickstrom, Richard D.; Tarbell, William W.

    1993-01-01

    Acceptance testing of explosive components requires a reliable and simple to use testing method that can discern less than optimal performance. For hot-wire detonators, traditional techniques use dent blocks or photographic diagnostic methods. More complicated approaches are avoided because of their inherent problems with setup and maintenance. A recently developed tester is based on using a laser interferometer to measure the velocity of flying plates accelerated by explosively actuated detonators. Unlike ordinary interferometers that monitor displacement of the test article, this device measures velocity directly and is commonly used with non-spectral surfaces. Most often referred to as the VISAR technique (Velocity Interferometer System for Any Reflecting Surface), it has become the most widely-accepted choice for accurate measurement of velocity in the range greater than 1 mm/micro-s. Traditional VISAR devices require extensive setup and adjustment and therefore are unacceptable in a production-testing environment. This paper describes a new VISAR approach which requires virtually no adjustments, yet provides data with accuracy comparable to the more complicated systems. The device, termed the Fixed-Cavity VISAR, is currently being developed to serve as a product verification tool for hot-wire detonators and slappers. An extensive data acquisition and analysis computer code was also created to automate the manipulation of raw data into final results.

  6. VCSEL-based miniature laser-Doppler interferometer

    NASA Astrophysics Data System (ADS)

    Pruijmboom, Armand; Schemmann, Marcel; Hellmig, Jochen; Schutte, Jeroen; Moench, Holger; Pankert, Joseph

    2008-02-01

    There are many applications for non-contact measurement of the displacement and velocity of moving objects, especially when achieved at low cost. An optical displacement sensor has been developed that can be compared to expensive laser-interferometry sensors, however at a cost compatible with requirements for consumer products. This miniature Laser-Doppler Interferometer works on all light scattering surfaces. The first large-scale application is in PC-mice. The measurement principle employs so-called "Laser Self Mixing", which occurs when laser light scattered on a surface, within the coherence length, is coupled back into the laser cavity. When the object is moving, the back-scattered light is continuously shifting in phase relative to the laser light at the laser mirror. This results in a periodic perturbation of the feedback into the laser cavity, which causes modulations of the light intensity in the cavity. The frequency of these modulations is proportional the speed of the object. A VCSEL, optimized for this application, is used as light source, a photo-diode in the sensor measures the intensity fluctuations and, finally, an integrated circuit transfers the photo-diode signal into velocity or displacement information. To determine the direction of the movement, a triangle modulation of the laser-current is used, which modulates the laser-temperature and hence the laser frequency. Next to the applications in PC-mice a much wider range of applications as input device in consumer products can be envisaged. For instance menu navigation by finger movement over a sensor in remote controls, mobile phones and lap tops. Furthermore a wide field of applications is envisaged in the manufacturing of industrial equipment, which requires non-contact measurement of the movement of materials. The small form factor of less than 0.2 cubic centimeters allows applications previously considered impossible.

  7. Laser Interferometer Space Antenna (LISA) Far Field Phase Pattern

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene

    1999-01-01

    The Laser Interferometry Space Antenna (LISA) for the detection of Gravitational Waves is a very long baseline interferometer that will measure the changes in the distance of a five million kilometer arm to pico meter accuracies. Knowledge of the phase deviations from a spherical wave and what causes these deviations are needed considerations in (as a minimum) the design of the telescope and in determining pointing requirements. Here we present the far field phase deviations from a spherical wave for given Zernike aberrations and obscurations of the exit pupil.

  8. Design of laser system for absolute gravimeter based on 87Rb atom interferometer

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Wang, Shaokai; Zhuang, Wei; Fang, Fang; Li, Tianchu

    2015-08-01

    We present a laser system design for an absolute gravimeter based on 87Rb atom interferometer. By skillful design, lasers with 9 different frequencies are based on two diode lasers including tapered amplifier. Two electrical feedback systems are used for laser frequency stabilization and the Raman lasers generation respectively. All other lasers are based on two Raman lasers and realized with frequency shift by acoustic optical modulators. This laser system not only has the compact and simple construction, but meets all requirements for laser power and frequency controlling for the atom interferometer. It has the characteristic of reliability and integrity.

  9. Path-length measurement performance evaluation of polarizing laser interferometer prototype

    NASA Astrophysics Data System (ADS)

    Li, Yu-qiong; Luo, Zi-ren; Liu, He-shan; Dong, Yu-hui; Jin, Gang

    2015-02-01

    The space laser interferometer has been considered the most promising means for detecting gravitational waves and improving the accuracy and spatial resolution of the Earth's gravity model. An on-ground polarizing laser interferometer prototype equipped with one reference interferometer and two measurement interferometers having equal-length arms is presented in the paper. The laser interferometer prototype is designed as the demonstration of a Chinese space laser interferometer antenna in the future, of which the path-length measurement performance evaluation and preliminary noise analysis are investigated here. The results show that the path-length measurement sensitivity is better than 200 pm/Hz½ in the frequency band of 10 mHz-1 Hz, and the sensitivity of measuring the motion of a sinusoidally driven testmass is better than 100 pm within the frequency regime of 1 mHz-1 Hz. In this way, laboratory activities have demonstrated the feasibility of this prototype to measure tiny path-length fluctuations of the simulated testmass. As a next step, adopting an integrated design of optics and optical substrate to enhance the stability of the laser interferometer is being planned, and other key techniques included in the space laser interferometer such as laser pointing modulation and laser phase-locking control are to be implanted into this prototype are under consideration.

  10. Orbit design for the Laser Interferometer Space Antenna (LISA)

    NASA Astrophysics Data System (ADS)

    Xia, Yan; Li, Guangyu; Heinzel, Gerhard; Rüdiger, Albrecht; Luo, Yongjie

    2010-01-01

    The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA mission for detecting low-frequency gravitational waves in the frequency range from 0.1 mHz to 1 Hz, by using accurate laser interferometry between three spacecrafts, which will be launched around 2018 and one year later reach their operational orbits around the Sun. In order to operate successfully, it is crucial for the constellation of the three spacecrafts to have extremely high stability. Based on the study of operational orbits for a 2015 launch, we design the operational orbits of beginning epoch on 2019-03-01, and introduce the method of orbit design and optimization. We design the orbits of the transfer from Earth to the operational orbits, including launch phase and separation phase; furthermore, the relationship between energy requirement and flight time of these two orbit phases is investigated. Finally, an example of the whole orbit design is presented.

  11. Selection of linear-cavity fibre laser radiation using a reflection interferometer

    SciTech Connect

    Terentyev, V S; Simonov, V A

    2013-08-31

    We consider the use of a two-mirror multibeam reflection interferometer as a selector of linear-cavity single-mode fibre laser radiation and present experimental data on continuous wavelength tuning of an erbium-doped fibre laser. Conditions are found for single-longitudinal-mode operation of the fibre laser cavity using a reflection interferometer, with the possibility of broadband wavelength tuning. (control of laser pulse parameters)

  12. Method for continuous end standard measurement utilizing laser interferometer

    NASA Astrophysics Data System (ADS)

    Cheng, Kai-Yu; Tang, Chung-Chi; Chang, Wei-Cheng; Chen, Chao-Jung; Wu, Tsai-Fu; Chou, Jung-Tsung

    2004-08-01

    For dimensional researches and applications, the end standard measurements are the popular subjects in high precision standard systems or instruments. In general, the gauge blocks are the representative of the end standards. The universal measurement machines (UMM) are usually utilized for the dimensional length of gauge blocks. However, for measuring the dimensional lengths of test gauge blocks (TGBs), they should be compared with the same lengths of the master gauge blocks (MGBs). Thus, there are different lengths of the MGBs needed to be prepared and the measuring procedures are usually very time consuming. In order to lower the cost of procurement and maintenance of MGBs, a continuous end standard measurement system (CESMS) was built for many different test ranges of TGBs. The features of the CESMS included at least one gauge block, the LVDT probes for positioning, the real lengths of the TGBs measured from the display value of the laser interferometer, and total procedures controlled by automation software. All of these parts were integrated onto a large platform and its moving carriage could travel up to 1.2-meter in distance. Within these ranges, the CESMS could measure different dimensional lengths of the TGBs and many pieces at the same time. The CESMS utilized the laser interferometer to acquire the accurate display values between two ends when the LVDT probe was touched and triggered the automation software to record. Owing to the recommended radiation of laser head, the CESMS could be traced to the meter, SI unit. Furthermore, the experiment results showed that the comparison results of certificated gauge block at 800 mm suited for calibration certificate by PTB.

  13. LIGO - The Laser Interferometer Gravitational-Wave Observatory

    NASA Technical Reports Server (NTRS)

    Abramovici, Alex; Althouse, William E.; Drever, Ronald W. P.; Gursel, Yekta; Kawamura, Seiji; Raab, Frederick J.; Shoemaker, David; Sievers, Lisa; Spero, Robert E.; Thorne, Kip S.

    1992-01-01

    The goal of the Laser Interferometer Gravitational-Wave Observatory (LIGO) Project is to detect and study astrophysical gravitational waves and use data from them for research in physics and astronomy. LIGO will support studies concerning the nature and nonlinear dynamics for gravity, the structures of black holes, and the equation of state of nuclear matter. It will also measure the masses, birth rates, collisions, and distributions of black holes and neutron stars in the universe and probe the cores of supernovae and the very early universe. The technology for LIGO has been developed during the past 20 years. Construction will begin in 1992, and under the present schedule, LIGO's gravitational-wave searches will begin in 1998.

  14. Listening to the Universe with the Laser Interferometer Space Antenna

    NASA Astrophysics Data System (ADS)

    Cornish, Neil J.; Crowder, J.; Porter, E.

    2006-12-01

    Gravitational Wave observatories here on Earth are poised to end the "silent era" of Astronomy by measuring the vibrations in spacetime caused by colliding black holes and other energetic events. NASA and ESA are working together to open up the source-rich low frequency portion of the gravitational wave spectrum with the Laser Interferometer Space Antenna (LISA). A major challenge for this mission is how to deal with a data stream that is expected to contain the signals from tens of thousands of sources, including massive black hole binaries, stellar remant captures by galactic black holes, and a foreground of compact binaries in our own galaxy. Here we describe a fast and robust technique for simultaneously resolving tens of thousands of overlapping signals and recovering the source parameters. Our approach has been sucessfully tested on simulated LISA data, including the blind data sets of the Mock LISA Data Challenge.

  15. Multicomponent wavefield characterization with a novel scanning laser interferometer.

    PubMed

    Blum, Thomas E; van Wijk, Kasper; Pouet, Bruno; Wartelle, Alexis

    2010-07-01

    The in-plane component of the wavefield provides valuable information about media properties from seismology to nondestructive testing. A new compact scanning laser ultrasonic interferometer collects light scattered away from the angle of incidence to provide the absolute ultrasonic displacement for both the out-of-plane and an in-plane components. This new system is tested by measuring the radial and vertical polarization of a Rayleigh wave in an aluminum half-space. The estimated amplitude ratio of the horizontal and vertical displacement agrees well with the theoretical value. The phase difference exhibits a small bias between the two components due to a slightly different frequency response between the two processing channels of the prototype electronic circuitry. PMID:20687699

  16. Multicomponent wavefield characterization with a novel scanning laser interferometer

    SciTech Connect

    Blum, Thomas E.; Wijk, Kasper van; Pouet, Bruno; Wartelle, Alexis

    2010-07-15

    The in-plane component of the wavefield provides valuable information about media properties from seismology to nondestructive testing. A new compact scanning laser ultrasonic interferometer collects light scattered away from the angle of incidence to provide the absolute ultrasonic displacement for both the out-of-plane and an in-plane components. This new system is tested by measuring the radial and vertical polarization of a Rayleigh wave in an aluminum half-space. The estimated amplitude ratio of the horizontal and vertical displacement agrees well with the theoretical value. The phase difference exhibits a small bias between the two components due to a slightly different frequency response between the two processing channels of the prototype electronic circuitry.

  17. 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).

  18. LIGO: the Laser Interferometer Gravitational-Wave Observatory

    NASA Astrophysics Data System (ADS)

    Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arain, M. A.; Araya, M.; Armandula, H.; Armor, P.; Aso, Y.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballmer, S.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Behnke, B.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bodiya, T. P.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Bridges, D. O.; Brinkmann, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Brunet, G.; Bullington, A.; Buonanno, A.; Burmeister, O.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Cannizzo, J.; Cannon, K. C.; Cao, J.; Cardenas, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Christensen, N.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cokelaer, T.; Colacino, C. N.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Davies, G.; Daw, E. J.; DeBra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drever, R. W. P.; Dueck, J.; Duke, I.; Dumas, J.-C.; Dwyer, J. G.; Echols, C.; Edgar, M.; Effler, A.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmenn, H.; Finn, L. S.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Franzen, A.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Garofoli, J. A.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Grimaldi, F.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Hoyland, D.; Hughey, B.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ito, M.; Ivanov, A.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kozak, D.; Krishnan, B.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, H.; Lei, M.; Leindecker, N.; Leonor, I.; Li, C.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Longo, M.; Lormand, M.; Lu, P.; Lubiński, M.; Lucianetti, A.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McIntyre, G.; McKechan, D. J. A.; McKenzie, K.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Menéndez, D. F.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miller, J.; Minelli, J.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreno, G.; Morioka, T.; Mors, K.; Mossavi, K.; Mow Lowry, C.; Mueller, G.; Müller-Ebhardt, H.; Muhammad, D.; Mukherjee, S.; Mukhopadhyay, H.; Mullavey, A.; Munch, J.; Murray, P. G.; Myers, E.; Myers, J.; Nash, T.; Nelson, J.; Newton, G.; Nishizawa, A.; Numata, K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Ogin, G. H.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pan, Y.; Pankow, C.; Papa, M. A.; Parameshwaraiah, V.; Patel, P.; Pedraza, M.; Penn, S.; Perraca, A.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Postiglione, F.; Principe, M.; Prix, R.; Prokhorov, L.; Punken, O.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rainer, N.; Rakhmanov, M.; Raymond, V.; Reed, C. M.; Reed, T.; Rehbein, H.; Reid, S.; Reitze, D. H.; Riesen, R.; Riles, K.; Rivera, B.; Roberts, P.; Robertson, N. A.; Robinson, C.; Robinson, E. L.; Roddy, S.; Röver, C.; Rollins, J.; Romano, J. D.; Romie, J. H.; Rowan, S.; Rüdiger, A.; Russell, P.; Ryan, K.; Sakata, S.; de la Jordana, L. Sancho; Sandberg, V.; Sannibale, V.; Santamaría, L.; Saraf, S.; Sarin, P.; Sathyaprakash, B. S.; Sato, S.; Satterthwaite, M.; Saulson, P. R.; Savage, R.; Savov, P.; Scanlan, M.; Schilling, R.; Schnabel, R.; Schofield, R.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sergeev, A.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sinha, S.; Sintes, A. M.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Stein, A.; Stein, L. C.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A.; Stuver, A. L.; Summerscales, T. Z.; Sun, K.-X.; Sung, M.; Sutton, P. J.; Szokoly, G. P.; Talukder, D.; Tang, L.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thacker, J.; Thorne, K. A.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C.; Traylor, G.; Trias, M.; Ugolini, D.; Ulmen, J.; Urbanek, K.; Vahlbruch, H.; Vallisneri, M.; van den Broeck, C.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vecchio, A.; Veitch, J.; Veitch, P.; Veltkamp, C.; Villar, A.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, R. L.; Weidner, A.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Wilmut, I.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Zanolin, M.; Zhang, J.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M. E.; Mühlen, H. zur; Zweizig, J.

    2009-07-01

    The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves (GWs) of astrophysical origin. Direct detection of GWs holds the promise of testing general relativity in the strong-field regime, of providing a new probe of exotic objects such as black holes and neutron stars and of uncovering unanticipated new astrophysics. LIGO, a joint Caltech-MIT project supported by the National Science Foundation, operates three multi-kilometer interferometers at two widely separated sites in the United States. These detectors are the result of decades of worldwide technology development, design, construction and commissioning. They are now operating at their design sensitivity, and are sensitive to gravitational wave strains smaller than one part in 1021. With this unprecedented sensitivity, the data are being analyzed to detect or place limits on GWs from a variety of potential astrophysical sources.

  19. Laser heterodyne interferometer for simultaneous measuring displacement and angle based on the Faraday effect.

    PubMed

    Zhang, Enzheng; Hao, Qun; Chen, Benyong; Yan, Liping; Liu, Yanna

    2014-10-20

    A laser heterodyne interferometer for simultaneous measuring displacement and angle based on the Faraday effect is proposed. The optical configuration of the proposed interferometer is designed and the mathematic model for measuring displacement and angle is established. The influences of the translational, lateral and rotational movements of the measuring reflector on displacement and angle measurement are analyzed in detail. The experimental setup based on the proposed interferometer was constructed and a series of experiments of angle comparison and simultaneous measuring displacement and angle were performed to verify the feasibility of the proposed interferometer for precision displacement and angle measurement. PMID:25401592

  20. Laser interferometer for space-based mapping of Earth's gravity field

    NASA Astrophysics Data System (ADS)

    Dehne, Marina; Sheard, Benjamin; Gerberding, Oliver; Mahrdt, Christoph; Heinzel, Gerhard; Danzmann, Karsten

    2010-05-01

    Laser interferometry will play a key role in the next generation of GRACE-type satellite gravity missions. The measurement concepts for future missions include a heterodyne laser interferometer. Furthermore, it is favourable to use polarising components in the laser interferometer for beam splitting. In the first step the influence of these components on the interferometer sensitivity has been investigated. Additionally, a length stability on a nm-scale has been validated. The next step will include a performance test of an interferometric SST system in an active symmetric transponder setup including two lasers and two optical benches. The design and construction of a quasi-monolithic interferometer for comparing the interferometric performance of non-polarising and polarising optics will be discussed. The results of the interferometric readout of a heterodyne configuration together with polarising optics will be presented to fulfil the phase sensitivity requirement of 1nm/√Hz-- for a typical SSI scenario.

  1. Laser beam collimation using a phase conjugate Twyman-Green interferometer

    NASA Technical Reports Server (NTRS)

    Shukla, R. P.; Dokhanian, M.; George, M. C.; Venkateswarlu, Putcha

    1991-01-01

    This paper presents an improved technique for testing laser beam collimation using a phase conjugate Twyman-Green interferometer. The technique is useful for measuring laser beam divergence. It is possible using this technique to detect the defocusing of the order of one micrometer for a well corrected collimating lens. A relation is derived for the defocusing that can be detected by the phase conjugate interferometer.

  2. In-Bore Projectile Velocity Measurement With Laser Interferometer

    NASA Astrophysics Data System (ADS)

    Wenhao, Zou; Guifang, Yuan; Qingzheng, Tian; Bo, Zheng; Cheng, Wu

    1989-06-01

    The measurement of axial motion of the projectile along the gun barrel against time is one of the important methods to study the work-doing ability of propellant powders. The interaction between gun bore and projectile is interesting to many ballistician and designers. The velocity of the projectile changes from zero to several thousand meters per second, so it is difficult to observe the velocity history because of its highly non-linear velocity history and short effective time interval. The whole course in barrel is of great interest. For designers, the shooting moment is the most interesting. The measurement of the data is the most difficult task, and therefore, the highest resolution of the instruments used is requised. Because of its high resolution, F-PVIS is the suitable equipment for measuring the projectile moving in the bore. The retroreflector used is the key element of success and must meet strict requirements. The CV' He-Ne laser beam is di-rected via a-4disposable mirror down the barrel onto the retroreflector glued to the projectile. The Dapple shift of wavelength of reflected beam is proportional to the projectile velocity. Then, the shifted beam passes through a F-P interferometer and is recorded with an image converter tube camera. The basic principles are discussed together with some typical results from the experiments on 30 mm smooth bore gun. It is important to seal powder gases and nylon driving band can be used.

  3. Remote laser interferometer with pseudo-heterodyne signal processing

    NASA Astrophysics Data System (ADS)

    Liokumovich, Leonid B.; Markov, Sergey I.

    2000-11-01

    Optic and fiber optic interference (phase) scheme are successfully used in creating of hydro-acoustic sensors, vibration sensors and measurers of other magnitudes. The most actual type of the interference sensors is a construction which utilize remote passive all optics sensitive interferometer (Fig. 1). In such devices the additional phase modulation and special methods of signal processing are traditionally used. The resolution of the interference sensor is limited by the noise factor of its elements. The final output noise level of the sensor depends of the optical scheme and method of signal processing. This report is devoted to the neutralization of the influence of the light intensity fluctuations on the sensor resolution using pseudo-heterodyne signal processing. Suppression of this factor in phase optical sensors is not often discussed in literature because laser intensity noise is usually insignificant relatively to other noise mechanisms. However in remote sensors with long distance between signal processing unit and sensitive element we have another situation. External influence (acoustics, vibrations) on lead in and lead out optical paths gives an essential income in the intensity noise at the optics exit. This income is especially sizable (up to tens percents) in remote sensors with opened air optical lead in and out. Sometimes they can even make signal measuring impossible.

  4. Laser Interferometer Space Antenna (LISA) Far Field Phase Patterns

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Obenschain, Arthur F. (Technical Monitor)

    2000-01-01

    The Laser Interferometer Space Antenna (LISA) consists of three spacecraft in orbit about the sun. The orbits are chosen such that the three spacecraft are always at (roughly) the vertices of a equilateral triangle with 5 million kilometer leg lengths. Even though the distances between the three spacecraft are 5 million kilometers, the expected phase shifts between any two beams, due to a gravitational wave, only correspond to a distance change of about 10 pico meters, which is about 10(exp -5) waves for a laser wavelength of 1064 nm. To obtain the best signal-to-noise ratio, noise sources such as changes in the apparent distances due to pointing jitter must be controlled carefully. This is the main reason for determining the far-field phase patterns of a LISA type telescope. Because of torque on the LISA spacecraft and other disturbances, continuous adjustments to the pointing of the telescopes are required. These pointing adjustments will be a "jitter" source. If the transmitted wave is perfectly spherical then rotations (Jitter) about its geometric center will not produce any effect at the receiving spacecraft. However, if the outgoing wave is not perfectly spherical, then pointing jitter will produce a phase variation at the receiving spacecraft. The following sections describe the "brute force" computational approach used to determine the scalar wave front as a function of exit pupil (Zernike) aberrations and to show the results (mostly graphically) of the computations. This approach is straightforward and produces believable phase variations to sub-pico meter accuracy over distances on the order of 5 million kilometers. As such this analyzes the far field phase sensitivity to exit pupil aberrations.

  5. New modulation technique for unambiguous measurements of phase changes in diode laser interferometers

    NASA Astrophysics Data System (ADS)

    Koltchanov, Igor; Petermann, Klaus; Roths, Johannes

    1997-09-01

    We present a new powerful modulation/demodulation technique for unambiguous measurements of phase changes in two-beam interferometers. The technique does not require any additional optics besides a basic interferometer setup and resolves the ambiguity of direction of phase changes by use of a simple two-tone modulation of the laser diode wavelength via injection current. The interference of two modulated light beams generates a signal at the photodetector which is similar to that of heterodyne interferometric setup. The optical phase is thus transferred to an electrical carrier frequency, which allows the phase detection by means of conventional electronic FM-signal processing. The new techniques can be used with any two-beam interferometers as e.g. the Michelson or Mach-Zehnder ones. In the present paper it was applied to a laser-diode, 'self- mixing interferometer' where a weak optical feedback from a target results in an interference with internal laser light.

  6. Signals of an intermodal fiber interferometer induced by laser frequency modulation

    NASA Astrophysics Data System (ADS)

    Kotov, O. I.; Chapalo, I. E.; Petrov, A. V.

    2016-01-01

    Signals of an intermodal fiber interferometer induced by laser optical frequency modulation are studied. Dependences of signal amplitudes and spectra on the laser frequency deviation are examined theoretically and experimentally for various optical fibers. It is established that the sensitivity of the intermodal fiber interferometer to the laser frequency variation essentially depends on the fiber refractive index profile. The minimal sensitivity corresponds to graded-index (α ≈ 2) multimode optical fibers. Step-index optical fibers (α = ∞) are more sensitive to the laser frequency variation by more than a factor of 100.

  7. Analytical model for ring heater thermal compensation in the Advanced Laser Interferometer Gravitational-wave Observatory.

    PubMed

    Ramette, Joshua; Kasprzack, Marie; Brooks, Aidan; Blair, Carl; Wang, Haoyu; Heintze, Matthew

    2016-04-01

    Advanced laser interferometer gravitational-wave detectors use high laser power to achieve design sensitivity. A small part of this power is absorbed in the interferometer cavity mirrors where it creates thermal lenses, causing aberrations in the main laser beam that must be minimized by the actuation of "ring heaters," which are additional heater elements that are aimed to reduce the temperature gradients in the mirrors. In this article we derive the first, to the best of our knowledge, analytical model of the temperature field generated by an ideal ring heater. We express the resulting optical aberration contribution to the main laser beam in this axisymmetric case. Used in conjunction with wavefront measurements, our model provides a more complete understanding of the thermal state of the cavity mirrors and will allow a more efficient use of the ring heaters in the Advanced Laser Interferometer Gravitational-wave Observatory. PMID:27139664

  8. Analytical model for ring heater thermal compensation in the Advanced Laser Interferometer Gravitational-wave Observatory

    NASA Astrophysics Data System (ADS)

    Ramette, Joshua; Kasprzack, Marie; Brooks, Aidan; Blair, Carl; Wang, Haoyu; Heintze, Matthew

    2016-04-01

    Advanced laser interferometer gravitational-wave detectors use high laser power to achieve design sensitivity. A small part of this power is absorbed in the interferometer cavity mirrors where it creates thermal lenses, causing aberrations in the main laser beam that must be minimized by the actuation of "ring heaters," which are additional heater elements that are aimed to reduce the temperature gradients in the mirrors. In this article we derive the first, to the best of our knowledge, analytical model of the temperature field generated by an ideal ring heater. We express the resulting optical aberration contribution to the main laser beam in this axisymmetric case. Used in conjunction with wavefront measurements, our model provides a more complete understanding of the thermal state of the cavity mirrors and will allow a more efficient use of the ring heaters in the Advanced Laser Interferometer Gravitational-wave Observatory.

  9. The frequency stabilization method of laser feedback interferometer based on external cavity modulation.

    PubMed

    Zeng, Zhaoli; Zhang, Shulian; Tan, Yidong; Wu, Yun; Li, Yan

    2013-02-01

    Laser frequency stabilization is one of the foremost factors that influence the accuracy of measurement using a laser feedback interferometer, especially when the system is in the presence of strong optical feedback. In this paper, we use external cavity modulation to demonstrate a simple and effective method of frequency stabilization for laser feedback interferometer with strong optical feedback. The external cavity modulation is realized by oscillating a feedback mirror driven by a piezoelectric ceramic, the stable feedback optical field is obtained that has strong performance of anti-disturbance. Meanwhile, we stabilize the laser frequency by the thermal frequency-stabilizing. These lead to the realization of stable laser feedback interferometer. The relative uncertainty of the frequency stabilization is less than 1 part in 10(7). PMID:23464252

  10. An extreme ultraviolet Michelson interferometer for experiments at free-electron lasers

    SciTech Connect

    Hilbert, Vinzenz; Fuchs, Silvio; Paulus, Gerhard G.; Zastrau, Ulf; Blinne, Alexander; Feigl, Torsten; Kämpfer, Tino; Rödel, Christian; Uschmann, Ingo; Wünsche, Martin; Förster, Eckhart; Helmholtz Institute, Fröbelstieg 3, 07743 Jena

    2013-09-15

    We present a Michelson interferometer for 13.5 nm soft x-ray radiation. It is characterized in a proof-of-principle experiment using synchrotron radiation, where the temporal coherence is measured to be 13 fs. The curvature of the thin-film beam splitter membrane is derived from the observed fringe pattern. The applicability of this Michelson interferometer at intense free-electron lasers is investigated, particularly with respect to radiation damage. This study highlights the potential role of such Michelson interferometers in solid density plasma investigations using, for instance, extreme soft x-ray free-electron lasers. A setup using the Michelson interferometer for pseudo-Nomarski-interferometry is proposed.

  11. Detection of low frequency hurricane emissions using a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Slaton, William V.; Kendall, Lauren M.

    2012-10-01

    Over the last decade, large horizontally mounted ring laser interferometers have demonstrated the capacity to measure numerous geophysical effects. In this paper, responses from large ring laser interferometers to low frequency hurricane emissions are presented. Hurricanes create a broad spectrum of noise that extends into the millihertz range. In addition to microseisms, hurricanes with established eyewalls were found to create distinct frequency peaks close to 7 mHz as they came ashore or moved over shallow water. Selected emissions from Hurricanes Katrina, Wilma, and Dean are presented. The exact coupling mechanism between the ˜7 mHz hurricane emissions and the ring lasers remains under active investigation.

  12. Development of CO{sub 2} laser dispersion interferometer with photoelastic modulator

    SciTech Connect

    Akiyama, T.; Kawahata, K.; Okajima, S.; Nakayama, K.

    2010-10-15

    A dispersion interferometer is one of the promising methods of the electron density measurement on large and high density fusion devices. This paper describes development of a CO{sub 2} laser dispersion interferometer with a photoelastic modulator for phase modulation. In order to make the dispersion interferometer free from variations of the detected intensity, a new phase extraction method is introduced: The phase shift is evaluated from a ratio of amplitudes of the fundamental and the second harmonics of the phase modulation frequency in the detected interference signal. The proof-of-principle experiments demonstrate the feasibility of this method.

  13. Cancellation of Laser Noise in an Unequal-arm Interferometer Detector of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, M.; Armstrong, J. W.

    1998-01-01

    In this paper we present a method for exactly cancelling the laser noise in a one-bounce unequal-arm Michelson interferometer. The method requries separate measurements of the phase difference in each arm, made by interfering the returning laser light in each arm with the outgoing light.

  14. Spacecraft to Spacecraft Coherent Laser Tracking as a Xylophone Interferometer Detector of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, M.

    1998-01-01

    Searches for gravitational radiation can be performed in space with two spacecraft tracking each other with coherent laser light. This experimental technique could be implemented with two spacecraft carrying an appropriate optical payload, or with the proposed broad-band, space-based laser interferometer detectors of gravitational waves operated in this non-interferometric mode.

  15. Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers.

    PubMed

    Dooley, Katherine L; Arain, Muzammil A; Feldbaum, David; Frolov, Valery V; Heintze, Matthew; Hoak, Daniel; Khazanov, Efim A; Lucianetti, Antonio; Martin, Rodica M; Mueller, Guido; Palashov, Oleg; Quetschke, Volker; Reitze, David H; Savage, R L; Tanner, D B; Williams, Luke F; Wu, Wan

    2012-03-01

    We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO. PMID:22462908

  16. Thermal effects in the Input Optics of the Enhanced Laser Interferometer Gravitational-Wave Observatory interferometers

    NASA Astrophysics Data System (ADS)

    Dooley, Katherine L.; Arain, Muzammil A.; Feldbaum, David; Frolov, Valery V.; Heintze, Matthew; Hoak, Daniel; Khazanov, Efim A.; Lucianetti, Antonio; Martin, Rodica M.; Mueller, Guido; Palashov, Oleg; Quetschke, Volker; Reitze, David H.; Savage, R. L.; Tanner, D. B.; Williams, Luke F.; Wu, Wan

    2012-03-01

    We present the design and performance of the LIGO Input Optics subsystem as implemented for the sixth science run of the LIGO interferometers. The Initial LIGO Input Optics experienced thermal side effects when operating with 7 W input power. We designed, built, and implemented improved versions of the Input Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO interferometers, designed to run with 30 W input power. At four times the power of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved performance including better optical isolation, less thermal drift, minimal thermal lensing, and higher optical efficiency. The success of the Input Optics design fosters confidence for its ability to perform well in Advanced LIGO.

  17. Measuring of object vibration using sinusoidal-modulation laser-diode active interferometer

    NASA Astrophysics Data System (ADS)

    Ai, Yong; Cao, Qinfeng; Lu, Su

    1996-09-01

    Using the character that the emitting optical frequency of the laser diode is controlled by the injected current, the ability of eliminating environmental disturbance of the sinusoidal modulation laser diode active interferometer will be raised by more than one hundred times through putting the disturbed interference signal produced by the environment into the interferometer. When vibrating frequency of objects is different from that of the sinusoidol modulation, 'beat- frequency' will be produced in the interfere signal, which can be analyzed to get the vibrating frequency of objects. This paper described the operation principle and theoretical delusion of the 'beat-frequency' method.

  18. Interspacecraft link simulator for the laser ranging interferometer onboard GRACE Follow-On.

    PubMed

    Sanjuan, Josep; Gohlke, Martin; Rasch, Stefan; Abich, Klaus; Görth, Alexander; Heinzel, Gerhard; Braxmaier, Claus

    2015-08-01

    Link acquisition strategies are key aspects for interspacecraft laser interferometers. We present an optical fiber-based setup able to simulate the interspacecraft link for the laser ranging interferometer (LRI) on gravity recovery and climate experiment Follow-On. It allows one to accurately recreate the far-field intensity profile depending on the mispointing between the spacecraft, Doppler shifts, and spacecraft attitude jitter. Furthermore, it can be used in late integration stages of the mission, since no physical contact with the spacecraft is required. The setup can also be easily adapted to other similar missions and different acquisition algorithms. PMID:26368080

  19. Cancellation of Laser Noise in Space-Based Interferometer Detectors of Gravitational Radiation

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo

    1999-01-01

    We presented a time-domain procedure for accurately cancelling laser noise fluctuations in an unequal-arm Michelson interferometer. The method involves separately measuring the phase of the returning light relative to the phase of the transmitted light in each arm. By suitable offsetting and differencing of these two time series, the common laser noise is cancelled exactly. The technique presented in this paper is general, in such that it can be implemented with any (Earth as well as space-based) unequal-arms Michelson interferometers,

  20. Digital quadrature amplitude modulation with optimized non-rectangular constellations for 100 Gb/s transmission by a directly-modulated laser.

    PubMed

    Ling, William A; Lyubomirsky, Ilya; Solgaard, Olav

    2014-05-01

    We study the performance of novel quadrature amplitude modulation (QAM) constellations for 100 Gb/s transmission by a directly-modulated laser. Due to the strong nonlinearity of a directly-modulated laser, rectangular constellations suffer a large penalty from their regular spacing between symbols. We present a method for synthesizing irregular constellations which position symbols more efficiently. We will demonstrate the improved performance of these novel constellations over the conventional rectangular constellation as well as the superior performance achievable with digital QAM compared to optimally bit-loaded discrete-multitone modulation. PMID:24921784

  1. A phase-modulated laser system of ultra-low phase noise for compact atom interferometers

    NASA Astrophysics Data System (ADS)

    Lee, Ki-Se; Kim, Jaewan; Lee, Sang-Bum; Park, Sang Eon; Kwon, Taek Yong

    2015-07-01

    A compact and robust laser system is essential for mobile atom interferometers. Phase modulation can provide the two necessary phase-coherent frequencies without sophisticated phase-locking between two different lasers. However, the additional laser frequencies generated can perturb the atom interferometer. In this article, we report on a novel method to produce a single high-power laser beam composed of two phase-coherent sidebands without the perturbing carrier mode. Light from a diode laser is phase-modulated by using a fiber-coupled electro-optic modulator driven at 3.4 GHz and passes through a Fabry-Perot cavity with a 6.8 GHz free spectral range. The cavity filters the carrier mode to leave the two first-order sidebands for the two-photon Raman transition between the two hyperfine ground states of 87Rb. The laser beam is then fed to a single tapered amplifier, and the two sidebands are both amplified without mode competition. The phase noise is lower than that of a state-of-the-art optically phase-locked external-cavity diode laser (-135 dBrad2/Hz at 10 kHz) at frequencies above 10 Hz. This technique can be used in all-fiber-based laser systems for future mobile atom interferometers.

  2. 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.

  3. Multichannel HCN laser interferometer for electron density measurements of the JIPP T-IIU tokamak

    SciTech Connect

    Kawahata, K.; Haba, K.; Fujita, J. ); Okajima, S. )

    1989-12-01

    A six-channel HCN laser interferometer system has been developed for the measurement of the electron density profile in the JIPP T-IIU tokamak. The fringe shift of the probe beam is directly read out using a reference beam, the frequency of which is Doppler shifted by 50 kHz with a rotating grating. The optical configuration is of the Michelson interferometer type, of which reflecting mirrors are directly attached on the wall of the vacuum vessel. An effective area of the optical window is only {phi}40 mm. This optical configuration enables us to make the electron density profile measurements by the multichannel laser interferometer with a single small optical window.

  4. A basic Michelson laser interferometer for the undergraduate teaching laboratory demonstrating picometer sensitivity

    NASA Astrophysics Data System (ADS)

    Libbrecht, Kenneth G.; Black, Eric D.

    2015-05-01

    We describe a basic Michelson laser interferometer experiment for the undergraduate teaching laboratory that achieves picometer sensitivity in a hands-on, table-top instrument. In addition to providing an introduction to interferometer physics and optical hardware, the experiment also focuses on precision measurement techniques including servo control, signal modulation, phase-sensitive detection, and different types of signal averaging. Students examine these techniques in a series of steps that take them from micron-scale sensitivity using direct fringe counting to picometer sensitivity using a modulated signal and phase-sensitive signal averaging. After students assemble, align, and characterize the interferometer, they then use it to measure nanoscale motions of a simple harmonic oscillator system as a substantive example of how laser interferometry can be used as an effective tool in experimental science.

  5. Laser-ranging long-baseline differential atom interferometers for space

    NASA Astrophysics Data System (ADS)

    Chiow, Sheng-wey; Williams, Jason; Yu, Nan

    2015-12-01

    High-sensitivity differential atom interferometers (AIs) are promising for precision measurements in science frontiers in space, including gravity-field mapping for Earth science studies and gravitational wave detection. Difficulties associated with implementing long-baseline differential AIs have previously included the need for a high optical power, large differential Doppler shifts, and narrow dynamic range. We propose a configuration of twin AIs connected by a laser-ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and also to phase-lock the two independent interferometer lasers over long distances, thereby drastically improving the practical feasibility of long-baseline differential AI measurements. We show that a properly implemented LRI-AI can achieve equivalent functionality to the conventional differential AI measurement configuration.

  6. Frequency Noise Suppression of a Single Mode Laser with an Unbalanced Fiber Interferometer for Subnanometer Interferometry

    PubMed Central

    Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Číp, Ondřej

    2015-01-01

    We present a method of noise suppression of laser diodes by an unbalanced Michelson fiber interferometer. The unstabilized laser source is represented by compact planar waveguide external cavity laser module, ORIONTM (Redfern Integrated Optics, Inc.), working at 1540.57 nm with a 1.5-kHz linewidth. We built up the unbalanced Michelson interferometer with a 2.09 km-long arm based on the standard telecommunication single-mode fiber (SMF-28) spool to suppress the frequency noise by the servo-loop control by 20 dB to 40 dB within the Fourier frequency range, remaining the tuning range of the laser frequency. PMID:25587980

  7. Terahertz frequency measurement of far-infrared laser with an improvement of Martin-Puplett interferometer

    NASA Astrophysics Data System (ADS)

    Liu, Wenxin; Wu, Dai; Wang, Yingxin; Tang, Chuanxiang; Huang, Wenhui; Zhao, Ziran

    2010-03-01

    In this paper, we present an improvement of Martin-Puplett interferometer (MPI) for terahertz frequency measurement, in which flat mirrors replace the roof ones. To understand the function of the improved MPI, its basic principle is described and the characteristics of electric field are analyzed. With the improved MPI, the operation frequency of a far-infrared laser is conveniently measured, and the experimental result is in good agreement with that of the far-infrared laser theoretical reported.

  8. Development of a new two color far infrared laser interferometer for future fusion devices

    SciTech Connect

    Kawahata, K.; Tanaka, K.; Tokuzawa, T.; Akiyama, T.; Ito, Y.; Okajima, S.; Nakayama, K.; Wylde, R.J.

    2004-10-01

    A new two color far infrared (FIR) laser interferometer under development for future fusion devices will be presented. The laser wavelength is optimized from the consideration of the beam refraction effect due to plasma density gradient and signal-to-noise ratio for an expected phase shift due to plasmas. Laser lines of 57.2 and 47.6 {mu}m are found to be suitable for the applications to high performance plasmas of Large Helical Device and future fusion devices such as the International Thermonuclear Experimental Reactor. The output power of 57.2 {mu}m CH{sub 3}OD laser is estimated to be {approx}1.6 W, which is the highest laser power in the FIR wavelength regime. The optical configuration of a new interferometer system using two colors will be proposed. In the system, one detector simultaneously detects the beat signals of the 57.2 and 47.6 {mu}m laser lines, and each interference signal can be separated electronically (1 MHz for 57.2 {mu}m and 0.84 MHz expected for 47.6 {mu}m). Mechanical vibration can be compensated by using the two color interferometer. The present status of the development of the system is also presented.

  9. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Investigation of single-frequency semiconductor lasers with a fiber Michelson interferometer

    NASA Astrophysics Data System (ADS)

    Belovolov, M. I.; Gur'yanov, A. N.; Gusovskiĭ, D. D.; Dianov, Evgenii M.; Kuznetsov, A. V.; Pencheva, V. Kh; Prokhorov, A. M.

    1987-04-01

    A fiber Michelson interferometer, which is an analog of a scanning Michelson interferometer, was constructed from single-mode fiber waveguides and several highly directional Y-type couplers operating at the wavelength of 0.85 μ. It was found that this interferometer could be used to investigate the coherence of radiation from single-frequency lasers with a spectral line width in the range from 10 kHz to 1 GHz. The experimental dependences of the degree of coherence on the optical path difference were determined for cw single-frequency AlGaAs double heterostructure lasers with an external dispersive resonator, operating in the regime of self-stabilization of single-frequency emission. It was found that the width of the spectral lines was between 10 kHz and 1 MHz, and that the line profiles were Lorentzian.

  10. Arm locking with the GRACE follow-on laser ranging interferometer

    NASA Astrophysics Data System (ADS)

    Thorpe, James Ira; McKenzie, Kirk

    2016-02-01

    Arm locking is a technique for stabilizing the frequency of a laser in an interspacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna, arm locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the laser ranging interferometer instrument flying aboard the upcoming Gravity Recovery and Climate Experiment follow-on (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly 2 orders of magnitude around a Fourier frequency of 1 Hz with conservative margins on the system's stability. We further demonstrate that "pulling" of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100 MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

  11. Development Towards a Space Qualified Laser Stabilization System in Support of Space-Based Optical Interferometers

    NASA Technical Reports Server (NTRS)

    Seidel, David J.; Dubovitsky, Serge

    2000-01-01

    We report on the development, functional performance and space-qualification status of a laser stabilization system supporting a space-based metrology source used to measure changes in optical path lengths in space-based stellar interferometers. The Space Interferometry Mission (SIM) and Deep Space 3 (DS-3) are two missions currently funded by the National Aeronautics and Space Administration (NASA) that are space-based optical interferometers. In order to properly recombine the starlight received at each telescope of the interferometer it is necessary to perform high resolution laser metrology to stabilize the interferometer. A potentially significant error source in performing high resolution metrology length measurements is the potential for fluctuations in the laser gauge itself. If the laser frequency or wavelength is changing over time it will be misinterpreted as a length change in one of the legs of the interferometer. An analysis of the frequency stability requirement for SIM resulted in a fractional frequency stability requirement of square root (S(sub y)(f)) = <2 x 10(exp -12)/square root(Hz) at Fourier frequencies between 10 Hz and 1000 Hz. The DS-3 mission stability requirement is further increased to square root (S(sub y)(f)) = <5 x 10(exp -14)/Square root(Hz) at Fourier frequencies between 0.2 Hz and 10 kHz with a goal of extending the low frequency range to 0.05 Hz. The free running performance of the Lightwave Electronics NPRO lasers, which are the baseline laser for both SIM and DS-3 vary in stability and we have measured them to perform as follows (9 x l0(exp -11)/ f(Hz))(Hz)/square root(Hz)) = <( square root (S(sub y)(f)) = <(1.3 x l0(exp -8)/ f(Hz))/Square root(Hz). In order to improve the frequency stability of the laser we stabilize the laser to a high finesse optical cavity by locking the optical frequency of the laser to one of the transmission modes of the cavity. At JPL we have built a prototype space-qualifiable system meeting the stability requirements of SIM, which has been delivered to one of the SIM testbeds. We have also started on the development of a system to meet the stability needs of DS-3.

  12. Measuring the spatial frequency transfer function of phase measuring interferometers for laser optics

    SciTech Connect

    Wolfe, C.R.; Downie, J.D.; Lawson, J.K.

    1996-06-27

    The power spectral density (PSD) function is being employed to specify the surface finish and transmitted wavefront in the mid- spatial frequency regime for laser beam optics of the National Ignition Facility (NIF). The instrument used to measure the PSD is a phase measuring Fizeau interferometer. The phase map produced by the interferometer is digitally processed to create the PSD. Before one can use the PSD information, it is necessary to evaluate the fidelity of the interferometer spatial frequency response. Specifically, one must measure the overall transfer function of the instrument. To accomplish this, we perform a two-step ``calibration`` process. We first measure a known precision phase object with the interferometer and then compare the measured PSD to an ideal numerical simulation which represents the theoretical PSD. The square root of the ratio of the measured function to the simulation is defined as the transfer function of the instrument. We present experimental results for both reflective and transmissive test objects, including effects such as the test object orientation and longitudinal location in the interferometer cavity. We also evaluate the accuracy levels obtained using different test objects. 11 refs., 5 figs.

  13. Experimental demonstration of time-delay interferometry for the laser interferometer space antenna.

    PubMed

    de Vine, Glenn; Ware, Brent; McKenzie, Kirk; Spero, Robert E; Klipstein, William M; Shaddock, Daniel A

    2010-05-28

    We report on the first demonstration of time-delay interferometry (TDI) for LISA, the Laser Interferometer Space Antenna. TDI was implemented in a laboratory experiment designed to mimic the noise couplings that will occur in LISA. TDI suppressed laser frequency noise by approximately 10(9) and clock phase noise by 6×10(4), recovering the intrinsic displacement noise floor of our laboratory test bed. This removal of laser frequency noise and clock phase noise in postprocessing marks the first experimental validation of the LISA measurement scheme. PMID:20867084

  14. 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

  15. Laser noise mitigation through time delay interferometry for space-based gravitational wave interferometers using the UF laser interferometry simulator

    NASA Astrophysics Data System (ADS)

    Mitryk, Shawn J.

    2012-06-01

    The existence of gravitational waves was theorized in 1916 by Albert Einstein in accordance with the linearized theory of general relativity. Most experiments and observations to date have supported general relativity, but now, nearly 100 years later, the scientific community has yet devise a method to directly measure gravitational radiation. With the first attempts towards a gravitational wave measurement in the 1960s, many methods have been proposed and tested since then, all failing thus far to provide a positive detection. The most promising gravitational radiation detection method is through the use of a space-based laser interferometer and with the advancement of modern technologies, these space-based gravitational wave measurements will eventually provide important scientific data to physics, astro-physics, and astronomy communities. The Laser Interferometer Space Antenna (LISA) is one such space-based laser interferometer. LISA's proposed design objective is to measure gravitational radiation in the frequency range from 30 microHz to 1 Hz using a modified Michelson interferometer. The interferometer arms are 5 Gm in length measured between each of the 3 spacecraft in the interferometer constellation. The differential arm-length will be measured to an accuracy of 18 pm/ Hz resulting in a baseline strain sensitivity of 3.6 x 10 --21 / Hz . Unfortunately, the dynamics of the spacecraft orbits complicate the differential arm-length measurements. The arms of the interferometer change in length resulting in time-dependent, unequal arm-lengths and laser Doppler shifts. Thus, to cancel the laser noise, laser beatnotes are formed between lasers on separate SC and, using these one-way laser phase measurements, one can reconstruct an equal-arm interferometer in post-processing. This is commonly referred to as time-delay interferometry (TDI) and can be exploited to cancel the laser phase noise and extract the gravitational wave (GW) induced arm-length strain. The author has assisted in the development and enhancement of The University of Florida Laser Interferometry Simulator (UFLIS) to perform more accurate LISA-like simulations. UFLIS is a hardware-in-the-loop simulator of the LISA interferometry system replicating as many of the characteristics of the LISA mission as possible. This includes the development of laser pre-stabilization systems, the modeling of the delayed inter-SC laser phase transmission, and the microcycle phase measurements of MHz laser beatnotes. The content of this dissertation discusses the general GW detection methods and possible GW sources as well as the specific characteristics of the LISA mission's design. A theoretical analysis of the phasemeter and TDI performance is presented along with experimental verification measurements. The development of UFLIS is described including a comparison of the UFLIS noise sources with the actual LISA mission. Finally, the enhanced UFLIS design is used to perform a second-order TDI simulation with artificial GW injection. The results are presented along with an analysis of relevant LISA characteristics and GW data-extraction methods.

  16. Active laser frequency stabilization and resolution enhancement of interferometers for the measurement of gravitational waves in space

    NASA Astrophysics Data System (ADS)

    Herz, Markus

    2005-09-01

    Laser frequency stabilization is notably one of the major challenges on the way to a space-borne gravitational wave observatory. The proposed Laser Interferometer Space Antenna (LISA) is presently under development in an ESA, NASA collaboration. We present a novel method for active laser stabilization and phase noise suppression in such a gravitational wave detector. The proposed approach is a further evolution of the "arm-locking" method, which in essence consists of using an interferometer arm as an optical cavity, exploiting the extreme long-run stability of the cavity size in the frequency band of interest. We extend this method by using the natural interferometer arm length differences and existing interferometer signals as additional information sources for the reconstruction and active suppression of the quasi-periodic laser frequency noise, enhancing the resolution power of space-borne gravitational wave detectors.

  17. Absolute distance measurement in a combined-dispersive interferometer using a femtosecond pulse laser

    NASA Astrophysics Data System (ADS)

    Wu, Hanzhong; Zhang, Fumin; Meng, Fei; Liu, Tingyang; Li, Jianshuang; Pan, Liang; Qu, Xinghua

    2016-01-01

    In this paper, a ranging system using dispersive interferometry is developed with a femtosecond pulse laser, aiming to eliminate the measurement dead zones by using a greatly unbalanced Mach-Zehnder interferometer. The distance can be measured by the frequency of the spectral modulation. We indicate that the integer number of the pulse-to-pulse length can be determined by changing the repetition frequency. In the short distance measurement, the results show an agreement within 1.5 μm compared with an incremental He-Ne laser in the 1 m measurement range. We do large-scale experiments on a long optical rail using a typical Michelson interferometer, and an agreement well within 25 μm is obtained in a range up to 75 m, corresponding to a relative precision of 3.3  ×  10-7. Additionally, we experimentally optimize the system set-up to minimize the measurement uncertainty.

  18. Recent Progress of the HL-2A Multi-Channel HCOOH Laser Interferometer/Polarimeter

    NASA Astrophysics Data System (ADS)

    Li, Yonggao; Zhou, Yan; Deng, Zhongchao; Li, Yuan; Yi, Jiang; Wang, Haoxi

    2015-05-01

    A multichannel methanoic acid (HCOOH, λ = 432.5 μm) laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide (HCN, λ = 337 μm) laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of ˜30 mW, and a power stability <10% in 50 min. A beam waist (diameter d0 ≈12.0 mm, about 200 mm away from the outlet) is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase-comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign. supported by the National Magnetic Confinement Fusion Science Programs of China (Nos. 2010GB101002 and 2014GB109001), and National Natural Science Foundation of China (Nos. 11075048 and 11275059)

  19. Pulsed laser spectral measurement using a Fabry-Perot interferometer: Limits to resolution

    NASA Technical Reports Server (NTRS)

    Notari, Anthony; Gentry, Bruce M.

    1992-01-01

    We are developing a Doppler lidar system using the edge technique to measure atmospheric wind profiles. The edge technique requires a laser with a narrow spectral bandwidth and a high resolution optical filter. The lidar system will use a Nd:YAG laser operating at 1.064 microns and a high resolution Fabry-Perot interferometer for the edge filter. The Doppler shift measurement is made by locating the laser on the edge of the filter's spectral response function. Due to the steep slope on the edge, large changes in the filter transmission will be observed for small changes in frequency. The Doppler shift can be determined from a measurement of this change in filter transmission if the filter spectral response function in the region of the measurement is well known. Recently developed injection seeded solid state lasers have made near transform limited laser output readily available for lidar work. Injection-seeded Nd:YAG laser exhibit single mode output with smooth Gaussian temporal pulse shapes. Results of an experiment we conducted to evaluate the effects of a short Gaussian temporal input pulse on the spectral response of a high resolution Fabry-Perot interferometer are presented.

  20. Analysis of the measurement uncertainty of a positional error calibrator based on a laser interferometer

    NASA Astrophysics Data System (ADS)

    Qu, Zhiyong; Yao, Yu

    2005-12-01

    A positional error calibrator for evaluating the positioning accuracy of 6-dof simulation system under dynamic conditions has been developed. It is based on the Hewlett Packard 5529A laser interferometer, which is capable of performing dynamic calibration. This laser interferometer measures the position of the slide as it moves continuously along the simulation system axis under test. The data are collected on a position basis by triggering the laser interferometer from a position-based reference signal. A software package has been developed for data acquisition and presentation of the positional errors in accordance with ISO 230-2 standard. This paper deals with the evaluation of the measurement uncertainty of this positional error calibrator. In order to assess the total measurement uncertainty of this calibrator, an analysis of the individual errors that make up the accuracy and repeatability error budgets has been carried out. These error budgets consist of three components. This uncertainty analysis was carried out when this calibrator was used to assess the positional errors of a 6-dof simulation system.

  1. Multi-wavelength fiber laser based on a fiber Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Estudillo-Ayala, J. M.; Jauregui-Vazquez, D.; Haus, J. W.; Perez-Maciel, M.; Sierra-Hernandez, J. M.; Avila-Garcia, M. S.; Rojas-Laguna, R.; Lopez-Dieguez, Y.; Hernandez-Garcia, J. C.

    2015-12-01

    In this work we report experimental studies of an erbium-doped fiber laser design that simultaneously emits up to three wavelengths. The laser cavity configuration has an all-fiber, Fabry-Perot interferometer, based on the insertion of air cavities in the fiber, near one end of a conventional single-mode fiber. The laser emissions have a side-mode suppression ratio over 25 dB, wavelength variations around 0.04 nm, and 2 dB power fluctuations. By using a simple, controlled fiber curvature technique cavity losses are varied over a section of convectional single-mode fiber and the laser output is switched between single-, dual-, and triple-wavelength emission. Moreover, by applying a refractive index change over the fiber filter the emission wavelengths are shifted. The fiber laser offers a compact, simple, and low-cost design for a multiple wavelength outputs that can be adopted in future applications.

  2. Fast wavelength-scanning interferometry technique with derivative detection of quadrature signals

    NASA Astrophysics Data System (ADS)

    Číp, O.; Mikel, B.; Lazar, J.

    2006-04-01

    We present a laser interferometer where a narrow-line width tuneable VCSEL laser (Vertical-Cavity Surface-Emitting Laser) working at 760 nm is used. For the detection of an absolute distance, we have used a fast wavelength-scanning interferometry technique. In the first part of the work we introduce the absolute laser interferometer as a demonstrator for research of a digital detection of quadrature signals (X-cos and Y-sin). This interferometer uses polarized beams and magnitude division of interference fringes. The wavelength of VCSEL laser is swept with the mode-hop free tuning range more than 1.2 nm, by means of the amplitude modulation of the injection current. At the same time, the operating temperature of the VCSEL is stabilized with a fast digital temperature controller. We control the wavelength value and whole tuning process of the laser with the frequency lock to selected modes of an external Fabry-Perot etalon. Except the frequency lock, the Fabry-Perot mode spectrum identifies wavelength-tuning interval of VCSEL during each sweep. A digital signal processor (DSP) is heart of the control and detection system. It samples intensity signal from Fabry- Perot etalon and X-Y quadrature signals from the detection unit of the interferometer. After 1 nm sweep of the VCSEL wavelength, we obtain a number of passed interference fringes and the number of passed Fabry-Perot resonance modes, at the same time. On basis of these measured quantities we are able to calculate the instantaneous value of the optical path length difference between the measuring and reference arm of the demonstrational interferometer. The other part of the work is oriented to research and experimental testing of the digital detection of quadrature signals (X-cos and Y-sin) processed only on basis of one intensity signal (X-axis) that is produced by a simple photo-detector. On basis of traditional inversion function arctan(Y/X) we are able to determine instantaneous phase between interference beams in each part of recorded signals. In the work the first introduction of the method and measured records are presented.

  3. Measuring preheat in laser-drive aluminum using velocity interferometer system for any reflector: Experiment

    SciTech Connect

    Shu, Hua; Fu, Sizu; Huang, Xiuguang; Wu, Jiang; Xie, Zhiyong; Zhang, Fan; Ye, Junjian; Jia, Guo; Zhou, Huazhen

    2014-08-15

    In this paper, we systematically study preheating in laser-direct-drive shocks by using a velocity interferometer system for any reflector (VISAR). Using the VISAR, we measured free surface velocity histories of Al samples over time, 1070??m thick, driven directly by a laser at different frequencies (2?, 3?). Analyzing our experimental results, we concluded that the dominant preheating source was X-ray radiation. We also discussed how preheating affected the material initial density and the measurement of Hugoniot data for high-Z materials (such as Au) using impedance matching. To reduce preheating, we proposed and tested three kinds of targets.

  4. Two-color CO2/HeNe laser interferometer for C-2 experiment.

    PubMed

    Gornostaeva, O; Deng, B H; Garate, E; Gota, H; Kinley, J; Schroeder, J; Tuszewski, M

    2010-10-01

    A six-channel two-color interferometer has been developed for plasma electron density measurements in the C-2 field reversed configuration experiment. A CO(2) laser is utilized as the main probe beams, while copropagating visible HeNe laser beams are mainly sensitive to vibration. Density measurements in C-2 plasmas have shown that this is a reliable turn-key system. The maximum residual phase noise after vibration compensation is less than ±5°, corresponding to a line integral density of 3×10(18) m(-2). The time resolution for routine operation is 2 μs. PMID:21033871

  5. Status of advanced ground-based laser interferometers for gravitational-wave detection

    NASA Astrophysics Data System (ADS)

    Dooley, K. L.; Akutsu, T.; Dwyer, S.; Puppo, P.

    2015-05-01

    Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years’ worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO 600 and KAGRA.

  6. A nonintrusive laser interferometer method for measurement of skin friction

    NASA Technical Reports Server (NTRS)

    Monson, D. J.

    1982-01-01

    A method is described for monitoring the changing thickness of a thin oil film subject to an aerodynamic shear stress using two focused laser beams. The measurement is then simply analyzed in terms of the surface skin friction of the flow. The analysis includes the effects of arbitrarily large pressure and skin friction gradients, gravity, and time varying oil temperature. It may also be applied to three dimensional flows with unknown direction. Applications are presented for a variety of flows including two dimensional flows, three dimensional swirling flows, separated flow, supersonic high Reynolds number flows, and delta wing vortical flows.

  7. Experiments with an 834 m2 ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Hurst, R. B.; Stedman, G. E.; Schreiber, K. U.; Thirkettle, R. J.; Graham, R. D.; Rabeendran, N.; Wells, J.-P. R.

    2009-06-01

    An ultralarge ring He-Ne ring laser gyroscope, UG-2, with area 834 m2 and dimensions 39.7×21 m2, has been built underground at Cashmere Cavern, Christchurch, New Zealand (latitude -43.575°). Earth rotation is sufficient to unlock it, giving a Sagnac frequency of 2.18 kHz. Supermirrors are used with transmission ˜0.18 parts per million (ppm) and optical loss unexpectedly high at ˜200 ppm per reflection. The cavity Q is 1.5×1012. Residual Sagnac frequency error caused by backscatter coupling is measured as <2 parts in 108. Its best stability is achieved for an averaging time of ˜2000 s, for which the Allan Deviation of the Sagnac frequency is 0.08 mHz, or four parts in 108 of Earth rotation rate. The dominant processes generating the residual rotational noise are, for times <10 s, microseismic ground movements, and for times >1000 s, mechanical movement of the mirror assemblies, which act to change the geometrical dimensions and tilt. At all averaging times the residual rotational noise is well above the limit imposed by quantum phase fluctuations. It is concluded from comparisons among many large ring lasers that the excess mirror losses arise from high order aberrations, and UG-2 may be larger than the optimum size.

  8. Interferometer for the measurement of plasma density

    DOEpatents

    Jacobson, Abram R.

    1980-01-01

    An interferometer which combines the advantages of a coupled cavity interferometer requiring alignment of only one light beam, and a quadrature interferometer which has the ability to track multi-fringe phase excursions unambiguously. The device utilizes a Bragg cell for generating a signal which is electronically analyzed to unambiguously determine phase modulation which is proportional to the path integral of the plasma density.

  9. Squeezing quadrature rotation in the acoustic band via optomechanics

    NASA Astrophysics Data System (ADS)

    Guccione, Giovanni; Slatyer, Harry J.; Carvalho, André R. R.; Buchler, Ben C.; Lam, Ping Koy

    2016-03-01

    We examine the use of optomechanically generated squeezing to obtain a sensitivity enhancement for interferometers in the gravitational-wave band. The intrinsic dispersion characteristics of optomechanical squeezing around the mechanical frequency are able to produce squeezing at different quadratures over the spectrum, a feature required by gravitational-wave interferometers to beat the standard quantum limit over an extended frequency range. Under realistic assumptions we show that the amount of available squeezing and the intrinsic quadrature rotation may provide, compared to similar amounts of fixed-quadrature squeezing, a detection advantage. A significant challenge for this scheme, however, is the amount of excess noise that is generated in the unsqueezed quadrature at frequencies near the mechanical resonance.

  10. Searching for a Stochastic Background of Gravitational Waves with the Laser Interferometer Gravitational-Wave Observatory

    NASA Astrophysics Data System (ADS)

    Abbott, B.; Abbott, R.; Adhikari, R.; Agresti, J.; Ajith, P.; Allen, B.; Amin, R.; Anderson, S. B.; Anderson, W. G.; Araya, M.; Armandula, H.; Ashley, M.; Aston, S.; Aulbert, C.; Babak, S.; Ballmer, S.; Barish, B. C.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barton, M. A.; Bayer, K.; Belczynski, K.; Betzwieser, J.; Beyersdorf, P.; Bhawal, B.; Bilenko, I. A.; Billingsley, G.; Black, E.; Blackburn, K.; Blackburn, L.; Blair, D.; Bland, B.; Bogue, L.; Bork, R.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Brooks, A.; Brown, D. A.; Bullington, A.; Bunkowski, A.; Buonanno, A.; Burman, R.; Busby, D.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Camp, J. B.; Cannizzo, J.; Cannon, K.; Cantley, C. A.; Cao, J.; Cardenas, L.; Casey, M. M.; Cepeda, C.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Chin, D.; Chin, E.; Chow, J.; Christensen, N.; Cokelaer, T.; Colacino, C. N.; Coldwell, R.; Cook, D.; Corbitt, T.; Coward, D.; Coyne, D.; Creighton, J. D. E.; Creighton, T. D.; Crooks, D. R. M.; Cruise, A. M.; Cumming, A.; Cutler, C.; Dalrymple, J.; D'Ambrosio, E.; Danzmann, K.; Davies, G.; de Vine, G.; DeBra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandar, S.; Di Credico, A.; Díaz, M.; Dickson, J.; Diederichs, G.; Dietz, A.; Doomes, E. E.; Drever, R. W. P.; Dumas, J.-C.; Dupuis, R. J.; Ehrens, P.; Elliffe, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Fan, Y.; Fejer, M. M.; Finn, L. S.; Fotopoulos, N.; Franzen, A.; Franzen, K. Y.; Frey, R. E.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Garofoli, J.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Goda, K.; Goetz, E.; Goggin, L.; González, G.; Gossler, S.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, J.; Gretarsson, A. M.; Grimmett, D.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, R.; Hage, B.; Hanna, C.; Hanson, J.; Hardham, C.; Harms, J.; Harry, G.; Harstad, E.; Hayler, T.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Heurs, M.; Hewitson, M.; Hild, S.; Hindman, N.; Hirose, E.; Hoak, D.; Hoang, P.; Hosken, D.; Hough, J.; Howell, E.; Hoyland, D.; Hua, W.; Huttner, S.; Ingram, D.; Ito, M.; Itoh, Y.; Ivanov, A.; Jackrel, D.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Khalili, F. Ya.; Khan, A.; Kim, C.; King, P.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Kozak, D.; Krishnan, B.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lee, B.; Lei, M.; Leonhardt, V.; Leonor, I.; Libbrecht, K.; Lindquist, P.; Lockerbie, N. A.; Lormand, M.; Lubiński, M.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Malec, M.; Mandic, V.; Márka, S.; Markowitz, J.; Maros, E.; Martin, I.; Marx, J. N.; Mason, K.; Matone, L.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McKenzie, K.; McNabb, J. W. C.; Meier, T.; Melissinos, A.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messaritaki, E.; Messenger, C. J.; Meyers, D.; Mikhailov, E.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Mohanty, S.; Moreno, G.; Mossavi, K.; MowLowry, C.; Moylan, A.; Mudge, D.; Mueller, G.; Müller-Ebhardt, H.; Mukherjee, S.; Munch, J.; Murray, P.; Myers, E.; Myers, J.; Newton, G.; Numata, K.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pan, Y.; Papa, M. A.; Parameshwaraiah, V.; Pedraza, M.; Penn, S.; Pitkin, M.; Plissi, M. V.; Prix, R.; Quetschke, V.; Raab, F.; Rabeling, D.; Radkins, H.; Rahkola, R.; Rakhmanov, M.; Rawlins, K.; Ray-Majumder, S.; Re, V.; Rehbein, H.; Reid, S.; Reitze, D. H.; Ribichini, L.; Riesen, R.; Riles, K.; Rivera, B.; Robertson, D. I.; Robertson, N. A.; Robinson, C.; Roddy, S.; Rodriguez, A.; Rogan, A. M.; Rollins, J.; Romano, J. D.; Romie, J.; Route, R.; Rowan, S.; Rüdiger, A.; Ruet, L.; Russell, P.; Ryan, K.; Sakata, S.; Samidi, M.; de la Jordana, L. Sancho; Sandberg, V.; Sannibale, V.; Saraf, S.; Sarin, P.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R.; Schediwy, S.; Schilling, R.; Schnabel, R.; Schofield, R.; Schutz, B. F.; Schwinberg, P.; Scott, S. M.; Seader, S. E.; Searle, A. C.; Sears, B.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Shawhan, P.; Sheard, B.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Sintes, A. M.; Slagmolen, B.; Slutsky, J.; Smith, J.; Smith, M. R.; Sneddon, P.; Somiya, K.; Speake, C.; Spjeld, O.; Strain, K. A.; Strom, D. M.; Stuver, A.; Summerscales, T.; Sun, K.; Sung, M.; Sutton, P. J.; Tanner, D. B.; Tarallo, M.; Taylor, R.; Taylor, R.; Thacker, J.; Thorne, K. A.; Thorne, K. S.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C.; Traylor, G.; Trias, M.; Tyler, W.; Ugolini, D.; Ungarelli, C.; Vahlbruch, H.; Vallisneri, M.; Varvella, M.; Vass, S.; Vecchio, A.; Veitch, J.; Veitch, P.; Vigeland, S.; Villar, A.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Ward, H.; Ward, R.; Watts, K.; Webber, D.; Weidner, A.; Weinstein, A.; Weiss, R.; Wen, S.; Wette, K.; Whelan, J. T.; Whitbeck, D. M.; Whitcomb, S. E.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Willke, B.; Wilmut, I.; Winkler, W.; Wipf, C. C.; Wise, S.; Wiseman, A. G.; Woan, G.; Woods, D.; Wooley, R.; Worden, J.; Wu, W.; Yakushin, I.; Yamamoto, H.; Yan, Z.; Yoshida, S.; Yunes, N.; Zanolin, M.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M.; zur Mühlen, H.; Zweizig, J.; LIGO Scientific Collaboration

    2007-04-01

    The Laser Interferometer Gravitational-Wave Observatory (LIGO) has performed the fourth science run, S4, with significantly improved interferometer sensitivities with respect to previous runs. Using data acquired during this science run, we place a limit on the amplitude of a stochastic background of gravitational waves. For a frequency independent spectrum, the new Bayesian 90% upper limit is ΩGW×[H0/(72 km s-1 Mpc-1)2<6.5×10-5. This is currently the most sensitive result in the frequency range 51-150 Hz, with a factor of 13 improvement over the previous LIGO result. We discuss the complementarity of the new result with other constraints on a stochastic background of gravitational waves, and we investigate implications of the new result for different models of this background.

  11. Sub-hertz relative frequency stabilization of two-diode laser-pumped Nd:YAG lasers locked to a Fabry-Perot interferometer

    NASA Technical Reports Server (NTRS)

    Day, Timothy; Gustafson, Eric K.; Byer, Robert L.

    1992-01-01

    Two-diode laser-pumped Nd:YAG lasers have been frequency stabilized to a commercial 6.327-GHz free spectral range Fabry-Perot interferometer yielding a best-case beatnote linewidth of 330 mHz. In addition, a Fabry-Perot interferometer with a free spectral range of 680 MHz, a linewidth of 25 kHz, and a finesse of 27,500 has been built, and when substituted in place of the commercial interferometer produced a robust and easily repeatable beatnote linewidth of 700 MHz.

  12. SUNLITE program. Sub-Hertz relative frequency stabilization of two diode laser pumped Nd:YAG lasers locked to a Fabry-Perot interferometer

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1990-01-01

    Two laser pumped Nd:YAG lasers were frequency stabilized to a commercial 6.327 GHz free spectral range Fabry-Perot interferometer yielding a best case beatnote linewidth of 330 MHz. In addition, a Fabry-Perot interferometer with a free spectral range of 680 MHz, a linewidth of 25 kHz, and a finesse of 27,500 was built, and when it was substituted in place of the commercial interferometer, it produced a robust and easily repeatable beatnote linewidth of 700 MHz.

  13. Construction and performance of a Fabry-Perot-interferometer-based airborne autonomous wavemeter for laser tuning

    NASA Astrophysics Data System (ADS)

    Goad, Joseph H.

    1990-04-01

    This paper summarizes a continuing effort to develop, design, construct, and evaluate the performance of an airborne autonomous wavemeter for laser tuning. The wavemeter supports tunable solid-state lasers that are used for atmospheric remote sensing. This sensing approach is the Differential Absorption Lidar (DIAL) technique. One atmospheric species, water vapor is measured by tuning one laser to line center of a water vapor line and by tuning another laser off the line. The two sets of received backscattered radiation are ratioed and corrected to determine the vertical profiles of water vapor. On a spacecraft platform, an advanced system could monitor the global water vapor profiles. This would provide a technology improvement for meteorological forecasting. One experiment to make water vapor DIAL measurements from a down-looking airborne platform is the NASA-LASE (Lidar Atmos pheric Sensing Experiment) Project instrument1 to be flown on a NASA ER-2 aircraft. Breadboard results have been obtained that predict that a wavemeter can be built to survive the harsh air-borne environment of low temperatures and low pressures that exist in high altitude flight. Based on the breadboard results, the airborne wavemeter consist of three stages of Fabry-Perot interferometers. Stages #1 and #2 provide the necessary information to provide laser wavelength centroid measurements to the required accuracy of less than 0-.25 picometers. This provides the real-time information necessary for tuning the two tunable alexandrite lasers for the water vapor measurement. A high resolution stage #3 interferometer provides the laser spectral profile measurement with an instrumental profile less than 0.5 picometers full-width at half-maximum amplitude for the post-flight science data reduction. To maintain interferometric stability, the first two stages are thermally controlled and contained in a vacuum chamber. A two level control approach is used to stabilize the interferometers above the highest ambient temperature. Techniques have been developed to evaluate the accuracy of the wavelength centroid algorithms. By using a single wavelength stabilized He-Ne laser as a perfect source, the end-to-end random errors (short term stability) are determined in a period too short for any thermal/mechanical response. The end--to-end sys

  14. Compressive imaging and dual moire laser interferometer as metrology tools

    NASA Astrophysics Data System (ADS)

    Abolbashari, Mehrdad

    Metrology is the science of measurement and deals with measuring different physical aspects of objects. In this research the focus has been on two basic problems that metrologists encounter. The first problem is the trade-off between the range of measurement and the corresponding resolution; measurement of physical parameters of a large object or scene accompanies by losing detailed information about small regions of the object. Indeed, instruments and techniques that perform coarse measurements are different from those that make fine measurements. This problem persists in the field of surface metrology, which deals with accurate measurement and detailed analysis of surfaces. For example, laser interferometry is used for fine measurement (in nanometer scale) while to measure the form of in object, which lies in the field of coarse measurement, a different technique like moire technique is used. We introduced a new technique to combine measurement from instruments with better resolution and smaller measurement range with those with coarser resolution and larger measurement range. We first measure the form of the object with coarse measurement techniques and then make some fine measurement for features in regions of interest. The second problem is the measurement conditions that lead to difficulties in measurement. These conditions include low light condition, large range of intensity variation, hyperspectral measurement, etc. Under low light condition there is not enough light for detector to detect light from object, which results in poor measurements. Large range of intensity variation results in a measurement with some saturated regions on the camera as well as some dark regions. We use compressive sampling based imaging systems to address these problems. Single pixel compressive imaging uses a single detector instead of array of detectors and reconstructs a complete image after several measurements. In this research we examined compressive imaging for different applications including low light imaging, high dynamic range imaging and hyperspectral imaging.

  15. Phase-locked, low-noise, frequency agile titanium:sapphire lasers for simultaneous atom interferometers.

    PubMed

    Müller, Holger; Chiow, Sheng-wey; Long, Quan; Chu, Steven

    2006-01-15

    We demonstrate a laser system consisting of a >1.6 W titanium:sapphire laser that is phase locked to another free-running titanium:sapphire laser at a wavelength of 852 nm with a phase noise of -138 dBc/Hz at 1 MHz from the carrier, using an intracavity electro-optic phase modulator. The residual phase variance is 2.5 x 10(-8) rad2 integrated from 1 Hz to 10 kHz. This system can phase-continuously change the offset frequency within 200 ns with frequency steps up to 4 MHz. Simultaneous atom interferometers can make full use of this ultralow phase noise in differential measurements, where influences from the vibration of optics are greatly suppressed in common mode. PMID:16441030

  16. Self-mixing type of phase-locked laser diode interferometer

    NASA Astrophysics Data System (ADS)

    Suzuki, Takamasa; Hirabayashi, Shigeyuki; Sasaki, Osami; Maruyama, Takeo

    1999-03-01

    A new type of phase-locked laser diode interferometer that uses self-mixing interference in the optical system is described. The self-mixing interference (SMI) signal is obtained easily by optical feedback, i.e., feeding back the laser beam from the object to the laser diode (LD). The SMI signal can be detected by a photodiode in the package of the LD. Therefore, a beamsplitter, reference mirror, and external photodetector are not required, and an interference signal is obtained using a simple optical system. Although the mechanism of SMI is completely different from that of conventional interference, it is shown that the response of the SMI signal to phase changes is the same as that of conventional interference. We used the phase-locked technique to fix the phase change and demonstrated measurement of absolute distance and displacement.

  17. Investigation on chaotic dynamics of ytterbium-doped fiber laser with Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Yang, Lingzhen; Wang, Feifei; Cui, Liqin; Qin, Jianmin

    2016-01-01

    Chaotic dynamics are observed experimentally from an ytterbium-doped fiber laser when the polarization controller is adjusted to an appropriate position and the pump power is increased. But chaotic signals hide the cavity-length signature of ytterbium-doped fiber laser and the cavity-length can be identified by the sidelobes of chaotic autocorrelation. The perturbation of variable optical attenuator inserted to the ytterbium-doped fiber laser and the interference effect induced by the optical path difference (OPD) of a fiber optical Mach-Zehnder interferometer (MZI) are adopted to investigate the chaotic dynamics. The results show that such sidelobes can be completely suppressed by exerting the perturbation and by the interference effect of MZI with optimum OPD which is demonstrated theoretically and experimentally. Moreover, the optimum OPD corresponding to the delay-time of MZI is intimately related to the relaxation oscillation period.

  18. Note: Design of a laser feedback interferometer with double diffraction system

    SciTech Connect

    Guo, Dongmei Wang, Ming

    2015-09-15

    A novel laser feedback interferometer with double diffraction system is proposed in this paper. A beam emitted from the laser is incident onto a transmission grating. The mth order beam is vertically reflected by a mirror and diffracted again by the grating. The double-diffracted beam returns into the laser cavity and mixes with the light inside the active cavity, thus generating a modulation of both the amplitude and the frequency of the lasing field. Theoretical analysis and experimental observations show that the output signal of the proposed system depends on the grating pitch and the direction of the phase movement can be obtained from inclination of the interference signal. It provides a potential displacement sensor with high stability and quite a compact configuration.

  19. Sightline optimization of the multichannel laser interferometer for W7-X

    NASA Astrophysics Data System (ADS)

    Airila, M. I.; Dumbrajs, O.; Hirsch, M.; Geiger, J.; Neuner, U.; Hartfuss, H.-J.

    2005-02-01

    A multichannel CO2 laser interferometer is planned for electron density profile measurements in the Wendelstein 7-X stellarator under construction. This article describes the mathematical methods used to find the optimum orientation of the various sightlines. The problem of reconstructing local densities from line integrated density measurements can be formulated as a matrix inversion. The quality of the reconstruction is largely determined by the condition number of the matrix describing the problem, which has to be minimized, i.e., the sightlines have to be chosen such that the information content of different channels is maximally distinct. For the W7-X interferometer four- and eight-sightline arrangements are investigated and their orientations are optimized for standard conditions of magnetic configuration and density profile. The optimized arrangements are tested by simulating the inversion of hypothetical reference density profiles in a number of different magnetic configurations. In the ideal case the error of a reconstruction using four sightlines is typically a few times larger than that with eight sightlines. The robustness of the optimization is demonstrated by a variation of the position of the whole interferometer, and the influence of noisy phase data on the reconstructed profiles is investigated. These factors significantly narrow the difference between the four- and eight-beam setups. Finally, the use of regularization methods for the analysis of experimental data is briefly discussed.

  20. High-frequency angular vibration calibration using the mirror assembly diffraction grating heterodyne laser interferometer

    NASA Astrophysics Data System (ADS)

    Xue, Jingfeng; Zhang, Dazhi; Li, Xinliang; Zhao, Weiqian

    2014-09-01

    In order to improve the dynamic evaluating capabilities of the inertial devices and realize the traceability in angular vibration, the angular vibration calibration devices are developed and it is very important to measure the angular vibration accurately for calibration devices. In this paper, a new diffraction grating heterodyne laser interferometer method was introduced for high-frequency and micro-amplitude angular-vibration measurement, which uses a differential and symmetrical optical-path arrangement. The proposed method has the advantages of high-precision, high anti-interference and convenient debugging, and could achieve the angular measurement resolution within 0.02?.

  1. Visibility oscillation in a multimode laser interferometer signal and its use in optimizing path lengths

    NASA Astrophysics Data System (ADS)

    Ruden, E. L.; Camacho, J. F.; Lynn, A. G.

    2013-10-01

    The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference ZS between the probe and reference beam optical path lengths and the spectral separation kS between the center of the laser gain profile and the nearest laser mode of higher frequency. kS has a significant effect on V for a given ZS. This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying ZS (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in kS for a given ZS is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 μm HeNe lasers with similar specifications. In the first case, the function W(ZS) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of ZS values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto-optically upshifted by that amount, while kS spontaneously varies on an acoustic time scale. A single high-bandwidth waveform record for each ZS, therefore, provides all the information needed to determine W. Despite the second laser's gain profile apparently differing in detail, qualitative agreement is achieved between the two methods sufficient to validate the technique.

  2. MHD instability fluctuation measurement on the HL-2A tokamak by using the HCN laser interferometer

    NASA Astrophysics Data System (ADS)

    Li, Y. G.; Zhou, Y.; Deng, Z. C.; Yi, J.; Li, Y.; Wang, H. X.; Ji, X. Q.; Deng, W.

    2014-10-01

    The multichannel HCN laser interferometer has been routinely used to measure the electron density ( n e) on the HL-2A tokamak for several years. In order to explore its capability for qualitatively evaluating the Magnetohydrodynamic (MHD) fluctuation in plasmas from the probing signal, we implemented two important modifications on the hardware of channel #3 (r = -10.5 cm): (1) application of the high-response Schottky diode waveguide detector, and (2) utilization of a preamplifier with a broad pass-band of up to 500 kHz so as not to filter the fluctuation component mixed with the intermediate frequency (IF). Many MHD fluctuation phenomena, such as tearing modes (TMs), fishbones, long lived modes (LLMs), have been successfully detected by using the modified channel #3 in the HL-2A experimental campaign, and the results were quite coincident with those derived from the magnetic probe and the soft X-ray systems. We propose to apply this novel approach to more channels of the HCN laser interferometer.

  3. Q-switching of a high-power solid-state laser by a fast scanning Fabry-Perot interferometer

    SciTech Connect

    Baburin, N V; Borozdov, Yu V; Danileiko, Yu K; Denker, B I; Ivanov, A D; Osiko, Vyacheslav V; Sverchkov, S E; Sidorin, A V; Chikov, V A; Ifflander, R; Hack, R; Kertesz, I; Kroo, N

    1998-07-31

    An investigation was made of the suitability of a Q-switch, based on a piezoelectrically scanned short-base Fabry-Perot interferometer, for an Nd{sup 3+}:YAG laser with an average output radiation power up to 2 kW. The proposed switch made it possible to generate of giant pulses of 60 - 300 ns duration at a repetition rate of 20 - 100 kHz. Throughout the investigated range of the pulse repetition rates the average power was at least equal to that obtained by cw lasing. Special requirements to be satisfied by the interferometer, essential for efficient Q-switching, were considered. (control of laser radiation parameters)

  4. Automatic deformation analysis by a TV speckle interferometer using a laser diode.

    PubMed

    Kato, J; Yamaguchi, I; Ping, Q

    1993-01-01

    A phase-shifting TV speckle interferometer is developed by using the frequency modulation capability of a laser diode and is applied to automatic deformation measurements. Temperature modulation is used for generating the frequency shift of a laser diode. We store four speckle interferograms with relative phase differences of pi/2 in a frame grabber by monitoring a phase-shift signal, which is obtained by integrating the fringe intensity over a local window. The optimum size of the local window is examined experimentally. Then, the optimum processing conditions for reducing the speckle noise in interferograms,including an averaging window size, are found. Experimental results of the automatic deformation analysis indicate a displacement accuracy of better than lambda/30. PMID:20802664

  5. LISA Mission Concept Study, Laser Interferometer Space Antenna for the Detection and Observation of Gravitational Waves

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; Bender, P. L.; Stebbins, R. T.

    1998-01-01

    This document presents the results of a design feasibility study for LISA (Laser Interferometer Space Antenna). The goal of LISA is to detect and study low-frequency astrophysical gravitational radiation from strongly relativistic regions. Astrophysical sources potentially visible to LISA include extra-galactic massive black hole binaries at cosmological distances, binary systems composed of a compact star and a massive black hole, galactic neutron star-black hole binaries, and background radiation from the Big Bang. The LISA mission will comprise three spacecraft located five million kilometers apart forming an equilateral triangle in an Earth-trailing orbit. Fluctuations in separation between shielded test masses located within each spacecraft will be determined by optical interferometry which determines the phase shift of laser light transmitted between the test masses.

  6. LISA Mission Concept Study, Laser Interferometer Space Antenna for the Detection and Observation of Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Folkner, W. M.; Bender, P. L.; Stebbins, R. T.

    1998-03-01

    This document presents the results of a design feasibility study for LISA (Laser Interferometer Space Antenna). The goal of LISA is to detect and study low-frequency astrophysical gravitational radiation from strongly relativistic regions. Astrophysical sources potentially visible to LISA include extra-galactic massive black hole binaries at cosmological distances, binary systems composed of a compact star and a massive black hole, galactic neutron star-black hole binaries, and background radiation from the Big Bang. The LISA mission will comprise three spacecraft located five million kilometers apart forming an equilateral triangle in an Earth-trailing orbit. Fluctuations in separation between shielded test masses located within each spacecraft will be determined by optical interferometry which determines the phase shift of laser light transmitted between the test masses.

  7. Four-level atomic interferometer driven by shaped ultrafast laser pulses

    SciTech Connect

    Clow, Stephen; Weinacht, Thomas

    2010-08-15

    We analyze the behavior of a four-state, two-path atomic interferometer driven by shaped ultrafast laser pulses. The laser pulses interact with atomic rubidium, exciting the atoms to the 5D state via two intermediate resonances (the 5P{sub 1/2} and 5P{sub 3/2}). The relative phase of the two paths can be modified by applying a varying spectral phase at the wavelength corresponding to one of the resonant transitions for each pathway. We trace out the behavior of the system from the simplest case of weak-field excitation with resonant fields to strong-field excitation with a broadband source. Our measurements and analysis reveal that while interference is observed for all field strengths and spectral widths, the character of the interference changes substantially.

  8. Study on formation and transformation of the optical nonlinearity harmonics in the heterodyne laser interferometer

    NASA Astrophysics Data System (ADS)

    Fu, Haijin; Tan, Jiubin; Fan, Zhigang

    2015-02-01

    The accuracy of the heterodyne laser interferometer is strongly restricted by the optical nonlinearity harmonics. In order to mathematically reveal the formation and transformation mechanism of optical nonlinearity harmonics, the behavior of the nonlinearity harmonics is investigated with an optical nonlinearity expression based on the optical mixing parameters in the measurement signal. It is found that the formation and transformation of the first-order and second-order nonlinearity harmonics are closely related to the orthogonality of the optical mixing parameters. When the optical mixing parameters satisfy the orthogonal relation, the optical nonlinearity is purely the second-order harmonic whose peak-to-peak value is at least one order smaller than that of the first-order harmonic in the same optical mixing degree, indicating that a larger optical mixing level does not necessarily lead to a considerable optical nonlinearity error, which provides the theoretical guidance for building a heterodyne laser measurement system with low optical nonlinearity.

  9. Design and performance of high laser power interferometers for gravitational-wave detection

    NASA Astrophysics Data System (ADS)

    Dooley, Katherine Laird

    A prediction of Einstein's general theory of relativity, gravitational waves (GWs) are perturbations of the flat space-time Minkowski metric that travel at the speed of light. Indirectly measured by Hulse and Taylor in the 1970s through the energy they carried away from a binary pulsar system, gravitational waves have yet to be detected directly. The Laser Interferometer Gravitational-wave Observatory (LIGO) is part of a global network of gravitational-wave detectors that seeks to detect directly gravitational waves and to study their sources. LIGO operates on the principle of measuring the gravitational wave's physical signature of a strain, or relative displacement of inertial masses. An extremely small effect whose biggest of expected transient signals on Earth is on the order of one part in 1023, gravitational-wave strain can only be measured by detectors so sensitive to displacement as to encounter the effects of quantum physics. To improve their sensitivities and to demonstrate advanced technologies, the LIGO observatories in Hanford, WA and Livingston, LA underwent an upgrade between fall 2007 and summer 2009 called Enhanced LIGO. This study focuses on the experimental challenges of one of the goals of the upgrade: operating at an increased laser power. I present the design and characterization of two of the interferometer subsystems that are critical for the path towards higher laser power: the Input Optics (IO) and the Angular Sensing and Control (ASC) subsystems. The IO required a new design so its optical components would not be susceptible to high power effects such as thermal lensing or thermal beam drift. The ASC required a new design in order to address static instabilities of the arm cavities caused by increased radiation pressure. In all, I demonstrate the capability of an interferometric GW detector to operate at several times the highest of laser powers previously used. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

  10. Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

    SciTech Connect

    Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro

    2011-04-15

    Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

  11. Positive quadrature formulas III

    NASA Astrophysics Data System (ADS)

    Peherstorfer, Franz

    2008-12-01

    First we discuss briefly our former characterization theorem for positive interpolation quadrature formulas (abbreviated qf), provide an equivalent characterization in terms of Jacobi matrices, and give links and applications to other qf, in particular to Gauss-Kronrod quadratures and recent rediscoveries. Then for any polynomial t_n which generates a positive qf, a weight function (depending on n ) is given with respect to which t_n is orthogonal to mathbb{P}_{n-1} . With the help of this result an asymptotic representation of the quadrature weights is derived. In general the asymptotic behaviour is different from that of the Gaussian weights. Only under additional conditions do the quadrature weights satisfy the so-called circle law. Corresponding results are obtained for positive qf of Radau and Lobatto type.

  12. The three-wave laser polarimeter-interferometer on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Zhuang, G.; Liu, Y.; Chen, J.; Gao, L.; Li, Q.; Xiong, C. Y.; Shi, P.; Zhou, Y. N.

    2016-02-01

    Motivated by increasing demands on high-quality measurement of interior magnetic field in tokamak plasma, a far-infrared laser-based polarimeter-interferometer system has been developed on J-TEXT. Three formic acid lasers separately pumped by three CO2 lasers are used as sources, providing more than 90 mW output power in total. High laser power along with usage of newly developed planar Schottky diode mixer enable high phase resolution < 1 mrad. Collinearity and polarization calibrations have been carefully done to improve the measurement reliability. Meanwhile, real-time feedback control of three-wave laser source has been realized for the first time, to fulfill the system stability. Based on three-wave technique, Faraday angle and integrated density phase along the laser path are simultaneously measured with high temporal resolution. In addition, the laser beam is expanded to cover the entire cross-section of the plasma to provide high spatial resolution measurement. With this system, MHD equilibrium of the J-TEXT plasma has been reconstructed. Obscure perturbations on magnetic topology and electron density associated with MHD instabilities, e.g. sawteeth and tearing modes have also been observed. In particular, some interesting features of disruptions in high-density discharges are identified by carefully interpreting the measured polarimeter-interferometer data. In the density ramp-up phase of a high density discharge, asymmetry in both electron density and current density profiles between the Low-Field-Side (LFS) edge (r > 0.8a) and the High-Field-Side (HFS) edge (r < -0.8a) would appear and extend gradually toward the center region. At the same time, a low-frequency (< 1 kHz) density perturbation suddenly occurs at the HFS edge and also gradually propagates into the center region. The disruption takes place when the electron density asymmetry/perturbation reaches the location nearly the m/n = 2/1 (where m and n are the toroidal mode number and the poloidal one, respectively) resonant surface. Evolution of the reconstructed electron density and current density profiles present the details on the asymmetrical behaviors and provide a possible explanation for the high density disruption.

  13. Reference Interferometer Using a Semiconductor Laser/LED Reference Source in a Cryogenic Fourier-Transform Spectrometer

    NASA Technical Reports Server (NTRS)

    Martino, Anthony J.; Cornwell, Donald M.

    1998-01-01

    A combination of a single mode AlGaAs laser diode and broadband LED was used in a Michelson interferometer to provide reference signals in a Fourier transform spectrometer, the Composite Infrared Spectrometer, on the Cassini mission to Saturn. The narrowband light from the laser produced continuous fringes throughout the travel of the interferometer, which were used to control the velocity of the scan mechanism and to trigger data sampling. The broadband light from the LED produced a burst of fringes at zero path difference, which was used as a fixed position reference. The system, including the sources, the interferometer, and the detectors, was designed to work both at room temperature and instrument operating temperature of 170 Kelvin. One major challenge that was overcome was preservation, from room temperature to 170 K, of alignment sufficient for high modulation of fringes from the broadband source. Another was the shift of the source spectra about 30 nm toward shorter wavelengths upon cooldown.

  14. Infrared intracavity laser absorption spectroscopy with a continuous-scan Fourier-transform interferometer.

    PubMed

    Cheng, J; Lin, H; Hu, S; He, S; Zhu, Q; Kachanov, A

    2000-05-01

    High-quality broadband infrared high-resolution spectra were obtained by use of the intracavity laser absorption spectroscopy technique with a Ti:sapphire laser in combination with a continuous-scan Fourier-transform (FT) interferometer. With electronic filtering used to smooth out the fluctuations of the laser power, the absorption of atmospheric water vapor in the range of 12,450-12,700 cm(-1) was recorded at a resolution of 0.05 cm(-1). A signal-to-noise ratio of greater than 300 was observed in this spectrum, corresponding to a minimum detectable absorption of approximately 2 x 10(-9) cm(-1). Comparison with previous measurements by use of a conventional FT technique shows that this method gives absorption spectra with highly accurate line positions along with reasonable line intensities. Investigation of the evolution of intracavity laser absorption spectra with the generation time is also shown to be possible with a continuous-scan FT spectrometer by use of the interleave rapid-scan method. PMID:18345128

  15. Analog quadrature signal to phase angle data conversion by a quadrature digitizer and quadrature counter

    DOEpatents

    Buchenauer, C. Jerald

    1984-01-01

    The quadrature phase angle .phi.(t) of a pair of quadrature signals S.sub.1 (t) and S.sub.2 (t) is digitally encoded on a real time basis by a quadrature digitizer for fractional .phi.(t) rotational excursions and by a quadrature up/down counter for full .phi.(t) rotations. The pair of quadrature signals are of the form S.sub.1 (t)=k(t) sin .phi.(t) and S.sub.2 (t)=k(t) cos .phi.(t) where k(t) is a signal common to both. The quadrature digitizer and the quadrature up/down counter may be used together or singularly as desired or required. Optionally, a digital-to-analog converter may follow the outputs of the quadrature digitizer and the quadrature up/down counter to provide an analog signal output of the quadrature phase angle .phi.(t).

  16. Analog quadrature signal to phase angle data conversion by a quadrature digitizer and quadrature counter

    DOEpatents

    Buchenauer, C.J.

    1981-09-23

    The quadrature phase angle phi (t) of a pair of quadrature signals S/sub 1/(t) and S/sub 2/(t) is digitally encoded on a real time basis by a quadrature digitizer for fractional phi (t) rotational excursions and by a quadrature up/down counter for full phi (t) rotations. The pair of quadrature signals are of the form S/sub 1/(t) = k(t) sin phi (t) and S/sub 2/(t) = k(t) cos phi (t) where k(t) is a signal common to both. The quadrature digitizer and the quadrature up/down counter may be used together or singularly as desired or required. Optionally, a digital-to-analog converter may follow the outputs of the quadrature digitizer and the quadrature up/down counter to provide an analog signal output of the quadrature phase angle phi (t).

  17. One-frequency laser interferometer using the optic fiber as a polarization-independent interference phase detector

    SciTech Connect

    Shu, D.

    1985-02-01

    A soft x-ray scanning microscope will be built on the NSLS x-ray ring's undulator beam line. It is expected that the beam line will provide more powerful coherent soft x-ray flux to improve the resolution of scanning microscopy to the sub-1000A range and form pictures in seconds rather than minutes. A laser interferometer has been developed for encoding the coordinates of the scanning plane of the soft x-ray microscope with 300A resolution. A pair of the optical fibers has been used as an interference fringe phase detector in the interferometer which can make the system phase adjustment simpler, more accurate, and polarization-independent. The last character is important because if the fringe phase detector is polarization dependent the interferometer's optical design will be complicated when the optical path of the interferometer has to include additional windows or mirrors which usually change the polarization situation. In the first section of this report we discuss the optical arrangement of the interferometer. In the following two sections we describe the schematic of the resolution extending unit and the interferometer's other possible applications.

  18. Phase-shifting interferometer using a frequency-tunable diode laser calibrated by an optical frequency comb.

    PubMed

    Wu, Xuejian; Zhang, Jitao; Wei, Haoyun; Li, Yan

    2012-07-01

    We present a phase-shifting interferometer based on a frequency-tunable diode laser calibrated by an optical frequency comb and the Carre? algorithm. By use of the frequency control strategies of locking the diode laser to different comb modes and scanning the repetition rate, an arbitrary single optical frequency synthesizer is obtained. The relative laser frequency uncertainty is 5.7 10(-12) for 1 s averaging time with tracing to an Rb clock and accurate phase steps are achieved by optical frequency tuning. The surface topography of a standard sphere is measured by this phase-shifting interferometer based on a flat reference. The phase measurement repeatability is ?/200. With this technique, phase measurement uncertainties from the laser frequency and phase steps are negligible. PMID:22852671

  19. Long-term monitoring crustal deformations in the North Caucasus by the laser interferometer

    NASA Astrophysics Data System (ADS)

    Milyukov, V.; Kopaev, A.; Kozyreva, A.; Klyachko, B.; Myasnikov, A.

    2003-04-01

    During several years SAI MSU carries out the long-term observation of crustal deformations in the North Caucasus, in one of the most active in geodynamic respect region of Russia. On the whole this region is characterized by the complex system of active faults, intensive movements of the Earth's crust and high seismicity. The wide-band laser interferometer strainmeter with a measurable armlength of 75 m is disposed in an underground tunnel. The optical scheme of the interferometer is the two passes (N=2) Michelson-type interferometer with unequal arms. The long-term monitoring strains of the Earth is provided in tree frequency bands: below 0.1 Hz (low frequency channel), in the bandwidth of 1 Hz around frequency of 30 Hz (seismic channel) and in the bandwidth of 0.5 Hz around frequency of 1.62 kHz (acoustic channel). Pressure and temperature are monitored too. Unique geodynamical features of the region, the proximity of the Elbrus volcanic structure and existing long-term wide-band and high-quality observed timeseries of deformations allow to study a wide class of geophysical phenomenae. Time variation of the tidal deformation parameters indicates the correlation with local seismicity of the region. The large number of global earthquakes recorded by the Baksan interferometer during several years where analyzed. The data are used for estimating the parameters of the free oscillations of the Earth (FOE) and resonances of the Elbrus volcano magma source. After subtraction of FOE from the experimental spectrums the additional resonance peaks were interpreted as the eigen frequencies of the magma source of the Elbrus volcano. Slight changes of these frequencies may certainly indicate changes of magma state, its temperature and saturation by volcanic gases. Continuous monitoring over the spectra of eigen frequencies of the magma source provide additional data for the general warning system for volcanic hazard assessment. This work is supported by the Russian Foundation for Basic Research under Grant No 00-05-64882 and 02-05-65012.

  20. Application of a Laser Interferometer Skin-Friction Meter in Complex Flows

    NASA Technical Reports Server (NTRS)

    Monson, D. J.; Driver, D. M.; Szodruch, J.

    1981-01-01

    A nonintrusive skin-friction meter has been found useful for a variety of complex wind-tunnel flows. This meter measures skin friction with a remotely located laser interferometer that monitors the thickness change of a thin oil film. Its accuracy has been proven in a low-speed flat-plate flow. The wind-tunnel flows described here include sub-sonic separated and reattached flow over a rearward-facing step, supersonic flow over a flat plate at high Reynolds numbers, and supersonic three - dimensional vortical flow over the lee of a delta wing at angle of attack. The data-reduction analysis was extended to apply to three-dimensional flows with unknown flow direction, large pressure and shear gradients, and large oil viscosity changes with time. The skin friction measurements were verified, where possible, with results from more conventional techniques and also from theoretical computations.

  1. Deciphering inflation with gravitational waves: Cosmic microwave background polarization vs direct detection with laser interferometers

    SciTech Connect

    Smith, Tristan L.; Peiris, Hiranya V.; Cooray, Asantha

    2006-06-15

    A detection of the primordial gravitational wave background is considered to be the 'smoking-gun' evidence for inflation. While superhorizon waves are probed with cosmic microwave background (CMB) polarization, the relic background will be studied with laser interferometers. The long lever arm spanned by the two techniques improves constraints on the inflationary potential and validation of consistency relations expected under inflation. If gravitational waves with a tensor-to-scalar amplitude ratio greater than 0.01 are detected by the CMB, then a direct-detection experiment with a sensitivity consistent with current concept studies should be pursued vigorously. If no primordial tensors are detected by the CMB, a direct-detection experiment to understand the simplest form of inflation must have a sensitivity improved by two to 3 orders of magnitude over current plans.

  2. Two-color interferometer for the study of laser filamentation triggered electric discharges in air

    SciTech Connect

    Point, Guillaume Brelet, Yohann; Arantchouk, Leonid; Carbonnel, Jérôme; Prade, Bernard; Mysyrowicz, André; Houard, Aurélien

    2014-12-15

    We present a space and time resolved interferometric plasma diagnostic for use on plasmas where neutral-bound electron contribution to the refractive index cannot be neglected. By recording simultaneously the plasma optical index at 532 and 1064 nm, we are able to extract independently the neutral and free electron density profiles. We report a phase resolution of 30 mrad, corresponding to a maximum resolution on the order of 4×10{sup 22} m{sup −3} for the electron density, and of 10{sup 24} m{sup −3} for the neutral density. The interferometer is demonstrated on centimeter-scale sparks triggered by laser filamentation in air with typical currents of a few tens of A.

  3. A Phase Measuring Radial Shear Interferometer For Measuring The Wavefronts Of Compact Disc Laser Pickups

    NASA Astrophysics Data System (ADS)

    Truax, Bruce E.

    1986-11-01

    A phase measuring radial shear interferometer has been developed that enables the user to measure the wavefront of Compact Disc or other optical storage laser pickups. The instrument is designed to operate over the wavelength range from 700nm to 830nm. It will accept the diverging wavefront of any optical storage laser pickup, and it includes a holder for the thin coverplate necessary to compensate for the plastic or glass overcoat on the optical storage media. The interferometer is equal path and has been achromatized over the wavelength range so that the source coherence length can be less than one millimeter. Compensation for variations in light source intensity is accomplished by a rotating variable neutral density disk driven by a servo system. This compensation system permits input light levels to vary from 0.1mw to as great as 100mw. Data processing options include: peak-to-valley and root-mean-square wavefront distortion computation with isometric and contour plotting as well as Zernike polynomials, point spread function, and modulation transfer function. System accuracy depends on the numerical aperture of the input source. With the standard collimating optics the input numerical aperture can be as large as 0.65. For this numerical aperture the instrument is typically better than 1/5 wave at 780nm. For 0.5 numerical aperture (typical for most Compact Disc pickups) the system performance is better than 1/10 wave. If more accurate measurements are required, the wavefront of the instrument must be stored and subtracted from the measurement of the pickup. Results of measurements of Compact Disc heads will be presented and other applications of the instrument will be discussed.

  4. Correlated quadratures of resonance fluorescence and the generalized uncertainty relation

    NASA Technical Reports Server (NTRS)

    Arnoldus, Henk F.; George, Thomas F.; Gross, Rolf W. F.

    1994-01-01

    Resonance fluorescence from a two-state atom has been predicted to exhibit quadrature squeezing below the Heisenberg uncertainty limit, provided that the optical parameters (Rabi frequency, detuning, laser linewidth, etc.) are chosen carefully. When the correlation between two quadratures of the radiation field does not vanish, however, the Heisenberg limit for quantum fluctuations might be an unrealistic lower bound. A generalized uncertainty relation, due to Schroedinger, takes into account the possible correlation between the quadrature components of the radiation, and it suggests a modified definition of squeezing. We show that the coherence between the two levels of a laser-driven atom is responsible for the correlation between the quadrature components of the emitted fluorescence, and that the Schrodinger uncertainty limit increases monotonically with the coherence. On the other hand, the fluctuations in the quadrature field diminish with an increasing coherence, and can disappear completely when the coherence reaches 1/2, provided that certain phase relations hold.

  5. Monitoring Rotational Components of Seismic Waves with a Ring Laser Interferometer

    NASA Astrophysics Data System (ADS)

    Gakundi, Jackson; Dunn, Robert

    2015-04-01

    It has been known for decades that seismic waves can introduce rotation in the surface of the Earth. There are historic records of tombstones in Japan being rotated after large earthquakes. Until fairly recently, the primary way to detect ground rotation from earthquakes was with an array of several seismographs. The development of large ring laser interferometers has provided a way for a single instrument to make extremely sensitive measurements of ground motion. In this poster, a diagram of a large ring laser will be presented. For comparison, seismograms recorded with a ring laser and a collocated standard seismograph will be presented. A major thrust of this research is the detection and analysis of seismic responses from directional drilling sites in Arkansas and Oklahoma. There are suggestions that the injection of pressurized water used to fracture gas bearing shale may cause small earthquakes. The Arkansas Oil and Gas Commission ordered the closing of certain waste water disposal wells in North Central Arkansas. Apparently, these wells injected waste water into a previously unknown fault causing it to slip. An attempt is being made to determine if the seismic wave patterns from earthquakes generated near directional drilling sites differ from those generated miles away.

  6. Implementation of real-time displacement precision measurement technology for the sinusoidal phase-shifting laser self-mixing interferometer

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Wang, Ming; Tao, Yufeng; Chen, Junbao; Hao, Hui; Guo, Dongmei

    2015-02-01

    An advanced sinusoidal phase-shifting technique and a time-domain phase demodulation method were used to improve the measurement accuracy and realize the real-time measurement speed of the laser self-mixing interferometer in a large range of displacement. An electro-optic crystal modulator (EOM) was used to realize the sinusoidal phase-shifting on the laser beam in the external cavity. The interference signal was demodulated using a time-domain phase demodulation method. The speed requirement could be met by combining the two together in a wide range of displacement measurement processes together with the real-time measurement requirement as an interferometer at the same time. It was experimentally verified that the displacement measurement precision of a sinusoidal phase-shifting laser self-mixing interferometer could reach less than 0.5 ?m in the hundred mm large-scale displacement measuring process. In addition, the factors affecting the interferometer's measurement speed in the real-time displacement measurement process is analyzed and the maximum speed of our system was obtained as well. Keywords: self-mixing interference; phase modulation; time-domain phase demodulation

  7. Gaussian quadrature for sums

    NASA Astrophysics Data System (ADS)

    Monien, H.

    2010-04-01

    Gaussian quadrature is a well-known technique for numerical integration. Recently Gaussian quadrature with respect to discrete measures corresponding to finite sums has found some new interest. In this paper we apply these ideas to infinite sums in general and give an explicit construction for the weights and abscissae of Gaussian formulas. The abscissae of the Gaussian summation have a very interesting asymptotic distribution function with a kink singularity. We apply the Gaussian summation technique to two problems which have been discussed in the literature. We find that the Gaussian summation has a very rapid convergence rate for the Hardy-Littlewood sum for a large range of parameters.

  8. Tunable double-clad ytterbium-doped fiber laser based on a double-pass Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Meng, Yichang; Zhang, Shumin; Wang, Xinzhan; Du, Juan; Li, Hongfei; Hao, Yanping; Li, Xingliang

    2012-03-01

    We have demonstrated an adjustable double-clad Yb 3+-doped fiber laser using a double-pass Mach-Zehnder interferometer. The laser is adjustable over a range of 40 nm from 1064 nm to 1104 nm. By adjusting the state of the polarization controller, which is placed in the double-pass Mach-Zehnder interferometer, we obtained central lasing wavelengths that can be accurately tuned with controllable spacing between different tunable wavelengths. The laser has a side mode suppression ratio of 42 dB, the 3 dB spectral width is less than 0.2 nm, and the slope efficiencies at 1068 nm, 1082 nm and 1098 nm are 23%, 32% and 26%, respectively. In addition, we have experimentally observed tunable multi-wavelengths lasing output.

  9. Internal magnetic field measurements by laser-based POlarimeter-INTerferometer (POINT) system on EAST

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zou, Z. Y.; Qian, J. P.; Li, W. M.; Yang, Y.; Zeng, L.; Zhang, S. B.; Lan, T.; Wang, S. X.; Hanada, K.; Wei, X. C.; Hu, L. Q.; Wan, B. N.

    2016-01-01

    A multi-channel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for fully diagnosing the internal magnetic field in the EAST tokamak. Double-pass, horizontal, radially-viewing chords access the plasma via an equatorial port. The laser source consists of three CW formic acid (HCOOH) FIR lasers at nominal wavelength 432.5 μm which are optically pumped by independent infrared CO2 lasers. Output power is more than 30 mW of per cavity. Novel molybdenum retro-reflectors, can with withstand baking temperature up to 350°C and discharge duration more than 1000 s, are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which provide real-time Faraday rotation angle and density phase shift output for plasma control, have been developed for the POINT system. Reliability of both polarimetric and interferometric measurement are obtained in 22 s long pulse H mode discharge and 8 s NBI H mode discharge, indicating the POINT system works for any heating scheme on EAST so far. The electron line-integrated density resolution of POINT is less than 1 × 1016 m-2 (< 1°), and the Faraday rotation angle rms phase noise is < 0.1°. With the high temporal (~ 1 μsec) and phase resolution (< 0.1°), perturbations associated with the sawtooth cycle and MHD activity have been observed. The current profile, density profile and safety factor (q) profile are reconstructed by using EFIT code from the external magnetic and the validation POINT data. Realtime EFIT with Faraday angle and density phase shift constraints will be implemented in the plasma control system in the future.

  10. Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflector.

    PubMed

    Moody, J D; Clancy, T J; Frieders, G; Celliers, P M; Ralph, J; Turnbull, D P

    2014-11-01

    Laser pre-pulse and early-time laser reflection from the hohlraum wall onto the capsule (termed "glint") can cause capsule imprint and unwanted early-time shocks on indirect drive implosion experiments. In a minor modification to the existing velocity interferometer system for any reflector diagnostic on NIF a fast-response vacuum photodiode was added to detect this light. The measurements show evidence of laser pre-pulse and possible light reflection off the hohlraum wall and onto the capsule. PMID:25430354

  11. A mechanically stable laser diode speckle interferometer for surface contouring and displacement measurement

    NASA Astrophysics Data System (ADS)

    Francis, Daniel; Masiyano, Dackson; Hodgkinson, Jane; Tatam, Ralph P.

    2015-05-01

    Electronic speckle pattern interferometry (ESPI) is demonstrated using a simple configuration consisting of a wedged window and a beamsplitter. The window serves to produce a reference beam which is in-line with the scattered object beam. The system is almost common-path and therefore provides much better mechanical stability than conventional ESPI configurations, which have widely separated beam paths. The configuration has collinear observation and illumination directions and therefore has maximum sensitivity to out-of-plane displacement. Wavelength modulation through adjustment of the laser diode control current provides a convenient method of phase shifting without the need for external moving parts. Further, variation of the laser diode control temperature allows extended wavelength tuning to adjacent longitudinal modes, facilitating surface contouring measurements via the two-wavelength technique. The interferometer is demonstrated for surface displacement measurement with a 3.3??m centre displacement measured over a 15?mm 15?mm region of a flat plate. Contour measurements of a shaped object are made using an equivalent wavelength of 1.38?mm.

  12. Skin Friction Measurements by a Dual-Laser-Beam Interferometer Technique

    NASA Technical Reports Server (NTRS)

    Monson, D. J.; Higuchi, H.

    1981-01-01

    A portable dual-laser-beam interferometer that nonintrusively measures skin friction by monitoring the thickness change of an oil film subject to shear stress is described. The method is an advance over past versions in that the troublesome and error-introducing need to measure the distance to the oil leading edge and the starting time for the oil flow has been eliminated. The validity of the method was verified by measuring oil viscosity in the laboratory, and then using those results to measure skin friction beneath the turbulent boundary layer in a low speed wind tunnel. The dual-laser-beam skin friction measurements are compared with Preston tube measurements, with mean velocity profile data in a "law-of-the-well" coordinate system, and with computations based on turbulent boundary-layer theory. Excellent agreement is found in all cases. (This validation and the aforementioned improvements appear to make the present form of the instrument usable to measure skin friction reliably and nonintrusively in a wide range of flow situations in which previous methods are not practical.)

  13. Modeling of optical quadrature microscopy for imaging mouse embryos

    NASA Astrophysics Data System (ADS)

    Warger, William C., II; DiMarzio, Charles A.

    2008-02-01

    Optical quadrature microscopy (OQM) has been shown to provide the optical path difference through a mouse embryo, and has led to a novel method to count the total number of cells further into development than current non-toxic imaging techniques used in the clinic. The cell counting method has the potential to provide an additional quantitative viability marker for blastocyst transfer during in vitro fertilization. OQM uses a 633 nm laser within a modified Mach-Zehnder interferometer configuration to measure the amplitude and phase of the signal beam that travels through the embryo. Four cameras preceded by multiple beamsplitters record the four interferograms that are used within a reconstruction algorithm to produce an image of the complex electric field amplitude. Here we present a model for the electric field through the primary optical components in the imaging configuration and the reconstruction algorithm to calculate the signal to noise ratio when imaging mouse embryos. The model includes magnitude and phase errors in the individual reference and sample paths, fixed pattern noise, and noise within the laser and detectors. This analysis provides the foundation for determining the imaging limitations of OQM and the basis to optimize the cell counting method in order to introduce additional quantitative viability markers.

  14. Quadrature, Interpolation and Observability

    NASA Technical Reports Server (NTRS)

    Hodges, Lucille McDaniel

    1997-01-01

    Methods of interpolation and quadrature have been used for over 300 years. Improvements in the techniques have been made by many, most notably by Gauss, whose technique applied to polynomials is referred to as Gaussian Quadrature. Stieltjes extended Gauss's method to certain non-polynomial functions as early as 1884. Conditions that guarantee the existence of quadrature formulas for certain collections of functions were studied by Tchebycheff, and his work was extended by others. Today, a class of functions which satisfies these conditions is called a Tchebycheff System. This thesis contains the definition of a Tchebycheff System, along with the theorems, proofs, and definitions necessary to guarantee the existence of quadrature formulas for such systems. Solutions of discretely observable linear control systems are of particular interest, and observability with respect to a given output function is defined. The output function is written as a linear combination of a collection of orthonormal functions. Orthonormal functions are defined, and their properties are discussed. The technique for evaluating the coefficients in the output function involves evaluating the definite integral of functions which can be shown to form a Tchebycheff system. Therefore, quadrature formulas for these integrals exist, and in many cases are known. The technique given is useful in cases where the method of direct calculation is unstable. The condition number of a matrix is defined and shown to be an indication of the the degree to which perturbations in data affect the accuracy of the solution. In special cases, the number of data points required for direct calculation is the same as the number required by the method presented in this thesis. But the method is shown to require more data points in other cases. A lower bound for the number of data points required is given.

  15. System simulation method for fiber-based homodyne multiple target interferometers using short coherence length laser sources

    NASA Astrophysics Data System (ADS)

    Fox, Maik; Beuth, Thorsten; Streck, Andreas; Stork, Wilhelm

    2015-09-01

    Homodyne laser interferometers for velocimetry are well-known optical systems used in many applications. While the detector power output signal of such a system, using a long coherence length laser and a single target, is easily modelled using the Doppler shift, scenarios with a short coherence length source, e.g. an unstabilized semiconductor laser, and multiple weak targets demand a more elaborated approach for simulation. Especially when using fiber components, the actual setup is an important factor for system performance as effects like return losses and multiple way propagation have to be taken into account. If the power received from the targets is in the same region as stray light created in the fiber setup, a complete system simulation becomes a necessity. In previous work, a phasor based signal simulation approach for interferometers based on short coherence length laser sources has been evaluated. To facilitate the use of the signal simulation, a fiber component ray tracer has since been developed that allows the creation of input files for the signal simulation environment. The software uses object oriented MATLAB code, simplifying the entry of different fiber setups and the extension of the ray tracer. Thus, a seamless way from a system description based on arbitrarily interconnected fiber components to a signal simulation for different target scenarios has been established. The ray tracer and signal simulation are being used for the evaluation of interferometer concepts incorporating delay lines to compensate for short coherence length.

  16. Observation of a critically refracted converted SP wave using laser Doppler interferometer

    NASA Astrophysics Data System (ADS)

    Gurevich, Boris; Lebedev, Maxim; Madadi, Mahyar; Bona, Andrej; Pevzner, Roman

    2015-04-01

    Laboratory measurements of elastic properties of rocks are important for calibration of seismic data and for corroboration of theoretical models of rocks. The most common way of determining the elastic properties of rock samples in laboratory settings is to estimate the velocities of ultrasonic waves propagating in different directions. The wave velocities are usually obtained from the travel times of waves generated and recorded by ultrasonic piezoelectric transducers. This approach has a large uncertainty associated with shear-wave travel time estimation and separation of differently polarised shear waves, as well as uncertainty as to whether phase or group velocity is measured. The problems are caused by the relatively large size and small number of transducers. One way to address some of these issues is by using laser Doppler interferometer, which records a particle like movement that can serve to separate the waves and to pick the travel times from which the ray velocities cab be estimated reliably, and with a huge data redundancy. In this paper, laser Doppler interferometer is used to record wave propagation in an anisotropic rock sample by measuring three orthogonal components of particle velocity on the sample surface. These measurements allow a clear separation of different wave types. The travel time of these waves are used for estimation of anisotropy parameters of the sample. A key observation is the very strong wave which at small offsets has traveltimes equal to those of the S-wave, but at large offsets travels with a velocity close to that of the P-wave. We interpret this wave as a converted SP wave critically refracted at the free surface. The nature and characteristics of this wave are confirmed by numerical simulations in both isotropic and anisotropic media. These simulations show the same traveltimes as measured in the experiment, but the amplitude of the converted SP wave is much stronger in the measured data. Analysis of this inconsistency is part of the future research, but perhaps one possible explanation is a complex radiation pattern of the source. Such a non-trivial radiation pattern is probably also the reason for the different frequency content in the SH and P-waves compared to the SV and the critically refracted SP wave. Knowledge of the radiation pattern of the source will allow it to be deconvolved from the observed data. Based on our preliminary results, such a deconvolution would also allow us to use semblance as a fitting algorithm, which would eliminate the need to pick the travel times and make the fitting more robust.

  17. Study of the second-order relativistic light deflection of the Sun using long-baseline fibre-linked interferometers: Laser-Interferometric Solar Relativity (LISOR) test

    NASA Technical Reports Server (NTRS)

    Ni, Wei-Tou; Shy, Jow-Tsong; Tseng, Shiao-Min; Shao, Michael

    1992-01-01

    A propasal to study the second order light deflection in the solar gravitational field is presented. It is proposed to use 1 to 2 W frequency stabilized lasers on two microspacecraft about 0.25 degree apart in the sky with apparent positions near the Sun, and observe the relative angle of two spacecraft using ground based fiber linked interferometers with 10 km baseline to determine the second order relativistic light deflection effects. The first two years of work would emphasize the establishment of a prototype stabilized laser system and fiber linked interferometer. The first year, a prototype fiber linked interferometer would be set up to study the phase noise produced by external perturbations to fiber links. The second year, a second interferometer would be set up. The cancellation of phase drift due to fiber links of both interferometers in the same environment would be investigated.

  18. Study of a defect detection accuracy of a granite nondestructive resonance technique based on a laser interferometer

    NASA Astrophysics Data System (ADS)

    Pod?orny, Tomasz; Budzy?, Grzegorz; Rzepka, Janusz; Tkaczyk, Jakub

    2014-05-01

    A nondestructive testing technique based on a resonance approach and a laser interferometer device is introduced in the presented paper. It utilizes a not synchronized with an acquisition device and low power excitation source. Induced vibrations are acquired using high resolution laser interferometer in a configuration of a vibrometer. As a result, the test equipment is significantly simplified and tailored to the industry requirements. Sample evaluation process is based on a processing that fits lowest order resonance frequencies to p-wave and s-wave frequencies. Obtained velocities are used to fit higher order resonance frequencies present in the response with positions and lengths of resonators formed by cracks or flaws. Presented research focuses on an assessment of accuracy and sensitivity of the introduced method. Performed measurements revealed that it is possible to obtain decent parameters for industry applications.

  19. Compact Mach-Zehnder interferometer based on photonic crystal fiber and its application in switchable multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Chen, Weiguo; Lou, Shuqin; Wang, Liwen; Li, Honglei; Guo, Tieying; Jian, Shuisheng

    2009-08-01

    The compact Mach-Zehnder interferometer is proposed by splicing a section of photonic crystal fiber (PCF) and two pieces of single mode fiber (SMF) with the air-holes of PCF intentionally collapsed in the vicinity of the splices. The depedence of the fringe spacing on the length of PCF is investigated. Based on the Mach-Zehnder interferometer as wavelength-selective filter, a switchable dual-wavelength fiber ring laser is demonstrated with a homemade erbiumdoped fiber amplifier (EDFA) as the gain medium at room temperature. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-and dual -wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

  20. MIRI: A multichannel far-infrared laser interferometer for electron density measurements on TFTR (Tokamak Fusion Test Reactor)

    SciTech Connect

    Mansfield, D.K.; Park, H.K.; Johnson, L.C.; Anderson, H.M.; Chouinard, R.; Foote, V.S.; Ma, C.H.; Clifton, B.J.

    1987-07-01

    A ten-channel far-infrared laser interferometer which is routinely used to measure the spatial and temporal behavior of the electron density profile on the TFTR tokamak is described and representative results are presented. This system has been designed for remote operation in the very hostile environment of a fusion reactor. The possible expansion of the system to include polarimetric measurements is briefly outlined. 13 refs., 8 figs.

  1. Precise density profile measurements by using a two color YAG/CO{sub 2} laser imaging Interferometer on LHD

    SciTech Connect

    Tanaka, K.; Sanin, A.L.; Vyacheslavov, L.N.; Akiyama, T.; Kawahata, K.; Tokuzawa, T.; Ito, Y.; Okajima, S.

    2004-10-01

    A multichannel imaging heterodyne interferometer is installed on Large Helical Device. Two branches of the interferometer: one with CO{sub 2} laser (wavelength {lambda}{sub i}=10.6 {mu}m) and other with diode pumped yttritium-aluminium-garnet (YAG) laser (wavelength {lambda}{sub i}=1.06 {mu}m) are used for electron density measurements and vibration compensation. Two slab beams and one circular beam are injected vertically. Liquid nitrogen cooled linear detector arrays are used for detection of slab beams and room temperature detector is employed for single circular beam for CO{sub 2} beams. Avalanche photodiodes record signals for YAG beams. Chordal resolution is from 15 to 22.5 mm, phase resolution is 10{sup -3} of CO{sub 2} fringe, which is determined by the electrical noise of phase counter. About 5x10{sup -3}{approx}10{sup -2} of CO{sub 2} fringe uncompensated signal remains after vibration compensation. Combining existing 13-channels far infrared (wavelength {lambda}{sub i}=119 {mu}m) laser interferometer, profile measurements at high density (>10{sup 20} m{sup -3}) become possible.

  2. A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak

    SciTech Connect

    Xiong, C. Y.; Chen, J. Li, Q.; Liu, Y.; Gao, L.

    2014-12-15

    A three-wave laser polarimeter-interferometer, equipped with three independent far-infrared laser sources, has been developed on Joint-TEXT (J-TEXT) tokamak. The diagnostic system is capable of high-resolution temporal and phase measurement of the Faraday angle and line-integrated density. However, for long-term operation (>10 min), the free-running lasers can lead to large drifts of the intermediate frequencies (∼100–∼500 kHz/10 min) and decay of laser power (∼10%–∼20%/10 min), which act to degrade diagnostic performance. In addition, these effects lead to increased maintenance cost and limit measurement applicability to long pulse/steady state experiments. To solve this problem, a real-time feedback control method of the laser source is proposed. By accurately controlling the length of each laser cavity, both the intermediate frequencies and laser power can be simultaneously controlled: the intermediate frequencies are controlled according to the pre-set values, while the laser powers are maintained at an optimal level. Based on this approach, a real-time feedback control system has been developed and applied on J-TEXT polarimeter-interferometer. Long-term (theoretically no time limit) feedback of intermediate frequencies (maximum change less than ±12 kHz) and laser powers (maximum relative power change less than ±7%) has been successfully achieved.

  3. DFB laser diode interferometer with image capture timing control for surface profile reconstruction

    NASA Astrophysics Data System (ADS)

    En, Bo; Fa-jie, Duan; Fan, Feng; Chang-rong, Lv; Xiao, Fu; Ting-ting, Huang

    2015-02-01

    A DFB laser diode interferometer with sinusoidal phase modulation (SPM) and image capture timing control was proposed for the reconstruction of surface profile. Sinusoidal phase modulation was achieved by controlling the injection current of light diode. The surface profile was reconstructed on four consecutive fringe images. Random phase error and low-frequency phase shift would be superposed on the interference fringes due to external disturbances such as mechanical vibration and temperature fluctuation. A simple peak detection circuit that would take less time consumption than phase generated carrier (PGC) was built for eliminating external disturbances, and the phase of fringe image could be stabilized in about one millisecond, which is conducive to real-time surface profile reconstruction. A novel method to capture four consecutive fringe images in adjacent modulation period was presented by controlling pulse sequence to trigger camera exposure and image readout operation. The whole system was tested on an optical table without vibration isolation and being kept in thermostatic chamber. The repeatability was about 0.018 wave (approximately 14 nm for 760 nm wavelength). The feasibility for high-resolution surface profile reconstruction had been verified.

  4. Linewidth reduction of a distributed-feedback diode laser using an all-fiber interferometer with short path imbalance.

    PubMed

    Lee, Won-Kyu; Park, Chang Yong; Mun, Jongchul; Yu, Dai-Hyuk

    2011-07-01

    The linewidth of a distributed-feedback (DFB) diode laser at 1156 nm, of which free-running linewidth was 3 MHz, was reduced to 15 kHz using an all-fiber interferometer with 5-m-long path imbalance. Optical power loss and bandwidth limitation were negligible with this short optical fiber patch cord. This result was achieved without acoustic and vibration isolations, and the frequency lock could be maintained over weeks. In addition to its simplicity, compactness, robustness, and cost-effectiveness, this technique can be applied at any wavelength owing to the availability of DFB diode lasers and fiber-optic components. PMID:21806170

  5. Real-time dynamic calibration of a tunable frequency laser source using a Fabry-Pérot interferometer.

    PubMed

    Mandula, Gábor; Kis, Zsolt; Lengyel, Krisztián

    2015-12-01

    We report on a method for real-time dynamic calibration of a tunable external cavity diode laser by using a partially mode-matched plano-concave Fabry-Pérot interferometer in reflection geometry. Wide range laser frequency scanning is carried out by piezo-driven tilting of a diffractive grating playing the role of a frequency selective mirror in the laser cavity. The grating tilting system has a considerable mechanical inertness, so static laser frequency calibration leads to false results. The proposed real-time dynamic calibration based on the identification of primary- and Gouy-effect type secondary interference peaks with known frequency and temporal history can be used for a wide scanning range (from 0.2 GHz to more than 1 GHz). A concave spherical mirror with a radius of R = 100 cm and a plain 1% transmitting mirror was used as a Fabry-Pérot interferometer with various resonator lengths to investigate and demonstrate real-time calibration procedures for two kinds of laser frequency scanning functions. PMID:26724003

  6. Real-time dynamic calibration of a tunable frequency laser source using a Fabry-Pérot interferometer

    NASA Astrophysics Data System (ADS)

    Mandula, Gábor; Kis, Zsolt; Lengyel, Krisztián

    2015-12-01

    We report on a method for real-time dynamic calibration of a tunable external cavity diode laser by using a partially mode-matched plano-concave Fabry-Pérot interferometer in reflection geometry. Wide range laser frequency scanning is carried out by piezo-driven tilting of a diffractive grating playing the role of a frequency selective mirror in the laser cavity. The grating tilting system has a considerable mechanical inertness, so static laser frequency calibration leads to false results. The proposed real-time dynamic calibration based on the identification of primary- and Gouy-effect type secondary interference peaks with known frequency and temporal history can be used for a wide scanning range (from 0.2 GHz to more than 1 GHz). A concave spherical mirror with a radius of R = 100 cm and a plain 1% transmitting mirror was used as a Fabry-Pérot interferometer with various resonator lengths to investigate and demonstrate real-time calibration procedures for two kinds of laser frequency scanning functions.

  7. Real-time dynamic calibration of a tunable frequency laser source using a Fabry-Pérot interferometer

    SciTech Connect

    Mandula, Gábor Kis, Zsolt; Lengyel, Krisztián

    2015-12-15

    We report on a method for real-time dynamic calibration of a tunable external cavity diode laser by using a partially mode-matched plano-concave Fabry-Pérot interferometer in reflection geometry. Wide range laser frequency scanning is carried out by piezo-driven tilting of a diffractive grating playing the role of a frequency selective mirror in the laser cavity. The grating tilting system has a considerable mechanical inertness, so static laser frequency calibration leads to false results. The proposed real-time dynamic calibration based on the identification of primary- and Gouy-effect type secondary interference peaks with known frequency and temporal history can be used for a wide scanning range (from 0.2 GHz to more than 1 GHz). A concave spherical mirror with a radius of R = 100 cm and a plain 1% transmitting mirror was used as a Fabry-Pérot interferometer with various resonator lengths to investigate and demonstrate real-time calibration procedures for two kinds of laser frequency scanning functions.

  8. Study of self-generated magnetic fields in laser produced plasmas using a three-channel polaro-interferometer

    SciTech Connect

    Prasad, Y. B. S. R.; Barnwal, S.; Naik, P. A.; Kamath, M. P.; Joshi, A. S.; Kumbhare, S. R.; Gupta, P. D.; Bolkhovitinov, E. A.; Rupasov, A. A.

    2011-12-15

    Self-generated magnetic fields produced in laser plasmas at moderate laser intensities have been measured using a three-channel polaro-interferometer. The main elements of this device are two birefringent calcite wedges placed between two crossed polarizers. Using this device, the spatial profiles of (a) the rotation angle (polarometry), (b) the electron density (interferometry), and (c) the transmitted probe beam intensity (shadowgraphy) are recorded simultaneously using a digital camera with a large format CCD in a single laser shot. Magnetic fields of 2-4 MG had been estimated in aluminum plasma at laser intensities {approx}10{sup 13} W/cm{sup 2}. It is also possible to use this device in other configurations to get time resolved information.

  9. Self-referencing Mach-Zehnder interferometer as a laser system diagnostic: Active and adaptive optical systems

    SciTech Connect

    Feldman, M.; Mockler, D.J.; English, R.E. Jr.; Byrd, J.L.; Salmon, J.T.

    1991-02-01

    We are incorporating a novel self-referencing Mach-Zehnder interferometer into a large scale laser system as a real time, interactive diagnostic tool for wavefront measurement. The instrument is capable of absolute wavefront measurements accurate to better than {lambda}/10 pv over a wavelength range > 300 nm without readjustment of the optical components. This performance is achieved through the design of both refractive optics and catadioptric collimator to achromatize the Mach-Zehnder reference arm. Other features include polarization insensitivity through the use of low angles of incidence on all beamsplitters as well as an equal path length configuration that allows measurement of either broad-band or closely spaced laser-line sources. Instrument accuracy is periodically monitored in place by means of a thermally and mechanically stable wavefront reference source that is calibrated off-line with a phase conjugate interferometer. Video interferograms are analyzed using Fourier transform techniques on a computer that includes dedicated array processor. Computer and video networks maintain distributed interferometers under the control of a single analysis computer with multiple user access. 7 refs., 11 figs.

  10. High-efficiency frequency doubling of a Nd:YAG laser in a two-pass quadrature frequency-conversion scheme using CsLiB6O10 crystals

    NASA Astrophysics Data System (ADS)

    Kiriyama, Hiromitsu; Nakano, Fumihiko; Yamakawa, Koichi

    2002-08-01

    A two-pass quadrature scheme using CsLiB6O10 (CLBO) crystals was used to frequency double a Nd:YAG laser with high efficiency with tens of watts of average output power and low input laser intensities. The 532-nm bidirectional output of this scheme is readily suited for pumping Ti:sapphire crystals, making it possible to build compact high-power chirped-pulse amplification systems. Using this scheme, we obtained 2.73 J of second-harmonic pulse energy from 3.27 J of input 1064-nm fundamental laser pulse energy at a modest intensity of 330 MW/cm2 and 10 Hz, corresponding to an energy-conversion efficiency of 83%. We discuss in detail the design and performance of this frequency-conversion scheme in terms of output parameters, stability, and scalability.

  11. Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser-induced water breakdown for refractive index sensing.

    PubMed

    Liu, Yi; Qu, Shiliang

    2014-01-20

    The Fabry-Perot interferometer (FPI) cavity in a single-mode fiber with two open faces was fabricated by using the method of femtosecond laser-induced water breakdown. Then the FPI cavity was annealed by the arc discharge to greatly smooth its internal surface. The whole fabrication process features simple operation and high efficiency. The fabricated FPI cavity exhibits a perfect interferometer spectrum with reflection loss of only -3 dB and fringe visibility of almost 30 dB. It can be used as a perfectly reliable liquid refractive index sensor, as it exhibits high sensitivity (1147.48 nm/RIU), good linearity (99.93%), good repeatability, high actual measurement accuracy (1.29×10(-4)RIU), large measurement range, and good temperature insensitive characteristic. PMID:24514135

  12. What Can be Expected from the GRACE-FO Laser Ranging Interferometer for Earth Science Applications?

    NASA Astrophysics Data System (ADS)

    Flechtner, Frank; Neumayer, Karl-Hans; Dahle, Christoph; Dobslaw, Henryk; Fagiolini, Elisa; Raimondo, Jean-Claude; Gntner, Andreas

    2015-09-01

    The primary objective of the gravity recovery and climate experiment follow-on (GRACE-FO) satellite mission, due for launch in August 2017, is to continue the GRACE time series of global monthly gravity field models. For this, evolved versions of the GRACE microwave instrument, GPS receiver, and accelerometer will be used. A secondary objective is to demonstrate the effectiveness of a laser ranging interferometer (LRI) in improving the satellite-to-satellite tracking measurement performance. In order to investigate the expected enhancement for Earth science applications, we have performed a full-scale simulation over the nominal mission lifetime of 5 years using a realistic orbit scenario and error assumptions both for instrument and background model errors. Unfiltered differences between the synthetic input and the finally recovered time-variable monthly gravity models show notable improvements with the LRI, on a global scale, of the order of 23 %. The gain is realized for wavelengths smaller than 240 km in case of Gaussian filtering but decreases to just a few percent when anisotropic filtering is applied. This is also confirmed for some typical regional Earth science applications which show randomly distributed patterns of small improvements but also degradations when using DDK4-filtered LRI-based models. Analysis of applied error models indicates that accelerometer noise followed by ocean tide and non-tidal mass variation errors are the main contributors to the overall GRACE-FO gravity model error. Improvements in these fields are therefore necessary, besides optimized constellations, to make use of the increased LRI accuracy and to significantly improve gravity field models from next-generation gravity missions.

  13. What Can be Expected from the GRACE-FO Laser Ranging Interferometer for Earth Science Applications?

    NASA Astrophysics Data System (ADS)

    Flechtner, Frank; Neumayer, Karl-Hans; Dahle, Christoph; Dobslaw, Henryk; Fagiolini, Elisa; Raimondo, Jean-Claude; Güntner, Andreas

    2016-03-01

    The primary objective of the gravity recovery and climate experiment follow-on (GRACE-FO) satellite mission, due for launch in August 2017, is to continue the GRACE time series of global monthly gravity field models. For this, evolved versions of the GRACE microwave instrument, GPS receiver, and accelerometer will be used. A secondary objective is to demonstrate the effectiveness of a laser ranging interferometer (LRI) in improving the satellite-to-satellite tracking measurement performance. In order to investigate the expected enhancement for Earth science applications, we have performed a full-scale simulation over the nominal mission lifetime of 5 years using a realistic orbit scenario and error assumptions both for instrument and background model errors. Unfiltered differences between the synthetic input and the finally recovered time-variable monthly gravity models show notable improvements with the LRI, on a global scale, of the order of 23 %. The gain is realized for wavelengths smaller than 240 km in case of Gaussian filtering but decreases to just a few percent when anisotropic filtering is applied. This is also confirmed for some typical regional Earth science applications which show randomly distributed patterns of small improvements but also degradations when using DDK4-filtered LRI-based models. Analysis of applied error models indicates that accelerometer noise followed by ocean tide and non-tidal mass variation errors are the main contributors to the overall GRACE-FO gravity model error. Improvements in these fields are therefore necessary, besides optimized constellations, to make use of the increased LRI accuracy and to significantly improve gravity field models from next-generation gravity missions.

  14. Laser Interferometer Space Antenna double black holes: dynamics in gaseous nuclear discs

    NASA Astrophysics Data System (ADS)

    Dotti, Massimo; Colpi, Monica; Haardt, Francesco

    2006-03-01

    We study the inspiral of double black holes, with masses in the Laser Interferometer Space Antenna (LISA) window of detectability, orbiting inside a massive circumnuclear, rotationally supported gaseous disc. Using high-resolution smoothed particle hydrodynamics simulations, we follow the black hole dynamics in the early phase when gas-dynamical friction acts on the black holes individually, and continue our simulation until they form a close binary. We find that in the early sinking the black holes lose memory of their initial orbital eccentricity if they corotate with the gaseous disc. As a consequence, the massive black holes bind forming a binary with a low eccentricity, consistent with zero within our numerical resolution limit. The cause of circularization resides in the rotation present in the gaseous background where dynamical friction operates. Circularization may hinder gravitational waves from taking over and leading the binary to coalescence. In the case of counter-rotating orbits, the initial eccentricity (if present) does not decrease, and the black holes may bind forming an eccentric binary. When dynamical friction has subsided, for equal mass black holes and regardless their initial eccentricity, angular momentum loss, driven by the gravitational torque exerted on the binary by surrounding gas, is nevertheless observable down to the smallest scale probed (~=1 pc). In the case of unequal masses, dynamical friction remains efficient down to our resolution limit, and there is no sign of formation of any ellipsoidal gas distribution that may further harden the binary. During inspiral, gravitational capture of gas by the black holes occurs mainly along circular orbits; eccentric orbits imply high relative velocities and weak gravitational focusing. Thus, the active galactic nucleus activity may be excited during the black hole pairing process and double active nuclei may form when circularization is completed, on distance scales of tens of parsecs.

  15. VISAR (Velocity Interferometer System for Any Reflector): Line-imaging interferometer

    SciTech Connect

    Hemsing, W.F.; Mathews, A.R.; Warnes, R.H.; Whittemore, G.R.

    1990-01-01

    This paper describes a Velocity Interferometer System for Any Reflector (VISAR) technique that extends velocity measurements from single points to a line. Single-frequency argon laser light was focused through a cylindrical lens to illuminate a line on a surface. The initially stationary, flat surface was accelerated unevenly during the experiment. Motion produced a Doppler-shift of light reflected from the surface that was proportional to the velocity at each point. The Doppler-shifted image of the illuminated line was focused from the surface through a push-pull VISAR interferometer where the light was split into four quadrature-coded images. When the surface accelerated, the Doppler-shift caused the interference for each point on each line image to oscillate sinusoidally. Coherent fiber optic bundles transmitted images from the interferometer to an electronic streak camera for sweeping in time and recording on film. Data reduction combined the images to yield a continuous velocity and displacement history for all points on the surface that reflected sufficient light. The technique was demonstrated in an experiment where most of the surface was rapidly driven to a saddle shape by an exploding foil. Computer graphics were used to display the measured velocity history and to aid visualization of the surface motion. 6 refs., 8 figs.

  16. Optimized quantum nondemolition measurement of a field quadrature

    NASA Astrophysics Data System (ADS)

    Paris, Matteo G.

    2002-01-01

    We suggest an interferometric scheme assisted by squeezing and linear feedback to realize the whole class of field-quadrature quantum nondemolition measurements, from Von Neumann projective measurement to a fully nondestructive noninformative one. In our setup, the signal under investigation is mixed with a squeezed probe in an interferometer and, at the output, one of the two modes is revealed through homodyne detection. The second beam is then amplitude-modulated according to the outcome of the measurement, and finally squeezed according to the transmittivity of the interferometer. Using strongly squeezed or antisqueezed probes respectively, one achieves either a projective measurement, i.e., homodyne statistics arbitrarily close to the intrinsic quadrature distribution of the signal, and conditional outputs approaching the corresponding eigenstates, or a fully nondestructive one, characterized by an almost uniform homodyne statistics, and by an output state arbitrarily close to the input signal. By varying the squeezing between these two extremes, or simply by tuning the internal phase shift of the interferometer, the whole set of intermediate cases may also be obtained. In particular, an optimal quantum nondemolition measurement of quadrature may be achieved, which minimizes the information gain versus state disturbance tradeoff.

  17. Ring cavity fiber laser based on Fabry-Prot interferometer for high-sensitive micro-displacement sensing

    NASA Astrophysics Data System (ADS)

    Bai, Yan; Yan, Feng-ping; Liu, Shuo; Tan, Si-yu; Wen, Xiao-dong

    2015-11-01

    A ring cavity fiber laser based on Fabry-Prot interferometer (FPI) is proposed and demonstrated experimentally for micro-displacement sensing. Simulation results show that the dips of the FPI transmission spectrum are sensitive to the cavity length of the FPI. With this characteristic, the relationship between wavelength shift and cavity length change can be established by means of the FPI with two aligned fiber end tips. The maximum sensitivity of 39.6 nm/?m is achieved experimentally, which is approximately 25 times higher than those in previous reports. The corresponding ring cavity fiber laser with the sensitivity for displacement measurement of about 6 nm/?m is implemented by applying the FPI as the filter. The proposed fiber laser has the advantages of simple structure, low cost and high sensitivity.

  18. A dual-pass Mach-Zehnder interferometer filter using a TCF loop mirror for double-wavelength fiber lasers

    NASA Astrophysics Data System (ADS)

    Zou, Hui; Lou, Shuqin; Su, Wei; Wang, Xin

    2013-09-01

    A dual-pass Mach-Zehnder interferometer filter using a section of twin-core fiber (TCF) loop mirror is proposed. The filter is theoretically and experimentally studied for various interferometer arm difference when TCF length is constant. Theoretical results are validated by the experimental demonstration and in good agreement with the experimental results. And then, by using the filter in a ring fiber laser, a stable and switchable dual-wavelength lasing is obtained experimentally. The 3-dB bandwidth and the SMSR of the output laser are 0.015 nm and higher than 62.4 dB, respectively. The peak power fluctuation and wavelength shift are also monitored to be less than 0.04 dB and 0.02 nm over an hour at room temperature. Furthermore, the output laser can be switched between single and dual wavelength by carefully adjusting the PCs. The experimental results show that the filter can suppress mode competition effectively, improve the SMSR availably, and enhance the stability of the output lasing.

  19. CO2 laser-based dispersion interferometer utilizing orientation-patterned gallium arsenide for plasma density measurements

    NASA Astrophysics Data System (ADS)

    Bamford, D. J.; Cummings, E. A.; Panasenko, D.; Fenner, D. B.; Hensley, J. M.; Boivin, R. L.; Carlstrom, T. N.; Van Zeeland, M. A.

    2013-09-01

    A dispersion interferometer based on the second-harmonic generation of a carbon dioxide laser in orientation-patterned gallium arsenide has been developed for measuring electron density in plasmas. The interferometer includes two nonlinear optical crystals placed on opposite sides of the plasma. This instrument has been used to measure electron line densities in a pulsed radio-frequency generated argon plasma. A simple phase-extraction technique based on combining measurements from two successive pulses of the plasma has been used. The noise-equivalent line density was measured to be 1.7 × 1017 m-2 in a detection bandwidth of 950 kHz. One of the orientation-patterned crystals produced 13 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 13 W of peak power. Two crystals arranged sequentially produced 58 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 37 W of peak power.

  20. Spatio-temporal coherence of free-electron laser radiation in the extreme ultraviolet determined by a Michelson interferometer

    SciTech Connect

    Hilbert, V.; Rödel, C.; Zastrau, U.; Brenner, G.; Düsterer, S.; Dziarzhytski, S.; Harmand, M.; Przystawik, A.; Redlin, H.; Toleikis, S.; Döppner, T.; Ma, T.; Fletcher, L.; Förster, E.; Glenzer, S. H.; Lee, H. J.; Hartley, N. J.; Kazak, L.; Komar, D.; Skruszewicz, S.; and others

    2014-09-08

    A key feature of extreme ultraviolet (XUV) radiation from free-electron lasers (FELs) is its spatial and temporal coherence. We measured the spatio-temporal coherence properties of monochromatized FEL pulses at 13.5 nm using a Michelson interferometer. A temporal coherence time of (59±8) fs has been determined, which is in good agreement with the spectral bandwidth given by the monochromator. Moreover, the spatial coherence in vertical direction amounts to about 15% of the beam diameter and about 12% in horizontal direction. The feasibility of measuring spatio-temporal coherence properties of XUV FEL radiation using interferometric techniques advances machine operation and experimental studies significantly.

  1. Highly sensitive refractive index fiber inline Mach-Zehnder interferometer fabricated by femtosecond laser micromachining and chemical etching

    NASA Astrophysics Data System (ADS)

    Sun, Xiao-Yan; Chu, Dong-Kai; Dong, Xin-Ran; Zhou, Chu; Li, Hai-Tao; Luo-Zhi; Hu, You-Wang; Zhou, Jian-Ying; Cong-Wang; Duan, Ji-An

    2016-03-01

    A High sensitive refractive index (RI) sensor based on Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed, which is fabricated by femtosecond laser transversal-scanning inscription method and chemical etching. A rectangular cavity structure is formed in part of fiber core and cladding interface. The MZI sensor shows excellent refractive index sensitivity and linearity, which exhibits an extremely high RI sensitivity of -17197 nm/RIU (refractive index unit) with the linearity of 0.9996 within the refractive index range of 1.3371-1.3407. The experimental results are consistent with theoretical analysis.

  2. Multiplexing of six micro-displacement suspended-core Sagnac interferometer sensors with a Raman-Erbium fiber laser.

    PubMed

    Bravo, Mikel; Fernández-Vallejo, Montserrat; Echapare, Mikel; López-Amo, Manuel; Kobelke, J; Schuster, K

    2013-02-11

    This work experimentally demonstrates a long-range optical fiber sensing network for the multiplexing of fiber sensors based on photonic crystal fibers. Specifically, six photonic crystal fiber sensors which are based on a Sagnac interferometer that includes a suspended-core fiber have been used. These sensors offer a high sensitivity for micro-displacement measurements. The fiber sensor network presents a ladder structure and its operation mode is based on a fiber ring laser which combines Raman and Erbium doped fiber amplification. Thus, we show the first demonstration of photonic crystal fiber sensors for remote measurement applications up to 75 km. PMID:23481755

  3. Digital quadrature phase detection

    DOEpatents

    Smith, J.A.; Johnson, J.A.

    1992-05-26

    A system for detecting the phase of a frequency or phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2[pi] when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2[pi] when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention. 6 figs.

  4. Digital quadrature phase detection

    DOEpatents

    Smith, James A.; Johnson, John A.

    1992-01-01

    A system for detecting the phase of a frequency of phase modulated signal that includes digital quadrature sampling of the frequency or phase modulated signal at two times that are one quarter of a cycle of a reference signal apart, determination of the arctangent of the ratio of a first sampling of the frequency or phase modulated signal to the second sampling of the frequency or phase modulated signal, and a determination of quadrant in which the phase determination is increased by 2.pi. when the quadrant changes from the first quadrant to the fourth quadrant and decreased by 2.pi. when the quadrant changes from the fourth quadrant to the first quadrant whereby the absolute phase of the frequency or phase modulated signal can be determined using an arbitrary reference convention.

  5. Diagonalization of the length sensing matrix of a dual recycled laser interferometer gravitational wave antenna

    SciTech Connect

    Sato, Shuichi; Kawamura, Seiji; Kokeyama, Keiko; Kawazoe, Fumiko; Somiya, Kentaro

    2007-04-15

    Next generation gravitational wave antennas employ resonant sideband extraction (RSE) interferometers with Fabry-Perot cavities in the arms as an optical configuration. In order to realize stable, robust control of the detector system, it is a key issue to extract appropriate control signals for longitudinal degrees of freedom of the complex coupled-cavity system. In this paper, a novel length sensing and control scheme is proposed for the tuned RSE interferometer that is both simple and efficient. The sensing matrix can be well diagonalized, owing to a simple allocation of two rf modulations and to a macroscopic displacement of the cavity mirrors, which cause a detuning of the rf modulation sidebands.

  6. Measuring a parity-violation signature in the early universe via ground-based laser interferometers.

    PubMed

    Seto, Naoki; Taruya, Atsushi

    2007-09-21

    We show that pairs of widely separated interferometers are advantageous for measuring the Stokes parameter V of a stochastic background of gravitational waves. This parameter characterizes asymmetry of amplitudes of right- and left-handed waves, and generation of the asymmetry is closely related to parity violation in the early universe. The advantageous pairs include the kilometer-size interferometers LIGO (Livingston)-LCGT and AIGO-Virgo, which are relatively insensitive to Omega(GW) (the simple intensity of the background). Using at least three detectors, information of the intensity Omega(GW) and the degree of asymmetry V can be separately measured. PMID:17930491

  7. Diagonalization of the length sensing matrix of a dual recycled laser interferometer gravitational wave antenna

    NASA Astrophysics Data System (ADS)

    Sato, Shuichi; Kawamura, Seiji; Kokeyama, Keiko; Kawazoe, Fumiko; Somiya, Kentaro

    2007-04-01

    Next generation gravitational wave antennas employ resonant sideband extraction (RSE) interferometers with Fabry-Perot cavities in the arms as an optical configuration. In order to realize stable, robust control of the detector system, it is a key issue to extract appropriate control signals for longitudinal degrees of freedom of the complex coupled-cavity system. In this paper, a novel length sensing and control scheme is proposed for the tuned RSE interferometer that is both simple and efficient. The sensing matrix can be well diagonalized, owing to a simple allocation of two rf modulations and to a macroscopic displacement of the cavity mirrors, which cause a detuning of the rf modulation sidebands.

  8. Laser straightness interferometer system with rotational error compensation and simultaneous measurement of six degrees of freedom error parameters.

    PubMed

    Chen, Benyong; Xu, Bin; Yan, Liping; Zhang, Enzheng; Liu, Yanna

    2015-04-01

    A laser straightness interferometer system with rotational error compensation and simultaneous measurement of six degrees of freedom error parameters is proposed. The optical configuration of the proposed system is designed and the mathematic model for simultaneously measuring six degrees of freedom parameters of the measured object including three rotational parameters of the yaw, pitch and roll errors and three linear parameters of the horizontal straightness error, vertical straightness error and straightness error's position is established. To address the influence of the rotational errors produced by the measuring reflector in laser straightness interferometer, the compensation method of the straightness error and its position is presented. An experimental setup was constructed and a series of experiments including separate comparison measurement of every parameter, compensation of straightness error and its position and simultaneous measurement of six degrees of freedom parameters of a precision linear stage were performed to demonstrate the feasibility of the proposed system. Experimental results show that the measurement data of the multiple degrees of freedom parameters obtained from the proposed system are in accordance with those obtained from the compared instruments and the presented compensation method can achieve good effect in eliminating the influence of rotational errors on the measurement of straightness error and its position. PMID:25968740

  9. Tunable 1210 GHz mode-locked semiconductor fiber laser incorporating a Mach-Zehnder interferometer filter

    NASA Astrophysics Data System (ADS)

    Wang, Fei

    2011-06-01

    A stable multiwavelength mode-locked semiconductor fiber ring laser incorporating a fiber Mach-Zehnder interferometer (MZI) filter was proposed and experimentally demonstrated. A semiconductor optical amplifier (SOA) serves as an optically controlled mode-locking element due to gain exhaustion caused by external injected optical pulses. Another SOA severs as a constant-gain medium. A fiber MZI filter with a temperature control is incorporated into the fiber ring cavity to acquire a stable and tunable multiwavelength oscillation. Twelve wavelengths are synchronously mode-locked at 10 GHz, pulse width of mode-locked pulse are about 30 ps. Proposed multiwavelength mode-locked semiconductor fiber ring laser has some distinct advantages, such as simple and compact structure, easy integration, convenient tuning, good stability, potential high repetition rate operating, which has potential application in the future WDM communication system.

  10. Fiber-optic gas pressure sensing with a laser-heated silicon-based Fabry-Perot interferometer.

    PubMed

    Liu, Guigen; Han, Ming

    2015-06-01

    We report a novel fiber-optic sensor for measurement of static gas pressure based on the natural convection of a heated silicon pillar attached to a fiber tip functioning as a Fabry-Perot interferometer (FPI). A visible laser beam is guided by the fiber to efficiently heat the silicon pillar, while an infrared whitelight source, also guided by the fiber, is used to measure the temperature of the FPI, which is influenced both by the laser power and the pressure through natural convection. We theoretically and experimentally show that, by monitoring the fringe shift caused by the laser heating, air pressure sensing with little temperature cross-sensitivity can be achieved. The pressure sensitivity can be easily tuned by adjusting the heating laser power. In our experiment, the sensor performance within the temperature range from 20°C to 50°C and the pressure range from 0 to 1400 psi has been characterized, showing an average sensitivity of -0.52  pm/psi. Compared to the passive version of the sensor, the pressure sensitivity was ∼15 times larger, and the temperature cross-sensitivity was ∼100 times smaller. PMID:26030532

  11. Dual surface interferometer

    DOEpatents

    Pardue, Robert M. (Knoxville, TN); Williams, Richard R. (Oak Ridge, TN)

    1982-01-01

    A double-pass interferometer is provided which allows direct measurement of relative displacement between opposed surfaces. A conventional plane mirror interferometer may be modified by replacing the beam-measuring path cube-corner reflector with an additional quarter-wave plate. The beam path is altered to extend to an opposed plane mirrored surface and the reflected beam is placed in interference with a retained reference beam split from dual-beam source and retroreflected by a reference cube-corner reflector mounted stationary with the interferometer housing. This permits direct measurement of opposed mirror surfaces by laser interferometry while doubling the resolution as with a conventional double-pass plane mirror laser interferometer system.

  12. Dual surface interferometer

    DOEpatents

    Pardue, R.M.; Williams, R.R.

    1980-09-12

    A double-pass interferometer is provided which allows direct measurement of relative displacement between opposed surfaces. A conventional plane mirror interferometer may be modified by replacing the beam-measuring path cube-corner reflector with an additional quarterwave plate. The beam path is altered to extend to an opposed plane mirrored surface and the reflected beam is placed in interference with a retained reference beam split from dual-beam source and retroreflected by a reference cube-corner reflector mounted stationary with the interferometer housing. This permits direct measurement of opposed mirror surfaces by laser interferometry while doubling the resolution as with a conventional double-pass plane mirror laser interferometer system.

  13. The Palomar Testbed Interferometer

    NASA Technical Reports Server (NTRS)

    Colavita, M. M.; Wallace, J. K.; Hines, B. E.; Gursel, Y.; Malbet, F.; Palmer, D. L.; Pan, X. P.; Shao, M.; Yu, J. W.; Boden, A. F.

    1999-01-01

    The Palomar Testbed Interferometer (PTI) is a long-baseline infrared interferometer located at Palomar Observatory, California. It was built as a testbed for interferometric techniques applicable to the Keck Interferometer. First fringes were obtained in 1995 July. PTI implements a dual-star architecture, tracking two stars simultaneously for phase referencing and narrow-angle astrometry. The three fixed 40 cm apertures can be combined pairwise to provide baselines to 110 m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 microns and active delay lines with a range of +/-38 m. Laser metrology of the delay lines allows for servo control, and laser metrology of the complete optical path enables narrow-angle astrometric measurements. The instrument is highly automated, using a multiprocessing computer system for instrument control and sequencing.

  14. Probing the anisotropies of a stochastic gravitational-wave background using a network of ground-based laser interferometers

    SciTech Connect

    Thrane, Eric; Mandic, Vuk; Ballmer, Stefan; Romano, Joseph D.; Mitra, Sanjit; Talukder, Dipongkar; Bose, Sukanta

    2009-12-15

    We present a maximum-likelihood analysis for estimating the angular distribution of power in an anisotropic stochastic gravitational-wave background using ground-based laser interferometers. The standard isotropic and gravitational-wave radiometer searches (optimal for point sources) are recovered as special limiting cases. The angular distribution can be decomposed with respect to any set of basis functions on the sky, and the single-baseline, cross-correlation analysis is easily extended to a network of three or more detectors--that is, to multiple baselines. A spherical-harmonic decomposition, which provides maximum-likelihood estimates of the multipole moments of the gravitational-wave sky, is described in detail. We also discuss (i) the covariance matrix of the estimators and its relationship to the detector response of a network of interferometers, (ii) a singular-value decomposition method for regularizing the deconvolution of the detector response from the measured sky map, (iii) the expected increase in sensitivity obtained by including multiple baselines, and (iv) the numerical results of this method when applied to simulated data consisting of both pointlike and diffuse sources. Comparisons between this general method and the standard isotropic and radiometer searches are given throughout, to make contact with the existing literature on stochastic background searches.

  15. A Comparison of Delayed Self-Heterodyne Interference Measurement of Laser Linewidth Using Mach-Zehnder and Michelson Interferometers

    PubMed Central

    Canagasabey, Albert; Michie, Andrew; Canning, John; Holdsworth, John; Fleming, Simon; Wang, Hsiao-Chuan; Åslund, Mattias L.

    2011-01-01

    Linewidth measurements of a distributed feedback (DFB) fibre laser are made using delayed self heterodyne interferometry (DHSI) with both Mach-Zehnder and Michelson interferometer configurations. Voigt fitting is used to extract and compare the Lorentzian and Gaussian linewidths and associated sources of noise. The respective measurements are wL (MZI) = (1.6 ± 0.2) kHz and wL (MI) = (1.4 ± 0.1) kHz. The Michelson with Faraday rotator mirrors gives a slightly narrower linewidth with significantly reduced error. This is explained by the unscrambling of polarisation drift using the Faraday rotator mirrors, confirmed by comparing with non-rotating standard gold coated fibre end mirrors. PMID:22163692

  16. Optical Computerized Tomography for Visualization of Ultrasonic Fields Using Michelson Interferometer

    NASA Astrophysics Data System (ADS)

    Obuchi, Takeshi; Masuyama, Hiroyuki; Mizutani, Koichi; Nakanishi, Satoshi

    2006-09-01

    We propose a method for the noncontact visualization of ultrasonic fields using the Michelson interferometer and optical computerized tomography (O-CT). The light source of the interferometer is a He-Ne laser. The test light passing through radiated sound fields is interfered by the reference light. Therefore, the index of refraction gradient including sound pressure information is transformed into the intensity of the interference light that can be electrically acquired by an avalanche photo-diode. Projection data along the optical axis is obtained by single linear scanning in the range of ± 32 mm and electronically quadrature-detected as complex amplitude. Thirty-six projections are acquired in the range of 0≤θ<π (rad), and complex sound fields are reconstructed in a region of 64× 64 mm2 by CT. The experimental results are in agreement with the numerical results.

  17. Fabrication of diffraction gratings for surface encoders by using a Lloyd's mirror interferometer with a 405 nm laser diode

    NASA Astrophysics Data System (ADS)

    Li, Xinghui; Shimizu, Yuki; Ito, So; Gao, Wei; Zeng, Lijiang

    2013-01-01

    To fabricate a scale grating for a surface encoder in a cost-effective way, a blue laser diode with a wavelength of 405 nm is employed in a Lloyd's mirror interferometer to carry out interference lithography (IL) of the grating. The beams from the laser diode are collimated by an aspherical collimating lens to form beams with a diameter of 50 mm. These beams are then projected towards the Lloyd's mirror and the grating substrate, which are aligned perpendicularly with each other and are mounted on a rotary stage. One half of the beam directly goes to the grating substrate, and the other half reaches to the grating substrate after being reflected by the mirror. The direct beam and the reflected beam interference with each other to generate and expose the interference fringes, which correspond to the scale grating structures, on the substrate coated with a photoresist layer. The pitch and area of the grating structures are set to be 570 nm and around 300 mm2, respectively. The fabricated grating structures are evaluated with an AFM to investigate the influence of the spectrum width of the laser beam.

  18. A High-Quality Mach-Zehnder Interferometer Fiber Sensor by Femtosecond Laser One-Step Processing

    PubMed Central

    Zhao, Longjiang; Jiang, Lan; Wang, Sumei; Xiao, Hai; Lu, Yongfeng; Tsai, Hai-Lung

    2011-01-01

    During new fiber sensor development experiments, an easy-to-fabricate simple sensing structure with a trench and partially ablated fiber core is fabricated by using an 800 nm 35 fs 1 kHz laser. It is demonstrated that the structure forms a Mach-Zehnder interferometer (MZI) with the interference between the laser light passing through the air in the trench cavity and that in the remained fiber core. The fringe visibilities are all more than 25 dB. The transmission spectra vary with the femtosecond (fs) laser ablation scanning cycle. The free spectral range (FSR) decreases as the trench length increases. The MZI structure is of very high fabrication and sensing repeatability. The sensing mechanism is theoretically discussed, which is in agreement with experiments. The test sensitivity for acetone vapor is about 104 nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ∼ 875 °C with a step of 25 °C. PMID:22346567

  19. Output power stability of a HCN laser using a stepping motor for the EAST interferometer system

    NASA Astrophysics Data System (ADS)

    Zhang, J. B.; Wei, X. C.; Liu, H. Q.; Shen, J. J.; Zeng, L.; Jie, Y. X.

    2015-11-01

    The HCN laser on EAST is a continuous wave glow discharge laser with 3.4 m cavity length and 120 mW power output at 337 μ m wavelength. Without a temperature-controlled system, the cavity length of the laser is very sensitive to the environmental temperature. An external power feedback control system is applied on the HCN laser to stabilize the laser output power. The feedback system is composed of a stepping motor, a PLC, a supervisory computer, and the corresponding control program. One step distance of the stepping motor is 1 μ m and the time response is 0.5 s. Based on the power feedback control system, a stable discharge for the HCN laser is obtained more than eight hours, which satisfies the EAST experiment.

  20. A neural network-based approach to noise identification of interferometric GW antennas: the case of the 40 m Caltech laser interferometer

    NASA Astrophysics Data System (ADS)

    Acernese, F.; Barone, F.; de Rosa, M.; De Rosa, R.; Eleuteri, A.; Milano, L.; Tagliaferri, R.

    2002-06-01

    In this paper, a neural network-based approach is presented for the real time noise identification of a GW laser interferometric antenna. The 40 m Caltech laser interferometer output data provide a realistic test bed for noise identification algorithms because of the presence of many relevant effects: violin resonances in the suspensions, main power harmonics, ring-down noise from servo control systems, electronic noises, glitches and so on. These effects can be assumed to be present in all the first interferometric long baseline GW antennas such as VIRGO, LIGO, GEO and TAMA. For noise identification, we used the Caltech-40 m laser interferometer data. The results we obtained are pretty good notwithstanding the high initial computational cost. The algorithm we propose is general and robust, taking into account that it does not require a priori information on the data, nor a precise model, and it constitutes a powerful tool for time series data analysis.

  1. Fiber Fizeau interferometer for remote passive sensing

    NASA Astrophysics Data System (ADS)

    Bush, Jeff; Suh, Kwang

    2012-06-01

    Fizeau sensors constitute a large proportion of the fiber optic interferometric type sensors in use today. These include EFPI, FFPI, certain MEMS devices and in-line fiber intrinsic dual-reflector type sensors. The vast majority of the published literature covering these sensor types models them with a "2-beam" interferometer approximation, and implement interrogation approaches considering the same. Analysis performed and results presented show that the 2-beam model is not sufficient when reflection coefficients exceed 1% and traditional quadrature interrogation can result in linearity or distortion errors roughly in directly proportion to the reflectivity coefficients of the Fizeau sensor. A 4-beam multi-path interferometer model is developed and exercised to demonstrate this problem. Further this model shows that the "errors" in comparison to an ideal 2-beam interferometer model are symmetric across the unit circle and suggests that linear interrogation may be accomplished if orthonormal sample sets over the entire unit circle are used to replace the traditional (simple) quadrature sampling. This is shown to be true in both modeling and lab evaluations. The resulting approach has capabilities of remote, passive sensor operation, high frequency response, large, linear dynamic range and low noise. The interrogation technique demonstrated involves a phase generated carrier with full fringe sampling and quadrature determination which cancels the errors experienced from simple quadrature determination. Such an improvement enables higher reflectivity, higher SNR, high-fidelity fiber Fizeau sensor designs. Applications include embedded sensors, line sensors, or mechanically adapted for acoustic, pressure, vibration, acceleration or seismic sensing.

  2. Sensitivity improvement of a laser interferometer limited by inelastic back-scattering, employing dual readout

    NASA Astrophysics Data System (ADS)

    Meinders, Melanie; Schnabel, Roman

    2015-10-01

    Inelastic back-scattering of stray light is a long-standing and fundamental problem in high-sensitivity interferometric measurements and a potential limitation for advanced gravitational-wave (GW) detectors. The emerging parasitic interferences cannot be distinguished from a scientific signal via conventional single readout. In this work, we propose the subtraction of inelastic back-scatter signals by employing dual homodyne detection on the output light, and demonstrate it for a table-top Michelson interferometer. The additional readout contains solely parasitic signals and is used to model the scatter source. Subtraction of the scatter signal reduces the noise spectral density and thus improves the measurement sensitivity. Our scheme is qualitatively different from the previously demonstrated vetoing of scatter signals and opens a new path for improving the sensitivity of future GW detectors and other back-scatter limited devices.

  3. Dynamic interference fringes generated by optical interferometer for laser speckle reduction

    NASA Astrophysics Data System (ADS)

    Tong, Zhaomin; Nadeem, Akram M.; Chen, Xuyuan

    2012-10-01

    A speckle reduction apparatus is proposed by using an optical interferometer to introduce temporally changing interference fringes. With the help of the vibration of a mirror, diverse interference fringes and speckle patterns are added together in the intensity basis during the exposure time of the CCD camera, which result in a summed speckle image having lower speckle contrast. Experimentally, we have demonstrated the speckle reduction efficiency by this method, and compared with another approach by only using the modulation beam. The obtained speckle contrast is 0.66 after using both the modulation beam and the reference beam, which is lower than the 0.77 speckle contrast by only using the modulation beam. We conclude that the introduction of interference fringes helps the speckle reduction.

  4. Carbon fiber reinforced polymer dimensional stability investigations for use on the laser interferometer space antenna mission telescope.

    PubMed

    Sanjuán, J; Preston, A; Korytov, D; Spector, A; Freise, A; Dixon, G; Livas, J; Mueller, G

    2011-12-01

    The laser interferometer space antenna (LISA) is a mission designed to detect low frequency gravitational waves. In order for LISA to succeed in its goal of direct measurement of gravitational waves, many subsystems must work together to measure the distance between proof masses on adjacent spacecraft. One such subsystem, the telescope, plays a critical role as it is the laser transmission and reception link between spacecraft. Not only must the material that makes up the telescope support structure be strong, stiff, and light, but it must have a dimensional stability of better than 1 pm Hz(-1/2) at 3 mHz and the distance between the primary and the secondary mirrors must change by less than 2.5 μm over the mission lifetime. Carbon fiber reinforced polymer is the current baseline material; however, it has not been tested to the pico meter level as required by the LISA mission. In this paper, we present dimensional stability results, outgassing effects occurring in the cavity and discuss its feasibility for use as the telescope spacer for the LISA spacecraft. PMID:22225234

  5. Measurement of air-refractive-index fluctuation from frequency change using a phase modulation homodyne interferometer and an external cavity laser diode

    NASA Astrophysics Data System (ADS)

    Ishige, Masashi; Aketagawa, Masato; Banh Quoc, Tuan; Hoshino, Yuta

    2009-08-01

    We present a method for air-refractive-index (nair) fluctuation measurement using a laser interferometer. The method is based on a combination of a phase modulation homodyne interferometer (PMHI), an external cavity laser diode (ECLD) and an ultralow thermal expansion material (ULTEM). The PMHI utilizes a Michelson interferometer which is constructed on the ULTEM plate under the condition of an air temperature fluctuation of less than 10 mK, so that the optical path change or the air-refractive-index fluctuation (Δnair) caused by the thermal disturbance can be neglected. Meanwhile, the ECLD is controlled by adjusting its frequency to track some of the dark fringes of the interferometer, so that Δnair can be derived from the ECLD frequency change. The uncertainty of the Δnair measurement in the experiment is of 10-8 order. However, it will be possible to decrease the uncertainty to 10-9 or less if the signal-to-noise ratio (SNR) of the control system is improved.

  6. Length Scales in Bayesian Automatic Adaptive Quadrature

    NASA Astrophysics Data System (ADS)

    Adam, Gh.; Adam, S.

    2016-02-01

    Two conceptual developments in the Bayesian automatic adaptive quadrature approach to the numerical solution of one-dimensional Riemann integrals [Gh. Adam, S. Adam, Springer LNCS 7125, 1-16 (2012)] are reported. First, it is shown that the numerical quadrature which avoids the overcomputing and minimizes the hidden floating point loss of precision asks for the consideration of three classes of integration domain lengths endowed with specific quadrature sums: microscopic (trapezoidal rule), mesoscopic (Simpson rule), and macroscopic (quadrature sums of high algebraic degrees of precision). Second, sensitive diagnostic tools for the Bayesian inference on macroscopic ranges, coming from the use of Clenshaw-Curtis quadrature, are derived.

  7. Visible intracavity laser spectroscopy with a step-scan Fourier-transform interferometer.

    PubMed

    Strong, K; Johnson, T J; Harris, G W

    1997-11-20

    A Fourier-transform spectrometer has been used in a step-scan mode to make time-resolved measurements of the evolving laser pulse in intracavity laser spectroscopy (ILS) experiments. Spectra of broadband dye laser pulses at approximately 615 nm were recorded at relatively high spectral (0.5-cm(-1)) and temporal (as high as 5-mus) resolution. In the absence of an absorber, the height of the pulse is shown to be proportional to t(g)(0.57) (where t(g) is the generation time) for generation times as high as 500 mus. The system was constructed for feasibility studies of future use at infrared and near-infrared wavelengths where conventional ILS that uses diode arrays would be either expensive or simply not possible. The CH(4) overtone transition at 619.68 nm was used to test the linearity and sensitivity of the system. Comparable performance to conventional ILS systems was demonstrated, as were the advantages of the present system for studies of laser and absorption dynamics. PMID:18264398

  8. Improved straightness interferometer for nanometrology

    NASA Astrophysics Data System (ADS)

    Wu, Chien-Ming

    2005-02-01

    The interferometers which measure the displacement parallel to the measurement axis are called linear interferometers, while those measure the displacement orthogonal to the measurement axis are called straightness interferometers. Theoretically, the orthogonal characteristic between the displacement and the measurement axis does not introduce optical path difference (OPD) and thus, makes null signal. These lead to the straightness interferometer difficult to be implemented. A generalized laser interferometer system based on three design principles, the heterodyne frequency, the avoiding mixing, and the perfect symmetry, is described. These design principles give rise to the interferometer a highly stable system with no periodic nonlinearity. A novel straightness sensor, consisting of a straightness prism and a straightness reflector, is incorporated into the generalized system to form a straightness interferometer. With the help of a Hewlett-Packard commercial linear interferometer, the validity of the developed straightness interferometer has verified. Based on the present design, the interferometer has a gain of 0.348, a periodic nonlinearity of less than 40 picometers, and a displacement noise of 4 pm/√Hz at bandwidth 7.8 kHz. This system is useful in precision straightness measurement.

  9. Optically Recording Velocity Interferometer System: Applications and Challenges

    NASA Astrophysics Data System (ADS)

    Cooper, Marcia

    2015-06-01

    The Optically Recording Velocity Interferometer System (ORVIS) is a useful variant of the single point Velocity Interferometer System Any Reflector (VISAR) for the measurement of spatially dependent surface motion. Despite being similar in name, the two systems fundamentally differ in terms of the light recombination afforded by the interferometer geometry and subsequent recording method of the fringe phase variations. While both techniques have long been established as useful measurement technologies in shock physics studies of homogeneous and heterogeneous materials, the number of researchers employing spatially resolved ORVIS remains small. The first part of this presentation will discuss the baseline system including data examples only possible with the diagnostic's ability for continuous spatial recording. Recent adaptations of the baseline system have extended capabilities to incorporate multiple interferometers and laser illumination sources for observations in multiple spatial dimensions and non-planar geometries. The second part of this presentation will discuss efforts to overcome noted practical challenges when fielding the diagnostic and post-processing of image data. Application to non-planar geometries and highly heterogeneous materials motivates an appreciation of the coupling between the target surface reflectance properties and the light collection optics which can be quantitatively assessed through the bidirectional reflectance distribution function (BRDF) of the reflector. Challenges of practically locating fringe jumps in post-processing are discussed in the context of appreciating the underlying quadrature relationships of the fringe records. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  10. A simple far-infrared laser interferometer for measuring electron densities in reactive low-temperature plasmas

    SciTech Connect

    Pargmann, C.; Singh, S.V.; Soltwisch, H.

    2005-11-15

    A sensitive far-infrared (fir) interferometer for electron density measurements in reactive low-temperature plasmas is described. The instrument is based on an optically pumped fir laser (wavelength range 50-600 {mu}m depending on the working gas) and makes use of the nonlinear relation between output power and cavity loss. The fir beam, which leaves the resonator through a coupling hole in the end mirror, is reflected back into the cavity, such that the coupling hole behaves like a variable 'leak' with a loss rate depending on the phase of the reentering wave relative to the standing wave within the resonator. As a result of the feedback, the output intensity undergoes strong nonlinear variations if the optical distance of the external mirror is changed by small amounts, {delta}z. The power variation is monitored through a small opening in the external mirror. Test experiments using a wavelength of 432.6 {mu}m and a Schottky-diode detector have yielded a minimum detectable pathlength variation of {delta}z=0.4 {mu}m, corresponding to a change of the line-integrated electron density n{sub e}xL of about 5x10{sup 15} m{sup -2}. A first application to argon plasmas in inductively coupled rf discharges has been made, and the results have been compared to concomitant Langmuir probe measurements.

  11. Laser Interferometer Skin-Friction measurements of crossing-shock wave/turbulent boundary-layer interactions

    NASA Technical Reports Server (NTRS)

    Garrison, T. J.; Settles, G. S.

    1993-01-01

    Wall shear stress measurements beneath crossingshock wave/turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symmetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 degrees at Mach 3 and 15 degrees at Mach 4. The measurements were made using a Laser Interferometer Skin Friction (LISF) meter; a device which determines the wail shear by optically measuring the time rate of thinning of an oil film placed on the test model surface. Results of the measurements reveal high skin friction coefficients in the vicinity of the fin/plate junction and the presence of quasi-two-dimensional flow separation on the interaction centerline. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k- model, are compared to the experimental results for the Mach 4, 15 degree interaction case. While the k- model did a reasonable job of predicting the overall trend in portions of the skin friction distribution, neither computation fully captured the physics of the near surface flow in this complex interaction.

  12. Laser Interferometer Skin-Friction measurements of crossing-shock wave/turbulent boundary-layer interactions

    NASA Astrophysics Data System (ADS)

    Garrison, T. J.; Settles, G. S.

    1993-07-01

    Wall shear stress measurements beneath crossingshock wave/turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symmetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 degrees at Mach 3 and 15 degrees at Mach 4. The measurements were made using a Laser Interferometer Skin Friction (LISF) meter; a device which determines the wail shear by optically measuring the time rate of thinning of an oil film placed on the test model surface. Results of the measurements reveal high skin friction coefficients in the vicinity of the fin/plate junction and the presence of quasi-two-dimensional flow separation on the interaction centerline. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k-~ model, are compared to the experimental results for the Mach 4, 15 degree interaction case. While the k-~ model did a reasonable job of predicting the overall trend in portions of the skin friction distribution, neither computation fully captured the physics of the near surface flow in this complex interaction.

  13. Interferometers adaptations to lidars

    NASA Technical Reports Server (NTRS)

    Porteneuve, J.

    1992-01-01

    To perform daytime measurements of the density and temperature by Rayleigh lidar, it is necessary to select the wavelength with a very narrow spectral system. This filter is composed by an interference filter and a Fabry Perot etalon. The Fabry Perot etalon is the more performent compound, and it is necessary to build a specific optic around it. The image of the entrance pupil or the field diaphragm is at the infinite and the other diaphragm is on the etalon. The optical quality of the optical system is linked to the spectral resolution of the system to optimize the reduction of the field of view. The resolution is given by the formula: R = 8(xD/Fd)exp 2 where R = lambda/delta(lambda), x = diameter of the field diaphragm, D = diameter of the reception mirror, F = focal length of the telescope, and d = useful diameter of the etalon. In the Doppler Rayleigh lidars, the PF interferometer is the main part of the experiment and the exact spectral adaptation is the most critical problem. In the spectral adaptation of interferometers, the transmittance of the system will be acceptable if the etalon is exactly adjusted to the wavelength of the laser. It is necessary to work with a monomode laser, and adjust the shift to the bandpass of the interferometer. We are working with an interferometer built with molecular optical contact. This interferometer is put in a special pressure closed chamber.

  14. Quadrature formulas for Fourier coefficients

    NASA Astrophysics Data System (ADS)

    Bojanov, Borislav; Petrova, Guergana

    2009-09-01

    We consider quadrature formulas of high degree of precision for the computation of the Fourier coefficients in expansions of functions with respect to a system of orthogonal polynomials. In particular, we show the uniqueness of a multiple node formula for the Fourier-Tchebycheff coefficients given by Micchelli and Sharma and construct new Gaussian formulas for the Fourier coefficients of a function, based on the values of the function and its derivatives.

  15. Switchable multi-wavelength erbium-doped fiber ring laser based on cascaded polarization maintaining fiber Bragg gratings in a Sagnac loop interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Ning, Tigang; Jian, Shuisheng

    2008-12-01

    A switchable multi-wavelength erbium-doped fiber (EDF) ring laser based on cascaded polarization maintaining fiber Bragg gratings (PMFBGs) in a Sagnac loop interferometer as the wavelength-selective filter at room temperature is proposed. Due to the polarization hole burning (PHB) enhanced by the PMFBGs, stable single-, dual-, three- and four-wavelength lasing operations can be obtained. The laser can be switched among the stable single-, dual-, three- and four-wavelength lasing operations by adjusting the polarization controllers (PCs). The optical signal-to-noise ratio (OSNR) is over 50 dB.

  16. Switchable multi-wavelength fiber ring laser based on a compact in-fiber Mach-Zehnder interferometer with photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Chen, W. G.; Lou, S. Q.; Feng, S. C.; Wang, L. W.; Li, H. L.; Guo, T. Y.; Jian, S. S.

    2009-11-01

    Switchable multi-wavelength fiber ring laser with an in-fiber Mach-Zehnder interferometer incorporated into the ring cavity serving as wavelength-selective filter at room temperature is demonstrated. The filter is formed by splicing a section of few-mode photonic crystal fiber (PCF) and two segments of single mode fiber (SMF) with the air-holes on the both sides of PCF intentionally collapsed in the vicinity of the splices. By adjusting the states of the polarization controller (PC) appropriately, the laser can be switched among the stable single-, dual- and triple-wavelength lasing operations by exploiting polarization hole burning (PHB) effect.

  17. Dual-wavelength erbium-doped fiber ring laser based on one polarization maintaining fiber Bragg grating in a Sagnac loop interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Li, Honglei; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2008-11-01

    Dual-wavelength with orthogonal polarizations erbium-doped fiber ring laser at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the polarization hole burning (PHB) enhanced by the PMFBG, the laser can operate in stable dual-wavelength operation with wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 52 dB. The amplitude variation in nearly one and half an hour is less than 0.6 dB for both wavelengths.

  18. Wide single-mode tuning in quantum cascade lasers with asymmetric Mach-Zehnder interferometer type cavities with separately biased arms

    NASA Astrophysics Data System (ADS)

    Zheng, Mei C.; Liu, Peter Q.; Wang, Xiaojun; Fan, Jen-Yu; Troccoli, Mariano; Gmachl, Claire F.

    2013-11-01

    We report on the experimental demonstration of a widely tunable single mode quantum cascade laser with Asymmetric Mach-Zehnder (AMZ) interferometer type cavities with separately biased arms. Current and, consequently, temperature tuning of the two arms of the AMZ type cavity resulted in a single mode tuning range of 20 cm-1 at 80 K in continuous-wave mode operation, a ten-fold improvement from the lasers under a single bias current. In addition, we also observed a five fold increase in the tuning rate as compared to the AMZ cavities controlled by one bias current.

  19. Phase modulated self-mixing interferometer of a fiber laser system

    NASA Astrophysics Data System (ADS)

    Hao, Hui; Wang, Ming; Xia, Wei; Guo, Dongmei; Lu, Huali

    2013-10-01

    In this paper, self-mixing interference measurement based on phase modulation is demonstrated using a fiber laser system. The measurement setup is built by an erbium-doped fiber laser and an integrated-optic phase modulator. Optical feedback and phase modulated interference is theoretically analyzed, and the phase demodulation algorithm of the interference signal is implemented by Fourier analysis. Error sources induced by the distortion of the interference signal in the presence of optical feedback and the imperfect alignment between the polarization of the light and the electro-optically active axis are evaluated in detail. The system is experimentally applied to reconstruct the motion of a high-precision commercial PZT and a displacement measurement accuracy of ?/20 is obtained, providing a practically feasible solution for displacement measurement based on all optical-fiber sensing applications with high precision.

  20. Laser Interferometer Measurements of the Viscoelastic Properties of Tectorial Membrane Mutants

    NASA Astrophysics Data System (ADS)

    Jones, Gareth; Russell, Ian; Lukashkin, Andrei

    2011-11-01

    The visco-elastic properties of the tectorial membrane (TM) can be determined by measuring the propagation velocity of travelling waves over a range of frequencies. This study presents a new method using laser interferometry and compares the TM's material properties (sheer storage modulus, G' and viscosity, η) at basal and apical locations in wild-type mice and basal locations of three mutant groups (TectaY1870C/+, Tectb-/- and Otoa-/-). The G' and η values calculated for the wild-type mice are similar to estimates derived using other methods whereas the mutant groups all exhibit slower wave propagation velocities and reduced longitudinal coupling.

  1. Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer

    NASA Astrophysics Data System (ADS)

    Hitachi, K.; Ishizawa, A.; Tadanaga, O.; Nishikawa, T.; Mashiko, H.; Sogawa, T.; Gotoh, H.

    2015-06-01

    We report the stabilization of the carrier-envelope offset (CEO) frequency of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer. The interferometer is implemented by a dual-pitch periodically poled lithium niobate ridge waveguide with two different quasi-phase matching pitch sizes. We obtain a 52-dB signal-to-noise ratio in the 100-kHz resolution bandwidth of a heterodyne beat signal, which is sufficient for frequency stabilization. We also demonstrate that the collinear geometry is robust against environmental perturbation by comparing in-loop and out-of-loop Allan deviations when the in-loop CEO frequency is stabilized with a phase-locked loop circuit.

  2. Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer

    SciTech Connect

    Hitachi, K. Ishizawa, A.; Mashiko, H.; Sogawa, T.; Gotoh, H.; Tadanaga, O.; Nishikawa, T.

    2015-06-08

    We report the stabilization of the carrier-envelope offset (CEO) frequency of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer. The interferometer is implemented by a dual-pitch periodically poled lithium niobate ridge waveguide with two different quasi-phase matching pitch sizes. We obtain a 52-dB signal-to-noise ratio in the 100-kHz resolution bandwidth of a heterodyne beat signal, which is sufficient for frequency stabilization. We also demonstrate that the collinear geometry is robust against environmental perturbation by comparing in-loop and out-of-loop Allan deviations when the in-loop CEO frequency is stabilized with a phase-locked loop circuit.

  3. 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.

  4. Instantaneous quadrature low-coherence interferometry with 3 x 3 fiber-optic couplers.

    PubMed

    Choma, Michael A; Yang, Changhuei; Izatt, Joseph A

    2003-11-15

    We describe fiber-based quadrature low-coherence interferometers that exploit the inherent phase shifts of 3 x 3 and higher-order fiber-optic couplers. We present a framework based on conservation of energy to account for the interferometric shifts in 3 x 3 interferometers, and we demonstrate that the resulting interferometers provide the entire complex interferometric signal instantaneously in homodyne and heterodyne systems. In heterodyne detection we demonstrate the capability for extraction of the magnitude and sign of Doppler shifts from the complex data. In homodyne detection we show the detection of subwavelength sample motion. N x N (N > 2) low-coherence interferometer topologies will be useful in Doppler optical coherence tomography (OCT), optical coherence microscopy, Fourier-domain OCT, optical frequency domain reflectometry, and phase-referenced interferometry. PMID:14649928

  5. Quadrature Component Analysis for interferometry

    NASA Astrophysics Data System (ADS)

    Vargas, J.; Sorzano, C. O. S.

    2013-05-01

    This work presents a generalization of the Principal Component Analysis (PCA) demodulation approach that is renamed as Quadrature Component Analysis. We show a new and general mathematical analysis of this demodulation algorithm and we demonstrate that this method is not affected by the number of fringes limitation. Additionally, we show that any asynchronous phase-shifting demodulation method is affected by a global phase sign indetermination, if no information is given about the phase-shifts. We have tested the proposed method with simulated and experimental interferograms obtaining satisfactory results. A complete MATLAB software package is provided in [http://goo.gl/JWNUr].

  6. Optical frequency comb generator based on a monolithically integrated passive mode-locked ring laser with a Mach-Zehnder interferometer.

    PubMed

    Corral, V; Guzmán, R; Gordón, C; Leijtens, X J M; Carpintero, G

    2016-05-01

    We report the demonstration of an optical-frequency comb generator based on a monolithically integrated ring laser fabricated in a multiproject wafer run in an active/passive integration process in a generic foundry using standardized building blocks. The device is based on a passive mode-locked ring laser architecture, which includes a Mach-Zehnder interferometer to flatten the spectral shape of the comb output. This structure allows monolithic integration with other optical components, such as optical filters for wavelength selection, or dual wavelength lasers for their stabilization. The results show a -10  dB span of the optical comb of 8.7 nm (1.08 THz), with comb spacing of 10.16 GHz. We also obtain a flatness of 44 lines within a 1.8 dB power variation. PMID:27128043

  7. Earth Strain Measurements with a Laser Interferometer: An 800-meter Michelson interferometer monitors the earth's strain field on the surface of the ground.

    PubMed

    Berger, J; Lovberg, R H

    1970-10-16

    The development of the laser as a source of coherent optical radiation has permitted the application of interferometric techniques to the problem of earth strain measurement. By use of this technology, an 800-meter laser strain meter has been developed which operates above the surface of the ground. The instrument has a strain least count of 10(-10), requires no calibration, and has a flat and linear response from zero frequency to 1 megahertz. The linearity and large dynamic range of the laser strain meter offer unprecedented versatility in the recording of seismic strains associated with earthquakes and nuclear blasts. The extremely wide bandwidth opens new areas of the strain spectrum to investigation. A key to the understanding of the state of stress of the earth and the association phenomona of tectonic activity and earthquakes is a knowledge of the spatial distribution of the earth strain. Measurements of secular strain and earth tides indicate that, even at these long periods, surface strain measurements are valid representations of earth strain at depth. The LSM thus provides a means of making crustal strain measurements at points selected for maximum geophysical interest and ultimately allow the mapping of strain field distributions. PMID:17731304

  8. Laser anemometer using a Fabry-Perot interferometer for measuring mean velocity and turbulence intensity along the optical axis in turbomachinery

    NASA Technical Reports Server (NTRS)

    Seasholtz, R. G.; Goldman, L. J.

    1982-01-01

    A technique for measuring a small optical axis velocity component in a flow with a large transverse velocity component is presented. Experimental results are given for a subsonic free jet operating in a laboratory environment, and for a 0.508 meter diameter turbine stator cascade. Satisfactory operation of the instrument was demonstrated in the stator cascade facility with an ambient acoustic noise level during operation of about 105 dB. In addition, the turbulence intensity measured with the interferometer was consistent with previous measurements taken with a fringe type laser anemometer.

  9. Quadrature drift of dynamically adjustable gyroscopes

    NASA Astrophysics Data System (ADS)

    Zbrutskii, A. V.; Shevchuk, N. P.; Vinogradov, G. M.

    Elastic deformations of the suspension are shown to cause the quadrature drift of dynamically adjustable gyroscopes. The forms of symmetry of the gimbal suspensions of one-ring and two-ring gyros in the case of which the drift is absent are defined. Analytical expressions are obtained for assessing the influence of fabrication-related flaws on the quadrature drift.

  10. Automatic quadrature control and measuring system

    NASA Technical Reports Server (NTRS)

    Hamlet, J. F.

    1973-01-01

    Quadrature is separated from amplified signal by use of phase detector, with phase shifter providing appropriate reference. Output of phase detector is further amplified and filtered by dc amplifier. Output of dc amplifier provides signal to neutralize quadrature component of transducer signal.

  11. Error Analysis of Quadrature Rules. Classroom Notes

    ERIC Educational Resources Information Center

    Glaister, P.

    2004-01-01

    Approaches to the determination of the error in numerical quadrature rules are discussed and compared. This article considers the problem of the determination of errors in numerical quadrature rules, taking Simpson's rule as the principal example. It suggests an approach based on truncation error analysis of numerical schemes for differential…

  12. Compact portable diffraction moire interferometer

    DOEpatents

    Deason, V.A.; Ward, M.B.

    1988-05-23

    A compact and portable moire interferometer used to determine surface deformations of an object. The improved interferometer is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent wave splitters, and collimating lenses directing the split beam at one or more specimen gratings. Observations means including film and video cameras may be used to view and record the resultant fringe patterns. 7 figs.

  13. Compact portable diffraction moire interferometer

    DOEpatents

    Deason, Vance A.; Ward, Michael B.

    1989-01-01

    A compact and portable moire interferometer used to determine surface deformations of an object. The improved interferometer is comprised of a laser beam, optical and fiber optics devices coupling the beam to one or more evanescent wave splitters, and collimating lenses directing the split beam at one or more specimen gratings. Observation means including film and video cameras may be used to view and record the resultant fringe patterns.

  14. Semiconductor laser self-mixing micro-vibration measuring technology based on Hilbert transform

    NASA Astrophysics Data System (ADS)

    Tao, Yufeng; Wang, Ming; Xia, Wei

    2016-06-01

    A signal-processing synthesizing Wavelet transform and Hilbert transform is employed to measurement of uniform or non-uniform vibrations in self-mixing interferometer on semiconductor laser diode with quantum well. Background noise and fringe inclination are solved by decomposing effect, fringe counting is adopted to automatic determine decomposing level, a couple of exact quadrature signals are produced by Hilbert transform to extract vibration. The tempting potential of real-time measuring micro vibration with high accuracy and wide dynamic response bandwidth using proposed method is proven by both simulation and experiment. Advantages and error sources are presented as well. Main features of proposed semiconductor laser self-mixing interferometer are constant current supply, high resolution, simplest optical path and much higher tolerance to feedback level than existing self-mixing interferometers, which is competitive for non-contact vibration measurement.

  15. Density Profile of the ZaP Flow Z-pinch Plasma using a 4-chord Interferometer

    NASA Astrophysics Data System (ADS)

    Chan, B. J.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.

    2007-11-01

    The ZaP experiment focuses on the goal of generating a sheared flow stable Z-pinch plasma. This study investigates the density measurements of ZaP using a 4-chord, Mach-Zehnder configuration, heterodyne quadrature interferometer driven by a HeNe laser with a 632.8 nm wavelength. A single Bragg cell is used to split the laser beam and add a 40 MHz beat to the reference beam. The beams can be as close as 4 mm while the plasma has a 1 cm characteristic radius during the quiescent period. Radial density profiles along the z-axis can be determined using an Abel inversion technique. The axial variation of the plasma can also be determined by distributing the chords axially. These measurements will augment the temperature measurements made by the Thomson scattering system, helping to determine the Z-pinch pressure and current profiles. Experimental density measurements will be presented.

  16. A multiwavelength Er-doped fiber laser using a nonlinear optical loop mirror and a twin-core fiber-based Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Zou, Hui

    2013-04-01

    A multiwavelength Er-doped fiber (EDF) laser was proposed and experimentally demonstrated using a nonlinear optical loop mirror (NOLM) and a twin-core fiber-based Mach-Zehnder interferometer (TCF MZI). A total of 40 lasing wavelengths around the wavelength of 1560 nm with an average signal-to-noise ratio (SNR) of 28 dB and 30 lasing wavelengths around the wavelength of 1530 nm with an average SNR of 20 dB were achieved when the EDF length was 6 and 2 m, respectively. To the best of our knowledge, this is the first time that multiwavelength oscillations have been obtained in the wavelength range of 1530 nm by using a NOLM. The wavelength spacing is ˜0.19 nm which is determined by the TCF MZI. In addition, the effects of the pump power and the state of polarization on the performance of the multiwavelength EDF laser were investigated.

  17. Switchable dual-wavelength erbium-doped fiber-ring laser based on one polarization maintaining fiber Bragg grating in a Sagnac loop interferometer

    NASA Astrophysics Data System (ADS)

    Feng, Suchun; Xu, Ou; Lu, Shaohua; Mao, Xiangqiao; Ning, Tigang; Jian, Shuisheng

    2009-04-01

    A switchable erbium-doped fiber-ring laser providing dual-wavelength outputs with orthogonal polarizations when operating at room temperature is proposed. One polarization-maintaining fiber Bragg grating (PMFBG) in a Sagnac loop interferometer is used as the wavelength-selective filter. Due to the enhancement of the polarization hole burning (PHB) by the PMFBG, the laser can be designed to operate in stable dual-wavelength or wavelength-switching modes with a wavelength spacing of 0.336 nm at room temperature by adjusting a polarization controller (PC). The optical signal-to-noise ratio (OSNR) is over 42 dB. The amplitude variation over 90 min is less than 0.6 dB for both wavelengths.

  18. A Martin-Puplett cartridge FIR interferometer

    SciTech Connect

    Smith, Roger J.; Penniman, Edwin E.; Jarboe, Thomas R.

    2004-10-01

    A compact prealigned Martin-Puplett interferometer (MPI) cartridge for plasma interferometry is described. The MPI cartridge groups all components of a MP interferometer, with the exception of the end mirror for the scene beam, on a stand-alone rigid platform. The interferometer system is completed by positioning a cartridge anywhere along and coaxial with the scene beam, considerably reducing the amount of effort in alignment over a discrete component layout. This allows the interferometer to be expanded to any number of interferometry chords consistent with optical access, limited only by the laser power. The cartridge interferometer has been successfully incorporated as a second chord on the Helicity Injected Torus II (HIT-II) far infrared interferometer system and a comparison with the discrete component system is presented. Given the utility and compactness of the cartridge, a possible design for a five-chord interferometer arrangement on the HIT-II device is described.

  19. Gaussian quadrature formulae for arbitrary positive measures.

    PubMed

    Fernandes, Andrew D; Atchley, William R

    2006-01-01

    We present computational methods and subroutines to compute Gaussian quadrature integration formulas for arbitrary positive measures. For expensive integrands that can be factored into well-known forms, Gaussian quadrature schemes allow for efficient evaluation of high-accuracy and -precision numerical integrals, especially compared to general ad hoc schemes. In addition, for certain well-known density measures (the normal, gamma, log-normal, Student's t, inverse-gamma, beta, and Fisher's F) we present exact formulae for computing the respective quadrature scheme. PMID:19455218

  20. Structured eigenvalue problems for rational gauss quadrature

    NASA Astrophysics Data System (ADS)

    Fasino, Dario; Gemignani, Luca

    2007-08-01

    The connection between Gauss quadrature rules and the algebraic eigenvalue problem for a Jacobi matrix was first exploited in the now classical paper by Golub and Welsch (Math. Comput. 23(106), 221?230, 1969). From then on many computational problems arising in the construction of (polynomial) Gauss quadrature formulas have been reduced to solving direct and inverse eigenvalue problems for symmetric tridiagonals. Over the last few years (rational) generalizations of the classical Gauss quadrature formulas have been studied, i.e., formulas integrating exactly in spaces of rational functions. This paper wants to illustrate that stable and efficient procedures based on structured numerical linear algebra techniques can also be devised for the solution of the eigenvalue problems arising in the field of rational Gauss quadrature.

  1. Liquid-Crystal Point-Diffraction Interferometer

    NASA Technical Reports Server (NTRS)

    Mercer, Carolyn R.

    1996-01-01

    Liquid-crystal point-diffraction interferometer (LCPDI) invented to combine flexible control of liquid-crystal phase-shifts with robustness of point-diffraction interferometers. Produces interferograms indicative of shapes of wavefronts of laser beams having passed through or reflected from objects of interest. Interferograms combined in computers to produce phase maps describing wavefronts.

  2. A low-noise transimpedance amplifier for the detection of “Violin-Mode” resonances in advanced Laser Interferometer Gravitational wave Observatory suspensions

    SciTech Connect

    Lockerbie, N. A.; Tokmakov, K. V.

    2014-11-15

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level “Violin-Mode” (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent “noise-gain peaking” arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations—this output being derived from the difference of the photodiodes’ two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m{sup −1}(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm.

  3. A low-noise transimpedance amplifier for the detection of "Violin-Mode" resonances in Advanced Laser Interferometer Gravitational wave Observatory suspensions.

    PubMed

    Lockerbie, N A; Tokmakov, K V

    2014-11-01

    This paper describes the design and performance of an extremely low-noise differential transimpedance amplifier, which takes its two inputs from separate photodiodes. The amplifier was planned to serve as the front-end electronics for a highly sensitive shadow-displacement sensing system, aimed at detecting very low-level "Violin-Mode" (VM) oscillations in 0.4 mm diameter by 600 mm long fused-silica suspension fibres. Four such highly tensioned fibres support the 40 kg test-masses/mirrors of the Advanced Laser Interferometer Gravitational wave Observatory interferometers. This novel design of amplifier incorporates features which prevent "noise-gain peaking" arising from large area photodiode (and cable) capacitances, and which also usefully separate the DC and AC photocurrents coming from the photodiodes. In consequence, the differential amplifier was able to generate straightforwardly two DC outputs, one per photodiode, as well as a single high-gain output for monitoring the VM oscillations-this output being derived from the difference of the photodiodes' two, naturally anti-phase, AC photocurrents. Following a displacement calibration, the amplifier's final VM signal output was found to have an AC displacement responsivity at 500 Hz of (9.43 ± 1.20) MV(rms) m(-1)(rms), and, therefore, a shot-noise limited sensitivity to such AC shadow- (i.e., fibre-) displacements of (69 ± 13) picometres/√Hz at this frequency, over a measuring span of ±0.1 mm. PMID:25430131

  4. Measurements of line-averaged electron density of pulsed plasmas using a He-Ne laser interferometer in a magnetized coaxial plasma gun device

    NASA Astrophysics Data System (ADS)

    Iwamoto, D.; Sakuma, I.; Kitagawa, Y.; Kikuchi, Y.; Fukumoto, N.; Nagata, M.

    2012-10-01

    In next step of fusion devices such as ITER, lifetime of plasma-facing materials (PFMs) is strongly affected by transient heat and particle loads during type I edge localized modes (ELMs) and disruption. To clarify damage characteristics of the PFMs, transient heat and particle loads have been simulated by using a plasma gun device. We have performed simulation experiments by using a magnetized coaxial plasma gun (MCPG) device at University of Hyogo. The line-averaged electron density measured by a He-Ne interferometer is 2x10^21 m-3 in a drift tube. The plasma velocity measured by a time of flight technique and ion Doppler spectrometer was 70 km/s, corresponding to the ion energy of 100 eV for helium. Thus, the ion flux density is 1.4x10^26 m-2s-1. On the other hand, the MCPG is connected to a target chamber for material irradiation experiments. It is important to measure plasma parameters in front of target materials in the target chamber. In particular, a vapor cloud layer in front of the target material produced by the pulsed plasma irradiation has to be characterized in order to understand surface damage of PFMs under ELM-like plasma bombardment. In the conference, preliminary results of application of the He-Ne laser interferometer for the above experiment will be shown.

  5. Quadrature demodulation technique for self-mixing interferometry displacement sensor

    NASA Astrophysics Data System (ADS)

    Guo, Dongmei

    2011-12-01

    A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.

  6. Modulator-free quadrature amplitude modulation signal synthesis.

    PubMed

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O'Carroll, John; Phelan, Richard; Richardson, David J; Slavík, Radan

    2014-01-01

    The ability to generate high-speed on-off-keyed telecommunication signals by directly modulating a semiconductor laser's drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s(-1)-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on-off-keyed 10 Gbit s(-1) systems and is absolutely prohibitive for today's (>)100 Gbit s(-1) coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions. PMID:25523757

  7. Wavelength independent interferometer

    NASA Technical Reports Server (NTRS)

    Hochberg, Eric B. (Inventor); Page, Norman A. (Inventor)

    1991-01-01

    A polychromatic interferometer utilizing a plurality of parabolic reflective surfaces to properly preserve the fidelity of light wavefronts irrespective of their wavelengths as they pass through the instrument is disclosed. A preferred embodiment of the invention utilizes an optical train which comprises three off-axis parabolas arranged in conjunction with a beam-splitter and a reference mirror to form a Twyman-Green interferometer. An illumination subsystem is provided and comprises a pair of lasers at different preselected wavelengths in the visible spectrum. The output light of the two lasers is coaxially combined by means of a plurality of reflectors and a grating beam combiner to form a single light source at the focal point of the first parabolic reflection surface which acts as a beam collimator for the rest of the optical train. By using visible light having two distinct wavelengths, the present invention provides a long equivalent wavelength interferogram which operates at visible light wherein the effective wavelength is equal to the product of the wavelengths of the two laser sources divided by their difference in wavelength. As a result, the invention provides the advantages of what amounts to long wavelength interferometry but without incurring the disadvantage of the negligible reflection coefficient of the human eye to long wavelength frequencies which would otherwise defeat any attempt to form an interferogram at that low frequency using only one light source.

  8. Analysis on error of laser frequency locking for fiber optical receiver in direct detection wind lidar based on Fabry-Perot interferometer and improvements

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Dou, Xiankang; Sun, Dongsong; Shu, Zhifeng; Xia, Haiyun; Gao, Yuanyuan; Hu, Dongdong; Shangguan, Mingjia

    2014-12-01

    Direct detection Doppler wind lidar (DWL) has been demonstrated for its capability of atmospheric wind detection ranging from the troposphere to stratosphere with high temporal and spatial resolution. We design and describe a fiber-based optical receiver for direct detection DWL. Then the locking error of the relative laser frequency is analyzed and the dependent variables turn out to be the relative error of the calibrated constant and the slope of the transmission function. For high accuracy measurement of the calibrated constant for a fiber-based system, an integrating sphere is employed for its uniform scattering. What is more, the feature of temporally widening the pulse laser allows more samples be acquired for the analog-to-digital card of the same sampling rate. The result shows a relative error of 0.7% for a calibrated constant. For the latter, a new improved locking filter for a Fabry-Perot Interferometer was considered and designed with a larger slope. With these two strategies, the locking error for the relative laser frequency is calculated to be about 3 MHz, which is equivalent to a radial velocity of about 0.53 m/s and demonstrates the effective improvements of frequency locking for a robust DWL.

  9. Infrared lateral shearing interferometers

    NASA Astrophysics Data System (ADS)

    Kwon, O.

    1980-04-01

    Recently IR interferometry has received much attention for its special capabilities of testing IR materials, diamond-turned metal mirrors, deep aspherics, unpolished rough surface optics, and other unconventional optics. A CW CO2 laser is used as a coherent light source at 10.6 microns, and germanium and zinc selenide optics are used for lenses and beam splitters. A pyroelectric vidicon (PEV) detects the modulated interference pattern through a TV monitor and video recorder-player. This paper presents three methods of IR lateral shear interferometry using (1) a germanium plane-parallel plate, (2) a Ronchi ruling, and (3) a double-grating lateral shear interferometer.

  10. Tip-tilt mirror suspension: beam steering for advanced laser interferometer gravitational wave observatory sensing and control signals.

    PubMed

    Slagmolen, Bram J J; Mullavey, Adam J; Miller, John; McClelland, David E; Fritschel, Peter

    2011-12-01

    We describe the design of a small optic suspension system, referred to as the tip-tilt mirror suspension, used to isolate selected small optics for the interferometer sensing and control beams in the advanced LIGO gravitational wave detectors. The suspended optics are isolated in all 6 degrees of freedom, with eigenmode frequencies between 1.3 Hz and 10 Hz. The suspended optic has voice-coil actuators which provide an angular range of ±4 mrad in the pitch and yaw degrees of freedom. PMID:22225250

  11. Tip-tilt mirror suspension: Beam steering for advanced laser interferometer gravitational wave observatory sensing and control signals

    NASA Astrophysics Data System (ADS)

    Slagmolen, Bram J. J.; Mullavey, Adam J.; Miller, John; McClelland, David E.; Fritschel, Peter

    2011-12-01

    We describe the design of a small optic suspension system, referred to as the tip-tilt mirror suspension, used to isolate selected small optics for the interferometer sensing and control beams in the advanced LIGO gravitational wave detectors. The suspended optics are isolated in all 6 degrees of freedom, with eigenmode frequencies between 1.3 Hz and 10 Hz. The suspended optic has voice-coil actuators which provide an angular range of ±4 mrad in the pitch and yaw degrees of freedom.

  12. Past and Future SOHO-Ulysses Quadratures

    NASA Technical Reports Server (NTRS)

    Suess, Steven; Poletto, G.

    2006-01-01

    With the launch of SOHO, it again became possible to carry out quadrature observations. In comparison with earlier observations, the new capabilities of coronal spectroscopy with UVCS and in situ ionization state and composition with Ulysses/SWICS enabled new types of studies. Results from two studies serve as examples: (i) The acceleration profile of wind from small coronal holes. (ii) A high-coronal reconnecting current sheet as the source of high ionization state Fe in a CME at Ulysses. Generally quadrature observations last only for a few days, when Ulysses is within ca. 5 degrees of the limb. This means luck is required for the phenomenon of interest to lie along the radial direction to Ulysses. However, when Ulysses is at high southern latitude in winter 2007 and high northern latitude in winter 2008, there will be unusually favorable configurations for quadrature observations with SOHO and corresponding bracketing limb observations from STEREO A/B. Specifically, Ulysses will be within 5 degrees of the limb from December 2006 to May 2007 and within 10 degrees of the limb from December 2007 to May 2008. These long-lasting quadratures and bracketing STEREO A/B observations overcome the limitations inherent in the short observation intervals of typical quadratures. Furthermore, ionization and charge state measurements like those on Ulysses will also be made on STEREO and these will be essential for identification of CME ejecta - one of the prime objectives for STEREO.

  13. Unequal-Arms Michelson Interferometers

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo; Armstrong, J. W.

    1999-01-01

    Michelson interferometers allow phase measurements many orders of magnitude below the phase stability of the laser light injected into their two almost equal-length arms. If, however, the two arms are unequal, the laser fluctuations can not be removed by simply recombining the two beams. This is because the laser jitters experience different time delays in the two arms, and therefore can not cancel at the photo detector. We present here a method for achieving exact laser noise cancellation, even in an unequal-arm interferometer. The method presented in this paper requires a separate readout of the relative phase in each arm, made by interfering the returning beam in each arm with a fraction of the outgoing beam. By linearly combining the two data sets with themselves, after they have been properly time-shifted, we show that it is possible to construct a new data set that is free of laser fluctuations. An application of this technique to future planned space-based laser interferometer detectors of gravitational radiation is discussed.

  14. Unequal-Arms Michelson Interferometers

    NASA Technical Reports Server (NTRS)

    Tinto, Massimo; Armstrong, J. W.

    2000-01-01

    Michelson interferometers allow phase measurements many orders of magnitude below the phase stability of the laser light injected into their two almost equal-length arms. If, however, the two arms are unequal, the laser fluctuations can not be removed by simply recombining the two beams. This is because the laser jitters experience different time delays in the two arms, and therefore can not cancel at the photo detector. We present here a method for achieving exact laser noise cancellation, even in an unequal-arm interferometer. The method presented in this paper requires a separate readout of the relative phase in each arm, made by interfering the returning beam in each arm with a fraction of the outgoing beam. By linearly combining the two data sets with themselves, after they have been properly time shifted, we show that it is possible to construct a new data set that is free of laser fluctuations. An application of this technique to future planned space-based laser interferometer detector3 of gravitational radiation is discussed.

  15. Handling accuracy in Bayesian automatic adaptive quadrature

    NASA Astrophysics Data System (ADS)

    Adam, Gh; Adam, S.

    2015-06-01

    New Bayesian inferences which significantly extend the coverage of the Bayesian automatic adaptive quadrature (BAAQ) approach to the solution of Riemann integrals are reported. The scrutiny of the possible floating-point machine number approximations of abscissa values inside an integration domain unveiled the occurrence of five classes of integration domains entering the quadrature problems: zero-length, open void, microscopic, mesoscopic, macroscopic. Correct approach to the class identifications and class adapted advancement to the solution are described. In the most complex, macroscopic case, the reversible addition of a new decision branch extends the BAAQ approach coverage to both difficult and easy integrals. The reliability of the code used for solving easy integrals was enhanced with four new analysis tools as compared to the standard automatic adaptive quadrature solution.

  16. Theory of the quadrature elliptic birdcage coil.

    PubMed

    Leifer, M C

    1997-11-01

    This paper presents the theory of the quadrature birdcage coil wound on an elliptic cylindrical former. A conformal transformation of the ellipse to a circular geometry is used to derive the optimal sampling of the continuous surface current distribution to produce uniform magnetic fields within an elliptic cylinder. The analysis is rigorous for ellipses of any aspect ratio and shows how to produce quadrature operation of the elliptic birdcage with a conventional hybrid combiner. Insight gained from the transformation is also used to analyze field homogeneity, find the optimal RF shield shape, and specify component values to produce the correct current distribution in practice. Measurements and images from a 16-leg elliptic birdcage coil at both low and high frequencies show good quadrature performance, homogeneity, and sensitivity. PMID:9358446

  17. Quadrature formulae for problems in mechanics

    NASA Astrophysics Data System (ADS)

    Milovanović, Gradimir V.; Igić, Tomislav; Tončev, Novica

    2012-09-01

    The fast progress in recent years in symbolic computation and variable-precision arithmetic provide a possibility for generating the recursion coefficients in the three-term recurrence relation for orthogonal polynomials with respect to several nonclassical weight functions, as well as the construction of the corresponding quadrature rules of Gaussian type. Such quadratures are very important in many applications in engineering (fracture mechanics, damage mechanics, etc.), as well as in other computational and applied sciences. The boundary element method (BEM), finite element method (FEM), methods for solving integral equations, etc. very often require the numerical evaluation of one dimensional or multiple integrals with singular or near singular integrands with a high precision. In this paper we give some improvements of quadrature rules of Gaussian type with logarithmic and/or algebraic singularities. A numerical examples is included.

  18. Robust Spatiotemporal Quadrature Filter for Multiphase Stepping

    NASA Astrophysics Data System (ADS)

    Rivera, Mariano; Marroquin, Jose L.; Botello, Salvador; Servín, Manuel

    2000-01-01

    A robust algorithm for phase recovery from multi-phase-stepping images is presented. This algorithm is based on the minimization of an energy (cost) functional and is equivalent to the simultaneous application of a fixed temporal quadrature filter and a spatial adaptive quadrature filter to the phase-stepping pattern ensemble. The algorithm, believed to be new, is specially suited for those applications in which a large number of phase-stepping images may be obtained, e.g., profilometry with a computer-controlled fringe projector. We discuss the selection of parameter values and present examples of its performance in both synthetic and real image sequences.

  19. Summation Paths in Clenshaw-Curtis Quadrature

    NASA Astrophysics Data System (ADS)

    Adam, S.; Adam, Gh.

    2016-02-01

    Two topics concerning the use of Clenshaw-Curtis quadrature within the Bayesian automatic adaptive quadrature approach to the numerical solution of Riemann integrals are considered. First, it is found that the efficient floating point computation of the coefficients of the Chebyshev series expansion of the integrand is to be done within a mathematical structure consisting of the union of coefficient families ordered into complete binary trees. Second, the scrutiny of the decay rates of the involved even and odd rank Chebyshev expansion coefficients with the increase of their rank labels enables the definition of Bayesian decision paths for the advancement to the numerical output.

  20. Tunable multi-wavelength erbium-doped fiber laser by cascading a standard Mach-Zehnder interferometer and a twin-core fiber-based filter

    NASA Astrophysics Data System (ADS)

    Yin, Guolu; Lou, Shuqin; Wang, Xin; Han, Bolin

    2013-12-01

    A tunable multi-wavelength erbium-doped fiber laser (MEDFL) based on a nonlinear optical loop mirror (NOLM) was proposed and experimentally demonstrated by cascading a standard Mach-Zehnder interferometer (MZI) and a twin-core fiber (TCF)-based filter. Due to the ‘blue shift’ of the transmission band of the TCF-based filter when the TCF was bent, a tunable lasing waveband was realized by moving the transmission band of the TCF-based filter to cover different channels provided by the standard MZI. Experimental results showed that the lasing waveband can be linearly tuned over a range of 24 nm from 1542 to 1566 nm with a channel spacing of 0.4 nm, a maximum lasing line amount of 19, and an optical signal to noise ratio (OSNR) of 39 dB. The stability of the laser spectra was verified with a wavelength drift of 0.04 nm and a power fluctuation of ±0.3 dB.

  1. Robust, accurate, and non-contacting vibration measurement systems: Summary of comparison measurements of the robust laser interferometer and typical accelerometer systems. Volume 1

    SciTech Connect

    Goodenow, T.C.; Shipman, R.L.; Holland, H.M.

    1995-06-01

    Epoch Engineering, Incorporated (EEI) has completed a series of vibration measurements comparing their newly-developed Robust Laser Interferometer (RLI) with accelerometer-based instrumentation systems. EEI has successfully demonstrated, on several pieces of commonplace machinery, that non-contact, line-of-sight measurements are practical and yield results equal to or, in some cases, better than customary field implementations of accelerometers. The demonstration included analysis and comparison of such phenomena as nonlinearity, transverse sensitivity, harmonics, and signal-to-noise ratio. Fast Fourier Transformations were performed on the accelerometer and the laser system outputs to provide a comparison basis. The RLI was demonstrated, within the limits of the task, to be a viable, line-of-sight, non-contact alternative to accelerometer systems. Several different kinds of machinery were instrumented and compared, including a small pump, a gear-driven cement mixer, a rotor kit, and two small fans. Known machinery vibration sources were verified and RLI system output file formats were verified to be compatible with commercial computer programs used for vibration monitoring and trend analysis. The RLI was also observed to be less subject to electromagnetic interference (EMI) and more capable at very low frequencies.

  2. Robust, accurate, and non-contacting vibration measurement systems: Supplemental appendices presenting comparison measurements of the robust laser interferometer and typical accelerometer systems. Volume 2

    SciTech Connect

    Goodenow, T.C.; Shipman, R.L.; Holland, H.M.

    1995-06-01

    Epoch Engineering, Incorporated (EEI) has completed a series of vibration measurements comparing their newly-developed Robust Laser Interferometer (RLI) with accelerometer-based instrumentation systems. EEI has successfully demonstrated, on several pieces of commonplace machinery, that non-contact, line-of-sight measurements are practical and yield results equal to or, in some cases, better than customary field implementations of accelerometers. The demonstration included analysis and comparison of such phenomena as nonlinearity, transverse sensitivity, harmonics, and signal-to-noise ratio. Fast Fourier Transformations were performed on the accelerometer and the laser system outputs to provide a comparison basis. The RLI was demonstrated, within the limits o the task, to be a viable, line-of-sight, non-contact alternative to accelerometer systems. Several different kinds of machinery were instrumented and. compared, including a small pump, a gear-driven cement mixer, a rotor kit, and two small fans. Known machinery vibration sources were verified and RLI system output file formats were verified to be compatible with commercial computer programs used for vibration monitoring and trend analysis. The RLI was also observed to be less subject to electromagnetic interference (EMI) and more capable at very low frequencies. This document, Volume 2, provides the appendices to this report.

  3. Composite Gauss-Legendre Quadrature with Error Control

    ERIC Educational Resources Information Center

    Prentice, J. S. C.

    2011-01-01

    We describe composite Gauss-Legendre quadrature for determining definite integrals, including a means of controlling the approximation error. We compare the form and performance of the algorithm with standard Newton-Cotes quadrature. (Contains 1 table.)

  4. Thin-thick quadrature frequency conversion

    SciTech Connect

    Eimerl, D.

    1985-02-07

    The quadrature conversion scheme is a method of generating the second harmonic. The scheme, which uses two crystals in series, has several advantages over single-crystal or other two crystal schemes. The most important is that it is capable of high conversion efficiency over a large dynamic range of drive intensity and detuning angle.

  5. Gauss-Laguerre interval quadrature rule

    NASA Astrophysics Data System (ADS)

    Milovanovic, Gradimir V.; Cvetkovic, Aleksandar S.

    2005-10-01

    In this paper we prove the existence and uniqueness of the Gaussian interval quadrature formula with respect to the generalized Laguerre weight function. An algorithm for numerical construction has also investigated and some suitable solutions are proposed. A few numerical examples are included.

  6. Numerical simulation by the quadrature and cubature methods

    SciTech Connect

    Civan, F.

    1994-12-31

    In this paper, practical quadrature and cubature formula for numerical differentiation, integration, interpolation, and extrapolation purposes are derived; the method for determination of the quadrature and cubature weights is given, and the procedure for development of finite-analytic quadrature and cubature schemes is presented. It is demonstrated that these methods provide rapid and practical means of obtaining algebraic discretization formula for numerical approximation.

  7. Error Bounds for Quadrature Methods Involving Lower Order Derivatives

    ERIC Educational Resources Information Center

    Engelbrecht, Johann; Fedotov, Igor; Fedotova, Tanya; Harding, Ansie

    2003-01-01

    Quadrature methods for approximating the definite integral of a function f(t) over an interval [a,b] are in common use. Examples of such methods are the Newton-Cotes formulas (midpoint, trapezoidal and Simpson methods etc.) and the Gauss-Legendre quadrature rules, to name two types of quadrature. Error bounds for these approximations involve…

  8. Novel interferometer

    NASA Astrophysics Data System (ADS)

    Williamson, Ray

    2004-01-01

    Thin, visibly opaque components for use in infrared transmission present a challenge in tolerancing and manufacture: Most optical shops do not have access to infrared interferometry and so must evaluate the opposing surfaces in visible light. The inevitable bending of thin parts will create surface deformations that are individually far in excess of allowable limits. However if the opposing surface deformations track each other, the part may be perfectly functional. The dilemma is between over-specification of the surfaces and consequent multiplication in costs and schedule; vs. verification in the infrared, thus eliminating most perfectly competent vendors. Herein, I present a novel interferometric cavity setup utilizing a standard, commercial interferometer, in which the test beam reflects twice from each side, in point by point registration across the aperture. I also present fringe-scaling factors based on angle of incidence and index of refraction. The cavity error can be conveniently subtracted. Small wedge can be measured or eliminated, or if desired, large wedge can be eliminated. The components can, thus, be specified and verified functionally with significant reduction in difficulty and cost. NOTE: this work was presented at SPIE in 1991, v 1527 p 188. The audience that day was very small. I think the technique remains valuable and virtually unknown.

  9. Comparative Sensitivities of Gravitational Wave Detectors Based on Atom Interferometers and Light Interferometers

    NASA Technical Reports Server (NTRS)

    Baker, John G.; Thorpe, J. I.

    2012-01-01

    We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe. Whether this potential advantage outweighs the additional complexity associated with including atom interferometers will require further study.

  10. Digital holographic interferometer using simultaneously three lasers and a single monochrome sensor for 3D displacement measurements.

    PubMed

    Saucedo-A, Tonatiuh; De la Torre-Ibarra, M H; Santoyo, F Mendoza; Moreno, Ivan

    2010-09-13

    The use of digital holographic interferometry for 3D measurements using simultaneously three illumination directions was demonstrated by Saucedo et al. (Optics Express 14(4) 2006). The technique records two consecutive images where each one contains three holograms in it, e.g., one before the deformation and one after the deformation. A short coherence length laser must be used to obtain the simultaneous 3D information from the same laser source. In this manuscript we present an extension of this technique now illuminating simultaneously with three different lasers at 458, 532 and 633 nm, and using only one high resolution monochrome CMOS sensor. This new configuration gives the opportunity to use long coherence length lasers allowing the measurement of large object areas. A series of digital holographic interferograms are recorded and the information corresponding to each laser is isolated in the Fourier spectral domain where the corresponding phase difference is calculated. Experimental results render the orthogonal displacement components u, v and w during a simple load deformation. PMID:20940878

  11. Automatic quadrature control and measuring system. [using optical coupling circuitry

    NASA Technical Reports Server (NTRS)

    Hamlet, J. F. (Inventor)

    1974-01-01

    A quadrature component cancellation and measuring system comprising a detection system for detecting the quadrature component from a primary signal, including reference circuitry to define the phase of the quadrature component for detection is described. A Raysistor optical coupling control device connects an output from the detection system to a circuit driven by a signal based upon the primary signal. Combining circuitry connects the primary signal and the circuit controlled by the Raysistor device to subtract quadrature components. A known current through the optically sensitive element produces a signal defining the magnitude of the quadrature component.

  12. Heterodyne Interferometer with Angstrom-level Periodic Nonlinearity

    SciTech Connect

    Schmitz, Tony L.; Beckwith, John F.

    2005-01-25

    Displacement measuring interferometer systems and methods are disclosed. One or more acousto-optic modulators for receiving a laser light beam from a laser light source can be utilized to split the laser light beam into two or more laser light beams, while spatially separating frequencies thereof. One or more reflective mechanisms can be utilized to reflect one or more of the laser light beams back to the acoustooptic modulator. Interference of two or more of the laser light beams generally at the acousto-optic modulator can provide an interfered laser light beam thereof. A detector for receiving the interfered laser light beam can be utilized to provide interferometer measurement data.

  13. An SOS MEMS interferometer

    NASA Astrophysics Data System (ADS)

    Tejada, Francisco; Wesolek, Danielle M.; Lehtonen, John; Miragliotta, Joseph A.; Andreou, Andreas G.; Osiander, Robert

    2004-01-01

    The function of a large number of MEMS and NEMS devices relies critically on the transduction method employed to convert the mechanical displacement into electrical signal. Optical transduction techniques have distinct advantages over more traditional capacitive and piezoelectric transduction methods. Optical interferometers can provide a much higher sensitivity, about 3 orders of magnitude, but are hardly compatible with standard MEMS and microelectronics processing. In this paper, we present a scalable architecture based in silicon on sapphire (SOS) CMOS 1 for building an interferometric optical detection system. This new detection system is currently being applied to the sense the motion of a resonating MEMS device, but can be used to detect the motion of any object to which the system is packaged. In the current hybrid approach the SOS CMOS device is packaged with both vertical cavity surface emitting lasers (VCSELs) and MEMS devices. The optical transparency of the sapphire substrate together with the ultra thin silicon PIN photodiodes available in this SOS process allows for the design of both a Michelson type and Fabry Perot type interferometer. The detectors, signal processing electronics and VCSEL drivers are built on the SOS CMOS for a complete system. We present experimental data demonstrating interferometric detection of a vibrating device.

  14. Large aperture Fizeau interferometer commissioning and preliminary measurements of a long x-ray mirror at European X-ray Free Electron Laser

    NASA Astrophysics Data System (ADS)

    Vannoni, M.; Freijo Martín, I.

    2016-05-01

    The European XFEL (X-ray Free Electron Laser) is a large facility under construction in Hamburg, Germany. It will provide a transversally fully coherent x-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 ms long pulse train at 10 Hz), short wavelength (down to 0.05 nm), short pulse (in the femtoseconds scale), and high average brilliance (1.6 ṡ 1025 (photons s-1 mm-2 mrad-2)/0.1% bandwidth). The beam has very high pulse energy; therefore, it has to be spread out on a relatively long mirror (about 1 m). Due to the very short wavelength, the mirrors need to have a high quality surface on their entire length, and this is considered very challenging even with the most advanced polishing methods. In order to measure the mirrors and to characterize their interaction with the mechanical mount, we equipped a metrology laboratory with a large aperture Fizeau interferometer. The system is a classical 100 mm diameter commercial Fizeau, with an additional expander providing a 300 mm diameter beam. Despite the commercial nature of the system, special care has been taken in the polishing of the reference flats and in the expander quality. We report the first commissioning of the instrument, its calibration, and performance characterization, together with some preliminary results with the measurement of a 950 mm silicon substrate. The intended application is to characterize the final XFEL mirrors with nanometer accuracy.

  15. Optically controlled quadrature coupler on silicon substrate

    NASA Astrophysics Data System (ADS)

    Bhadauria, Avanish; Sharma, Sonia; Sonania, Shikha; Akhtar, Jamil

    2016-03-01

    In this paper, we have proposed and studied an optically controlled quadrature coupler fabricated on silicon substrate. The optically controlled quadrature coupler can be realized by terminating its coupled or through ports by optically induced load. Simulation and experimental results show that by varying optical intensity, we can control the phase and amplitude of output RF signal and can realize optically controlled reflection type attenuator, reflection type phase-shifter and ultrafast switches. The new kind of proposed device can be useful for ultra-fast signal processing and modulation schemes in high speed communication especially in QPSK modulation. The optical control has several advantages over conventional techniques such as MEMS and other semiconductor switching, which have several inherent disadvantages and limitations like low response time, low power handling capacity, device parasitic and non-linearity.

  16. Single and double superimposing interferometer systems

    DOEpatents

    Erskine, David J.

    2000-01-01

    Interferometers which can imprint a coherent delay on a broadband uncollimated beam are described. The delay value can be independent of incident ray angle, allowing interferometry using uncollimated beams from common extended sources such as lamps and fiber bundles, and facilitating Fourier Transform spectroscopy of wide angle sources. Pairs of such interferometers matched in delay and dispersion can measure velocity and communicate using ordinary lamps, wide diameter optical fibers and arbitrary non-imaging paths, and not requiring a laser.

  17. 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

  18. Exponential fitting quadrature rule for functional equations

    NASA Astrophysics Data System (ADS)

    Cardone, A.; Paternoster, B.; Santomauro, G.

    2012-09-01

    A Gaussian quadrature rule for periodic integrand function is presented. The weights and nodes depend on the frequency of the problem and they are constructed by following the exponential fitting theory. The composite rule based on this formula is derived. The analysis of the error is carried out and it proves that the exponentially fitted Gaussian rule is more accurate than the classical Gauss-Legendre rule when oscillatory functions are treated. Some numerical tests are presented.

  19. Special relativity and interferometers

    NASA Technical Reports Server (NTRS)

    Han, D.; Kim, Y. S.

    1988-01-01

    A new generation of gravitational wave detectors is expected to be based on interferometers. Yurke et al. (1986) introduced a class of interferometers characterized by SU(1,1) which can in principle achieve a phase sensitivity approaching 1/N, where N is thte total number of photons entering the interferometer. It is shown here that the SU(1,1) interferometer can serve as an analog computer for Wigner's little group of the Poincare\\'| group.

  20. Two-color terahertz interferometer based on the frequency-splitted orthogonal polarization modes of the water vapor laser and designed for measuring the electron density profile in the L-2M stellarator

    SciTech Connect

    Letunov, A. A.; Logvinenko, V. P.; Zav'yalov, V. V.

    2008-03-15

    An upgraded diagnostics for measuring the electron density profile in the L-2M stellarator is proposed. The existing diagnostics employs an interferometer based on an HCN laser with a mechanical frequency shifter and unmagnetized InSb detectors cooled with liquid helium. It is proposed to replace the HCN laser with a water vapor laser operating simultaneously at two wavelengths (220 and 118 {mu}m). Being equipped with an anisotropic exit mirror, the water vapor laser allows the generation of orthogonally polarized, frequency-splitted modes at each of these wavelengths with a frequency difference of several tens of kilohertzs. Such a scheme makes it possible to get rid of the mechanical frequency shifter. Moreover, simultaneous measurements at two wavelengths allow one to reliably separate the phase increments introduced by the plasma electron component and by variations in the lengths of the interferometer arms. To take full advantage of this scheme, specially developed cryogenic receivers consisting of Ge and InSb photodetectors placed one after another will be used. To increase the response of the system near {lambda} = 220 {mu}m, the InSb detector is placed in a Almost-Equal-To 0.55-T magnetic field.

  1. Two-color terahertz interferometer based on the frequency-splitted orthogonal polarization modes of the water vapor laser and designed for measuring the electron density profile in the L-2M stellarator

    SciTech Connect

    Letunov, A. A.; Logvinenko, V. P.; Zav'yalov, V. V.

    2008-03-15

    An upgraded diagnostics for measuring the electron density profile in the L-2M stellarator is proposed. The existing diagnostics employs an interferometer based on an HCN laser with a mechanical frequency shifter and unmagnetized InSb detectors cooled with liquid helium. It is proposed to replace the HCN laser with a water vapor laser operating simultaneously at two wavelengths (220 and 118 {mu}m). Being equipped with an anisotropic exit mirror, the water vapor laser allows the generation of orthogonally polarized, frequency-splitted modes at each of these wavelengths with a frequency difference of several tens of kilohertzs. Such a scheme makes it possible to get rid of the mechanical frequency shifter. Moreover, simultaneous measurements at two wavelengths allow one to reliably separate the phase increments introduced by the plasma electron component and by variations in the lengths of the interferometer arms. To take full advantage of this scheme, specially developed cryogenic receivers consisting of Ge and InSb photodetectors placed one after another will be used. To increase the response of the system near {lambda} = 220 {mu}m, the InSb detector is placed in a {approx}0.55-T magnetic field.

  2. Comparison of Atom Interferometers and Light Interferometers as Space-Based Gravitational Wave Detectors

    NASA Technical Reports Server (NTRS)

    Baker, John G.

    2012-01-01

    We consider a class of proposed gravitational wave detectors based on multiple atomic interferometers separated by large baselines and referenced by common laser systems. We compute the sensitivity limits of these detectors due to intrinsic phase noise of the light sources, non-inertial motion of the light sources, and atomic shot noise and compare them to sensitivity limits for traditional light interferometers. We find that atom interferometers and light interferometers are limited in a nearly identical way by intrinsic phase noise and that both require similar mitigation strategies (e.g. multiple arm instruments) to reach interesting sensitivities. The sensitivity limit from motion of the light sources is slightly different and favors the atom interferometers in the low-frequency limit, although the limit in both cases is severe.

  3. Gauss Legendre Quadrature Formulae for Tetrahedra

    NASA Astrophysics Data System (ADS)

    Rathod, H. T.; Venkatesudu, B.; Nagaraja, K. V.

    2005-09-01

    In this paper we consider the Gauss Legendre quadrature method for numerical integration over the standard tetrahedron: {(x, y, z)|0 = x, y, z = 1, x + y + z = 1} in the Cartesian three-dimensional (x, y, z) space. The mathematical transformation from the (x, y, z) space to (?, ?, ?) space is described to map the standard tetrahedron in (x, y, z) space to a standard 2-cube: {(?, ?, ?)| - 1 = ?, ?,? = 1} in the (?, ?, ?) space. This overcomes the difficulties associated with the derivation of new weight co-efficients and sampling points. The effectiveness of the formulae is demonstrated by applying them to the integration of three nonpolynomial and three polynomial functions.

  4. Quadrature demultiplexing using a degenerate vector parametric amplifier.

    PubMed

    Lorences-Riesgo, Abel; Liu, Lan; Olsson, Samuel L I; Malik, Rohit; Kumpera, Aleš; Lundström, Carl; Radic, Stojan; Karlsson, Magnus; Andrekson, Peter A

    2014-12-01

    We report on quadrature demultiplexing of a quadrature phase-shift keying (QPSK) signal into two cross-polarized binary phase-shift keying (BPSK) signals with negligible penalty at bit-error rate (BER) equal to 10(-9). The all-optical quadrature demultiplexing is achieved using a degenerate vector parametric amplifier operating in phase-insensitive mode. We also propose and demonstrate the use of a novel and simple phase-locked loop (PLL) scheme based on detecting the envelope of one of the signals after demultiplexing in order to achieve stable quadrature decomposition. PMID:25606877

  5. Active noise cancellation in a suspended interferometer.

    PubMed

    Driggers, Jennifer C; Evans, Matthew; Pepper, Keenan; Adhikari, Rana

    2012-02-01

    We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results with theoretical estimates of the cancellation efficiency. Using data from the recent Laser Interferometer Gravitational Wave Observatory (LIGO) Science Run, we also estimate the impact of this technique on full scale gravitational wave interferometers. In the future, we expect to use this technique also to remove acoustic, magnetic, and gravitational noise perturbations from the LIGO interferometers. This noise cancellation technique is simple enough to implement in standard laboratory environments and can be used to improve signal-to-noise ratio for a variety of high precision experiments. PMID:22380106

  6. Interferometers for Displacement-Noise-Free Gravitational-Wave Detection

    SciTech Connect

    Chen, Yanbei; Pai, Archana; Somiya, Kentaro; Kawamura, Seiji; Sato, Shuichi; Kokeyama, Keiko; Ward, Robert L.; Goda, Keisuke; Mikhailov, Eugeniy E.

    2006-10-13

    We propose a class of displacement- and laser-noise-free gravitational-wave-interferometer configurations, which does not sense nongeodesic mirror motion and laser noise, but provides a nonvanishing gravitational-wave signal. Our interferometers consist of four mirrors and two beam splitters, which form four Mach-Zehnder interferometers. By contrast to previous works, no composite mirrors with multiple reflective surfaces are required. Each mirror in our configuration is sensed redundantly, by at least two pairs of incident and reflected beams. Displacement- and laser-noise-free detection is achieved when output signals from these four interferometers are combined appropriately. Our 3-dimensional interferometer configuration has a low-frequency response proportional to f{sup 2}, which is better than the f{sup 3} achievable by previous 2-dimensional configurations.

  7. Modulator-free quadrature amplitude modulation signal synthesis

    PubMed Central

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O’Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

    2014-01-01

    The ability to generate high-speed on–off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s−1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on–off-keyed 10 Gbit s−1 systems and is absolutely prohibitive for today’s (>)100 Gbit s−1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions. PMID:25523757

  8. Modulator-free quadrature amplitude modulation signal synthesis

    NASA Astrophysics Data System (ADS)

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O'Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

    2014-12-01

    The ability to generate high-speed on-off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s-1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on-off-keyed 10 Gbit s-1 systems and is absolutely prohibitive for today’s (>)100 Gbit s-1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions.

  9. Phase shifting interferometer

    DOEpatents

    Sommargren, G.E.

    1999-08-03

    An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.

  10. Phase shifting interferometer

    SciTech Connect

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  11. A Synthetic Quadrature Phase Detector/Demodulator for Fourier Transform Transform Spectrometers

    NASA Technical Reports Server (NTRS)

    Campbell, Joel

    2008-01-01

    A method is developed to demodulate (velocity correct) Fourier transform spectrometer (FTS) data that is taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low cost, high resolution audio digitizers to record high quality data without the need for an event timer or quadrature laser hardware, and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simplicity implementation makes it an attractive alternative in space based applications when compared to previous methods such as the Brault algorithm.

  12. Achromatic deep nulling with a three-dimensional Sagnac interferometer.

    PubMed

    Yokochi, Kaito; Tavrov, Alexander V; Nishikawa, Jun; Murakami, Naoshi; Abe, Lyu; Tamura, Motohide; Takeda, Mitsuo; Kurokawa, Takashi

    2009-07-01

    A 3-D Sagnac interferometer can null out light from an on-axis source achromatically. The 3-D Sagnac interferometer can make stable and achromatic pi phase shifts, because it has a common path structure. The achromaticity of the interferometer is theoretically proved by Jones calculus. The experimental setup is constructed, and its nulling characteristics are measured to be about 10(-6) at 5 lambda/d for green (lambda=532 nm) and red (lambda=633 nm) laser light simultaneously. This interferometer would be very useful for the direct detection of faint extrasolar planets. PMID:19571974

  13. Positive interpolatory quadrature formulas and para-orthogonal polynomials

    NASA Astrophysics Data System (ADS)

    Bultheel, Adhemar; Daruis, Leyla; Gonzalez-Vera, Pablo

    2005-07-01

    We establish a relation between quadrature formulas on the interval [-1,1] that approximate integrals of the form and Szego quadrature formulas on the unit circle that approximate integrals of the form . The functions [mu](x) and [omega]([theta]) are assumed to be weight functions on [-1,1] and [-[pi],[pi

  14. A novel interferometric vibration measurement sensor with quadrature detection based on 1/8 wave plate

    NASA Astrophysics Data System (ADS)

    Zhen, Shenglai; Chen, Bo; Yuan, Liang; Li, Min; Liang, Jing; Yu, Benli

    2010-03-01

    In-phase and quadrature-phase (I/Q) signals often need to be formed in the laser interferometric vibration measurement technique. To avoid the disadvantages of traditional I/Q signals forming methods such as effect of piezoelectric ceramic (PZT) for generating high frequency carrier, or optical configuration with complicated structure, a novel interferometric vibration measurement sensor with quadrature detection is proposed. The sensor utilizes simple optical configuration which contains 1/8 wave plate to generate two I/Q signals, then the signals were processed by arctangent algorithm which is compiled by Labview software through data acquisition card. Theoretical analysis and experimental Lissajous figures synthesis prove the phase orthogonality of the two signals. The experimental results indicate that the system can measure the vibration displacement accurately.

  15. Prism-pair interferometry by homodyne interferometers with a common light source for high-accuracy measurement of the absolute refractive index of glasses

    SciTech Connect

    Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru

    2011-03-10

    A prism-pair interferometer comprising two homodyne interferometers with a common light source was developed for high-precision measurements of the refractive index of optical glasses with an uncertainty of the order of 10{sup -6}. The two interferometers measure changes in the optical path length in the glass sample and in air, respectively. Uncertainties in the absolute wavelength of the common light source are cancelled out by calculating a ratio between the results from the interferometers. Uncertainties in phase measurement are suppressed by a quadrature detection system. The combined standard uncertainty of the developed system is evaluated as 1.1x10{sup -6}.

  16. 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.

  17. Coupled-Cavity Interferometer for the Optics Laboratory

    ERIC Educational Resources Information Center

    Peterson, R. W.

    1975-01-01

    Describes the construction of a flexible coupled-cavity interferometer for student use. A helium-neon laser and phonograph turntable are the main components. Lists activities which may be performed with the apparatus. (Author/CP)

  18. Two-frequency-dependent Gauss quadrature rules

    NASA Astrophysics Data System (ADS)

    Kim, Kyung Joong

    2005-02-01

    We construct two-frequency-dependent Gauss quadrature rules which can be applied for approximating the integration of the product of two oscillatory functions with different frequencies [beta]1 and [beta]2 of the forms,yi(x)=fi,1(x) cos([beta]ix)+fi,2(x) sin([beta]ix), i=1,2,where the functions fi,j(x) are smooth. A regularization procedure is presented to avoid the singularity of the Jacobian matrix of nonlinear system of equations which is induced as one frequency approaches the other frequency. We provide numerical results to compare the accuracy of the classical Gauss rule and one- and two-frequency-dependent rules.

  19. The May 1997 SOHO-Ulysses Quadrature

    NASA Technical Reports Server (NTRS)

    Suess, Steven T.; Poletto, G.; Romoli, M.; Neugebauer, M.; Goldstein, B. E.; Simnett, G.

    2000-01-01

    We present results from the May 1997 SOHO-Ulysses quadrature, near sunspot minimum. Ulysses was at 5.1 AU, 100 north of the solar equator, and off the east limb. It was, by chance, also at the very northern edge of the streamer belt. Nevertheless, SWOOPS detected only slow, relatively smooth wind and there was no direct evidence of fast wind from the northern polar coronal hole or of mixing with fast wind. LASCO images show that the streamer belt at 10 N was narrow and sharp at the beginning and end of the two week observation interval, but broadened in the middle. A corresponding change in density, but not flow speed, occurred at Ulysses. Coronal densities derived from UVCS show that physical parameters in the lower corona are closely related to those in the solar wind, both over quiet intervals and in transient events on the limb. One small transient observed by both LASCO and UVCS is analyzed in detail.

  20. Power flow control using quadrature boosters

    NASA Astrophysics Data System (ADS)

    Sadanandan, Sandeep N.

    A power system that can be controlled within security constraints would be an advantage to power planners and real-time operators. Controlling flows can lessen reliability issues such as thermal limit violations, power stability problems, and/or voltage stability conditions. Control of flows can also mitigate market issues by reducing congestion on some lines and rerouting power to less loaded lines or onto preferable paths. In the traditional control of power flows, phase shifters are often used. More advanced methods include using Flexible AC Transmission System (FACTS) Controllers. Some examples include Thyristor Controlled Series Capacitors, Synchronous Series Static Compensators, and Unified Power Flow Controllers. Quadrature Boosters (QBs) have similar structures to phase-shifters, but allow for higher voltage magnitude during real power flow control. In comparison with other FACTS controllers QBs are not as complex and not as expensive. The present study proposes to use QBs to control power flows on a power system. With the inclusion of QBs, real power flows can be controlled to desired scheduled values. In this thesis, the linearized power flow equations used for power flow analysis were modified for the control problem. This included modifying the Jacobian matrix, the power error vector, and calculating the voltage injected by the quadrature booster for the scheduled real power flow. Two scenarios were examined using the proposed power flow control method. First, the power flow in a line in a 5-bus system was modified with a QB using the method developed in this thesis. Simulation was carried out using Matlab. Second, the method was applied to a 30-bus system and then to a 118-bus system using several QBs. In all the cases, the calculated values of the QB voltages led to desired power flows in the designated line.

  1. Surface profiling interferometer

    SciTech Connect

    Takacs, Peter Z.; Qian, Shi-Nan

    1989-01-01

    The design of a long-trace surface profiler for the non-contact measurement of surface profile, slope error and curvature on cylindrical synchrotron radiation (SR) mirrors. The optical system is based upon the concept of a pencil-beam interferometer with an inherent large depth-of-field. The key feature of the optical system is the zero-path-difference beam splitter, which separates the laser beam into two colinear, variable-separation probe beams. A linear array detector is used to record the interference fringe in the image, and analysis of the fringe location as a function of scan position allows one to reconstruct the surface profile. The optical head is mounted on an air bearing slide with the capability to measure long aspheric optics, typical of those encountered in SR applications. A novel feature of the optical system is the use of a transverse "outrigger" beam which provides information on the relative alignment of the scan axis to the cylinder optic symmetry axis.

  2. Compressive optical image encryption with two-step-only quadrature phase-shifting digital holography

    NASA Astrophysics Data System (ADS)

    Li, Jun; Li, Hongbing; Li, Jiaosheng; Pan, Yangyang; Li, Rong

    2015-06-01

    An image encryption method which combines two-step-only quadrature phase-shifting digital holography with compressive sensing (CS) has been proposed in the fully optical domain. An object image is firstly encrypted to two on-axis quadrature-phase holograms using the two random phase masks in the Mach-Zehnder interferometer. Then, the two encrypted images are highly compressed to a one-dimensional signal using the single-pixel compressive holographic imaging in the optical domain. At the receiving terminal, the two compressive encrypted holograms are exactly reconstructed from much less than the Nyquist sampling number of observations by solving an optimization problem, and the original image can be decrypted with only two reconstructed holograms and the correct keys. This method largely decreases holograms data volume for the current optical image encryption system, and it is also suitable for some special optical imaging cases such as different wavelengths imaging and weak light imaging. Numerical simulation is performed to demonstrate the feasibility and validity of this novel image encryption method.

  3. The AEI 10 m prototype interferometer

    NASA Astrophysics Data System (ADS)

    Goßler, S.; Bertolini, A.; Born, M.; Chen, Y.; Dahl, K.; Gering, D.; Gräf, C.; Heinzel, G.; Hild, S.; Kawazoe, F.; Kranz, O.; Kühn, G.; Lück, H.; Mossavi, K.; Schnabel, R.; Somiya, K.; Strain, K. A.; Taylor, J. R.; Wanner, A.; Westphal, T.; Willke, B.; Danzmann, K.

    2010-04-01

    A 10 m prototype interferometer facility is currently being set up at the AEI in Hannover, Germany. The prototype interferometer will be housed inside a 100 m3 ultra-high vacuum envelope. Seismically isolated optical tables inside the vacuum system will be interferometrically interconnected via a suspension platform interferometer. Advanced isolation techniques will be used, such as inverted pendulums and geometrical anti-spring filters in combination with multiple-cascaded pendulum suspensions, containing an all-silica monolithic last stage. The light source is a 35 W Nd:YAG laser, geometrically filtered by passing it through a photonic crystal fibre and a rigid pre-modecleaner cavity. Laser frequency stabilisation will be achieved with the aid of a high finesse suspended reference cavity in conjunction with a molecular iodine reference. Coating thermal noise will be reduced by the use of Khalili cavities as compound end mirrors. Data acquisition and control of the experiments is based on the AdvLIGO digital control and data system. The aim of the project is to test advanced techniques for GEO 600 as well as to conduct experiments in macroscopic quantum mechanics. Reaching standard quantum-limit sensitivity for an interferometer with 100 g mirrors and subsequently breaching this limit, features most prominently among these experiments. In this paper we present the layout and current status of the AEI 10 m Prototype Interferometer project.

  4. Dispersion interferometer using modulation amplitudes on LHD (invited)

    SciTech Connect

    Akiyama, T. Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.

    2014-11-15

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup −3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup −3} can be overcome by a sufficient sampling rate of about 100 kHz.

  5. Optical measurements of the laser-inducedultrasonic waves on moving objects.

    PubMed

    Pozar, Tomaz; Gregorcic, Peter; Mozina, Janez

    2009-12-01

    We performed a single-shot, contactless measurement of ultrasonic waves on a laser-propelled rod with a homodyne quadrature laser interferometer (HQLI) during the entire duration of its motion. This is the first such experimental demonstration of the laser-induced motion of an elastic body where the most important mechanisms that reveal the nature of its motion are presented and explained. Furthermore, these measurements quantitatively demonstrate that the HQLI is an appropriate tool for monitoring high-amplitude (1.3 microm) and high-frequency (200 MHz) ultrasonic waves on moving objects. The applicability of the HQLI can also be extended to measure other optodynamic and high-frequency transient phenomena with a constant sensitivity and a resolution below 1 nm. PMID:20052217

  6. Ultrasonic Interferometers Revisited

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2007-03-01

    I have been tinkering with ultrasonic transducers once more. In earlier notes I reported on optics-like experiments performed with ultrasonics, described a number of ultrasonic interferometers,2 and showed how ultrasonic transducers can be used for Fourier analysis.3 This time I became interested in trying the technique of using two detectors in acoustic interferometers instead of the usual one.

  7. Self-calibrating interferometer

    SciTech Connect

    Nussmeier, T.A.

    1982-10-26

    A self-calibrating interferometer is disclosed which forms therein a pair of Michelson interferometers with one beam length of each Michelson interferometer being controlled by a common phase shifter. The transfer function measured from the phase shifter to either of a pair of detectors is sinusoidal with a full cycle for each half wavelength of phase shifter travel. The phase difference between these two sinusoidal detector outputs represents the optical phase difference between a path of known distance and a path of unknown distance.

  8. Ultracompact and highly sensitive common-path phase-shifting interferometer using photonic crystal polarizers as a reference mirror and a phase shifter.

    PubMed

    Nakata, Toshihiko; Watanabe, Masahiro

    2009-03-01

    We present a common-path phase-shifting interferometer in which photonic crystal polarizers (PCPs) are utilized as a reference mirror and a phase shifter, allowing ultracompact and highly sensitive optics. When a laser beam polarized at 45 degrees relative to the optical axis of the PCp-based reference mirror is incident, the polarization component parallel to the optical axis (s-polarized beam) is reflected and used as a reference beam. The perpendicular component (p-polarized beam) passes through the PCP coupled with a quarter-wave plate (QWP) and serves as a probe beam. This beam, with its polarization transformed in the sequence p, right-circular, s, left-circular, and p, irradiates the sample surface twice, doubling the phase change due to displacement of the sample. The probe beam is then retransmitted through the PCP, where it recombines with the reference beam. Four interferogram channels in phase quadrature are generated using a newly developed phase shifter, composed of a QWP and a monolithically integrated array of four PCPs. Preliminary experiments demonstrate that the PCPs perform successfully as a reference mirror and a phase shifter, and that the interferometer has a remarkable displacement sensitivity, as low as 40 pm. PMID:19252633

  9. Ray tracing through the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

    SciTech Connect

    Turner, A.

    1999-03-01

    The Omega laser is a system with many different parts that may cause imperfections. There are a multitude of lenses and mirrors, for example, that may not be polished correctly and can cause the laser wave front to have aberrations. The Liquid Crystal Point Diffraction Interferometer (L.C.P.D.I.) is a device whose main purpose is to read the wave front of the laser and measure any aberrations that may be on it. The way the L.C.P.D.I. reads the laser wave front and measures these aberrations is very complicated and has yet to be perfected. A ray-tracing model of the L.C.P.D.I. has been built, which calculates and models the ray trajectories, the optical paths of the rays, the O.P.D. between the object and reference beams, the absorption of the rays in the liquid crystal, and the intensities of each beam. It can predict an actual experiment by manipulating the different parameters of the program. It will be useful in optimization and further development of the L.C.P.D.I. Evidently, it is necessary to develop a liquid crystal solution with an O.D. greater than 0.3, and possibly as high as 2.0. This new solution would be able to reduce the intensity of the object beam sufficiently to make it comparable with the reference beam intensity. If this were achieved, the contrast, or visibility of the fringes would be better, and the interferogram could be used to diagnose the aberrations in the laser beam front. Then the cause of the aberrations could be fixed. This would result in a near-perfect laser front. If this were achieved, then it is possible that laser fusion could be made more efficient and possibly used as an energy source.

  10. Photothermal measurements with a Jamin interferometer

    NASA Astrophysics Data System (ADS)

    Cournoyer, Alain; Baulaigue, Pierre; Lazarides, Eric; Blancher, Henri; Bertrand, Lionel; Occelli, Roland

    1997-07-01

    We present a numerical study of the behavior of the signal in a photothermal experiment combining the mirage effect and a Jamin interferometer. Our analysis is limited to a square-pulse excitation by a weakly absorbed Gaussian pump laser beam with a large radius. We investigate the influence of three parameters: the time of illumination of the sample, the time of extinction of the pump beam, and the height of the probe-beam arm of the Jamin interferometer above the sample. We show that the path difference, which induces the variation of intensity at the output of the Jamin interferometer, is caused by both probe-beam deflection and temperature variation of the refractive index of air above the sample. The first effect is dominant for short times, and interferometry is a sensitive tool to monitor it.

  11. Infrared phase-shifting digital interferometer

    NASA Astrophysics Data System (ADS)

    Chen, Jinbang; Chen, Lei; Huang, Shenwang; Jin, Guoyou

    1996-10-01

    This paper describes theory and performance of a self- developed IR phase-shifting digital interferometer which uses a CO2 laser as light source, this instrument comprises of a Fizeau interferometer whose aperture reaches (Phi) 250mm with accuracy better than (lambda) /50, and a Twyman spherical interferometer. Using piezoelectric transducer to shift reference mirror, phase measurement interferometry can be carried out as well as the temperature modulation of PEV target. A series of software packages used as wavefront fitting, image quality evaluation, are incorporated into the instrument. With the help of microcomputer, this interferometric system can measure refractive-index homogeneity of IR transmitting materials, wavefront error of IR optical system and surface quality of rough surface etc., which can all be shown by detailed data of optical path difference, vivid 2D contour and 3D surface.

  12. Two integrator loop quadrature oscillators: A review

    PubMed Central

    Soliman, Ahmed M.

    2012-01-01

    A review of the two integrator loop oscillator circuits providing two quadrature sinusoidal output voltages is given. All the circuits considered employ the minimum number of capacitors namely two except one circuit which uses three capacitors. The circuits considered are classified to four different classes. The first class includes floating capacitors and floating resistors and the active building blocks realizing these circuits are the Op Amp or the OTRA. The second class employs grounded capacitors and includes floating resistors and the active building blocks realizing these circuits are the DCVC or the unity gain cells or the CFOA. The third class employs grounded capacitors and grounded resistors and the active building blocks realizing these circuits are the CCII. The fourth class employs grounded capacitors and no resistors and the active building blocks realizing these circuits are the TA. Transformation methods showing the generation of different classes from each other is given in details and this is one of the main objectives of this paper. PMID:25685396

  13. Two integrator loop quadrature oscillators: A review.

    PubMed

    Soliman, Ahmed M

    2013-01-01

    A review of the two integrator loop oscillator circuits providing two quadrature sinusoidal output voltages is given. All the circuits considered employ the minimum number of capacitors namely two except one circuit which uses three capacitors. The circuits considered are classified to four different classes. The first class includes floating capacitors and floating resistors and the active building blocks realizing these circuits are the Op Amp or the OTRA. The second class employs grounded capacitors and includes floating resistors and the active building blocks realizing these circuits are the DCVC or the unity gain cells or the CFOA. The third class employs grounded capacitors and grounded resistors and the active building blocks realizing these circuits are the CCII. The fourth class employs grounded capacitors and no resistors and the active building blocks realizing these circuits are the TA. Transformation methods showing the generation of different classes from each other is given in details and this is one of the main objectives of this paper. PMID:25685396

  14. Optical encryption system using quadrature multiplexing

    NASA Astrophysics Data System (ADS)

    Islam, Mohammed Nazrul; Alam, Mohammad S.

    2006-08-01

    Optical security systems have attracted much research interest recently for information security and fraud deterrent applications. A number of encryption techniques have been proposed in the literature, which includes double random-phase encryption, polarization encoding, encryption and verification using a multiplexed minimum average correlation energy phase-encrypted filter. Most of these reports employ a pseudo-random code for each information to be encrypted, where it requires individual storage capacity or transmission channel for further processing of each information. The objective of this paper is to develop an optical encryption system employing quadrature multiplexing to enhance the storage/transmission capacity of the system. Two information signals are encrypted using the same code but employing two orthogonal functions and then they are multiplexed together in the same domain. As the orthogonal functions have zero cross-correlation between them, so the encrypted information are expected to be unaffected by each other. Each encryption and multiplexing process can accommodate two information signals for a single code and a single storage cell or transmission channel. The same process can be performed in multiple steps to increase the multiplexing capability of the system. For decryption purpose, the composite encoded signal is correlated using the appropriate code and the appropriate function. The proposed technique has been found to work excellent in computer simulation with binary as well as gray level images. It has also been verified that the encrypted images remain secure, because no unwanted reproduction is possible without having the appropriate code and function.

  15. Algorithm 699 - A new representation of Patterson's quadrature formulae

    NASA Technical Reports Server (NTRS)

    Krogh, Fred T.; Van Snyder, W.

    1991-01-01

    A method is presented to reduce the number of coefficients necessary to represent Patterson's quadrature formulae. It also reduces the amount of storage necessary for storing function values, and produces slightly smaller error in evaluating the formulae.

  16. Orthogonal rational functions and quadrature on an interval

    NASA Astrophysics Data System (ADS)

    van Deun, J.; Bultheel, A.

    2003-04-01

    Rational functions with real poles and poles in the complex lower half-plane, orthogonal on the real line, are well known. Quadrature formulas similar to the Gauss formulas for orthogonal polynomials have been studied. We generalize to the case of arbitrary complex poles and study orthogonality on a finite interval. The zeros of the orthogonal rational functions are shown to satisfy a quadratic eigenvalue problem. In the case of real poles, these zeros are used as nodes in the quadrature formulas.

  17. An exponentially fitted quadrature rule over unbounded intervals

    NASA Astrophysics Data System (ADS)

    Conte, D.; Paternoster, B.; Santomauro, G.

    2012-09-01

    A new class of quadrature formulae for the computation of integrals over unbounded intervals with oscillating integrand is illustrated. Such formulae are a generalization of the gaussian quadrature formulae by exploiting the Exponential Fitting theory. The coefficients depend on the frequency of oscillation, in order to improve the accuracy of the solution. The construction of the methods with 1, 2 and 3 nodes is described, together with the comparison of the order of accuracy with respect to classical formulae.

  18. Fizeau plasma interferometer

    SciTech Connect

    Frank, A.M.

    1980-01-01

    This paper describes a technique by which the sensitivity of plasma interferometers can be increased. Stabilization and fractional fringe measurement techniques have improved to the point where additional optical sensitivity could be useful. (MOW)

  19. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E.

    1996-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  20. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, G.E.

    1996-08-29

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

  1. Furnace control apparatus using polarizing interferometer

    DOEpatents

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

    1995-03-28

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

  2. Process control system using polarizing interferometer

    DOEpatents

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

    1994-02-15

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

  3. Furnace control apparatus using polarizing interferometer

    DOEpatents

    Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

    1995-01-01

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

  4. Process control system using polarizing interferometer

    DOEpatents

    Schultz, Thomas J.; Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

    1994-01-01

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

  5. Quadrature mixture LO suppression via DSW DAC noise dither

    DOEpatents

    Dubbert, Dale F.; Dudley, Peter A.

    2007-08-21

    A Quadrature Error Corrected Digital Waveform Synthesizer (QECDWS) employs frequency dependent phase error corrections to, in effect, pre-distort the phase characteristic of the chirp to compensate for the frequency dependent phase nonlinearity of the RF and microwave subsystem. In addition, the QECDWS can employ frequency dependent correction vectors to the quadrature amplitude and phase of the synthesized output. The quadrature corrections cancel the radars' quadrature upconverter (mixer) errors to null the unwanted spectral image. A result is the direct generation of an RF waveform, which has a theoretical chirp bandwidth equal to the QECDWS clock frequency (1 to 1.2 GHz) with the high Spurious Free Dynamic Range (SFDR) necessary for high dynamic range radar systems such as SAR. To correct for the problematic upconverter local oscillator (LO) leakage, precision DC offsets can be applied over the chirped pulse using a pseudo-random noise dither. The present dither technique can effectively produce a quadrature DC bias which has the precision required to adequately suppress the LO leakage. A calibration technique can be employed to calculate both the quadrature correction vectors and the LO-nulling DC offsets using the radar built-in test capability.

  6. Accurate measurement of interferometer group delay using field-compensated scanning white light interferometer.

    PubMed

    Wan, Xiaoke; Wang, Ji; Ge, Jian

    2010-10-10

    Interferometers are key elements in radial velocity (RV) experiments in astronomy observations, and accurate calibration of the group delay of an interferometer is required for high precision measurements. A novel field-compensated white light scanning Michelson interferometer is introduced as an interferometer calibration tool. The optical path difference (OPD) scanning was achieved by translating a compensation prism, such that even if the light source were in low spatial coherence, the interference stays spatially phase coherent over a large interferometer scanning range. In the wavelength region of 500-560 nm, a multimode fiber-coupled LED was used as the light source, and high optical efficiency was essential in elevating the signal-to-noise ratio of the interferogram signal. The achromatic OPD scanning required a one-time calibration, and two methods using dual-laser wavelength references and an iodine absorption spectrum reference were employed and cross-verified. In an experiment measuring the group delay of a fixed Michelson interferometer, Fourier analysis was employed to process the interferogram data. The group delay was determined at an accuracy of 1×10(-5), and the phase angle precision was typically 2.5×10(-6) over the wide wavelength region. PMID:20935712

  7. Heterodyne interferometer with angstrom-level periodic nonlinearity

    DOEpatents

    Schmitz, Tony L.; Beckwith, John F.

    2005-01-25

    Displacement measuring interferometer systems and methods are disclosed. One or more acousto-optic modulators for receiving a laser light beam from a laser light source can be utilized to split the laser light beam into two or more laser light beams, while spatially separating frequencies thereof. One or more reflective mechanisms can be utilized to reflect one or more of the laser light beams back to the acousto-optic modulator. Interference of two or more of the laser light beams generally at the acousto-optic modulator can provide an interfered laser light beam thereof. A detector for receiving the interfered laser light beam can be utilized to provide interferometer measurement data.

  8. Monolithic interferometer for high precision radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Wan, Xiaoke; Ge, Jian; Wang, Ji; Lee, Brian

    2009-08-01

    In high precision radial velocity (RV) measurements for extrasolar planets searching and studies, a stable wide field Michelson interferometer is very critical in Exoplanet Tracker (ET) instruments. Adopting a new design, monolithic interferometers are homogenous and continuous in thermal expansion, and field compensation and thermal compensation are both satisfied. Interferometer design and fabrication are decrypted in details. In performance evaluations, field angle is typically 22° and thermal sensitivity is typically -1.7 x 10-6/°C, which corresponds to ~500 m/s /°C in RV scale. In interferometer stability monitoring using a wavelength stabilized laser source, phase shift data was continuously recorded for nearly seven days. Appling a frequent calibration every 30 minutes as in typical star observations, the interferometer instability contributes less than 1.4 m/s in RV error, in a conservative estimation.

  9. Integrated heterodyne interferometer with on-chip modulators and detectors.

    PubMed

    Cole, David B; Sorace-Agaskar, Cheryl; Moresco, Michele; Leake, Gerald; Coolbaugh, Douglas; Watts, Michael R

    2015-07-01

    We demonstrate, to our knowledge, the first on-chip heterodyne interferometer fabricated on a 300-mm CMOS compatible process that exhibits root-mean-square (RMS) position noise on the order of 2nm. Measuring 1mm by 6mm, the interferometer is also, to our knowledge, the smallest heterodyne interferometer demonstrated to date and will surely impact numerous interferometric and metrology applications, including displacement measurement, laser Doppler velocimetry and vibrometry, Fourier transform spectroscopy, imaging, and light detection and ranging (LIDAR). Here we present preliminary results that demonstrate the displacement mode. PMID:26125376

  10. On open electromagnetic resonators: relation between interferometers and resonators

    SciTech Connect

    Manenkov, Aleksandr A; Bykov, Vladimir P; Kuleshov, N V

    2010-05-26

    The physical difference between the concepts 'Fabry-Perot interferometer' and 'open resonator' is discussed. It is shown that the use of the term 'Fabry-Perot resonator' for open laser resonators is incorrect both from the historical viewpoint and from the viewpoint of the physical meaning of the processes occurring in these resonators. (laser beams and resonators)

  11. The Fall 2000 and Fall 2001 SOHO-Ulysses Quadratures

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Poletto, G.

    2000-01-01

    SOHO-Ulysses quadrature occurs when the SOHO-Sun-Ulysses included angle is 90 degrees. It is only at such times that the same plasma leaving the Sun in the direction of Ulysses can first be remotely analyzed with SOHO instruments and then later be sampled in situ by Ulysses instruments. The quadratures in December 2000 and 2001 are of special significance because Ulysses will be near the south and north heliographic poles, respectively, and the solar cycle will be near sunspot maximum. Quadrature geometry is sometimes confusing and observations are influenced by solar rotation. The Fall 2000 and 2001 quadratures are more complex than usual because Ulysses is not in a true polar orbit and the orbital speed of Ulysses about the Sun is becoming comparable to the speed of SOHO about the Sun. In 2000 Ulysses will always be slightly behind the pole but will appear to hang over the pole for over two months because it is moving around the Sun in the same direction as SOHO. In 20001, Ulysses will be slightly in front of the pole so that its footpoint will be directly observable. Detailed plots will be shown of the relative positions of SOHO and Ulysses will their relative positions. In neither case is true quadrature actually achieved, but this works to the observers advantage in 2001.

  12. The Fall 2000 and Fall 2001 SOHO-Ulysses Quadratures

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Poletto, G.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    SOHO-Ulysses quadrature occurs when the SOHO-Sun-Ulysses included angle is 90 degrees. It is only at such times that the same plasma leaving the Sun in the direction of Ulysses can first be remotely analyzed with SOHO instruments and then later be sampled in situ by Ulysses instruments. The quadratures in December 2000 and 2001 are of special significance because Ulysses will be near the south and north heliographic poles, respectively, and the solar cycle will be near sunspot maximum. Quadrature geometry is sometimes confusing and observations are influenced by solar rotation. The Fall 2000 and 2001 quadratures are more complex than usual because Ulysses is not in a true polar orbit and the orbital speed of Ulysses about the Sun is becoming comparable to the speed of SOHO about the Sun. In 2000 Ulysses will always be slightly behind the pole but will appear to hang over the pole for over two months because it is moving around the Sun in the same direction as SOHO. In 2001 Ulysses will be slightly in front of the pole so that its footpoint will be directly observable. Detailed plots will be shown of the relative positions of SOHO and Ulysses will their relative positions. In neither case is true quadrature actually achieved, but this works to the observers advantage in 2001.

  13. PDX multichannel interferometer

    SciTech Connect

    Bitzer, R.; Ernst, W.; Cutsogeorge, G.

    1980-10-01

    A 10 channel, 140 GHz homodyne interferometer is described for use on PDX. One feature of this interferometer is the separation of the signal source and electronics from the power splitters, delay line, and receiving systems. The latter is situated near the upper and lower vacuum ports between the toroidal field magnets. A second feature is the signal stabilization of the EIO source by means of an AFC system. The complete interferometer is described including block diagrams, circuit diagrams, test data, and magnetic field test conducted on the preamplifiers, microwave diodes, isolators, etc., to determine the extent of magnetic shielding required. The description of the tracking filters and digital phase display circuit is referenced to accompanying reports.

  14. 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.

  15. Optical diffraction interpretation: an alternative to interferometers

    NASA Astrophysics Data System (ADS)

    Bouillet, S.; Audo, F.; Fréville, S.; Eupherte, L.; Rouyer, C.; Daurios, J.

    2015-08-01

    The Laser MégaJoule (LMJ) is a French high power laser project that requires thousands of large optical components. The wavefront performances of all those optics are critical to achieve the desired focal spot shape and to limit the hot spots that could damage the components. Fizeau interferometers and interferometric microscopes are the most commonly used tools to cover the whole range of interesting spatial frequencies. Anyway, in some particular cases like diffractive and/or coated and/or aspheric optics, an interferometric set-up becomes very expensive with the need to build a costly reference component or a specific to-the-wavelength designed interferometer. Despite the increasing spatial resolution of Fizeau interferometers, it may even not be enough, if you are trying to access the highest spatial frequencies of a transmitted wavefront for instance. The method we developed is based upon laser beam diffraction intermediate field measurements and their interpretation with a Fourier analysis and the Talbot effect theory. We demonstrated in previous papers that it is a credible alternative to classical methods. In this paper we go further by analyzing main error sources and discussing main practical difficulties.

  16. Optical interferometer testbed

    NASA Technical Reports Server (NTRS)

    Blackwood, Gary H.

    1991-01-01

    Viewgraphs on optical interferometer testbed presented at the MIT Space Research Engineering Center 3rd Annual Symposium are included. Topics covered include: space-based optical interferometer; optical metrology; sensors and actuators; real time control hardware; controlled structures technology (CST) design methodology; identification for MIMO control; FEM/ID correlation for the naked truss; disturbance modeling; disturbance source implementation; structure design: passive damping; low authority control; active isolation of lightweight mirrors on flexible structures; open loop transfer function of mirror; and global/high authority control.

  17. Gauss Quadratures - the Keystone of Lattice Boltzmann Models

    NASA Astrophysics Data System (ADS)

    Piaud, Benjamin; Blanco, Stéphane; Fournier, Richard; Ambruş, Victor Eugen; Sofonea, Victor

    2014-01-01

    In this paper, we compare two families of Lattice Boltzmann (LB) models derived by means of Gauss quadratures in the momentum space. The first one is the HLB(N;Qx,Qy,Qz) family, derived by using the Cartesian coordinate system and the Gauss-Hermite quadrature. The second one is the SLB(N;K,L,M) family, derived by using the spherical coordinate system and the Gauss-Laguerre, as well as the Gauss-Legendre quadratures. These models order themselves according to the maximum order N of the moments of the equilibrium distribution function that are exactly recovered. Microfluidics effects (slip velocity, temperature jump, as well as the longitudinal heat flux that is not driven by a temperature gradient) are accurately captured during the simulation of Couette flow for Knudsen number (kn) up to 0.25.

  18. Excess noise reduction by optical technique in amplitude-sensitive heterodyne interferometer for small differential phase detection

    SciTech Connect

    Teng, H.-K.; Lang, K.-C

    2008-12-20

    An amplitude-sensitive technique associated with a heterodyne interferometer for detecting small differential phase is reported. The excess noise with the amplitude-sensitive technique is reduced by optical subtraction instead of electronic subtraction. The differential phase introduced by the orthogonally polarized laser beams is converted to the amplitudes of two heterodyne interferometric signals, which presents amplitude and phase quadrature simultaneously. Thus the excess noise power and quantum noise power are both differential phase dependent. The advantages of differential and additive operations by optical technique and the real time differential phase determination without phase lock in are demonstrated experimentally. The theoretical signal-to-noise ratio (SNR) and minimum detectable differential phase are derived, which takes quantum noise and excess noise into consideration. The experimental results demonstrated the resolutions of differential phase detection closes to 10{sup -6} rad/{radical}Hz (10{sup -13} m/{radical}Hz) level over 100 kHz bandwidth and at 10{sup -8} rad/{radical}Hz (10{sup -15} m/{radical}Hz) level over 125 MHz bandwidth, respectively, under 2.5 mW incident power.

  19. Discrete ordinate quadrature selection for reactor-based Eigenvalue problems

    SciTech Connect

    Jarrell, J. J.; Evans, T. M.; Davidson, G. G.

    2013-07-01

    In this paper we analyze the effect of various quadrature sets on the eigenvalues of several reactor-based problems, including a two-dimensional (2D) fuel pin, a 2D lattice of fuel pins, and a three-dimensional (3D) reactor core problem. While many quadrature sets have been applied to neutral particle discrete ordinate transport calculations, the Level Symmetric (LS) and the Gauss-Chebyshev product (GC) sets are the most widely used in production-level reactor simulations. Other quadrature sets, such as Quadruple Range (QR) sets, have been shown to be more accurate in shielding applications. In this paper, we compare the LS, GC, QR, and the recently developed linear-discontinuous finite element (LDFE) sets, as well as give a brief overview of other proposed quadrature sets. We show that, for a given number of angles, the QR sets are more accurate than the LS and GC in all types of reactor problems analyzed (2D and 3D). We also show that the LDFE sets are more accurate than the LS and GC sets for these problems. We conclude that, for problems where tens to hundreds of quadrature points (directions) per octant are appropriate, QR sets should regularly be used because they have similar integration properties as the LS and GC sets, have no noticeable impact on the speed of convergence of the solution when compared with other quadrature sets, and yield more accurate results. We note that, for very high-order scattering problems, the QR sets exactly integrate fewer angular flux moments over the unit sphere than the GC sets. The effects of those inexact integrations have yet to be analyzed. We also note that the LDFE sets only exactly integrate the zeroth and first angular flux moments. Pin power comparisons and analyses are not included in this paper and are left for future work. (authors)

  20. Self-mixing interferometry based on quadrature demodulation technique for displacement measurement

    NASA Astrophysics Data System (ADS)

    Guo, Dongmei; Hao, Hui; Han, Daofu

    2010-10-01

    A new, to the best of our knowledge, method for the measurement of the micro-displacement of a remote target based on the laser diode self-mixing interferometry(LDSMI) is presented. Quadrature demodulation technique is introduced to improve the measurement accuracy. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement accuracy of the LDSMI system to a few nanometers.

  1. Mesoscopic Interferometers for Electron Waves

    SciTech Connect

    Rohrlich, D.

    2005-09-15

    Mesoscopic interferometers are electronic analogues of optical interferometers, with 'quantum point contacts' playing the role of optical beam splitters. Mesoscopic analogues of two-slit, Mach-Zehnder and Fabry-Perot interferometers have been built. A fundamental difference between electron and photon interferometry is that electron interferometry is nonlocal.

  2. Phase-Shifting Shearing Interferometer

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.

    2001-01-01

    A single-element phase-shifting interferometer has been developed based on the lateral shearing interferometer. This new interferometer requires no precise alignment, and the phase is continuously varied by changes in the voltage across a commercially available liquid-crystal phase retarder.

  3. Offset quadrature communications with decision-feedback carrier synchronization

    NASA Technical Reports Server (NTRS)

    Simon, M. K.; Smith, J. G.

    1974-01-01

    In order to accommodate a quadrature amplitude-shift-keyed (QASK) signal, Simon and Smith (1974) have modified the decision-feedback loop which tracks a quadrature phase-shift-keyed (QPSK). In the investigation reported approaches are considered to modify the loops in such a way that offset QASK signals can be tracked, giving attention to the special case of an offset QPSK. The development of the stochastic integro-differential equation of operation for a decision-feedback offset QASK loop is discussed along with the probability density function of the phase error process.

  4. Error estimates for Gaussian quadratures of analytic functions

    NASA Astrophysics Data System (ADS)

    Milovanovic, Gradimir V.; Spalevic, Miodrag M.; Pranic, Miroslav S.

    2009-12-01

    For analytic functions the remainder term of Gaussian quadrature formula and its Kronrod extension can be represented as a contour integral with a complex kernel. We study these kernels on elliptic contours with foci at the points ±1 and the sum of semi-axes [varrho]>1 for the Chebyshev weight functions of the first, second and third kind, and derive representation of their difference. Using this representation and following Kronrod's method of obtaining a practical error estimate in numerical integration, we derive new error estimates for Gaussian quadratures.

  5. The development of accurate and efficient methods of numerical quadrature

    NASA Technical Reports Server (NTRS)

    Feagin, T.

    1973-01-01

    Some new methods for performing numerical quadrature of an integrable function over a finite interval are described. Each method provides a sequence of approximations of increasing order to the value of the integral. Each approximation makes use of all previously computed values of the integrand. The points at which new values of the integrand are computed are selected in such a way that the order of the approximation is maximized. The methods are compared with the quadrature methods of Clenshaw and Curtis, Gauss, Patterson, and Romberg using several examples.

  6. Vibration analysis of structural elements using differential quadrature method.

    PubMed

    Nassar, Mohamed; Matbuly, Mohamed S; Ragb, Ola

    2013-01-01

    The method of differential quadrature is employed to analyze the free vibration of a cracked cantilever beam resting on elastic foundation. The beam is made of a functionally graded material and rests on a Winkler-Pasternak foundation. The crack action is simulated by a line spring model. Also, the differential quadrature method with a geometric mapping are applied to study the free vibration of irregular plates. The obtained results agreed with the previous studies in the literature. Further, a parametric study is introduced to investigate the effects of geometric and elastic characteristics of the problem on the natural frequencies. PMID:25685406

  7. Vibration analysis of structural elements using differential quadrature method

    PubMed Central

    Nassar, Mohamed; Matbuly, Mohamed S.; Ragb, Ola

    2012-01-01

    The method of differential quadrature is employed to analyze the free vibration of a cracked cantilever beam resting on elastic foundation. The beam is made of a functionally graded material and rests on a Winkler–Pasternak foundation. The crack action is simulated by a line spring model. Also, the differential quadrature method with a geometric mapping are applied to study the free vibration of irregular plates. The obtained results agreed with the previous studies in the literature. Further, a parametric study is introduced to investigate the effects of geometric and elastic characteristics of the problem on the natural frequencies. PMID:25685406

  8. Ultrasonic Interferometers Revisited

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    2007-01-01

    I have been tinkering with ultrasonic transducers once more. In earlier notes I reported on optics-like experiments performed with ultrasonics, described a number of ultrasonic interferometers, and showed how ultrasonic transducers can be used for Fourier analysis. This time I became interested in trying the technique of using two detectors in…

  9. Multispectral infrared imaging interferometer

    NASA Technical Reports Server (NTRS)

    Potter, A. E., Jr.

    1971-01-01

    Device permitting simultaneous viewing of infrared images at different wavelengths consists of imaging lens, Michelson interferometer, array of infrared detectors, data processing equipment for Fourier transformation of detector signal, and image display unit. Invention is useful in earth resources applications, nondestructive testing, and medical diagnoses.

  10. Dual beam optical interferometer

    NASA Technical Reports Server (NTRS)

    Gutierrez, Roman C. (Inventor)

    2003-01-01

    A dual beam interferometer device is disclosed that enables moving an optics module in a direction, which changes the path lengths of two beams of light. The two beams reflect off a surface of an object and generate different speckle patterns detected by an element, such as a camera. The camera detects a characteristic of the surface.

  11. Four-point bisensitivity velocity interferometer with a multireflection etalon

    SciTech Connect

    Peng Qixian; Ma Ruchao; Li Zeren; Liu Jun; Chen Guanghua

    2007-11-15

    A four-point bisensitivity velocity interferometer system for any reflector (VISAR) with a renovative delay etalon is proposed and demonstrated. In this interferometer, we introduce a new film-coating strategy to accurately measure small velocity with relatively short and cheap etalon. Laser pointing to the etalon is split into two beams with different incident angles with each beam going through the etalon in different path. The beam with the smaller incident angle is reflected three times before it leaves the etalon, while the other beam with larger incident angle goes through the etalon to and forth only once. The delay time of the laser beam with smaller incident angle is almost three times longer than that of the beam with larger incident angle. In the example of the laser with a smaller incident angle, the velocity per fringe of this interferometer can be reduced by approximately three times. The etalon is optimized so that four laser beams can be penetrated in the vertical direction at the meantime. With an etalon of 200 mm in diameter and 150 mm in length, a four-point bisensitivity velocity interferometer can achieve the velocity per fringe of 100 and 350 m/s fringe. A measurement has been successfully undertaken for the steel flyer driven by the explosive where the developed interferometer applies.

  12. Wave-Based Inversion & Imaging for the Optical Quadrature Microscope

    SciTech Connect

    Lehman, S K

    2005-10-27

    The Center for Subsurface Sensing & Imaging System's (CenSSIS) Optical Quadrature Microscope (OQM) is a narrow band visible light microscope capable of measuring both amplitude and phase of a scattered field. We develop a diffraction tomography, that is, wave-based, scattered field inversion and imaging algorithm, for reconstructing the refractive index of the scattering object.

  13. Gaussian rational quadrature formulas for ill-scaled integrands

    NASA Astrophysics Data System (ADS)

    Illán González, J. R.

    2009-12-01

    A flexible treatment of Gaussian quadrature formulas based on rational functions is given to evaluate the integral , when f is meromorphic in a neighborhood V of the interval I and W(x) is an ill-scaled weight function. Some numerical tests illustrate the power of this approach in comparison with Gautschi's method.

  14. From Lobatto Quadrature to the Euler Constant "e"

    ERIC Educational Resources Information Center

    Khattri, Sanjay Kumar

    2010-01-01

    Based on the Lobatto quadrature, we develop several new closed form approximations to the mathematical constant "e." For validating effectiveness of our approximations, a comparison of our results to the existing approximations is also presented. Another objective of our work is to inspire students to formulate other better approximations by using…

  15. Archimedes Quadrature of the Parabola: A Mechanical View

    ERIC Educational Resources Information Center

    Oster, Thomas J.

    2006-01-01

    In his famous quadrature of the parabola, Archimedes found the area of the region bounded by a parabola and a chord. His method was to fill the region with infinitely many triangles each of whose area he could calculate. In his solution, he stated, without proof, three preliminary propositions about parabolas that were known in his time, but are…

  16. Trapezoidal rule quadrature algorithms for MIMD distributed memory computers

    SciTech Connect

    Lyness, J.N.; Plowman, S.E.

    1994-08-01

    An approach to multi-dimensional quadrature, designed to exploit parallel architectures, is described. This involves transforming the integral in such a way that an accurate result is given by the trapezoidal rule; and by evaluating the resulting sum in a manner which may be efficiently implemented on parallel architectures. This approach is to be implemented in the Liverpool NAG transputer library.

  17. Achromatic self-referencing interferometer

    DOEpatents

    Feldman, M.

    1994-04-19

    A self-referencing Mach-Zehnder interferometer is described for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and registers the resulting interference pattern ([open quotes]first[close quotes] interferogram) at a first detector. Optionally, subportions of the measurement portion are diverted to second and third detectors, which respectively register intensity and interferogram signals which can be processed to reduce the first interferogram's sensitivity to input noise. The reference arm includes a spatial filter producing a high quality spherical beam from the reference portion, a tilted wedge plate compensating for off-axis aberrations in the spatial filter output, and mirror collimating the radiation transmitted through the tilted wedge plate. The apparatus includes a thermally and mechanically stable baseplate which supports all reference arm optics, or at least the spatial filter, tilted wedge plate, and the collimator. The tilted wedge plate is mounted adjustably with respect to the spatial filter and collimator, so that it can be maintained in an orientation in which it does not introduce significant wave front errors into the beam propagating through the reference arm. The apparatus is polarization insensitive and has an equal path length configuration enabling measurement of radiation from broadband as well as closely spaced laser line sources. 3 figures.

  18. Achromatic self-referencing interferometer

    DOEpatents

    Feldman, Mark

    1994-01-01

    A self-referencing Mach-Zehnder interferometer for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and registers the resulting interference pattern ("first" interferogram) at a first detector. Optionally, subportions of the measurement portion are diverted to second and third detectors, which respectively register intensity and interferogram signals which can be processed to reduce the first interferogram's sensitivity to input noise. The reference arm includes a spatial filter producing a high quality spherical beam from the reference portion, a tilted wedge plate compensating for off-axis aberrations in the spatial filter output, and mirror collimating the radiation transmitted through the tilted wedge plate. The apparatus includes a thermally and mechanically stable baseplate which supports all reference arm optics, or at least the spatial filter, tilted wedge plate, and the collimator. The tilted wedge plate is mounted adjustably with respect to the spatial filter and collimator, so that it can be maintained in an orientation in which it does not introduce significant wave front errors into the beam propagating through the reference arm. The apparatus is polarization insensitive and has an equal path length configuration enabling measurement of radiation from broadband as well as closely spaced laser line sources.

  19. Parametric oscillatory instability in a signal-recycled LIGO interferometer

    SciTech Connect

    Vyatchanin, S P; Strigin, S E

    2007-12-31

    The undesirable effect of parametric oscillatory instability in a LIGO (Laser Interferometer Gravitational-Wave Observatory) laser gravitational-wave antenna with a signal-recirculation mirror is analysed in detail. The instability is manifested in excitation of the Stokes optical mode and elastic mechanical mode of the mirror. It is shown that, if the eigenfrequencies of Fabry-Perot resonators in the interferometer arms are different, the parametric instability is quite small due to a small passband band width. (fifth seminar in memory of d.n. klyshko)

  20. Nd:YAG holographic interferometer for aerodynamic research

    NASA Technical Reports Server (NTRS)

    Craig, J. E.; Lee, G.; Bachalo, W. D.

    1983-01-01

    A holographic interferometer system has been installed in the NASA Ames 2- by 2-Foot Transonic Wind Tunnel. The system incorporates a modern 10 pps, Nd:YAG pulsed laser which provides reliable operation and is easy to align. The spatial filtering requirements of the unstable resonator beam are described, as well as the integration of the system into the existing schlieren system. A two-plate holographic interferometer is used to reconstruct flow field data. For static wind tunnel models, the single exposure holograms are recorded in the usual manner; however, for dynamic models such as oscillating airfoils, synchronous laser hologram recording is used.

  1. Increasing the Sensitivity of the Michelson Interferometer through Multiple Reflection

    NASA Astrophysics Data System (ADS)

    Youn, Woonghee

    Michelson interferometry has been one of the most famous and popular optical interference system for analyzing optical components and measuring optical metrology properties. Typical Michelson interferometer can measure object displacement with wavefront shapes to one half of the laser wavelength. As testing components and devices size reduce to micro and nano dimension, Michelson interferometer sensitivity is not suitable. The purpose of this study is to design and develop the Michelson interferometer using the concept of multiple reflections. This thesis proposes a new and novel design for a multiple reflection interferometer, where the number of reflections does not affect the quality of the interference. Theoretically we show that more than 1000 reflections can be achieved. Experimental results of greater than 100 reflections are presented in this thesis.

  2. Achromatic registration of quadrature components of the optical spectrum in spectral domain optical coherence tomography

    SciTech Connect

    Shilyagin, P A; Gelikonov, G V; Gelikonov, V M; Moiseev, A A; Terpelov, D A

    2014-07-31

    We have thoroughly investigated the method of simultaneous reception of spectral components with the achromatised quadrature phase shift between two portions of a reference wave, designed for the effective suppression of the 'mirror' artefact in the resulting image obtained by means of spectral domain optical coherence tomography (SD OCT). We have developed and experimentally tested a phase-shifting element consisting of a beam divider, which splits the reference optical beam into the two beams, and of delay lines being individual for each beam, which create a mutual phase difference of π/2 in the double pass of the reference beam. The phase shift achromatism over a wide spectral range is achieved by using in the delay lines the individual elements with different dispersion characteristics. The ranges of admissible adjustment parameters of the achromatised delay line are estimated for exact and inexact conformity of the geometric characteristics of its components to those calculated. A possibility of simultaneous recording of the close-to-quadrature spectral components with a single linear photodetector element is experimentally confirmed. The suppression of the artefact mirror peak in the OCT-signal by an additional 9 dB relative to the level of its suppression is experimentally achieved when the air delay line is used. Two-dimensional images of the surface positioned at an angle to the axis of the probe beam are obtained with the correction of the 'mirror' artefact while maintaining the dynamic range of the image. (laser biophotonics)

  3. A continuous cold atomic beam interferometer

    SciTech Connect

    Xue, Hongbo; Feng, Yanying Yan, Xueshu; Jiang, Zhikun; Chen, Shu; Wang, Xiaojia; Zhou, Zhaoying

    2015-03-07

    We demonstrate an atom interferometer that uses a laser-cooled continuous beam of {sup 87}Rb atoms having velocities of 10–20 m/s. With spatially separated Raman beams to coherently manipulate the atomic wave packets, Mach–Zehnder interference fringes are observed at an interference distance of 2L = 19 mm. The apparatus operates within a small enclosed area of 0.07 mm{sup 2} at a bandwidth of 190 Hz with a deduced sensitivity of 7.8×10{sup −5} rad/s/√(Hz) for rotations. Using a low-velocity continuous atomic source in an atom interferometer enables high sampling rates and bandwidths without sacrificing sensitivity and compactness, which are important for applications in real dynamic environments.

  4. Analysis of a free oscillation atom interferometer

    SciTech Connect

    Kafle, Rudra P.; Zozulya, Alex A.; Anderson, Dana Z.

    2011-09-15

    We analyze a Bose-Einstein condensate (BEC)-based free oscillation atom Michelson interferometer in a weakly confining harmonic magnetic trap. A BEC at the center of the trap is split into two harmonics by a laser standing wave. The harmonics move in opposite directions with equal speeds and turn back under the influence of the trapping potential at their classical turning points. The harmonics are allowed to pass through each other and a recombination pulse is applied when they overlap at the end of a cycle after they return for the second time. We derive an expression for the contrast of the interferometric fringes and obtain the fundamental limit of performance of the interferometer in the parameter space.

  5. Multipulsed dynamic moire interferometer

    DOEpatents

    Deason, Vance A.

    1991-01-01

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

  6. Cold Lithium Atom Interferometer

    NASA Astrophysics Data System (ADS)

    Cassella, Kayleigh; Copenhaver, Eric; Lai, Chen; Hamilton, Paul; Estey, Brian; Feng, Yanying; Mueller, Holger

    2015-05-01

    Atom interferometers often use heavy alkali atoms such as rubidium or cesium. In contrast, interferometry with light atoms offers a larger recoil velocity and recoil energy, yielding a larger interference signal. This would allow for sensitive measurements of the fine structure constant, gravity gradients and spatially varying potentials. We have built the first light-pulse cold-atom interferometer with lithium in a Mach-Zehnder geometry based on short (100 ns), intense (2.5 W/cm2) pulses. We initially capture approximately 107 lithium atoms at a temperature of about 300 ?K in a magneto-optical trap. To perform interferometry, we couple the F = 1 and F = 2 hyperfine levels of the ground state with a sequence of two-photon Raman transitions, red-detuned from lithium's unresolved 2P3/2 state. Cold lithium atoms offer a broad range of new possibilities for atom interferometry including a large recoil velocity and a fermionic and bosonic isotope. Lithium's isotopes also allow for independent measurements of gravity thus constraining the equivalence principle violations predicted by the Standard-Model Extension. In the near future, we plan to perform a recoil measurement using a Ramsey-Bord interferometer.

  7. The Keck Interferometer

    NASA Astrophysics Data System (ADS)

    Colavita, M. M.; Wizinowich, P. L.; Akeson, R. L.; Ragland, S.; Woillez, J. M.; Millan-Gabet, R.; Serabyn, E.; Abajian, M.; Acton, D. S.; Appleby, E.; Beletic, J. W.; Beichman, C. A.; Bell, J.; Berkey, B. C.; Berlin, J.; Boden, A. F.; Booth, A. J.; Boutell, R.; Chaffee, F. H.; Chan, D.; Chin, J.; Chock, J.; Cohen, R.; Cooper, A.; Crawford, S. L.; Creech-Eakman, M. J.; Dahl, W.; Eychaner, G.; Fanson, J. L.; Felizardo, C.; Garcia-Gathright, J. I.; Gathright, J. T.; Hardy, G.; Henderson, H.; Herstein, J. S.; Hess, M.; Hovland, E. E.; Hrynevych, M. A.; Johansson, E.; Johnson, R. L.; Kelley, J.; Kendrick, R.; Koresko, C. D.; Kurpis, P.; Le Mignant, D.; Lewis, H. A.; Ligon, E. R.; Lupton, W.; McBride, D.; Medeiros, D. W.; Mennesson, B. P.; Moore, J. D.; Morrison, D.; Nance, C.; Neyman, C.; Niessner, A.; Paine, C. G.; Palmer, D. L.; Panteleeva, T.; Papin, M.; Parvin, B.; Reder, L.; Rudeen, A.; Saloga, T.; Sargent, A.; Shao, M.; Smith, B.; Smythe, R. F.; Stomski, P.; Summers, K. R.; Swain, M. R.; Swanson, P.; Thompson, R.; Tsubota, K.; Tumminello, A.; Tyau, C.; van Belle, G. T.; Vasisht, G.; Vause, J.; Vescelus, F.; Walker, J.; Wallace, J. K.; Wehmeier, U.; Wetherell, E.

    2013-10-01

    The Keck Interferometer (KI) combined the two 10 m W. M. Keck Observatory telescopes on Mauna Kea, Hawaii, as a long-baseline near- and mid-infrared interferometer. Funded by NASA, it operated from 2001 until 2012. KI used adaptive optics on the two Keck telescopes to correct the individual wavefronts, as well as active fringe tracking in all modes for path-length control, including the implementation of cophasing to provide long coherent integration times. KI implemented high sensitivity fringe-visibility measurements at H (1.6 μm), K (2.2 μm), and L (3.8 μm) bands, and nulling measurements at N band (10 μm), which were used to address a broad range of science topics. Supporting these capabilities was an extensive interferometer infrastructure and unique instrumentation, including some additional functionality added as part of the NSF-funded ASTRA program. This paper provides an overview of the instrument architecture and some of the key design and implementation decisions, as well as a description of all of the key elements and their configuration at the end of the project. The objective is to provide a view of KI as an integrated system, and to provide adequate technical detail to assess the implementation. Included is a discussion of the operational aspects of the system, as well as of the achieved system performance. Finally, details on V2 calibration in the presence of detector nonlinearities as applied in the data pipeline are provided.

  8. Recirculating fibre ring interferometer with compensation for losses in the cavity

    SciTech Connect

    Alekseev, E I; Bazarov, E N; Gubin, Vladimir P; Sazonov, Aleksandr I; Starostin, M I; Oussov, Aleksey I

    2001-12-31

    A new recirculating fibre ring interferometer with an intracavity fibre amplifier and a broadband light source is developed. A substantial increase in the threshold sensitivity of the interferometer to rotation and an increase in the scale factor are experimentally demonstrated in the near-threshold regime. (laser applications and other topics in quantum electronics)

  9. Atom-Light Hybrid Interferometer.

    PubMed

    Chen, Bing; Qiu, Cheng; Chen, Shuying; Guo, Jinxian; Chen, L Q; Ou, Z Y; Zhang, Weiping

    2015-07-24

    A new type of hybrid atom-light interferometer is demonstrated with atomic Raman amplification processes replacing the beam splitting elements in a traditional interferometer. This nonconventional interferometer involves correlated optical and atomic waves in the two arms. The correlation between atoms and light developed with the Raman process makes this interferometer different from conventional interferometers with linear beam splitters. It is observed that the high-contrast interference fringes are sensitive to the optical phase via a path change as well as the atomic phase via a magnetic field change. This new atom-light correlated hybrid interferometer is a sensitive probe of the atomic internal state and should find wide applications in precision measurement and quantum control with atoms and photons. PMID:26252684

  10. A Robust Ramsey Interferometer for Atomic Timekeeping in Dynamic Environments

    NASA Astrophysics Data System (ADS)

    Kotru, Krish; Brown, Justin; Butts, David; Choy, Jennifer; Galfond, Marissa; Johnson, David M.; Kinast, Joseph; Timmons, Brian; Stoner, Richard

    2014-05-01

    We present a laser-based approach to atomic timekeeping, in which atomic phase information is extracted using modified Raman pulses in a Ramsey sequence. We overcome systematic effects associated with differential AC Stark shifts by employing atom optics derived from Raman adiabatic rapid passage (ARP). ARP drives coherent transfer between two hyperfine ground states by sweeping the frequency difference of two optical fields and maintaining a large single-photon detuning. Compared to resonant, pulsed Raman transitions, ARP atom optics afford a >150x reduction in sensitivity to differential AC Stark shifts in a Ramsey interferometer. We also demonstrate that ARP preserves fringe contrast in Ramsey interferometers for cloud displacements reaching the 1/e2 intensity radius of the laser beam. ARP can thus be expected to improve the robustness of clock interferometers operating in dynamic environments. Copyright 2014 by The Charles Stark Draper Laboratory, Inc. All rights reserved.

  11. White light interferometer: applications in research and industry

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Sujit

    2015-06-01

    Applications of interferometer are countless both in the research and commercial world. Laser sources offer precise measurements of relative path difference between two interfering beams. An exciting example is LIGO (laser Interferometer for Gravitational Observatory), which is aiming to resolve length change as small as 10-19 m over a 4 km length for detection of gravitational waves. However, laser is a disadvantage for microscopic imaging and surface topography applications usually required in semiconductor industry. A different approach for microscopy is to use white light in place of laser. White light due to its limited temporal coherence offers a multitude of benefits for imaging applications. An immediate benefit from white light is the sharp localisation of interference fringe that makes the 3D topography construction or OCT (Optical Coherence Topography) realisable using a Scanning White Light Interferometer (SWLI) imager. In Mirau Mode, SWLI performs high resolution imaging; whereas in Michelson mode Fourier Transform Spectroscopy (FTS) is realised. SWLI can easily be modified into PUPS (Pupil Plane SWLI) for Ellipsometry. Superimposing Michelson Interferometer known as VISAR (Velocity Interferometer System for Any reflector) can form interference fringes even in presence of wide angle light scattered from a moving illuminated object. This paper describes work undertaken at Nanometrics (UK) on simulation of SWLI fringes including high Numerical Aperture (NA) applications, thin film characterisation, OCT generation and Zemax modelling of compact dispersion-free vibration-immune Fourier-Transformed spectrometer. VISAR as a modified Mach-Zehnder Interferometer is also discussed based on the work at Rutherford-Appleton laboratory (UK).

  12. On Gauss-Kronrod quadrature formulae of Chebyshev type

    NASA Astrophysics Data System (ADS)

    Notaris, Sotirios E.

    1992-04-01

    We prove that there is no positive measure d? on (a, b) such that the corresponding Gauss-Kronrod quadrature formula is also a Chebyshev quadrature formula. The same is true if we consider measures of the form d? (t) = ? (t)dt , where ? (t) is even, on a symmetric interval ( - a,a) , and the Gauss-Kronrod formula is required to have equal weights only for n even. We also show that the only positive and even measure d? (t) = d? ( - t) on ( - 1,1) for which the Gauss-Kronrod formula has all weights equal if n = 1 , or has the form int _{ - 1}^1f(t)d? (t) = w? _{? = 1}^nf({?_?}) + {w_1}f(1) + w? _{? = 2}^nf(?_? ^ast) + {w_1}f( - 1) + R_n^K(f) for all n ? 2 , is the Chebyshev measure of the first kind d{? _C}(t) = {(1 - {t^2})^{ - 1/2}}dt .

  13. On a quadrature formula of Gori and Micchelli

    NASA Astrophysics Data System (ADS)

    Yang, Shijun

    2005-04-01

    Sparked by Bojanov (J. Comput. Appl. Math. 70 (1996) 349), we provide an alternate approach to quadrature formulas based on the zeros of the Chebyshev polynomial of the first kind for any weight function w introduced and studied in Gori and Micchelli (Math. Comp. 65 (1996) 1567), thereby improving on their observations. Upon expansion of the divided differences, we obtain explicit expressions for the corresponding Cotes coefficients in Gauss-Turan quadrature formulas for and I(fTn;w) for a Gori-Micchelli weight function. It is also interesting to mention what has been neglected for about 30 years by the literature is that, as a consequence of expansion of the divided differences in the special case when , the solution of the famous Turan's Problem 26 raised in 1980 was in fact implied by a result of Micchelli and Rivlin (IBM J. Res. Develop. 16 (1972) 372) in 1972. Some concluding comments are made in the final section.

  14. Accurate Computation of Gaussian Quadrature for Tension Powers

    NASA Astrophysics Data System (ADS)

    Singer, Saša

    2007-09-01

    We consider Gaussian quadrature formulæ which exactly integrate a system of tension powers 1,x,x2,…,xn-3, sinh(px), cosh(px), on a given interval [a,b], where n⩾4 is an even integer and p>0 is a given tension parameter. In some applications it is essential that p can be changed dynamically, and we need an efficient "on-demand" algorithm that calculates the nodes and weights of Gaussian quadrature formulas for many different values of p, which are not known in advance. It is an interesting numerical challenge to achieve the required full machine precision accuracy in such an algorithm, for all possible values of p. By exploiting various analytic and numerical techniques, we show that this can be done efficiently for all reasonably low values of n that are of any practical importance.

  15. Extraction of quadrature phase information from multiple pulse NMR signals

    NASA Technical Reports Server (NTRS)

    Rhim, W.-K.; Burum, D. P.; Vaughan, R. W.

    1976-01-01

    A multiple pulse sequence (8-pulse sequence) used for high-resolution solid state NMR is analyzed with regard to the information available from each of the four wide sampling windows. It is demonstrated that full quadrature phase information can be obtained using only a single phase detector and that, for the commonly encountered situation where the spectral width is much less than the folding frequency, the signals from the various windows can be combined easily using standard complex Fourier transform software. An improvement in the signal-to-noise ratio equal to the square root of 3 is obtained over either standard single or quadrature phase detection schemes. Procedures for correcting spectral distortions are presented.

  16. FIR interferometer and scattering measurements of ATF

    SciTech Connect

    Ma, C.H.; Hutchinson, D.P.; Fockedey, Y.; Vander Sluis, K.L.; Bennett, C.A.

    1989-01-01

    A 15-channel far-infrared (FIR) interferometer system has been constructed to measure the electron densities on the ATF plasmas. The system consists of a pair of cw 214-..mu..m difluoromethane (CH/sub 2/F/sub 2/) lasers, optically pumped by separate CO/sub 2/ lasers. The large number of channels is achieved by the use of reflective beam expansion optics to create a beam of 2 cm /times/ 45 cm. After passing through the plasma discharge, the elongated beam produced by the cylindrical mirrors is dissected by an array of 15 off-axis paraboloid reflectors, each of which illuminates a single Schottky-diode detector. The use of the beam expanding optics system reduces the number of optical elements required for the interferometer to approximately 2-3 per channel. The FIR laser beams are transported from the laser room to the experimental area by 25 mm i.d. dielectric waveguides purged with dry nitrogen. The system can also be operated at a wavelength of 119-..mu..m by changing the gas in FIR laser cavities to methanol for high density experiments. Details of the system are described. A study is underway to determine the optimum design of a FIR scattering system for the ATF. This scattering system will be used to investigate density fluctuations with scale lengths from 0.1 cm to the plasma radius. The laser for this scattering system may be operated at wavelengths of 447, 307, 214, 184, and 119 ..mu..m with power levels of 100 to 500 mW. A summary of the study is presented. 6 refs., 1 fig.

  17. The Design and Operation of Ultra-Sensitive and Tunable Radio-Frequency Interferometers

    PubMed Central

    Cui, Yan; Wang, Pingshan

    2015-01-01

    Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many applications, including lab-on-chip development where sample volumes are small with a wide range of dynamic processes to probe. In this work, we present the design and operation considerations of radio-frequency (RF) interferometers that are based on power-dividers (PDs) and quadrature-hybrids (QHs). Such interferometers are proposed to address the sensitivity and frequency tuning challenges of current DS techniques. Verified algorithms together with mathematical models are presented to quantify material properties from scattering parameters for three common transmission line sensing structures, i.e., coplanar waveguides (CPWs), conductor-backed CPWs, and microstrip lines. A high-sensitivity and stable QH-based interferometer is demonstrated by measuring glucose–water solution at a concentration level that is ten times lower than some recent RF sensors while our sample volume is ~1 nL. Composition analysis of ternary mixture solutions are also demonstrated with a PD-based interferometer. Further work is needed to address issues like system automation, model improvement at high frequencies, and interferometer scaling. PMID:26549891

  18. Solar Wind Characteristics from SOHO-Sun-Ulysses Quadrature Observations

    NASA Technical Reports Server (NTRS)

    Poletto, Giannina; Suess, Steve T.; Six, N. Frank (Technical Monitor)

    2002-01-01

    Over the past few years, we have been running SOHO (Solar and Heliospheric Observatory)-Sun-Ulysses quadrature campaigns, aimed at comparing the plasma properties at coronal altitudes with plasma properties at interplanetary distances. Coronal plasma has been observed by SOHO experiments: mainly, we used LASCO (Large Angle and Spectrometric Coronagraph Experiment) data to understand the overall coronal configuration at the time of quadratures and analyzed SUMER (Solar Ultraviolet Measurements of Emitted Radiation), CDS (Coronal Diagnostic Spectrometer) and UVCS (Ultraviolet Coronagraph Spectrometer) data to derive its physical characteristics. At interplanetary distances, SWICS (Solar Wind Ion Composition Spectrometer) and SWOOPS (Solar Wind Observation over the Poles of the Sun) aboard Ulysses provided us with interplanetary plasma data. Here we report on results from some of the campaigns. We notice that, depending on the geometry of the quadrature, i.e. on whether the radial to Ulysses traverses the corona at high or low latitudes, we are able to study different kinds of solar wind. In particular, a comparison between low-latitude and high-latitude wind, allowed us to provide evidence for differences in the acceleration of polar, fast plasma and equatorial, slow plasma: the latter occurring at higher levels and through a more extended region than fast wind. These properties are shared by both the proton and heavy ions outflows. Quadrature observations may provide useful information also on coronal vs. in situ elemental composition. To this end, we analyzed spectra taken in the corona, at altitudes ranging between approx. 1.02 and 2.2 solar radii, and derived the abundances of a number of ions, including oxygen and iron. Values of the O/Fe ratio, at coronal levels, have been compared with measurements of this ratio made by SWICS at interplanetary distances. Our results are compared with previous findings and predictions from modeling efforts.

  19. Best quadrature formula on Sobolev class with Chebyshev weight

    NASA Astrophysics Data System (ADS)

    Xie, Congcong

    2008-05-01

    Using best interpolation function based on a given function information, we present a best quadrature rule of function on Sobolev class KWr[-1,1] with Chebyshev weight. The given function information means that the values of a function f[set membership, variant]KWr[-1,1] and its derivatives up to r-1 order at a set of nodes x are given. Error bounds are obtained, and the method is illustrated by some examples.

  20. Some new applications of truncated Gauss-Laguerre quadrature formulas

    NASA Astrophysics Data System (ADS)

    Mastroianni, G.; Monegato, G.

    2008-12-01

    We show how truncated Gauss-Laguerre quadrature formulas can be used to produce accurate approximations and high rates of convergence, also when they are applied to integrand functions having only an algebraic type decay to zero at infinity. The approach presented in the paper is proposed for the computation of integrals and for the construction of Nyström type interpolants for some second kind integral equations.

  1. Mark-3 interferometer

    NASA Astrophysics Data System (ADS)

    Staelin, David H.; Barrett, John W.; Kim, Edward J.; Stuart, Howard R.

    1989-09-01

    The development and testing of the Mark-3 stellar interferometer is considered. The instrument employs a two color technique to reduce position errors due to atmospheric turbulence, and can operate with four possible baseline configurations ranging from 9 to 20 meters. Despite its function as a technology development platform, it is also capable of stellar separation and stellar diameter measurements with nearly unprecedented accuracy and sensitivity. The major contributions are the development of a dispersed-fringe group delay measurement system which can boost the system sensitivity by several stellar magnitudes, and the initial stages of development of an infrared capability, which should increase the future scientific interest of the facility.

  2. In situ measurement of absorption in high-power interferometers by using beam diameter measurements.

    PubMed

    Ottaway, David; Betzwieser, Joseph; Ballmer, Stefan; Waldman, Sam; Kells, William

    2006-02-15

    We present a simple technique to make in situ measurements of the absorption in the optics of high-power laser interferometers. The measurement is particularly useful to those commissioning large-scale high power optical systems. PMID:16496883

  3. MIKES’ primary phase stepping gauge block interferometer

    NASA Astrophysics Data System (ADS)

    Byman, V.; Lassila, A.

    2015-08-01

    MIKES’ modernized phase stepping interferometer for gauge block calibration (PSIGB) will be described. The instrument is based on the well-regarded NPL-TESA gauge block interferometer from 1994. The decision to upgrade the instrument resulted from several components, such as the PC and charge-coupled device (CCD) camera, having reached the end of their lifetime. In this paper modernized components, measurement method and analysis will be explained. The lasers are coupled to the instrument using single mode fiber. The instrument uses phase stepping generated by an added optical window on a controllable rotatory table in the reference arm with a recently developed nine-position phase stepping algorithm. Unwrapping is done with a robust path following algorithm. Procedures for adjusting the interferometer are explained. Determination and elimination of wavefront error, coherent noise and analysis of their influence on the results is described. Flatness and variation in length are also important parameters of gauge blocks to be characterized, and the corresponding analysis method is clarified. Uncertainty analysis for the central length, flatness and variation in length is also described. The results are compared against those of the old hardware and software. The standard uncertainty for central length measurement is u = [(9.5 nm)2 + (121 × 10-9 L)2]½, where L is measured length.

  4. Fast evaluation of quadrature formulae on the sphere

    NASA Astrophysics Data System (ADS)

    Keiner, Jens; Potts, Daniel

    2008-03-01

    Recently, a fast approximate algorithm for the evaluation of expansions in terms of standard mathrm{L}^2left(mathbb{S}^2right) -orthonormal spherical harmonics at arbitrary nodes on the sphere mathbb{S}^2 has been proposed in [S. Kunis and D. Potts. Fast spherical Fourier algorithms. JE Comput. Appl. Math., 161:75-98, 2003]. The aim of this paper is to develop a new fast algorithm for the adjoint problem which can be used to compute expansion coefficients from sampled data by means of quadrature rules. We give a formulation in matrix-vector notation and an explicit factorisation of the spherical Fourier matrix based on the former algorithm. Starting from this, we obtain the corresponding factorisation of the adjoint spherical Fourier matrix and are able to describe the associated algorithm for the adjoint transformation which can be employed to evaluate quadrature rules for arbitrary weights and nodes on the sphere. We provide results of numerical tests showing the stability of the obtained algorithm using as examples classical Gauss-Legendre and Clenshaw-Curtis quadrature rules as well as the HEALPix pixelation scheme and an equidistribution.

  5. An Application of the Quadrature-Free Discontinuous Galerkin Method

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Atkins, Harold L.

    2000-01-01

    The process of generating a block-structured mesh with the smoothness required for high-accuracy schemes is still a time-consuming process often measured in weeks or months. Unstructured grids about complex geometries are more easily generated, and for this reason, methods using unstructured grids have gained favor for aerodynamic analyses. The discontinuous Galerkin (DG) method is a compact finite-element projection method that provides a practical framework for the development of a high-order method using unstructured grids. Higher-order accuracy is obtained by representing the solution as a high-degree polynomial whose time evolution is governed by a local Galerkin projection. The traditional implementation of the discontinuous Galerkin uses quadrature for the evaluation of the integral projections and is prohibitively expensive. Atkins and Shu introduced the quadrature-free formulation in which the integrals are evaluated a-priori and exactly for a similarity element. The approach has been demonstrated to possess the accuracy required for acoustics even in cases where the grid is not smooth. Other issues such as boundary conditions and the treatment of non-linear fluxes have also been studied in earlier work This paper describes the application of the quadrature-free discontinuous Galerkin method to a two-dimensional shear layer problem. First, a brief description of the method is given. Next, the problem is described and the solution is presented. Finally, the resources required to perform the calculations are given.

  6. First gravity measurements using the mobile atom interferometer GAIN

    NASA Astrophysics Data System (ADS)

    Hauth, M.; Freier, C.; Schkolnik, V.; Senger, A.; Schmidt, M.; Peters, A.

    2013-10-01

    We present the compact Gravimetric Atom Interferometer (GAIN), based on laser-cooled 87Rb atoms, and discuss its first measurements of the local gravitational acceleration. In this context, we also describe an active vibration isolation system and a tip-tilt stage, which allow for a suppression of vibrational noise and systematic effects like the Coriolis force due to Earth's rotation.

  7. Dual-arm multiple-reflection Michelson interferometer for large multiple reflections and increased sensitivity

    NASA Astrophysics Data System (ADS)

    Joenathan, Charles; Bernal, Ashley; Woonghee, Youn; Bunch, Robert M.; Hakoda, Christopher

    2016-02-01

    Michelson interferometer is one of the most popular optical interferometric systems used in optical metrology. Typically, Michelson interferometers are used to measure object displacement with wavefront shapes to one half of the laser wavelength. As testing components and device sizes reduce to micro and nano size, a sensitivity of half the wavelength of light cannot be used to measure several hundred picometer displacement. Multiple-reflection interferometers have been proposed and are used to increase the sensitivity in a Michelson interferometer; however, when altering the number of reflections, the system alignment becomes cumbersome. We describe some of the problems associated with the current multiple-reflection interferometer and introduce a setup for matching path lengths to increase the resolution and allow for the reduction of the stringent requirement on the coherence length of the lasers used. Theoretically, we show that more than 1000 reflections can be achieved. Experimental results of up to 100 reflections are presented in this paper.

  8. Laser-interference methods in hydroacoustic systems

    NASA Astrophysics Data System (ADS)

    Dolgikh, G. I.; Plotnikov, A. A.

    2008-03-01

    In article the description of bottom station is resulted, basic measuring device is laser-interference hydrophone. Laser-interference hydrophone is created on a basis Michelson interferometer of equal-arm type. As a light source in interferometer the semi-conductor laser is used. A sensitive element of a laser hydrophone is the round membrane which is included in system <>.

  9. Interferometer using RF switching matrix

    NASA Technical Reports Server (NTRS)

    Vanvleet, R. N.

    1972-01-01

    Radio frequency switching technique for single receiver and data processing channel to be used for phase movement measurement is discussed. Components of interferometer radio frequency unit, X-band receiver, and interferometer data processing unit are illustrated. Elimination of major measurement error source is described.

  10. Advanced quadratures and periodic boundary conditions in parallel 3D S{sub n} transport

    SciTech Connect

    Manalo, K.; Yi, C.; Huang, M.; Sjoden, G.

    2013-07-01

    Significant updates in numerical quadratures have warranted investigation with 3D Sn discrete ordinates transport. We show new applications of quadrature departing from level symmetric (S{sub 2}o). investigating 3 recently developed quadratures: Even-Odd (EO), Linear-Discontinuous Finite Element - Surface Area (LDFE-SA), and the non-symmetric Icosahedral Quadrature (IC). We discuss implementation changes to 3D Sn codes (applied to Hybrid MOC-Sn TITAN and 3D parallel PENTRAN) that can be performed to accommodate Icosahedral Quadrature, as this quadrature is not 90-degree rotation invariant. In particular, as demonstrated using PENTRAN, the properties of Icosahedral Quadrature are suitable for trivial application using periodic BCs versus that of reflective BCs. In addition to implementing periodic BCs for 3D Sn PENTRAN, we implemented a technique termed 'angular re-sweep' which properly conditions periodic BCs for outer eigenvalue iterative loop convergence. As demonstrated by two simple transport problems (3-group fixed source and 3-group reflected/periodic eigenvalue pin cell), we remark that all of the quadratures we investigated are generally superior to level symmetric quadrature, with Icosahedral Quadrature performing the most efficiently for problems tested. (authors)

  11. Rational choices for the wavelengths of a two color interferometer

    SciTech Connect

    Jobes, F.C.

    1995-07-01

    If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO{sub 2} lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers.

  12. 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.

  13. Optimization of the HCN interferometer on J-TEXT tokamak

    NASA Astrophysics Data System (ADS)

    Shi, P.; Gao, L.; Xiong, C. Y.; Liu, Y.; Chen, J.; Zhuang, G.

    2015-12-01

    Recently, the HCN interferometer on J-TEXT has been optimized in many aspects. Firstly, the output power of laser source is more stable after using a new designed movable mirror frame and upgrading the oil thermostatic system. Secondly, the electromagnetic interferences have been eliminated by designing a shielding system. Additionally, the signal-to-noise ratio of intermediate frequency (IF) signal has been increased more than five times by improving the detector circuit. The density resolution has been increased from 1×1018 m-3 to 2×1017 m-3 and the sawtooth oscillation has also been measured by the HCN interferometer on J- TEXT after optimizations.

  14. The high accuracy data processing system of laser interferometry signals based on MSP430

    NASA Astrophysics Data System (ADS)

    Qi, Yong-yue; Lin, Yu-chi; Zhao, Mei-rong

    2009-07-01

    Generally speaking there are two orthogonal signals used in single-frequency laser interferometer for differentiating direction and electronic subdivision. However there usually exist three errors with the interferential signals: zero offsets error, unequal amplitude error and quadrature phase shift error. These three errors have a serious impact on subdivision precision. Based on Heydemann error compensation algorithm, it is proposed to achieve compensation of the three errors. Due to complicated operation of the Heydemann mode, a improved arithmetic is advanced to decrease the calculating time effectively in accordance with the special characteristic that only one item of data will be changed in each fitting algorithm operation. Then a real-time and dynamic compensatory circuit is designed. Taking microchip MSP430 as the core of hardware system, two input signals with the three errors are turned into digital quantity by the AD7862. After data processing in line with improved arithmetic, two ideal signals without errors are output by the AD7225. At the same time two original signals are turned into relevant square wave and imported to the differentiating direction circuit. The impulse exported from the distinguishing direction circuit is counted by the timer of the microchip. According to the number of the pulse and the soft subdivision the final result is showed by LED. The arithmetic and the circuit are adopted to test the capability of a laser interferometer with 8 times optical path difference and the measuring accuracy of 12-14nm is achieved.

  15. Mark 3 interferometer

    NASA Astrophysics Data System (ADS)

    Staelin, David H.; Barrett, John W.; Kim, Edward J.; Stuart, Howard R.

    1990-01-01

    This work is a continuation of that begun under Naval Research Laboratory Contracts N00014-84-C-2082 and N00014-86-C-2114. All three of these contracts involved participation in the development and testing of the Mark-III stellar interferometer at the Mount Wilson Observatory in California. This instrument employs a two-color technique to reduce position errors due to atmospheric turbulence, and can operate with four possible baseline configurations ranging from 9 to 20 meters. Despite its function as a technology development platform, it is also capable of stellar separation and stellar diameter measurements with nearly unprecedented accuracy and sensitivity. The major contributions of this work are the development of a dispersed-fringe group delay measurement system which can boost the system sensitivity be several stellar magnitudes, and the initial stages of development of an infrared capability, which should increase the future scientific interest of the facility.

  16. Heterodyne imaging speckle interferometer

    NASA Astrophysics Data System (ADS)

    Wang, Shengjia; Gao, Zhan; Feng, Ziang; Zhang, Xiaoqiong; Yang, Dong; Yuan, Hao

    2015-03-01

    A heterodyne imaging speckle interferometer coupled with lithium niobate is developed for whole field dynamic deformation imaging. In this device, the carrier frequency is introduced by the dual-transverse linear electro-optic effect. It is electrically controlled within a large range, which is twice the angular velocity of the driving alternating electric fields. By setting the angular velocity, the carrier frequency can fit most of area-array detectors, making it feasible to achieve whole field real time imaging. By using temporal evolution of the light intensity in heterodyne interferometry, the temporal intensity analysis method is employed to extract the deformation at each pixel dynamically. The principle and system configuration are described. The preliminary experiment is conducted with a cantilever beam and the results are compared with theoretical simulations to validate the proposed approach.

  17. The Fizeau Interferometer Testbed

    NASA Technical Reports Server (NTRS)

    Zhang, Xiaolei; Carpenter, Kenneth G.; Lyon, Richard G,; Huet, Hubert; Marzouk, Joe; Solyar, Gregory

    2003-01-01

    The Fizeau Interferometer Testbed (FIT) is a collaborative effort between NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Space Corporation, and the University of Maryland. The testbed will be used to explore the principles of and the requirements for the full, as well as the pathfinder, Stellar Imager mission concept. It has a long term goal of demonstrating closed-loop control of a sparse array of numerous articulated mirrors to keep optical beams in phase and optimize interferometric synthesis imaging. In this paper we present the optical and data acquisition system design of the testbed, and discuss the wavefront sensing and control algorithms to be used. Currently we have completed the initial design and hardware procurement for the FIT. The assembly and testing of the Testbed will be underway at Goddard's Instrument Development Lab in the coming months.

  18. THE KECK INTERFEROMETER NULLER

    SciTech Connect

    Serabyn, E.; Mennesson, B.; Colavita, M. M.; Koresko, C.; Kuchner, M. J.

    2012-03-20

    The Keck Interferometer Nuller (KIN), the first operational separated-aperture infrared nulling interferometer, was designed to null the mid-infrared emission from nearby stars so as to ease the measurement of faint circumstellar emission. This paper describes the basis of the KIN's four-beam, two-stage measurement approach and compares it to the simpler case of a two-beam nuller. In the four-beam KIN system, the starlight is first nulled in a pair of nullers operating on parallel 85 m Keck-Keck baselines, after which 'cross-combination' on 4 m baselines across the Keck apertures is used to modulate and detect residual coherent off-axis emission. Comparison to the constructive stellar fringe provides calibration. The response to an extended source is similar in the two cases, except that the four-beam response includes a term due to the visibility of the source on the cross-combiner baseline-a small effect for relatively compact sources. The characteristics of the dominant null depth errors are also compared for the two cases. In the two-beam nuller, instrumental imperfections and asymmetries lead to a series of quadratic, positive-definite null leakage terms. For the four-beam nuller, the leakage is instead a series of correlation cross-terms combining corresponding errors in each of the two nullers, which contribute offsets only to the extent that these errors are correlated on the timescale of the measurement. This four-beam architecture has allowed a significant ({approx}order of magnitude) improvement in mid-infrared long-baseline fringe-visibility accuracies.

  19. The Keck Interferometer Nuller

    NASA Technical Reports Server (NTRS)

    Serabyn, E.; Mennesson, B.; Colavita, M. M.; Koresko, C.; Kuchner, M. J.

    2012-01-01

    The Keck Interferometer Nuller (KIN), the first operational separated-aperture infrared nulling interferometer, was designed to null the mid-infrared emission from nearby stars so as to ease the measurement of faint circumstellar emission. This paper describes the basis of the KIN's four-beam, two-stage measurement approach and compares it 10 the simpler case of a two-beam nuller. In the four-beam KIN system, the starlight is first nulled in a pair of nullers operating on parallel 85 m Keck-Keck baselines, after which "cross-combination" on 4 m baselines across the Keck apertures is used to modulate and detect residual coherent off-axis emission. Comparison to the constructive itellar fringe provides calibration. The response to an extended source is similar in the two cases, except that the four-beam response includes a term due to the visibility of the source on the cross-combiner baseline-a small effect for relatively compact sources. The characteristics of the dominant null depth errors are also compared for the two cases. In the two-beam nuller, instrumental imperfections and asymmetries lead to a series of quadratic, positivedefinite null leakage terms. For the four-beam nuller, the leakage is instead a series of correlation cross-tenns combining corresponding errors in each of the two nullers, which contribute offsets only to the extent that these errors are correlated on the timescale of the measurement. This four-beam architecture has allowed a significant (approx. order of magnitude) improvement in mid-infrared long-baseline fringe-visibility accuracies.

  20. MIT's interferometer CST testbed

    NASA Technical Reports Server (NTRS)

    Hyde, Tupper; Kim, ED; Anderson, Eric; Blackwood, Gary; Lublin, Leonard

    1990-01-01

    The MIT Space Engineering Research Center (SERC) has developed a controlled structures technology (CST) testbed based on one design for a space-based optical interferometer. The role of the testbed is to provide a versatile platform for experimental investigation and discovery of CST approaches. In particular, it will serve as the focus for experimental verification of CSI methodologies and control strategies at SERC. The testbed program has an emphasis on experimental CST--incorporating a broad suite of actuators and sensors, active struts, system identification, passive damping, active mirror mounts, and precision component characterization. The SERC testbed represents a one-tenth scaled version of an optical interferometer concept based on an inherently rigid tetrahedral configuration with collecting apertures on one face. The testbed consists of six 3.5 meter long truss legs joined at four vertices and is suspended with attachment points at three vertices. Each aluminum leg has a 0.2 m by 0.2 m by 0.25 m triangular cross-section. The structure has a first flexible mode at 31 Hz and has over 50 global modes below 200 Hz. The stiff tetrahedral design differs from similar testbeds (such as the JPL Phase B) in that the structural topology is closed. The tetrahedral design minimizes structural deflections at the vertices (site of optical components for maximum baseline) resulting in reduced stroke requirements for isolation and pointing of optics. Typical total light path length stability goals are on the order of lambda/20, with a wavelength of light, lambda, of roughly 500 nanometers. It is expected that active structural control will be necessary to achieve this goal in the presence of disturbances.

  1. Finite mass beam splitter in high power interferometers

    SciTech Connect

    Harms, Jan; Schnabel, Roman; Danzmann, Karsten

    2004-11-15

    The beam splitter in high-power interferometers is subject to significant radiation-pressure fluctuations. As a consequence, the phase relations which appear in the beam splitter coupling equations oscillate and phase modulation fields are generated which add to the reflected fields. In this paper, the transfer function of the various input fields impinging on the beam splitter from all four ports onto the output field is presented including radiation-pressure effects. We apply the general solution of the coupling equations to evaluate the input-output relations of the dual-recycled laser-interferometer topology of the gravitational-wave detector GEO 600 and the power-recycling, signal-extraction topology of advanced LIGO. We show that the input-output relation exhibits a bright-port dark-port coupling. This mechanism is responsible for bright port contributions to the noise density of the output field and technical laser noise is expected to decrease the interferometer's sensitivity at low frequencies. It is shown quantitatively that the issue of technical laser noise is unimportant in this context if the interferometer contains arm cavities.

  2. Quadrature rules with multiple nodes for evaluating integrals with strong singularities

    NASA Astrophysics Data System (ADS)

    Milovanovic, Gradimir V.; Spalevic, Miodrag M.

    2006-05-01

    We present a method based on the Chakalov-Popoviciu quadrature formula of Lobatto type, a rather general case of quadrature with multiple nodes, for approximating integrals defined by Cauchy principal values or by Hadamard finite parts. As a starting point we use the results obtained by L. Gori and E. Santi (cf. On the evaluation of Hilbert transforms by means of a particular class of Turan quadrature rules, Numer. Algorithms 10 (1995), 27-39; Quadrature rules based on s-orthogonal polynomials for evaluating integrals with strong singularities, Oberwolfach Proceedings: Applications and Computation of Orthogonal Polynomials, ISNM 131, Birkhauser, Basel, 1999, pp. 109-119). We generalize their results by using some of our numerical procedures for stable calculation of the quadrature formula with multiple nodes of Gaussian type and proposed methods for estimating the remainder term in such type of quadrature formulae. Numerical examples, illustrations and comparisons are also shown.

  3. White light velocity interferometer

    SciTech Connect

    Erskine, David J.

    1999-01-01

    The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

  4. White light velocity interferometer

    SciTech Connect

    Erskine, David J.

    1997-01-01

    The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s.

  5. White light velocity interferometer

    DOEpatents

    Erskine, D.J.

    1999-06-08

    The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

  6. White light velocity interferometer

    DOEpatents

    Erskine, D.J.

    1997-06-24

    The invention is a technique that allows the use of broadband and incoherent illumination. Although denoted white light velocimetry, this principle can be applied to any wave phenomenon. For the first time, powerful, compact or inexpensive sources can be used for remote target velocimetry. These include flash and arc lamps, light from detonations, pulsed lasers, chirped frequency lasers, and lasers operating simultaneously in several wavelengths. The technique is demonstrated with white light from an incandescent source to measure a target moving at 16 m/s. 41 figs.

  7. A Stationary Hadamard Transform Interferometer

    NASA Astrophysics Data System (ADS)

    Tate, James D.; Curnutte, Basil; Hammaker, Robert M.; Fateley, William G.

    1989-12-01

    Optical interferometers have been used extensively in many applied fields of science including chemistry and physics. Conventional interferometers have provided one, if not more of the following advantages over conventional dispersive spectrometers: (1) multiplex advantage (Fellgett's advantage) (2) high frequency precision (Connes' advantage) (3) high optical etendue' or throughput (Jacquinot advantage) There are many different types of optical interferometers available on the market today (e.g. Fizeau, Fabry-Perot, etc.,) but perhaps the most important, at least historically, is the Michelson interferometer. Most Fourier transform infrared spectrometers today are based on this design. The Michelson-type interferometer, which employs a beamsplitter and a moving mirror can be thought of as an amplitude splitting device. In other words, the original beam from the source is split in half by a beamspliiter with each half traversing one "arm" of the interferometer. One arm contains a movable mirror which modulates the interference fringe pattern generated as the two halves (i.e. each arm) are recombined by the beamsplitter. Since the movable mirror is translated with time, the interferogram is effectively recorded as a function of time. This temporal interferogram can be further related back to the optical path difference between the two arms of the interferometer. Stroke and Funkhouser proposed a Fourier transform spectrometer which created a spatial interferogram as opposed to the temporal interferogram produced by conventional Michelson-type interferometers. Some have referred to this device as a holographic spectrometer or source doubling interferometer. These devices can be thought of as wavefront splitting devices analogous to Young' double slit experiment or the Fresnel biprism. The primary source is split into two coherent secondary sources which will exhibit constructive and destructive interference in the plane. An appropiate Fourier transform of this interferogram will reconstruct the cosine frequency components of the primary source. There are many devices that make use of a spatial interferogram. Presently, in our laboratory, work is underway to develop a stationary Hadamard transform (HT) interferometer that utilizes a liquid crystal optical shutter array to encode a spatial interferogram created by a Fizeau interferometer design. Thus, the HT stationary interferometer becomes a no moving parts spectrometer.

  8. Parametric generation of quadrature squeezing of mirrors in cavity optomechanics

    SciTech Connect

    Liao, Jie-Qiao; Law, C. K.

    2011-03-15

    We propose a method to generate quadrature-squeezed states of a moving mirror in a Fabry-Perot cavity. This is achieved by exploiting the fact that when the cavity is driven by an external field with a large detuning, the moving mirror behaves as a parametric oscillator. We show that parametric resonance can be reached approximately by modulating the driving field amplitude at a frequency matching the frequency shift of the mirror. The parametric resonance leads to an efficient generation of squeezing, which is limited by the thermal noise of the environment.

  9. Noise-cancelling quadrature magnetic position, speed and direction sensor

    DOEpatents

    Preston, Mark A.; King, Robert D.

    1996-01-01

    An array of three magnetic sensors in a single package is employed with a single bias magnet for sensing shaft position, speed and direction of a motor in a high magnetic noise environment. Two of the three magnetic sensors are situated in an anti-phase relationship (i.e., 180.degree. out-of-phase) with respect to the relationship between the other of the two sensors and magnetically salient target, and the third magnetic sensor is situated between the anti-phase sensors. The result is quadrature sensing with noise immunity for accurate relative position, speed and direction measurements.

  10. New system of miniaturization online testing of spherical interferometer

    NASA Astrophysics Data System (ADS)

    Lin, Jian; Han, Zhenhua; Zhuo, Jinzhai; Wang, Min

    2011-11-01

    With the aim to measure the radius of curvature deviation and the surface form deviation of optical elements online in the workshop, based on laser testing technique, two solutions of miniaturization without precision guider sphericity interferometer systems are described, and the principle of systems are analyzed. Compared with the traditional sphericity interferometer, the systems designed are particularly suitable for testing mirror noncontact online in workshop, advantaged in compact structure, no precision guider, high efficiency and low costs. The interferometer systems use the different radius of curvature of existing spherical test plates in the production workshop to produce reference wavefront. The systems can not only get the astigmatism and local deviation of lens, but also can reflect the radius of curvature deviation, which provides rapid and nondestructive noncontact online testing.

  11. Dual interferometer system for measuring index of refraction

    NASA Astrophysics Data System (ADS)

    Goodwin, Eric Peter

    The optical power of a lens is determined by the surface curvature and the refractive index, n. Knowledge of the index is required for accurate lens design models and for examining material variations from sample to sample. The refractive index of glass can be accurately measured using a prism spectrometer, but measuring the index of soft contact lens materials presents many challenges. These materials are non-rigid, thin, and must remain hydrated in a saline solution during testing. Clearly an alternative to a prism spectrometer must be used to accurately measure index. A Dual Interferometer System has been designed, built and characterized as a novel method for measuring the refractive index of transparent optical materials, including soft contact lens materials. The first interferometer is a Low Coherence Interferometer in a Twyman-Green configuration with a scanning reference mirror. The contact lens material sample is placed in a measurement cuvette, where it remains hydrated. By measuring the locations of the multiple optical interfaces, the physical thickness t of the material is measured. A new algorithm has been developed for processing the low coherence signals obtained from the reflection at each optical interface. The second interferometer is a Mach-Zehnder interferometer with a tunable HeNe laser light source. This interferometer measures the optical path length (OPL) of the test sample in the cuvette in transmission as a function of five wavelengths in the visible spectrum. This is done using phase-shifting interferometry. Multiple thickness regions are used to solve 2pi phase ambiguities in the OPL. The outputs of the two interferometers are combined to determine the refractive index as a function of wavelength: n(lambda) = OPL(lambda)/t. Since both t and OPL are measured using a detector array, n is measured at hundreds of thousands of data points. A measurement accuracy of 0.0001 in refractive index is achieved with this new instrument, which is verified using custom glass calibration samples.

  12. Two-chord interferometry using 3.39 μm He-Ne laser on a flux-coil-generated FRCa)

    NASA Astrophysics Data System (ADS)

    Gota, H.; Bolte, N.; Deng, B. H.; Gupta, D.; Kiyashko, V.; Knapp, K.; Mendoza, R.; Morehouse, M.; Roche, T.; Wessel, F.

    2010-10-01

    A two-chord λIR˜3.39 μm He-Ne laser interferometer system was developed for a flux-coil-generated field-reversed configuration to estimate the electron density and the total temperature of the field-reversed configuration (FRC) plasma. This two-chord heterodyne interferometer system consists of a single ˜2 mW infrared He-Ne laser, a visible (λvis˜632.8 nm) He-Ne laser for the alignment, a 40 MHz acousto-optic modulator, photodetectors, and quadrature phase detectors. Initial measurement was performed and the measured average electron densities were 2-10×1019 m-3 at two different radial positions in the midplane. A time shift in density was observed as the FRC expands radially. The time evolution of the line-averaged density agrees with the density estimated from the in situ internal magnetic probes, based on a rigid-rotor profile model.

  13. Two-chord interferometry using 3.39 μm He-Ne laser on a flux-coil-generated FRC.

    PubMed

    Gota, H; Bolte, N; Deng, B H; Gupta, D; Kiyashko, V; Knapp, K; Mendoza, R; Morehouse, M; Roche, T; Wessel, F

    2010-10-01

    A two-chord λ(IR)∼3.39 μm He-Ne laser interferometer system was developed for a flux-coil-generated field-reversed configuration to estimate the electron density and the total temperature of the field-reversed configuration (FRC) plasma. This two-chord heterodyne interferometer system consists of a single ∼2 mW infrared He-Ne laser, a visible (λ(vis)∼632.8 nm) He-Ne laser for the alignment, a 40 MHz acousto-optic modulator, photodetectors, and quadrature phase detectors. Initial measurement was performed and the measured average electron densities were 2-10×10(19) m(-3) at two different radial positions in the midplane. A time shift in density was observed as the FRC expands radially. The time evolution of the line-averaged density agrees with the density estimated from the in situ internal magnetic probes, based on a rigid-rotor profile model. PMID:21033867

  14. Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2002-01-01

    A new method to control microparticles was developed in-house at the NASA Glenn Research Center in support of the nanotechnology project under NASA's Aerospace Propulsion and Power Base Research Program. A prototype interferometer-controlled optical tweezers was constructed to manipulate scanning probe microscope (SPM) tips. A laser beam passed through a Mach-Zehnder interferometer, and a microscope objective then produced an optical trap from the coaxial beams. The trap levitated and generated the coarse motion of a 10-mm polystyrene sphere used to simulate a SPM tip. The interference between the beams provided fine control of the forces and moments on the sphere. The interferometer included a piezoelectric-scanned mirror to modulate the interference pattern. The 10-mm sphere was observed to oscillate about 1 mm as the mirror and fringe pattern oscillated. The prototype tweezers proved the feasibility of constructing a more sophisticated interferometer tweezers to hold and manipulate SPM tips. The SPM tips are intended to interrogate and manipulate nanostructures. A more powerful laser will be used to generate multiple traps to hold nanostructures and SPM tips. The vibrating mirror in the interferometer will be replaced with a spatial light modulator. The modulator will allow the optical phase distribution in one leg of the interferometer to be programmed independently at 640 by 480 points for detailed control of the forces and moments. The interference patterns will be monitored to measure the motion of the SPM tips. Neuralnetwork technology will provide fast analysis of the interference patterns for diagnostic purposes and for local or remote feedback control of the tips. This effort also requires theoretical and modeling support in the form of scattering calculations for twin coherent beams from nonspherical particles.

  15. Balloon Exoplanet Nulling Interferometer (BENI)

    NASA Technical Reports Server (NTRS)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Ford, Holland; Petro, Larry; Herman, Jay; Rinehart, Stephen; Carpenter, Kenneth; Marzouk, Joe

    2009-01-01

    We evaluate the feasibility of using a balloon-borne nulling interferometer to detect and characterize exosolar planets and debris disks. The existing instrument consists of a 3-telescope Fizeau imaging interferometer with 3 fast steering mirrors and 3 delay lines operating at 800 Hz for closed-loop control of wavefront errors and fine pointing. A compact visible nulling interferometer is under development which when coupled to the imaging interferometer would in-principle allow deep suppression of starlight. We have conducted atmospheric simulations of the environment above 100,000 feet and believe balloons are a feasible path forward towards detection and characterization of a limited set of exoplanets and their debris disks. Herein we will discuss the BENI instrument, the balloon environment and the feasibility of such as mission.

  16. Measurements of the phase shift on reflection for low-order infrared Fabry-Perot interferometer dielectric stack mirrors.

    PubMed

    Mielke, S L; Ryan, R E; Hilgeman, T; Lesyna, L; Madonna, R G; Van Nostrand, W C

    1997-11-01

    A simple technique based on a Fizeau interferometer to measure the absolute phase shift on reflection for a Fabry-Perot interferometer dielectric stack mirror is described. Excellent agreement between the measured and predicted phase shift on reflection was found. Also described are the salient features of low-order Fabry-Perot interferometers and the demonstration of a near ideal low-order (1-10) Fabry-Perot interferometer through minimizing the phase dispersion on reflection of the dielectric stack. This near ideal performance of a low-order Fabry-Perot interferometer should enable several applications such as compact spectral imagers for solid and gas detection. The large free spectral range of such systems combined with an active control system will also allow simple interactive tuning of wavelength agile laser sources such as CO(2) lasers, external cavity diode lasers, and optical parametric oscillators. PMID:18264347

  17. Polarizing optical interferometer having a dual use optical element

    DOEpatents

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

    1995-04-04

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

  18. Polarizing optical interferometer having a dual use optical element

    DOEpatents

    Kotidis, Petros A.; Woodroffe, Jaime A.; Rostler, Peter S.

    1995-01-01

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

  19. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  20. Enhanced 16 Spiral quadrature amplitude modulation scheme for coherent optical orthogonal frequency division multiplexing systems

    NASA Astrophysics Data System (ADS)

    He, Jing; Li, Chong; Chen, Lin; Chen, Ming

    2014-09-01

    We propose an enhanced 16 Spiral quadrature amplitude modulation (QAM) (16 E-Spiral QAM) scheme to overcome the laser phase noise in a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Considering both additive white Gaussian noise and large phase noise, 16 E-Spiral QAM schemes have a better transmission performance compared to conventional 16 QAM CO-OFDM systems. The simulated results show that the required optical signal-to-noise ratio (OSNR) of the proposed 16 QAM is, respectively, 0.8 and 2.3 dB less than 16 Spiral and conventional 16 QAM at a bit error rate (BER) of 10-3 in a back-to-back case. After 800-km transmission over a single-mode fiber, the tolerance for the laser linewidth of the 16 E-Spiral QAM can improve about 30 kHz with an OSNR of 18 dB compared to that of a conventional 16 QAM.

  1. Michelson Interferometer (MINT)

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew; Carlson, Barbara

    1993-01-01

    MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.

  2. Michelson Interferometer (MINT)

    NASA Astrophysics Data System (ADS)

    Lacis, Andrew; Carlson, Barbara

    1993-09-01

    MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.

  3. Atmospheric Emitted Radiance Interferometer

    DOE Data Explorer

    Gero, Jonathan; Ermold, Brian; Gaustad, Krista; Koontz, Annette; Hackel, Denny; Garcia, Raymond

    2005-01-01

    The atmospheric emitted radiance interferometer (AERI) is a ground-based instrument that measures the downwelling infrared radiance from the Earth’s atmosphere. The observations have broad spectral content and sufficient spectral resolution to discriminate among gaseous emitters (e.g., carbon dioxide and water vapor) and suspended matter (e.g., aerosols, water droplets, and ice crystals). These upward-looking surface observations can be used to obtain vertical profiles of tropospheric temperature and water vapor, as well as measurements of trace gases (e.g., ozone, carbon monoxide, and methane) and downwelling infrared spectral signatures of clouds and aerosols. The AERI is a passive remote sounding instrument, employing a Fourier transform spectrometer operating in the spectral range 3.3–19.2 μm (520–3020 cm-1) at an unapodized resolution of 0.5 cm-1 (max optical path difference of 1 cm). The extended-range AERI (ER-AERI) deployed in dry climates, like in Alaska, have a spectral range of 3.3–25.0 μm (400–3020 cm-1) that allow measurements in the far-infrared region. Typically, the AERI averages views of the sky over a 16-second interval and operates continuously.

  4. Multiple beam Fizeau interferometer with filtered frequency comb illumination

    NASA Astrophysics Data System (ADS)

    Schwider, J.

    2009-08-01

    Real wedge interferometers of the Fizeau-type do not allow for fringes in case of a spectral broadband source - or in short: for white light fringes. Here, the use of a suitable frequency comb source will help to overcome this limitation on the one hand and on the other will offer the capability for enhanced phase sensitivity in high precision measurements of surface deviations. Frequency combs can be produced either by using a pulse train from a fs-laser or by passive filtering of the light emitted by a broadband source as a superlum-diode or a fs-laser. The frequency comb produced by a common fs-laser is extremely fine, i.e., the frequency difference of consecutive peaks is very small or the distance of consecutive pulses of the pulse train might be of the order of 1 m. Therefore, the pulse train produced by passive filtering of a broadband source is better adapted to the needs of surface testing interferometers. White light fringes are either applied for the profiling of discontinuous surfaces and/or can serve as an indication for the correct choice of multiplication factors in superposition interferometry. During the last decennium it became more and more clear that spatially incoherent sources provide better measuring accuracy in surface measurements due to the reduced influence of dust diffraction patterns. The advantage of laser illumination can nevertheless be maintained if the laser light is made spatially incoherent through moving scatterers in the light path. Here, we will discuss the application of spatially incoherent broadband light frequency filtered through a Fabry-Perot filter. The main applications are in the following fields: (1) surface profiling applications using two-beam Fizeau interferometers, (2) selection of single cavities out of a series of interlaced cavities, and (3) sensitivity enhancement for multi-beam interferometers for planeness or sphericity measurements. Some of the discussed possibilities will be experimentally demonstrated.

  5. Determining Fault Orientation with Sagnac Interferometers

    NASA Astrophysics Data System (ADS)

    Gruenwald, Konstantin; Dunn, Robert

    2014-03-01

    Typically, earthquake fault ruptures emit seismic waves in directions dependent on the fault's orientation. Specifically, as the fault slips to release strain, compressional P-waves propagate parallel and perpendicular to the fault plane, and transverse S-waves propagate at 45 degree angles to the fault-a result of the double-couple model of fault slippage. Sagnac Interferometers (ring-lasers) have been used to study wave components of several natural phenomena. We used the initial responses of a ring-laser from transverse S-waves to determine the orientation of the nearby Guy/Greenbrier fault, the source of an earthquake swarm in 2010-11 purportedly caused by hydraulic fracturing. This orientation was compared to the structure of the fault extracted by nearby seismogram responses. Our goal was to determine if ring-lasers could reinforce or add to the models of fault orientation constructed from seismographs. The results indicate that the ring-laser's responses can aid in constructing fault orientation in a manner similar to traditional seismographs. Funded by the Arkansas Space Grant Consortium and the National Science Foundation.

  6. Efficient Modified Filon-Type Quadrature for Highly Oscillatory Bessel Transformations

    SciTech Connect

    Xiang, S.

    2008-10-30

    In this paper, we consider efficient modified Filon-type method for the integration of systems containing Bessel function and gives error analysis for these quadratures. Preliminary numerical results show the effectiveness and accuracy of the quadrature for large arguments of integral systems.

  7. General n-dimensional quadrature transform and its application to interferogram demodulation

    NASA Astrophysics Data System (ADS)

    Servin, Manuel; Quiroga, Juan Antonio; Marroquin, Jose Luis

    2003-05-01

    Quadrature operators are useful for obtaining the modulating phase φ in interferometry and temporal signals in electrical communications. In carrier-frequency interferometry and electrical communications, one uses the Hilbert transform to obtain the quadrature of the signal. In these cases the Hilbert transform gives the desired quadrature because the modulating phase is monotonically increasing. We propose an n-dimensional quadrature operator that transforms cos(f) into -sin(f) regardless of the frequency spectrum of the signal. With the quadrature of the phase-modulated signal, one can easily calculate the value of f over all the domain of interest. Our quadrature operator is composed of two n-dimensional vector fields: One is related to the gradient of the image normalized with respect to local frequency magnitude, and the other is related to the sign of the local frequency of the signal. The inner product of these two vector fields gives us the desired quadrature signal. This quadrature operator is derived in the image space by use of differential vector calculus and in the frequency domain by use of a n-dimensional generalization of the Hilbert transform. A robust numerical algorithm is given to find the modulating phase of two-dimensional single-image closed-fringe interferograms by use of the ideas put forward.

  8. Regenerative Fourier transformation for dual-quadrature regeneration of multilevel rectangular QAM.

    PubMed

    Sorokina, Mariia; Sygletos, Stylianos; Ellis, Andrew; Turitsyn, Sergei

    2015-07-01

    We propose a new nonlinear optical loop mirror based configuration capable of regenerating regular rectangular quadrature amplitude modulated (QAM) signals. The scheme achieves suppression of noise distortion on both signal quadratures through the realization of two orthogonal regenerative Fourier transformations. Numerical simulations show the performance of the scheme for high constellation complexities (including 256-QAM formats). PMID:26125381

  9. A Family of Exponential Fitting Direct Quadrature Methods for Volterra Integral Equations

    NASA Astrophysics Data System (ADS)

    Cardone, A.; Ferro, M.; Ixaru, L. Gr.; Paternoster, B.

    2010-09-01

    A new class of direct quadrature methods for the solution of Volterra Integral Equations with periodic solution is illustrated. Such methods are based on an exponential fitting gaussian quadrature formula, whose coefficients depend on the problem parameters, in order to better reproduce the behavior the analytical solution. The construction of the methods is described, together with the analysis of the order of accuracy.

  10. The Nature of the Nodes, Weights and Degree of Precision in Gaussian Quadrature Rules

    ERIC Educational Resources Information Center

    Prentice, J. S. C.

    2011-01-01

    We present a comprehensive proof of the theorem that relates the weights and nodes of a Gaussian quadrature rule to its degree of precision. This level of detail is often absent in modern texts on numerical analysis. We show that the degree of precision is maximal, and that the approximation error in Gaussian quadrature is minimal, in a…

  11. A simple air wedge shearing interferometer for studying exploding wires

    NASA Astrophysics Data System (ADS)

    Pikuz, S. A.; Romanova, V. M.; Baryshnikov, N. V.; Hu, Min; Kusse, B. R.; Sinars, D. B.; Shelkovenko, T. A.; Hammer, D. A.

    2001-01-01

    A new type of shearing interferometer using an air wedge is described. This interferometer is based on a beam splitter constructed using two 90-degree prisms. A small air gap, which varies in spacing from top-to-bottom, separates the second prism from the first and forms the air wedge. The single incident laser beam is focused near the gap, and the two primary reflections from the long sides of each prism form the two coherent virtual sources necessary for interferometry. The shift between the two images of the object at the detector, as well as the orientation and frequency of the fringes, can be independently adjusted by altering the air gap thickness and angle, as well as the position of the laser focus in the gap. This interferometry scheme is inexpensive and easily aligned, and has been successfully and reliably used in exploding wire experiments.

  12. Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics

    NASA Technical Reports Server (NTRS)

    Griffin, DeVon W.; Marshall, Keneth L.

    2002-01-01

    The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal tends to become more transparent, thus introducing a rather large amount of error into the phase-shifting measurement. While that error can be greatly reduced by normalization, we prefer eliminating the source of the error. To that end, we have pursued development of a 'blend' of custom dyes that will not exhibit these properties. That goal has not yet been fully achieved. Guardalben, et al, presented a similar set of interferograms in a paper partially funded by this grant. Shearing interferometers are a second class of common path interferometers. Typically they consist of a thick glass plate optimized for equal reflection from the front and back surface. While not part of the original thrust of the project, through the course of laboratory work, we demonstrated a prototype of a shearing interferometer capable of phase shifting using a commercial liquid crystal retardation plate. A schematic of this liquid crystal shearing interferometer (LCSI) and a sample set of interferograms are in the reference. This work was also supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. Additional information is included in the original extended abstract.

  13. Automatic control system design of laser interferometer

    NASA Astrophysics Data System (ADS)

    Lu, Qingjie; Li, Chunjie; Sun, Hao; Ren, Shaohua; Han, Sen

    2015-10-01

    There are a lot of shortcomings with traditional optical adjustment in interferometry, such as low accuracy, time-consuming, labor-intensive, uncontrollability, and bad repetitiveness, so we treat the problem by using wireless remote control system. Comparing to the traditional method, the effect of vibration and air turbulence will be avoided. In addition the system has some peculiarities of low cost, high reliability and easy operation etc. Furthermore, the switching between two charge coupled devices (CCDs) can be easily achieved with this wireless remote control system, which is used to collect different images. The wireless transmission is achieved by using Radio Frequency (RF) module and programming the controller, pulse width modulation (PWM) of direct current (DC) motor, real-time switching of relay and high-accuracy displacement control of FAULHABER motor are available. The results of verification test show that the control system has good stability with less than 5% packet loss rate, high control accuracy and millisecond response speed.

  14. Mach-Zehnder interferometer for movement monitoring

    NASA Astrophysics Data System (ADS)

    Vasinek, Vladimir; Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Latal, Jan; Koudelka, Petr

    2012-06-01

    Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons around the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 kHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and the gained spectra at repeated drops of balls were compared. Those stroked upon the same place and from the same elevation and dispersion of the obtained frequency spectra was evaluated. These experiments were performed on the series of 20 repeated drops from highs of 0,5 and 1m. The evaluation of experiments displayed that the dispersion of measured values is lower than 4%. Frequency response has been verified with the loudspeaker connected to signal generator and amplifier. Various slabs have been measured and frequency ranges were compared for particular slab designs.

  15. Residual Distribution Schemes for Conservation Laws Via Adaptive Quadrature

    NASA Technical Reports Server (NTRS)

    Barth, Timothy; Abgrall, Remi; Biegel, Bryan (Technical Monitor)

    2000-01-01

    This paper considers a family of nonconservative numerical discretizations for conservation laws which retains the correct weak solution behavior in the limit of mesh refinement whenever sufficient order numerical quadrature is used. Our analysis of 2-D discretizations in nonconservative form follows the 1-D analysis of Hou and Le Floch. For a specific family of nonconservative discretizations, it is shown under mild assumptions that the error arising from non-conservation is strictly smaller than the discretization error in the scheme. In the limit of mesh refinement under the same assumptions, solutions are shown to satisfy an entropy inequality. Using results from this analysis, a variant of the "N" (Narrow) residual distribution scheme of van der Weide and Deconinck is developed for first-order systems of conservation laws. The modified form of the N-scheme supplants the usual exact single-state mean-value linearization of flux divergence, typically used for the Euler equations of gasdynamics, by an equivalent integral form on simplex interiors. This integral form is then numerically approximated using an adaptive quadrature procedure. This renders the scheme nonconservative in the sense described earlier so that correct weak solutions are still obtained in the limit of mesh refinement. Consequently, we then show that the modified form of the N-scheme can be easily applied to general (non-simplicial) element shapes and general systems of first-order conservation laws equipped with an entropy inequality where exact mean-value linearization of the flux divergence is not readily obtained, e.g. magnetohydrodynamics, the Euler equations with certain forms of chemistry, etc. Numerical examples of subsonic, transonic and supersonic flows containing discontinuities together with multi-level mesh refinement are provided to verify the analysis.

  16. Quadrature squeezed photons from a two-level system.

    PubMed

    Schulte, Carsten H H; Hansom, Jack; Jones, Alex E; Matthiesen, Clemens; Le Gall, Claire; Atatüre, Mete

    2015-09-10

    Resonance fluorescence arises from the interaction of an optical field with a two-level system, and has played a fundamental role in the development of quantum optics and its applications. Despite its conceptual simplicity, it entails a wide range of intriguing phenomena, such as the Mollow-triplet emission spectrum, photon antibunching and coherent photon emission. One fundamental aspect of resonance fluorescence--squeezing in the form of reduced quantum fluctuations in the single photon stream from an atom in free space--was predicted more than 30 years ago. However, the requirement to operate in the weak excitation regime, together with the combination of modest oscillator strength of atoms and low collection efficiencies, has continued to necessitate stringent experimental conditions for the observation of squeezing with atoms. Attempts to circumvent these issues had to sacrifice antibunching, owing to either stimulated forward scattering from atomic ensembles or multi-photon transitions inside optical cavities. Here, we use an artificial atom with a large optical dipole enabling 100-fold improvement of the photon detection rate over the natural atom counterpart and reach the necessary conditions for the observation of quadrature squeezing in single resonance-fluorescence photons. By implementing phase-dependent homodyne intensity-correlation detection, we demonstrate that the electric field quadrature variance of resonance fluorescence is three per cent below the fundamental limit set by vacuum fluctuations, while the photon statistics remain antibunched. The presence of squeezing and antibunching simultaneously is a fully non-classical outcome of the wave-particle duality of photons. PMID:26322581

  17. Quadrature squeezed photons from a two-level system

    NASA Astrophysics Data System (ADS)

    Schulte, Carsten H. H.; Hansom, Jack; Jones, Alex E.; Matthiesen, Clemens; Le Gall, Claire; Atatre, Mete

    2015-09-01

    Resonance fluorescence arises from the interaction of an optical field with a two-level system, and has played a fundamental role in the development of quantum optics and its applications. Despite its conceptual simplicity, it entails a wide range of intriguing phenomena, such as the Mollow-triplet emission spectrum, photon antibunching and coherent photon emission. One fundamental aspect of resonance fluorescence--squeezing in the form of reduced quantum fluctuations in the single photon stream from an atom in free space--was predicted more than 30 years ago. However, the requirement to operate in the weak excitation regime, together with the combination of modest oscillator strength of atoms and low collection efficiencies, has continued to necessitate stringent experimental conditions for the observation of squeezing with atoms. Attempts to circumvent these issues had to sacrifice antibunching, owing to either stimulated forward scattering from atomic ensembles or multi-photon transitions inside optical cavities. Here, we use an artificial atom with a large optical dipole enabling 100-fold improvement of the photon detection rate over the natural atom counterpart and reach the necessary conditions for the observation of quadrature squeezing in single resonance-fluorescence photons. By implementing phase-dependent homodyne intensity-correlation detection, we demonstrate that the electric field quadrature variance of resonance fluorescence is three per cent below the fundamental limit set by vacuum fluctuations, while the photon statistics remain antibunched. The presence of squeezing and antibunching simultaneously is a fully non-classical outcome of the wave-particle duality of photons.

  18. Global feed-forward vibration isolation in a km scale interferometer

    NASA Astrophysics Data System (ADS)

    DeRosa, Ryan; Driggers, Jennifer C.; Atkinson, Dani; Miao, Haixing; Frolov, Valery; Landry, Michael; Giaime, Joseph A.; Adhikari, Rana X.

    2012-11-01

    Using a network of seismometers and sets of optimal filters, we implemented a feed-forward control technique to minimize the seismic contribution to multiple interferometric degrees of freedom of the Laser Interferometer Gravitational-wave Observatory interferometers. The filters are constructed by using the Levinson-Durbin recursion relation to approximate the optimal Wiener filter. By reducing the RMS of the interferometer feedback signals below ˜10 Hz, we have improved the stability and duty cycle of the joint network of gravitational wave detectors. By suppressing the large control forces and mirror motions, we have dramatically reduced the rate of non-Gaussian transients in the gravitational wave signal stream.

  19. Conversion of conventional gravitational-wave interferometers into quantum nondemolition interferometers by modifying their input and/or output optics

    NASA Astrophysics Data System (ADS)

    Kimble, H. J.; Levin, Yuri; Matsko, Andrey B.; Thorne, Kip S.; Vyatchanin, Sergey P.

    2002-01-01

    The LIGO-II gravitational-wave interferometers (ca. 2006-2008) are designed to have sensitivities near the standard quantum limit (SQL) in the vicinity of 100 Hz. This paper describes and analyzes possible designs for subsequent LIGO-III interferometers that can beat the SQL. These designs are identical to a conventional broad band interferometer (without signal recycling), except for new input and/or output optics. Three designs are analyzed: (i) a squeezed-input interferometer (conceived by Unruh based on earlier work of Caves) in which squeezed vacuum with frequency-dependent (FD) squeeze angle is injected into the interferometer's dark port; (ii) a variational-output interferometer (conceived in a different form by Vyatchanin, Matsko and Zubova), in which homodyne detection with FD homodyne phase is performed on the output light; and (iii) a squeezed-variational interferometer with squeezed input and FD-homodyne output. It is shown that the FD squeezed-input light can be produced by sending ordinary squeezed light through two successive Fabry-Pérot filter cavities before injection into the interferometer, and FD-homodyne detection can be achieved by sending the output light through two filter cavities before ordinary homodyne detection. With anticipated technology (power squeeze factor e-2R=0.1 for input squeezed vacuum and net fractional loss of signal power in arm cavities and output optical train ɛ*=0.01) and using an input laser power Io in units of that required to reach the SQL (the planned LIGO-II power, ISQL), the three types of interferometer could beat the amplitude SQL at 100 Hz by the following amounts μ≡(Sh)/(SSQLh) and with the following corresponding increase V=1/μ3 in the volume of the universe that can be searched for a given noncosmological source: Squeezed input-μ~=(e-2R)~=0.3 and V~=1/0.33~=30 using Io/ISQL=1. Variational-output-μ~=ɛ1/4*~=0.3 and V~=30 but only if the optics can handle a ten times larger power: Io/ISQL~=1/(ɛ*)=10. Squeezed varational-μ=1.3(e-2Rɛ*)1/4~=0.24 and V~=80 using Io/ISQL=1; and μ~=(e-2Rɛ*)1/4~=0.18 and V~=180 using Io/ISQL=(e-2R/ɛ*)~=3.2.

  20. Measurement of the carrier envelope offset frequency of a femtosecond frequency comb using a Fabry-Perot interferometer

    SciTech Connect

    Basnak, D V; Bikmukhametov, K A; Dmitrieva, N I; Dmitriev, Aleksandr K; Lugovoi, A A; Pokasov, P V; Chepurov, S V

    2010-10-15

    A method for measuring the carrier envelope offset (CEO) frequency of the femtosecond frequency comb with a bandwidth of less than one octave by using a Fabry-Perot interferometer is proposed and experimentally demonstrated. (laser components)

  1. Application of a digital phase comparator technique to interferometer data

    NASA Astrophysics Data System (ADS)

    Jiang, Y.; Brower, D. L.; Zeng, L.; Howard, J.

    1997-01-01

    Substantial improvements have been made to increase the frequency bandwidth of the UCLA multichannel interferometer system on TEXT-Upgrade. Recently, a digital phase comparator technique was implemented that has several advantages over the conventional analog phase comparator. The probe and reference wave forms are directly digitized and the phase computed in software using a numerical demodulation algorithm. For the purpose of reducing the data load, aliasing of the laser difference frequency is employed to vary the time response according to experimental demands.

  2. Bidirectional phase-shifting point diffraction interferometer for wavefronts testing

    NASA Astrophysics Data System (ADS)

    Chen, Sanbin; Zhou, Shouhuan; Tang, Xiaojun; Hong, Zhao

    2015-10-01

    The wavefront of the laser beam was tested by a point-diffraction interferometer with bidirectional phase-shifting. The phase-shifting is obtained by the bidirectional modulated of the electro-optic effect lithium niobate crystal combining with a pinhole filter in half-wave film. The wavefront aberration of incoming beam is directly measured by analyzing five frames phase-shifted interferograms captured by a CCD camera.

  3. Improving the performances of current optical interferometers & future designs

    NASA Astrophysics Data System (ADS)

    Arnold, L.; Le Coroller, H.; Surdej, J.

    2014-04-01

    The number of astrophysical studies making use of interferometers has steadily increased during the past 15 years. Nevertheless, the performances of interferometers are still limited: their sensitivity does not exceed magnitude V=12, and their imaging capability could yet be improved by increasing the number of telescopes/sub-apertures. In the context of the ELTs, it is not certain how future interferometry projects will be financed. However, interferometry remains the only way to observe compact astrophysical objects at very high angular resolution (< milli-arcsecond), like gravitational micro-lensing events, central engines of AGNs, proto-planetary disks, exoplanets, etc. The aim of this workshop was to review and discuss the development of technologies that could improve the performances of current and future interferometers: new optical designs; techniques to improve the accuracy of measurements (visibility, closure-phase, etc.); progress on delay-line performances; solutions without delay-lines; technologies for larger apertures at lower cost (ex: lightweight replica mirrors); optimized beam combiners (integrated optic, pupil densifier, etc.); fringe tracking systems; laser telemetry applied to interferometry; heterodyne interferometry; progress in heterodyne detection using new technologies (laser comb, time propagation technologies, etc.); progress in image reconstruction techniques; progress in nulling interferometry; and important science cases that could benefit from progress in interferometry (report of observations at the limit of current interferometers). Nearly 50 oral presentations have been delivered, followed by very lively discussions which eventually emerged with the proposition to organize the "Planet Formation Interferometer/Imager" (PFI) project. The present proceedings reflect most of the highlights of this international colloquium.

  4. Theoretical modeling of acousto-optic modulated stroboscopic interferometer

    NASA Astrophysics Data System (ADS)

    Pai Sreenivasan, Murali Manohar; Sivakumar, N. R.; Packirisamy, M.

    2006-09-01

    A requirement to advance consistency and predictability of Micro-Electro Mechanical System (MEMS) device has triggered research to have precise measurements and visual means to characterize dynamic parameters. Time resolved measurements of entire surface in a microdevice to nanometer level accuracy are difficult using conventional metrology system such as optical interferometer and optical microscopy. Laser Doppler Vibrometer (LDV) has found their applications to some extent. Due to Single point technique, scanning is a must in LDV which sets drawback for characterization in Microsystems. In this paper we propose the use of Acousto Optic Modulator (AOM) as a strobing device with a continuous wave laser to develop a stroboscopic interferometer for static and dynamic characterization of out of plane motion. Due to high random access time (typical 150 nanoseconds) AOM improves the capability of the tool to test MEMS devices of higher frequencies. Detail study is done on the strobe frequency to correlate the pulsating frequency of the laser by the AOM and the driven frequency of the microdevice. Theoretical modeling of the stroboscopic interferometer is carried out by formulating the understanding between strobe frequency and the MEMS device.

  5. A Robust Ramsey Interferometer for Atomic Timekeeping in Dynamic Environments

    NASA Astrophysics Data System (ADS)

    Kotru, Krish; Brown, Justin; Butts, David; Choy, Jennifer; Galfond, Marissa; Johnson, David M.; Kinast, Joseph; Timmons, Brian; Stoner, Richard

    2014-05-01

    We present a laser-based approach to atomic timekeeping, in which atomic phase information is extracted using modified Raman pulses in a Ramsey sequence. We overcome systematic effects associated with differential AC Stark shifts and variations in laser beam intensity by employing atom optics derived from Raman adiabatic rapid passage (ARP). This technique drives coherent transfer between two hyperfine ground states by sweeping the frequency difference of two optical fields and maintaining a large single-photon detuning. Compared to a Raman-pulse Ramsey interferometer, we show a >150x reduction in sensitivity to differential AC Stark shifts. We also demonstrate that ARP preserves fringe contrast in Ramsey interferometers for cloud displacements reaching the 1/e2 intensity radius of the laser beam. Deviations of the phase in response to changes in duration, rate, and range of the ARP frequency sweep are bounded to <7 mrad, implying a per-shot fractional frequency uncertainty of 1e-11 for an interrogation time of 10 ms. These characteristics are expected to improve the robustness of clock interferometers operating in dynamic environments. Copyright 2014 by The Charles Stark Draper Laboratory, Inc. All rights reserved.

  6. Finite mass beam splitter in high power interferometers

    NASA Astrophysics Data System (ADS)

    Harms, Jan; Schnabel, Roman; Danzmann, Karsten

    2004-11-01

    The beam splitter in high-power interferometers is subject to significant radiation-pressure fluctuations. As a consequence, the phase relations which appear in the beam splitter coupling equations oscillate and phase modulation fields are generated which add to the reflected fields. In this paper, the transfer function of the various input fields impinging on the beam splitter from all four ports onto the output field is presented including radiation-pressure effects. We apply the general solution of the coupling equations to evaluate the input-output relations of the dual-recycled laser-interferometer topology of the gravitational-wave detector GEO 600 and the power-recycling, signal-extraction topology of advanced LIGO. We show that the input-output relation exhibits a bright-port dark-port coupling. This mechanism is responsible for bright port contributions to the noise density of the output field and technical laser noise is expected to decrease the interferometer’s sensitivity at low frequencies. It is shown quantitatively that the issue of technical laser noise is unimportant in this context if the interferometer contains arm cavities.

  7. Interferometer mirror tilt correcting system

    NASA Technical Reports Server (NTRS)

    Schindler, R. A. (Inventor)

    1977-01-01

    An interferometer is described, having several means for automatically adjusting the angular tilt of a reflecting surface in one of two paths to maintain the exit beams from the two paths parallel to each other. Three detectors at the output of the interferometer were disposed on mutually perpendicular axes which define a plane normal to the nominal exit beam axis. One detector at the origin of the axes was used as a reference for separate phase difference comparison with the outputs of the other two detectors on the X and Y axes to develop servo error signals.

  8. Automatic Alignment of Displacement-Measuring Interferometer

    NASA Technical Reports Server (NTRS)

    Halverson, Peter; Regehr, Martin; Spero, Robert; Alvarez-Salazar, Oscar; Loya, Frank; Logan, Jennifer

    2006-01-01

    A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error. On the basis of the geometrical optics of corner-cube reflectors, the length of the optical path can be shown to be L = L(sub 0)cos theta, where L(sub 0) is the distance between the corner points and theta is the misalignment angle. Therefore, the measurement error is given by DeltaL = L(sub 0)(cos theta - 1). In the usual case in which the misalignment is small, this error can be approximated as DeltaL approximately equal to -L(sub 0)theta sup 2/2. The control system (see figure) is implemented partly in hardware and partly in software. The control system includes three piezoelectric actuators for rapid, fine adjustment of the direction of the laser beam. The voltages applied to the piezoelectric actuators include components designed to scan the beam in a circular pattern so that the beam traces out a narrow cone (60 microradians wide in the initial application) about the direction in which it is nominally aimed. This scan is performed at a frequency (2.5 Hz in the initial application) well below the resonance frequency of any vibration of the interferometer. The laser beam makes a round trip to both corner-cube reflectors and then interferes with the launched beam. The interference is detected on a photodiode. The length of the optical path is measured by a heterodyne technique: A 100- kHz frequency shift between the launched beam and a reference beam imposes, on the detected signal, an interferometric phase shift proportional to the length of the optical path. A phase meter comprising analog filters and specialized digital circuitry converts the phase shift to an indication of displacement, generating a digital signal proportional to the path length.

  9. Digital Fringe Counting for Intrinsic Fabry-Perot Interferometers

    NASA Technical Reports Server (NTRS)

    Froggatt, Mark; Melvin, Leland

    1996-01-01

    A digital dual-wavelength method of demodulating long (17cm) Intrinsic Fabry-Perot Interferometers (IFPI) is presented. The method builds upon previous techniques using small shifts in the lasing wavelength of a laser diode induced by changes in the driving current. The intensity of the light reflected from the IFPI is sampled at two carefully selected values of laser diode drive current. Digital logic is then used to count fringes based upon these two sampled values. Experimental verification of the method is described.

  10. Spatial-domain interferometer for measuring plasma mirror expansion.

    PubMed

    Bocoum, Maïmouna; Böhle, Frederik; Vernier, Aline; Jullien, Aurélie; Faure, Jérôme; Lopez-Martens, Rodrigo

    2015-07-01

    We present a practical spatial-domain interferometer for characterizing the electronic density gradient of laser-induced plasma mirrors with sub-30-femtosecond temporal resolution. Time-resolved spatial imaging of an intensity-shaped pulse reflecting off an expanding plasma mirror induced by a time-delayed pre-pulse allows us to measure characteristic plasma gradients of 10-100 nm with an expansion velocity of 10.8 nm/ps. Spatial-domain interferometry (SDI) can be generalized to the ultrafast imaging of nm to μm size laser-induced phenomena at surfaces. PMID:26125354

  11. Microwave interferometer controls cutting depth of plastics

    NASA Technical Reports Server (NTRS)

    Heisman, R. M.; Iceland, W. F.

    1969-01-01

    Microwave interferometer system controls the cutting of plastic materials to a prescribed depth. The interferometer is mounted on a carriage with a spindle and cutting tool. A cross slide, mounted on the carriage, allows the interferometer and cutter to move toward or away from the plastic workpiece.

  12. A heterodyne interferometer for high-performance industrial metrology

    NASA Astrophysics Data System (ADS)

    Schuldt, Thilo; Gohlke, Martin; Weise, Dennis; Johann, Ulrich; Peters, Achim; Braxmaier, Claus

    2008-11-01

    We developed a compact, fiber-coupled heterodyne interferometer for translation and tilt metrology. Noise levels below 5 pm/√Hz in translation and below 10 nrad/√Hz in tilt measurement, both for frequencies above 10-2 Hz, were demonstrated in lab experiments. While this setup was developed with respect to the LISA (Laser Interferometer Space Antenna) space mission current activities focus on its adaptation for dimensional characterization of ultra-stable materials and industrial metrology. The interferometer is used in high-accuracy dilatometry measuring the coefficient of thermal expansion (CTE) of dimensionally highly stable materials such as carbon-fiber reinforced plastic (CFRP) and Zerodur. The facility offers the possibility to measure the CTE with an accuracy better 10-8/K. We also develop a very compact and quasi-monolithic sensor head utilizing ultra-low expansion glass material which is the basis for a future space-qualifiable interferometer setup and serves as a prototype for a sensor head used in industrial environment. For high resolution 3D profilometry and surface property measurements (i. e. roughness, evenness and roundness), a low-noise (<=1nm/√ Hz) actuator will be implemented which enables a scan of the measurement beam over the surface under investigation.

  13. MIKES fibre-coupled differential dynamic line scale interferometer

    NASA Astrophysics Data System (ADS)

    Lassila, Antti

    2012-09-01

    An instrument developed for high accuracy calibration of line scales up to 1.16 m is described. The instrument is based on an earlier design from the early 1990s. Since then, in order to improve performance and achieve smaller uncertainty, large portions of software, mechanics and optics have been redesigned and several uncertainty components better characterized. The software has been developed to be less sensitive to imperfections of the line mark. In order to decrease noise and deformation coupling in interferometric measurement, the interferometer operating principle has been designed to use a fibre-coupled laser light, interferometer optics have been improved for better phase adjustment and detection and a differential interferometer principle has been taken into use. In order to minimize the effects due to deformations of the stone table rail with moving heavy carriage, a separate bed has been designed under line scale supports. The bed with fixed differential reflector prevents deformations of the table from affecting the line scale versus interferometer position. The main properties of the instrument are described and an uncertainty estimate is presented. The expanded uncertainty (k = 2) for line distance calibration of high-quality low-thermal-expansion line scale is U = [(4.5 nm)2 + (43 × 10-9 L)2]½, where L is the measured length. The results of international comparisons support the uncertainty estimate.

  14. Improved Mach-Zehnder interferometer-based shearography

    NASA Astrophysics Data System (ADS)

    Cai, Changqing; He, Lingfeng

    2012-12-01

    Digital shearography based on Mach-Zehnder interferometer suffers from the disadvantage of a small angle of view due to the structure. A novel digital shearography set-up with a large angle of view, which is based on the combination of new CCD technology, a semiconductor laser, a Mach-Zehnder shear interferometer and a 4f system, is demonstrated. Independent control of the shear and the frequency of the spatial carrier can be attained with this set-up. In the optical arrangement, the imaging lens is placed in front of the Mach-Zehnder interferometer instead of behind it as in the traditional digital shearography. So the angle of view is no longer limited by the Mach-Zehnder interferometer. Phase extraction is obtained by both advanced sinusoidal-fitting method and Fourier transform method, which are applied to interference patterns with a spatial carrier in the primary fringes. The experimental implementation of the set-up and the results obtained with it are presented and discussed.

  15. Gaussian quadrature for optical design with noncircular pupils and fields, and broad wavelength range

    NASA Astrophysics Data System (ADS)

    Bauman, Brian J.; Xiao, Hong

    2010-08-01

    Forbes introduced the usage of Gaussian quadratures in optical design for circular pupils and fields, and for a specific visible wavelength band. In this paper, Gaussian quadrature methods of selecting rays in ray-tracing are derived for noncircular pupil shapes, such as obscured and vignetted apertures. In addition, these methods are generalized for square fields, and for integrating performance over arbitrary wavelength bands. Integration over wavelength is aided by the use of a novel chromatic coordinate. These quadratures achieve low calculations with fewer rays (by orders of magnitude) than uniform sampling schemes.

  16. Optimal displacement in apparent motion and quadrature models of motion sensing

    NASA Technical Reports Server (NTRS)

    Watson, Andrew B.

    1990-01-01

    A grating appears to move if it is displaced by some amount between two brief presentations, or between multiple successive presentations. A number of recent experiments have examined the influence of displacement size upon either the sensitivity to motion, or upon the induced motion aftereffect. Several recent motion models are based upon quadrature filters that respond in opposite quadrants in the spatiotemporal frequency plane. Predictions of the quadrature model are derived for both two-frame and multiframe displays. Quadrature models generally predict an optimal displacement of 1/4 cycle for two-frame displays, but in the multiframe case the prediction depends entirely on the frame rate.

  17. Programs for computing abscissas and weights for classical and nonclassical Gaussian quadrature formulas

    NASA Technical Reports Server (NTRS)

    Desmarais, R. N.

    1975-01-01

    Computer programs for computing Gaussian quadrature abscissas and weights are described. For the classical case the programs use Laguerre iteration to compute abscissas as zeros of orthogonal polynomials. The polynomials are evaluated from known recursion coefficients. The nonclassical case is handled similarly except that the recursion coefficients are computed by numerical integration. A sample problem, with input and output, is presented to illustrate the use of the programs. It computes the quadrature abscissas and weights associated with the weight function over the interval (0,1) for quadrature orders from 16 to 96 in increments of 8.

  18. Sensitivity of the Lanczos recurrence to Gaussian quadrature data: How malignant can small weights be?

    NASA Astrophysics Data System (ADS)

    Knizhnerman, Leonid

    2010-01-01

    Stability of passing from Gaussian quadrature data to the Lanczos recurrence coefficients is considered. Special attention is paid to estimates explicitly expressed in terms of quadrature data and not having weights in denominators. It has been shown that the recent approach, exploiting integral representation of Hankel determinants, implies quantitative improvement of D. Laurie's constructive estimate. It has also been demonstrated that a particular implementation on the Hankel determinant approach gives an estimate being unimprovable up to a coefficient; the corresponding example involves quadrature data with a small but not too small weight. It follows that polynomial increase of a general case upper bound in terms of the dimension is unavoidable.

  19. Multidimensional Hermite-Gaussian quadrature formulae and their application to nonlinear estimation

    NASA Technical Reports Server (NTRS)

    Mcreynolds, S. R.

    1975-01-01

    A simplified technique is proposed for calculating multidimensional Hermite-Gaussian quadratures that involves taking the square root of a matrix by the Cholesky algorithm rather than computation of the eigenvectors of the matrix. Ways of reducing the dimension, number, and order of the quadratures are set forth. If the function f(x) under the integral sign is not well approximated by a low-order algebraic expression, the order of the quadrature may be reduced by factoring f(x) into an expression that is nearly algebraic and one that is Gaussian.

  20. Common interferometer control systems architecture

    NASA Astrophysics Data System (ADS)

    Hines, Braden E.; Johnson, Richard L.; Starr, Kenneth M.

    1998-07-01

    Astronomical interferometry at the JPL has grown rapidly in the last two years. JPL is now engaged in a number of interferometry projects and is also developing a number of internal testbeds to support those projects. While each of these projects and testbeds has its own unique properties, they do share a lot of common features, and JPL is striving, through its interferometer technology program (ITP), to develop common components, software, and hardware that can be reused by multiple projects. The discipline where this commonality is probably most apparent is in the area of realtime control systems, specifically the software and electronics that drive the instrument control loops and sequence the subsystems. To this end, within the ITP, JPL has developed the realtime interferometer control systems testbed (RICST) as a facility where a common software and electronics core, essentially a control system for a generic interferometer, can be developed. The realtime control (RTC) team in the ITP program consists of about 20 full-time equivalent engineers, technicians, quality assurance personnel, architects, and managers. The remainder of this paper will describe the interferometry landscape at JPL, the RTC effort, an overview of the RICST testbed, and the generic interferometer control system architecture that has been developed.

  1. Holographic Twyman-Green interferometer

    NASA Technical Reports Server (NTRS)

    Chen, C. W.; Breckinridge, J. B.

    1982-01-01

    A dichromated gelatin off-axis Fresnel zone plate was designed, fabricated, and used in a new type of interferometer for optical metrology. This single hologram optical element combines the functions of a beam splitter, beam diverger, and aberrated null lens. Data presented show the successful application for an interferometric test of an f/6, 200-mm diam parabolic mirror.

  2. Stitching interferometer for large optics: recent developments of a system

    NASA Astrophysics Data System (ADS)

    Bray, Michael

    1999-07-01

    We have developed a stitching interferometer for use with large optics, such as those used in Laser MegaJoule and NIF. The idea behind this technique is that, to keep resolution at its highest value, a 'small' aperture phase-shifting interferometer must be used. But this means that measurement of the complete component has to be performed by stitching the individual sub-apertures together. We have overcome most of the obstacles involved in stitching interferometry, and have been using one such system at our optical and laser production facility in Orleans for some years. We have previously reported transmission measurements performed on a Phebus laser slab. We present here measurements performed on Laser MegaJoule transport mirrors measured in a horizontal position, and on glass inhomogeneity without oil plates. This latter requires multiple takes on each sub-aperture, and additional computing, but the whole process has been automated. In addition, we contribute to the pretty picture department by showing graphical results perhaps never previously seen. This work was performed under contract from CEA-LV, as part of the Laser Megajoule development.

  3. Analyzing algorithms for nonlinear and spatially nonuniform phase shifts in the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

    SciTech Connect

    Jain, N.

    1999-03-01

    Phase-shifting interferometry has many advantages, and the phase shifting nature of the Liquid Crystal Point Diffraction Interferometer (LCPDI) promises to provide significant improvement over other current OMEGA wavefront sensors. However, while phase-shifting capabilities improve its accuracy as an interferometer, phase-shifting itself introduces errors. Phase-shifting algorithms are designed to eliminate certain types of phase-shift errors, and it is important to chose an algorithm that is best suited for use with the LCPDI. Using polarization microscopy, the authors have observed a correlation between LC alignment around the microsphere and fringe behavior. After designing a procedure to compare phase-shifting algorithms, they were able to predict the accuracy of two particular algorithms through computer modeling of device-specific phase shift-errors.

  4. A Cross-Correlated Trellis-Coded Quadrature Modulation Representation of MIL-STD Shaped Offset Quadrature Phase-Shift Keying

    NASA Astrophysics Data System (ADS)

    Simon, M. K.; Li, L.

    2003-08-01

    We show that MIL-STD shaped offset quadrature phase-shift keying (SOQPSK), a highly bandwidth-efficient constant-envelope modulation, can be represented in the form of a cross-correlated trellis-coded quadrature modulation, a generic structure containing both memory and cross-correlation between the in-phase and quadrature-phase channels. Such a representation allows identification of the optimum form of receiver for MIL-STD SOQPSK and at the same time, through modification of the equivalent I and Q encoders to recursive types, allows for it to be embedded as the inner code of a serial or parallel (turbo-like) concatenated coding structure together with iterative decoding.

  5. Design of a dual species atom interferometer for space

    NASA Astrophysics Data System (ADS)

    Schuldt, Thilo; Schubert, Christian; Krutzik, Markus; Bote, Lluis Gesa; Gaaloul, Naceur; Hartwig, Jonas; Ahlers, Holger; Herr, Waldemar; Posso-Trujillo, Katerine; Rudolph, Jan; Seidel, Stephan; Wendrich, Thijs; Ertmer, Wolfgang; Herrmann, Sven; Kubelka-Lange, André; Milke, Alexander; Rievers, Benny; Rocco, Emanuele; Hinton, Andrew; Bongs, Kai; Oswald, Markus; Franz, Matthias; Hauth, Matthias; Peters, Achim; Bawamia, Ahmad; Wicht, Andreas; Battelier, Baptiste; Bertoldi, Andrea; Bouyer, Philippe; Landragin, Arnaud; Massonnet, Didier; Lévèque, Thomas; Wenzlawski, Andre; Hellmig, Ortwin; Windpassinger, Patrick; Sengstock, Klaus; von Klitzing, Wolf; Chaloner, Chris; Summers, David; Ireland, Philip; Mateos, Ignacio; Sopuerta, Carlos F.; Sorrentino, Fiodor; Tino, Guglielmo M.; Williams, Michael; Trenkel, Christian; Gerardi, Domenico; Chwalla, Michael; Burkhardt, Johannes; Johann, Ulrich; Heske, Astrid; Wille, Eric; Gehler, Martin; Cacciapuoti, Luigi; Gürlebeck, Norman; Braxmaier, Claus; Rasel, Ernst

    2015-06-01

    Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth's gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species 85Rb/87Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry, the detection unit, the vacuum system for 10-11 mbar ultra-high vacuum generation, and the high-suppression factor magnetic shielding as well as the thermal control system. The laser system is based on a hybrid approach using fiber-based telecom components and high-power laser diode technology and includes all laser sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and switching of the laser beams is carried out on an optical bench using Zerodur bonding technology. The instrument consists of 9 units with an overall mass of 221 kg, an average power consumption of 608 W (814 W peak), and a volume of 470 liters which would well fit on a satellite to be launched with a Soyuz rocket, as system studies have shown.

  6. Radiation transport modeling using extended quadrature method of moments

    SciTech Connect

    Vikas, V.; Hauck, C.D.; Wang, Z.J.; Fox, R.O.

    2013-08-01

    The radiative transfer equation describes the propagation of radiation through a material medium. While it provides a highly accurate description of the radiation field, the large phase space on which the equation is defined makes it numerically challenging. As a consequence, significant effort has gone into the development of accurate approximation methods. Recently, an extended quadrature method of moments (EQMOM) has been developed to solve univariate population balance equations, which also have a large phase space and thus face similar computational challenges. The distinct advantage of the EQMOM approach over other moment methods is that it generates moment equations that are consistent with a positive phase space density and has a moment inversion algorithm that is fast and efficient. The goal of the current paper is to present the EQMOM method in the context of radiation transport, to discuss advantages and disadvantages, and to demonstrate its performance on a set of standard one-dimensional benchmark problems that encompass optically thin, thick, and transition regimes. Special attention is given in the implementation to the issue of realizability—that is, consistency with a positive phase space density. Numerical results in one dimension are promising and lay the foundation for extending the same framework to multiple dimensions.

  7. Information entropy of Gegenbauer polynomials and Gaussian quadrature

    NASA Astrophysics Data System (ADS)

    Sánchez-Ruiz, Jorge

    2003-05-01

    In a recent paper (Buyarov V S, López-Artés P, Martínez-Finkelshtein A and Van Assche W 2000 J. Phys. A: Math. Gen. 33 6549-60), an efficient method was provided for evaluating in closed form the information entropy of the Gegenbauer polynomials C(lambda)n(x) in the case when lambda = l in Bbb N. For given values of n and l, this method requires the computation by means of recurrence relations of two auxiliary polynomials, P(x) and H(x), of degrees 2l - 2 and 2l - 4, respectively. Here it is shown that P(x) is related to the coefficients of the Gaussian quadrature formula for the Gegenbauer weights wl(x) = (1 - x2)l-1/2, and this fact is used to obtain the explicit expression of P(x). From this result, an explicit formula is also given for the polynomial S(x) = limnrightarrowinfty P(1 - x/(2n2)), which is relevant to the study of the asymptotic (n rightarrow infty with l fixed) behaviour of the entropy.

  8. Efficient Implementations of the Quadrature-Free Discontinuous Galerkin Method

    NASA Technical Reports Server (NTRS)

    Lockard, David P.; Atkins, Harold L.

    1999-01-01

    The efficiency of the quadrature-free form of the dis- continuous Galerkin method in two dimensions, and briefly in three dimensions, is examined. Most of the work for constant-coefficient, linear problems involves the volume and edge integrations, and the transformation of information from the volume to the edges. These operations can be viewed as matrix-vector multiplications. Many of the matrices are sparse as a result of symmetry, and blocking and specialized multiplication routines are used to account for the sparsity. By optimizing these operations, a 35% reduction in total CPU time is achieved. For nonlinear problems, the calculation of the flux becomes dominant because of the cost associated with polynomial products and inversion. This component of the work can be reduced by up to 75% when the products are approximated by truncating terms. Because the cost is high for nonlinear problems on general elements, it is suggested that simplified physics and the most efficient element types be used over most of the domain.

  9. Squeezed quadrature fluctuations in a gravitational wave detector using squeezed light.

    PubMed

    Dwyer, S; Barsotti, L; Chua, S S Y; Evans, M; Factourovich, M; Gustafson, D; Isogai, T; Kawabe, K; Khalaidovski, A; Lam, P K; Landry, M; Mavalvala, N; McClelland, D E; Meadors, G D; Mow-Lowry, C M; Schnabel, R; Schofield, R M S; Smith-Lefebvre, N; Stefszky, M; Vorvick, C; Sigg, D

    2013-08-12

    Squeezed states of light are an important tool for optical measurements below the shot noise limit and for optical realizations of quantum information systems. Recently, squeezed vacuum states were deployed to enhance the shot noise limited performance of gravitational wave detectors. In most practical implementations of squeezing enhancement, relative fluctuations between the squeezed quadrature angle and the measured quadrature (sometimes called squeezing angle jitter or phase noise) are one limit to the noise reduction that can be achieved. We present calculations of several effects that lead to quadrature fluctuations, and use these estimates to account for the observed quadrature fluctuations in a LIGO gravitational wave detector. We discuss the implications of this work for quantum enhanced advanced detectors and even more sensitive third generation detectors. PMID:23938820

  10. Regularized quadrature and phase tracking from a single closed-fringe interferogram

    NASA Astrophysics Data System (ADS)

    Servin, Manuel; Marroquin, Jose Luis; Quiroga, Juan Antonio

    2004-03-01

    A new sequential phase demodulator based on a regularized quadrature and phase tracker system (RQPT) is applied to demodulate two-dimensional fringe patterns. This RQPT system tracks the fringe pattern's quadrature and phase in a sequential way by following the path of the fringes. To make the RQPT system more robust to noise, the modulating phase around a small neighborhood is modeled as a plane and the quadrature of the signal is estimated simultaneously with the fringe's modulating phase. By sequentially calculating the quadrature of the fringe pattern, one obtains a more robust sequential demodulator than was previously possible. This system may be applied to the demodulation of a single interferogram having closed fringes.

  11. On numerical integration with high-order quadratures: with application to the Rayleigh-Sommerfeld integral

    NASA Astrophysics Data System (ADS)

    Evans, W. A. B.; Torre, A.

    2012-11-01

    The paper focusses on the advantages of using high-order Gauss-Legendre quadratures for the precise evaluation of integrals with both smooth and rapidly changing integrands. Aspects of their precision are analysed in the light of Gauss' error formula. Some "test examples" are considered and evaluated in multiple precision to ≈ 200 significant decimal digits with David Bailey's multiprecision package to eliminate truncation/rounding errors. The increase of precision on doubling the number of subintervals is analysed, the relevant quadrature attribute being the precision increment. In order to exemplify the advantages that high-order quadrature afford, the technique is then used to evaluate several plots of the Rayleigh-Sommerfeld diffraction integral for axi-symmetric source fields defined on a planar aperture. A comparison of the high-order quadrature method against various FFT-based methods is finally given.

  12. Reissner-Mindlin Legendre Spectral Finite Elements with Mixed Reduced Quadrature

    SciTech Connect

    Brito, K. D.; Sprague, M. A.

    2012-10-01

    Legendre spectral finite elements (LSFEs) are examined through numerical experiments for static and dynamic Reissner-Mindlin plate bending and a mixed-quadrature scheme is proposed. LSFEs are high-order Lagrangian-interpolant finite elements with nodes located at the Gauss-Lobatto-Legendre quadrature points. Solutions on unstructured meshes are examined in terms of accuracy as a function of the number of model nodes and total operations. While nodal-quadrature LSFEs have been shown elsewhere to be free of shear locking on structured grids, locking is demonstrated here on unstructured grids. LSFEs with mixed quadrature are, however, locking free and are significantly more accurate than low-order finite-elements for a given model size or total computation time.

  13. Static and (quasi)dynamic calibration of stroboscopic scanning white light interferometer

    NASA Astrophysics Data System (ADS)

    Seppä, Jeremias; Kassamakov, Ivan; Nolvi, Anton; Heikkinen, Ville; Paulin, Tor; Lassila, Antti; Hao, Ling; Hæggsröm, Edward

    2013-04-01

    A scanning white light interferometer can characterize out of plane features and motion in M(N)EMS devices. Like any other form and displacement measuring instrument, the scanning interferometer results should be linked to the metre definition to be comparable and unambiguous. Traceability is built up by careful error characterization and calibration of the interferometer. The main challenge in this calibration is to have a reference device producing accurate and reproducible dynamic out-of-plane displacement when submitted to standard loads. We use a flat mirror attached to a piezoelectric transducer for static and (quasi)dynamic calibration of a stroboscopic scanning light interferometer. First we calibrated the piezo-scanned flexure guided transducer stage using a symmetric differential heterodyne laser interferometer developed at the Centre for Metrology and Accreditation (MIKES). The standard uncertainty of the piezo stage motion calibration was 3.0 nm. Then we used the piezo-stage as a transfer standard to calibrate our stroboscopic interferometer whose light source was pulsed at 200 Hz and 400 Hz with 0.5% duty cycle. We measured the static position and (quasi)dynamic motion of the attached mirror relative to a reference surface. This methodology permits calibrating the vertical scale of the stroboscopic scanning white light interferometer.

  14. Standing waves in fiber-optic interferometers.

    PubMed

    de Haan, V; Santbergen, R; Tijssen, M; Zeman, M

    2011-10-10

    A study is presented giving the response of three types of fiber-optic interferometers by which a standing wave through an object is investigated. The three types are a Sagnac, Mach-Zehnder and Michelson-Morley interferometer. The response of the Mach-Zehnder interferometer is similar to the Sagnac interferometer. However, the Sagnac interferometer is much harder to study because of the fact that one input port and output port coincide. Further, the Mach-Zehnder interferometer has the advantage that the output ports are symmetric, reducing the systematic effects. Examples of standing wave light absorption in several simple objects are given. Attention is drawn to the influence of standing waves in fiber-optic interferometers with weak-absorbing layers incorporated. A method is described for how these can be theoretically analyzed and experimentally measured. Further experiments are needed for a thorough comparison between theory and experiment. PMID:22015361

  15. Optimization and Experimentation of Dual-Mass MEMS Gyroscope Quadrature Error Correction Methods

    PubMed Central

    Cao, Huiliang; Li, Hongsheng; Kou, Zhiwei; Shi, Yunbo; Tang, Jun; Ma, Zongmin; Shen, Chong; Liu, Jun

    2016-01-01

    This paper focuses on an optimal quadrature error correction method for the dual-mass MEMS gyroscope, in order to reduce the long term bias drift. It is known that the coupling stiffness and demodulation error are important elements causing bias drift. The coupling stiffness in dual-mass structures is analyzed. The experiment proves that the left and right masses’ quadrature errors are different, and the quadrature correction system should be arranged independently. The process leading to quadrature error is proposed, and the Charge Injecting Correction (CIC), Quadrature Force Correction (QFC) and Coupling Stiffness Correction (CSC) methods are introduced. The correction objects of these three methods are the quadrature error signal, force and the coupling stiffness, respectively. The three methods are investigated through control theory analysis, model simulation and circuit experiments, and the results support the theoretical analysis. The bias stability results based on CIC, QFC and CSC are 48 °/h, 9.9 °/h and 3.7 °/h, respectively, and this value is 38 °/h before quadrature error correction. The CSC method is proved to be the better method for quadrature correction, and it improves the Angle Random Walking (ARW) value, increasing it from 0.66 °/√h to 0.21 °/√h. The CSC system general test results show that it works well across the full temperature range, and the bias stabilities of the six groups’ output data are 3.8 °/h, 3.6 °/h, 3.4 °/h, 3.1 °/h, 3.0 °/h and 4.2 °/h, respectively, which proves the system has excellent repeatability. PMID:26751455

  16. Direct modulation at L-band using a quadrature modulator with feedback

    NASA Technical Reports Server (NTRS)

    Datta, Ravi; Crozier, Stewart N.

    1995-01-01

    This paper describes how a high quality modulated signal can be generated directly at the frequency of transmission, using a standard quadrature modulator and other commercially-available, low-cost building blocks. The method uses a feedback technique for automatic correction of carrier leakage, differential gain and phase mismatch errors in the quadrature modulator, and other building blocks, by providing guidance to the digital baseband portion of the modulator. Experimental results are presented for direct modulation at 1.65 GHz.

  17. A fast method of numerical quadrature for p-version finite element matrices

    NASA Technical Reports Server (NTRS)

    Hinnant, Howard E.

    1993-01-01

    A new technique of numerical quadrature especially suited for p-version finite element matrices is presented. This new technique separates the integrand into two parts, and numerically operates on each part separately. The objective of this scheme is to minimize the computational cost of integrating the entire element matrix as opposed to minimizing the cost of integrating a single function. The efficiency of the new technique is compared with Gaussian quadrature and found to take a small fraction of the computational effort.

  18. Optimization and Experimentation of Dual-Mass MEMS Gyroscope Quadrature Error Correction Methods.

    PubMed

    Cao, Huiliang; Li, Hongsheng; Kou, Zhiwei; Shi, Yunbo; Tang, Jun; Ma, Zongmin; Shen, Chong; Liu, Jun

    2016-01-01

    This paper focuses on an optimal quadrature error correction method for the dual-mass MEMS gyroscope, in order to reduce the long term bias drift. It is known that the coupling stiffness and demodulation error are important elements causing bias drift. The coupling stiffness in dual-mass structures is analyzed. The experiment proves that the left and right masses' quadrature errors are different, and the quadrature correction system should be arranged independently. The process leading to quadrature error is proposed, and the Charge Injecting Correction (CIC), Quadrature Force Correction (QFC) and Coupling Stiffness Correction (CSC) methods are introduced. The correction objects of these three methods are the quadrature error signal, force and the coupling stiffness, respectively. The three methods are investigated through control theory analysis, model simulation and circuit experiments, and the results support the theoretical analysis. The bias stability results based on CIC, QFC and CSC are 48 °/h, 9.9 °/h and 3.7 °/h, respectively, and this value is 38 °/h before quadrature error correction. The CSC method is proved to be the better method for quadrature correction, and it improves the Angle Random Walking (ARW) value, increasing it from 0.66 °/√h to 0.21 °/√h. The CSC system general test results show that it works well across the full temperature range, and the bias stabilities of the six groups' output data are 3.8 °/h, 3.6 °/h, 3.4 °/h, 3.1 °/h, 3.0 °/h and 4.2 °/h, respectively, which proves the system has excellent repeatability. PMID:26751455

  19. Implementation of a Reference Interferometer for Nanodetection

    PubMed Central

    Lu, Tao

    2014-01-01

    A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system’s ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events. PMID:24798706

  20. Implementation of a reference interferometer for nanodetection.

    PubMed

    Vincent, Serge; Yu, Wenyan; Lu, Tao

    2014-01-01

    A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system's ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events. PMID:24798706

  1. Directional dual-tree complex wavelet packet transforms for processing quadrature signals.

    PubMed

    Serbes, Gorkem; Gulcur, Halil Ozcan; Aydin, Nizamettin

    2016-03-01

    Quadrature signals containing in-phase and quadrature-phase components are used in many signal processing applications in every field of science and engineering. Specifically, Doppler ultrasound systems used to evaluate cardiovascular disorders noninvasively also result in quadrature format signals. In order to obtain directional blood flow information, the quadrature outputs have to be preprocessed using methods such as asymmetrical and symmetrical phasing filter techniques. These resultant directional signals can be employed in order to detect asymptomatic embolic signals caused by small emboli, which are indicators of a possible future stroke, in the cerebral circulation. Various transform-based methods such as Fourier and wavelet were frequently used in processing embolic signals. However, most of the times, the Fourier and discrete wavelet transforms are not appropriate for the analysis of embolic signals due to their non-stationary time-frequency behavior. Alternatively, discrete wavelet packet transform can perform an adaptive decomposition of the time-frequency axis. In this study, directional discrete wavelet packet transforms, which have the ability to map directional information while processing quadrature signals and have less computational complexity than the existing wavelet packet-based methods, are introduced. The performances of proposed methods are examined in detail by using single-frequency, synthetic narrow-band, and embolic quadrature signals. PMID:25388779

  2. Incoherent holography to obtain depth information by a rotational shearing interferometer

    NASA Astrophysics Data System (ADS)

    Watanabe, Kaho; Nomura, Takanori

    2015-09-01

    The system to record incoherent holograms using a rotational shearing interferometer is proposed. It enables us to record a hologram without coherent illumination such as a laser. The systems can record an incoherent hologram by self-interference. A rotational shearing interferometer to record incoherent cosine hologram is described. Furthermore, a rotational shearing interferometer with lenses to record incoherent hologram is described. It has the advantage of obtaining depth information by the reconstruction owing to lenses for the shear which is parallel to the optical axis. The preliminary experiments were performed. An LED and a liquid crystal display with an LED backlight were used as incoherent objects. The incoherent holograms were recorded. The object images were reconstructed numerically. The experimental results confirm the proposed incoherent holography using a rotational shearing interferometer.

  3. V-groove all-fiber core-cladding intermodal interferometer for high-temperature sensing.

    PubMed

    Yin, Zhen; Geng, Youfu; Li, Xuejin; Tan, Xiaoling; Gao, Rong

    2015-01-10

    Novel V-groove all-fiber core-cladding intermodal interferometers fabricated by CO2 laser irradiation on a standard single-mode fiber are described. The high-order cladding modes are excited due to the special V-groove structure. The interferometers are classified as Mach-Zehnder and Michelson type based on the way they are structured. Benefiting from the large difference of thermal coefficients of the core and high-order cladding modes, both types receive high temperature sensitivity by monitoring the wavelength shift of the interference spectrum, and their responses to temperature are similar. Compared with the Mach-Zehnder interferometer, the Michelson interferometer is more compact and more flexible in application. PMID:25967632

  4. Error motion compensating tracking interferometer for the position measurement of objects with rotational degree of freedom

    NASA Astrophysics Data System (ADS)

    Holler, Mirko; Raabe, Jörg

    2015-05-01

    The nonaxial interferometric position measurement of rotating objects can be performed by imaging the laser beam of the interferometer to a rotating mirror which can be a sphere or a cylinder. This, however, requires such rotating mirrors to be centered on the axis of rotation as a wobble would result in loss of the interference signal. We present a tracking-type interferometer that performs such measurement in a general case where the rotating mirror may wobble on the axis of rotation, or even where the axis of rotation may be translating in space. Aside from tracking, meaning to measure and follow the position of the rotating mirror, the interferometric measurement errors induced by the tracking motion of the interferometer itself are optically compensated, preserving nanometric measurement accuracy. As an example, we show the application of this interferometer in a scanning x-ray tomography instrument.

  5. A Fiber Interferometer for the Magnetized Shock Experiment

    SciTech Connect

    Yoo, Christian

    2012-08-30

    The Magnetized Shock Experiment (MSX) at Los Alamos National Laboratory requires remote diagnostics of plasma density. Laser interferometry can be used to determine the line-integrated density of the plasma. A multi-chord heterodyne fiber optic Mach-Zehnder interferometer is being assembled and integrated into the experiment. The advantage of the fiber coupling is that many different view chords can be easily obtained by simply moving transmit and receive fiber couplers. Several such fiber sets will be implemented to provide a time history of line-averaged density for several chords at once. The multiple chord data can then be Abel inverted to provide radially resolved spatial profiles of density. We describe the design and execution of this multiple fiber interferometer.

  6. Development of a self-referencing interferometer wavefront sensor

    NASA Astrophysics Data System (ADS)

    Rhoadarmer, Troy A.

    2004-10-01

    The self-referencing interferometer (SRI) is an innovative wavefront sensor (WFS) developed specifically for applications requiring laser propagation in strong scintillation. The performance of conventional gradient sensors, like Shack-Hartmann WFSs or lateral shearing interferometers, are severely limited in these environments due to the presence of branch points in the wavefront phase. In comparison, the SRI WFS directly measures the wavefront field so its performance is not affected by the presence of branch points. Over the last two years the Starfire Optical Range has been developing a prototype SRI WFS to demonstrate its advantages in strong scintillation environments. This paper discusses some practical lessons learned in building and operating an SRI WFS and presents initial results from laboratory tests.

  7. A cryogenic tunable Fabry-Perot interferometer for astronomical observations

    NASA Astrophysics Data System (ADS)

    Chow, Jonathan K.; Ryder, Leigh Ann; Chapman, Ira; Horner, Scott; Dean, Peter D.

    2007-09-01

    The Lockheed Martin - University of Arizona Infrared Spectrometer (LAIRS) is designed to image the emission lines of celestial objects in the 1.3-2.5 μm regime. The Instrument has been built and tested at the Lockheed Martin Space Systems Advanced Technology Center, and demonstrated to work at cryogenic temperatures. The Instrument employs a tunable Fabry-Perot Interferometer (FPI) to select the wavelength at which the Instrument images targets. The FPI employs voice coil actuators and capacitive sensors to maintain parallelism of its reflective lenses and control their gap spacing. During functional tests of the FPI and the LAIRS instrument, finesse numbers of 60 and 24 were measured for the interferometer at room temperature and 80K, respectively. This measurement was performed using a laser operating at 1529.33 nm. This paper presents an overview of the optical, mechanical, and control design of the FPI, as well as a summary of cryogenic test results.

  8. Matter-wave soliton interferometer based on a nonlinear splitter

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Hidetsugu; Malomed, Boris A.

    2016-02-01

    We elaborate a model of the interferometer which, unlike previously studied ones, uses a local (δ-functional) nonlinear repulsive potential, embedded into a harmonic-oscillator trapping potential, as the splitter for the incident soliton. An estimate demonstrates that this setting may be implemented by means of the localized Feshbach resonance controlled by a focused laser beam. The same system may be realized as a nonlinear waveguide in optics. Subsequent analysis produces an exact solution for scattering of a plane wave in the linear medium on the δ -functional nonlinear repulsive potential, and an approximate solution for splitting of the incident soliton when the ambient medium is nonlinear. The most essential result, obtained by means of systematic simulations, is that the use of the nonlinear splitter provides the sensitivity of the soliton-based interferometer to the target, inserted into one of its arms, which is much higher than the sensitivity provided by the usual linear splitter.

  9. Divertor interferometer diagnostic for ITER

    SciTech Connect

    Brower, D. L.; Deng, B. H.; Ding, W. X.

    2006-10-15

    In the harsh environment of the divertor region in ITER, plasmas spanning a huge density range from 10{sup 19} to 10{sup 22} m{sup -3} are anticipated making measurement of the electron density particularly challenging. For any reasonable wavelength choice, the total phase measured by a conventional two-color interferometer system is always >>2{pi} and therefore subject to fringe counting errors. This problem can be remedied by adding a polarimeter capability whereby the Cotton-Mouton effect is measured or by employing differential interferometry. Using either approach, the total phase is always <<2{pi}. The conceptual design of an interferometer system along with possible wavelength choices will be explored.

  10. Keck Interferometer nuller instrument performance

    NASA Astrophysics Data System (ADS)

    Colavita, M. M.; Serabyn, E.; Ragland, S.; Millan-Gabet, R.; Akeson, R. L.

    2010-07-01

    The Keck Interferometer combines the two 10 m Keck telescopes as a long baseline interferometer. It is funded by NASA as a joint development among the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the NASA Exoplanet Science Institute. In February 2008, the 10 um nulling mode began a 32 night observing program with three key science teams to perform a survey of nearby stars for exozodiacal dust. This program has recently concluded, and has been followed by nuller observing on a variety of science topics through the standard proposal process. We provide a review and update of the nuller implementation, and describe the data reduction process, including the calibration approach. We then review the technical performance of the instrument based on the full key science data set, including sensitivity and systematic errors. We also provide some summary data on atmospheric effects applicable to the cophasing approach.

  11. Status of the LBT interferometer

    NASA Astrophysics Data System (ADS)

    Hinz, Philip M.; Bippert-Plymate, Teresa; Breuninger, Andy; Connors, Tom; Duffy, Brian; Esposito, Simone; Hoffmann, William; Kim, Jihun; Kraus, Joe; McMahon, Thomas; Montoya, Manny; Nash, Richard; Durney, Olivier; Solheid, Elliott; Tozzi, Andrea; Vaitheeswaran, Vidhya

    2008-07-01

    The Large Binocular Telescope Interferometer, a thermal infrared imager and nulling interferometer for the LBT, is currently being integrated and tested at Steward Observatory. The system consists of a general purpose or universal beamcombiner (UBC) and three camera ports, one of which is populated currently by the Nulling and Imaging Camera (NIC). Wavefront sensing is carried out using pyramid-based "W" units developed at Arcetri Observatory. The system is designed for high spatial resolution, high dynamic range imaging in the thermal infrared. A key project for the program is to survey nearby stars for debris disks down to levels which may obscure detection of Earth-like planets. During 2007-2008 the UBC portion of the LBTI was assembled and tested at Steward Observatory. Initial integration of the system with the LBT is currently in progress as the W units and NIC are being completed in parallel.

  12. Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space

    NASA Technical Reports Server (NTRS)

    Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, M. Charles; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William; Zielinski, Robert J.; Lillie, Charles F.

    1996-01-01

    POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

  13. Stellar Interferometer Technology Experiment (SITE)

    NASA Astrophysics Data System (ADS)

    Crawley, Edward F.; Miller, David; Laskin, Robert; Shao, Michael

    1995-02-01

    The MIT Space Engineering Research Center and the Jet Propulsion Laboratory stand ready to advance science sensor technology for discrete-aperture astronomical instruments such as space-based optical interferometers. The objective of the Stellar Interferometer Technology Experiment (SITE) is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled-Structures Technologies (CST). SITE mounts to the Mission Peculiar Experiment Support System inside the Shuttle payload bay. Starlight, entering through two apertures, is steered to a combining plate where it is interferred. Interference requires 27 nanometer pathlength (phasing) and 0.29 archsecond wavefront-tilt (pointing) control. The resulting 15 milli-archsecond angular resolution exceeds that of current earth-orbiting telescopes while maintaining low cost by exploiting active optics and structural control technologies. With these technologies, unforeseen and time-varying disturbances can be rejected while relaxing reliance on ground alignment and calibration. SITE will reduce the risk and cost of advanced optical space systems by validating critical technologies in their operational environment. Moreover, these technologies are directly applicable to commercially driven applications such as precision matching, optical scanning, and vibration and noise control systems for the aerospace, medical, and automotive sectors. The SITE team consists of experienced university, government, and industry researchers, scientists, and engineers with extensive expertise in optical interferometry, nano-precision opto-mechanical control and spaceflight experimentation. The experience exists and the technology is mature. SITE will validate these technologies on a functioning interferometer science sensor in order to confirm definitely their readiness to be baselined for future science missions.

  14. Stellar Interferometer Technology Experiment (SITE)

    NASA Technical Reports Server (NTRS)

    Crawley, Edward F.; Miller, David; Laskin, Robert; Shao, Michael

    1995-01-01

    The MIT Space Engineering Research Center and the Jet Propulsion Laboratory stand ready to advance science sensor technology for discrete-aperture astronomical instruments such as space-based optical interferometers. The objective of the Stellar Interferometer Technology Experiment (SITE) is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled-Structures Technologies (CST). SITE mounts to the Mission Peculiar Experiment Support System inside the Shuttle payload bay. Starlight, entering through two apertures, is steered to a combining plate where it is interferred. Interference requires 27 nanometer pathlength (phasing) and 0.29 archsecond wavefront-tilt (pointing) control. The resulting 15 milli-archsecond angular resolution exceeds that of current earth-orbiting telescopes while maintaining low cost by exploiting active optics and structural control technologies. With these technologies, unforeseen and time-varying disturbances can be rejected while relaxing reliance on ground alignment and calibration. SITE will reduce the risk and cost of advanced optical space systems by validating critical technologies in their operational environment. Moreover, these technologies are directly applicable to commercially driven applications such as precision matching, optical scanning, and vibration and noise control systems for the aerospace, medical, and automotive sectors. The SITE team consists of experienced university, government, and industry researchers, scientists, and engineers with extensive expertise in optical interferometry, nano-precision opto-mechanical control and spaceflight experimentation. The experience exists and the technology is mature. SITE will validate these technologies on a functioning interferometer science sensor in order to confirm definitely their readiness to be baselined for future science missions.

  15. The TEXT upgrade vertical interferometer

    NASA Astrophysics Data System (ADS)

    Hallock, G. A.; Gartman, M. L.; Li, W.; Chiang, K.; Shin, S.; Castles, R. L.; Chatterjee, R.; Rahman, A. S.

    1992-10-01

    A far-infrared interferometer has been installed on TEXT upgrade to obtain electron density profiles. The primary system views the plasma vertically through a set of large (60-cm radial×7.62-cm toroidal) diagnostic ports. A 1-cm channel spacing (59 channels total) and fast electronic time response is used, to provide high resolution for radial profiles and perturbation experiments. Initial operation of the vertical system was obtained late in 1991, with six operating channels.

  16. Polarized-interferometer feasibility study

    NASA Technical Reports Server (NTRS)

    Raab, F. H.

    1983-01-01

    The feasibility of using a polarized-interferometer system as a rendezvous and docking sensor for two cooperating spacecraft was studied. The polarized interferometer is a radio frequency system for long range, real time determination of relative position and attitude. Range is determined by round trip signal timing. Direction is determined by radio interferometry. Relative roll is determined from signal polarization. Each spacecraft is equipped with a transponder and an antenna array. The antenna arrays consist of four crossed dipoles that can transmit or receive either circularly or linearly polarized signals. The active spacecraft is equipped with a sophisticated transponder and makes all measurements. The transponder on the passive spacecraft is a relatively simple repeater. An initialization algorithm is developed to estimate position and attitude without any a priori information. A tracking algorithm based upon minimum variance linear estimators is also developed. Techniques to simplify the transponder on the passive spacecraft are investigated and a suitable configuration is determined. A multiple carrier CW signal format is selected. The dependence of range accuracy and ambiguity resolution error probability are derived and used to design a candidate system. The validity of the design and the feasibility of the polarized interferometer concept are verified by simulation.

  17. Modulated white-LED interferometer

    NASA Astrophysics Data System (ADS)

    Shiina, Tatsuo; Izuhara, Noboru; Ito, Masafumi; Okamura, Yasuyuki

    2002-09-01

    ZnSe and InGaN based white-LEDs have been utilized for an interferometer. These white-LED consist of blue-LED light and yellowish green one. When these white-LED were modulated by rectangular wave, there were differences in response speed between blue-LED light and yellowish light. The response speed of blue-LED light of ZnSe type white-LED was 50ns, while that of yellowish light was 5us. The spectral bandwidths of the blue-LED light and the yellowish light were 10nm and 100nm, respectively. Coherence lengths of these lights were 10um and 2um, respectively. Combining the blue-LED light with the yellowish light, we observe an unique interference when scanning the optical path of the low coherence interferometer. We also propose a method for a color separation of an interference in a low coherence interferometer with the ZnSe white-LED modulation. The ZnSe white-LED was modulated with much higher frequency (100kHz) than the Doppler frequency of the above interference. The interference fringe of white light appeared at the upper side on the rectangular modulated light emission, while that of the residual yellowish light was presented at the bottom. The interference fringe of the blue light was derived by subtracting the yellowish light interference from the white light one.

  18. Demodulation of diaphragm based acoustic sensor using Sagnac interferometer with stable phase bias.

    PubMed

    Ma, Jun; Yu, Yongqin; Jin, Wei

    2015-11-01

    A stable phase demodulation system for diaphragm-based acoustic sensors is reported. The system is based on a modified fiber-optic Sagnac interferometer with a stable quadrature phase bias, which is independent of the parameters of the sensor head. The phase bias is achieved passively by introducing a nonreciprocal frequency shift between the counter-propagating waves, avoiding the use of complicated active servo-control. A 100 nm-thick graphite diaphragm-based acoustic sensor interrogated by the proposed demodulation system demonstrated a minimum detectable pressure level of ~450 µPa/Hz(1/2) and an output signal stability of less than 0.35 dB over an 8-hour period. The system may be useful as a universal phase demodulation unit for diaphragm-based acoustic sensors as well as other sensors operating in a reflection mode. PMID:26561196

  19. Nonlocal polarization interferometer for entanglement detection

    SciTech Connect

    Williams, Brian P; Humble, Travis S; Grice, Warren P

    2014-01-01

    We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt Bell test where the local reality is the photon polarization. We present the relevant theory and experimental results.

  20. Nonlocal polarization interferometer for entanglement detection

    DOE PAGESBeta

    Williams, Brian P; Humble, Travis S; Grice, Warren P

    2014-01-01

    We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt Bell test where the local reality is the photon polarization. We present themore » relevant theory and experimental results.« less