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1

Dual-probe homodyne quadrature laser interferometer.  

PubMed

We present a dual-probe homodyne quadrature laser interferometer for the measurements of displacement at two separate spatial locations. This is a coupled homodyne interferometer with inverted polarity of probe signals featuring a wide dynamic range and constant sensitivity. As an application of this dual-probe interferometer, we demonstrate how to locate the pulsed-laser interaction site on a plate without knowing the propagation velocities of the laser-induced mechanical waves. PMID:22722276

Požar, Tomaž; Možina, Janez

2012-06-20

2

Quadrature phase-shift error analysis using a homodyne laser interferometer.  

PubMed

The influence of quadrature phase shift on the measured displacement error was experimentally investigated using a two-detector polarizing homodyne laser interferometer with a quadrature detection system. Common nonlinearities, including the phase-shift error, were determined and effectively corrected by a robust data-processing algorithm. The measured phase-shift error perfectly agrees with the theoretically determined phase-shift error region. This error is systematic, periodic and severely asymmetrical around the nominal displacement value. The main results presented in this paper can also be used to assess and correct the detector errors of other interferometric and non-interferometric displacement-measuring devices based on phase-quadrature detection. PMID:19724631

Gregorcic, Peter; Pozar, Tomaz; Mozina, Janez

2009-08-31

3

A homodyne quadrature laser interferometer for micro-asperity deformation analysis.  

PubMed

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

Poga?nik, Aljaž; Požar, Tomaž; Kalin, Mitjan; Možina, Janez

2013-01-01

4

A Homodyne Quadrature Laser Interferometer for Micro-Asperity Deformation Analysis  

PubMed Central

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

PogaCnik, Aljaz; Pozar, Tomaz; Kalin, Mitjan; Mozina, Janez

2013-01-01

5

Quadrature phase interferometer for high resolution force spectroscopy  

SciTech Connect

In this article, we present a deflection measurement setup for Atomic Force Microscopy (AFM). It is based on a quadrature phase differential interferometer: we measure the optical path difference between a laser beam reflecting above the cantilever tip and a reference beam reflecting on the static base of the sensor. A design with very low environmental susceptibility and another allowing calibrated measurements on a wide spectral range are described. Both enable a very high resolution (down to 2.5×10{sup ?15}?m/?(Hz)), illustrated by thermal noise measurements on AFM cantilevers. They present an excellent long-term stability and a constant sensitivity independent of the optical phase of the interferometer. A quick review shows that our precision is equaling or out-performing the best results reported in the literature, but for a much larger deflection range, up to a few ?m.

Paolino, Pierdomenico; Aguilar Sandoval, Felipe A.; Bellon, Ludovic [Laboratoire de physique, Université de Lyon, ENS Lyon, CNRS, Lyon 69364 (France)] [Laboratoire de physique, Université de Lyon, ENS Lyon, CNRS, Lyon 69364 (France)

2013-09-15

6

Optimization of displacement-measuring quadrature interferometers considering the real properties of optical components  

SciTech Connect

We present the influence of alignment and the real properties of optical components on the performance of a two-detector homodyne displacement-measuring quadrature laser interferometer. An experimental method, based on the optimization of visibility and sensitivity, was established and theoretically described to assess the performance and stability of the interferometer. We show that the optimal performance of such interferometers is achieved with the iterative alignment procedure described.

Pozar, Tomaz; Gregorcic, Peter; Mozina, Janez

2011-03-20

7

Optimization of displacement-measuring quadrature interferometers considering the real properties of optical components.  

PubMed

We present the influence of alignment and the real properties of optical components on the performance of a two-detector homodyne displacement-measuring quadrature laser interferometer. An experimental method, based on the optimization of visibility and sensitivity, was established and theoretically described to assess the performance and stability of the interferometer. We show that the optimal performance of such interferometers is achieved with the iterative alignment procedure described. PMID:21460992

Požar, Tomaž; Gregor?i?, Peter; Možina, Janez

2011-03-20

8

Digital holography with a quadrature phase-shifting interferometer.  

PubMed

An alternative method for digital holography using a quadrature phase-shifting interferometer for high-speed measurement is presented. We show that it has image quality equal to the four-bucket method. In addition, it requires fewer imaging devices. Two quadrature phase-shifting fringe patterns are acquired in each state of an object changed temporally. The phase calculation method with these four fringe patterns gives the phase distribution of the hologram. This digital phase hologram is reconstructed to yield an object image by the Fresnel transform using digital convolutions with the fast Fourier transform algorithm. Verification results of simulations and experiments are given. PMID:19252631

Kiire, Tomohiro; Nakadate, Suezou; Shibuya, Masato

2009-03-01

9

Photoacoustic tomography using a Michelson interferometer with quadrature phase detection  

NASA Astrophysics Data System (ADS)

We present a pressure sensor based on a Michelson interferometer, for use in photoacoustic tomography. Quadrature phase detection is employed allowing measurement at any point on the mirror surface without having to retune the interferometer, as is typically required by Fabry-Perot type detectors. This opens the door to rapid full surface detection, which is necessary for clinical applications. Theory relating acoustic pressure to detected acoustic particle displacements is used to calculate the detector sensitivity, which is validated with measurement. Proof-of-concept tomographic images of blood vessel phantoms have been taken with sub-millimeter resolution at depths of several millimeters.

Speirs, Rory W.; Bishop, Alexis I.

2013-07-01

10

RAPID COMMUNICATION: Quadrature Mach Zehnder interferometer with application in optical coherence tomography  

NASA Astrophysics Data System (ADS)

A novel quadrature interferometer based on Mach-Zehnder configuration and a 3 × 3 fibre coupler is presented. Measurements showing instantaneous extraction of both real and complex parts of the interferometric signal are described. The features of this quadrature interferometric platform are discussed with a focus on signal-to-noise ratio and optical power handling.

Flueraru, C.; Kumazaki, H.; Sherif, S.; Chang, S.; Mao, Y.

2007-04-01

11

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

NASA Technical Reports Server (NTRS)

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". .

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

2003-01-01

12

Detection of Interference Phase by Digital Computation of Quadrature Signals in Homodyne Laser Interferometry  

PubMed Central

We have proposed an approach to the interference phase extraction in the homodyne laser interferometry. The method employs a series of computational steps to reconstruct the signals for quadrature detection from an interference signal from a non-polarising interferometer sampled by a simple photodetector. The complexity trade-off is the use of laser beam with frequency modulation capability. It is analytically derived and its validity and performance is experimentally verified. The method has proven to be a feasible alternative for the traditional homodyne detection since it performs with comparable accuracy, especially where the optical setup complexity is principal issue and the modulation of laser beam is not a heavy burden (e.g., in multi-axis sensor or laser diode based systems). PMID:23202038

Rerucha, Simon; Buchta, Zdenek; Sarbort, Martin; Lazar, Josef; Cip, Ondrej

2012-01-01

13

Thermal stability of laser tracking interferometer calibration  

Microsoft Academic Search

Uncompensated thermomechanical errors in laser tracking interferometers are examined by evaluating the difference between tracking interferometer compensations in a controlled laboratory environment versus being compensated in a factory environment. The hypothesis under test was that compensation in a factory environment does not adversely affect, and may actually improve, the uncertainty of laser tracker systems. This hypothesis was confirmed by measuring

Scott C. Sandwith

1999-01-01

14

Exploring the QED vacuum with laser interferometers  

Microsoft Academic Search

It is demonstrated that the nonlinear, and as yet unobserved, QED effect of slowing down light by application of a strong magnetic field may be observable with large laser interferometers like for instance LIGO or GEO600.

Daniel Boer; Jan-Willem van Holten

2002-01-01

15

Non-contact detection of laser-generated surface acoustic waves using fiber optic Sagnac interferometer.  

PubMed

A high powered Q-switched Nd:YAG laser was used to excite the surface waves, and an optical fiber sensor was used to detect the out-of-plane displacements due to the propagating waves. This sensor is based on the fiber optic Sagnac interferometer, which has the path-matched configuration and does not require active stabilization. Quadrature phase bias between two interfering laser beams in the Sagnac loop is applied by controlling the birefringence in an optical path using a fiber polarization controller. A stable quadrature phase bias can be confirmed by observing the interferometer output according to the change of phase bias. Additional signal processing is not needed for the detection of ultrasonic waves using the Sagnac interferometer. The performance of the fiber optic Sagnac interferometer was investigated, and laser-generated surface wave signals were detected using this fiber optic sensor. The developed fiber optic sensor configured in this study is very simple and is effective for non-contact detection of ultrasonic waves. PMID:12160048

Jang, Tae Seong; Lee, Jung Ju; Yoon, Dong Jin; Lee, Seung Seok

2002-05-01

16

Modeling the Laser Interferometer Space Antenna Optics  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

17

Atmospheric and hydrospheric laser interferometers  

Microsoft Academic Search

The paper presents the description and estimation of the sensitivity of laser nanobarograph, laser strainmeter, and laser meter of the hydrosphere pressure variations that have been developed on the basis of modern laser-interference methods using frequency-stabilized lasers. These sets are designed for study of the laws of generation, dynamics, and transformation of oscillations and waves of low-frequency and super low-frequency

G. I. Dolgikh; I. V. Batyushina; D. I. Valentin; S. G. Dolgikh; S. V. Kovalev; I. A. Koren; E. D. Kholodkevich; V. A. Shvets; S. V. Yakovenko

2003-01-01

18

Measuring Cyclic Error in Laser Heterodyne Interferometers  

NASA Technical Reports Server (NTRS)

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-

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

2010-01-01

19

Modified Phasemeter for a Heterodyne Laser Interferometer  

NASA Technical Reports Server (NTRS)

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.

Loya, Frank M.

2010-01-01

20

Gravitational Wave Detection with Single-Laser Atom Interferometers  

NASA Technical Reports Server (NTRS)

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.

Yu, Nan; Tinto, Massimo

2011-01-01

21

Laser frequency stability transfer using a fiber-based interferometer.  

PubMed

We have demonstrated a method for laser frequency stability transfer using a fiber-based Young's interferometer. An 858 nm external cavity diode laser is stabilized to within 1e-8 from 10 s to 4000 s, referenced to a Rubidium stabilized 780 nm DBR diode laser using the interferometer as a frequency-stability-transferring link. The system is simple to build and can link any two laser wavelengths within the fiber operating range. PMID:24922216

Wang, Z B; Zhang, J W; Wang, S G; Miao, K; Wang, L J

2014-05-20

22

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

SciTech Connect

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.

Ivanov, D. A. [Physical Faculty, St. Petersburg State University, Ul'yanovskaya 1, 198504 Petrodvoretz, St. Petersburg (Russian Federation)

2010-04-15

23

Experimental generation of broadband quadrature entanglement using laser pulses  

SciTech Connect

We report on the generation of broadband pulsed quadrature entanglement by combining two squeezed vacua, which are generated from two degenerate optical parametric amplifiers (OPAs), on a beam splitter. With a single pass through OPA, in which a periodically poled lithium niobate waveguide is used as a nonlinear material, the noise reduction of 3.4{+-}0.2 dB below the shot noise limit is observed with a bandwidth of more than 200 MHz. The entanglement correlation or EPR correlation is confirmed with a sufficient criterion <{delta}{sup 2}(X{sub a}+X{sub b})>+<{delta}{sup 2}(Y{sub a}-Y{sub b})>=1.28<2.

Zhang, Yun; Furuta, Tatsuya; Okubo, Ryuhi; Takahashi, Kosuke; Hirano, Takuya [Department of Physics, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo, 171-8588, Japan CREST, Japan Science and Technology Agency, 1-9-9 Yaesu, Chuo-ku, Tokyo, 103-0028 (Japan)

2007-07-15

24

Pulsed laser diode optical fiber interferometer for absolute distance measurement  

NASA Astrophysics Data System (ADS)

An interferometry system for absolute distance measurement is described. In the system, an optical fiber Mach-Zehnder interferometer with a chirped laser diode is employed to position the measured object. Another interferometer with He-Ne laser is used to measure the optical path difference. The coherence-length of the pulsed multimode laser diode is studied. In the experiments, the system measured the absolute distance up to 1 meter with the accuracy of 2 micrometer.

Wang, Chunhe; Xiao, Hai; Hong, Haitao; Ye, Shenghua

1996-10-01

25

Double heterodyne interferometer using a multimode laser diode  

Microsoft Academic Search

A double heterodyne interferometer using a multimode laser diode with a synthetic wavelength of approximately 1 mm has been established and the stability of the synthetic wavelength has been investigated.

S. Han; E. Dalhoff; Edgar Fischer; S. Heim; Hans J. Tiziani

1994-01-01

26

Two-laser heterodyne metrology for a separated spacecraft interferometer  

Microsoft Academic Search

The proposed New Millennium Interferometer consists of three spacecraft separated by up to several kilometers. A heterodyne laser metrology system is proposed to measure the relative distances between the spacecraft. Because diffraction losses for a round-trip measurement are prohibitively large, a two-laser metrology system has been suggested in which each spacecraft has both a laser and a receiver. The system

Rhonda Morgan; Stuart B. Shaklan; Jeffrey W. Yu

1996-01-01

27

Long-term laser frequency stabilization using fiber interferometers  

E-print Network

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. 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 laser and an atomic reference.

Kong, Jia; Jimenez-Martinez, Ricardo; Mitchell, Morgan W

2014-01-01

28

Low-coherence interferometer using a pulsation laser diode  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

29

Ellipse fitting by nonlinear constraints to demodulate quadrature homodyne interferometer signals and to determine the statistical uncertainty of the interferometric phase  

NASA Astrophysics Data System (ADS)

Optical interferometers are widely used in dimensional metrology applications. Among them are many quadrature homodyne interferometers. These exhibit two sinusoidal interference signals shifted, in the ideal case, by 90° to allow a direction sensitive detection of the motion responsible for the actual phase change. But practically encountered signals exhibit additional offsets, unequal amplitudes and a phase shift that differs from 90°. In order to demodulate the interference signals the so called Heydemann correction is used in almost all cases, i.e. an ellipse is fitted to both signals simultaneously to obtain the offsets, amplitude and the phase lag. Such methods are typically based on a simplified least squares fit that leads to a system of linear equations, which can be solved directly in one step. Although many papers related to this subject have been published already only a few of them consider the uncertainties related to this demodulation scheme. In this paper we propose a new method for fitting the ellipse, based on minimization of the geometric distance between the measured and fitted signal values, which provides locally best linear unbiased estimators (BLUEs) of the unknown model parameters, and simultaneously also estimates of the related statistical uncertainties, including the uncertainties of estimated phases and/or displacements.

Köning, Rainer; Wimmer, Gejza; Witkovský, Viktor

2014-11-01

30

Multicomponent wavefield characterization with a novel scanning laser interferometer  

E-print Network

noncontacting technique to transducers.1 Ultra- sonic laser interferometers and vibrometers have a broad- band a fixed optical path inside the device. The receiver uses two-wave mixing in a photorefrac- tive crystal in the photorefractive crystal to form a real-time hologram which diffracts each beam into the other direction

Boise State University

31

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

NASA Astrophysics Data System (ADS)

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.

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

2011-05-01

32

Testing the optical bench of the Laser Interferometer Space Antenna  

NASA Astrophysics Data System (ADS)

The space-based gravitational-wave detector Laser Interferometer Space Antenna (LISA) shall detect gravitational-waves by measuring distance changes between its three satellites with in-terferometers. Currently, the first prototype of the so-called optical bench, that contains the interferometric setups for the lengths measurements of LISA, is being built for the European Space Agengy (ESA). This optical bench will be tested at the Albert-Einstein-Institute and its functionality and sensitivity will be characterised. For this purpose, special tools and pre-experiments are necessary, that will be discussed in this talk.

Tröbs, Michael; Baune, Christoph; Bogenstahl, Johanna; D'Arcio, Luigi; Dehne, Marina; Diekmann, Christian; Fitzsimons, Ewan; Fleddermann, Roland; Granova, Evgenia; Heinzel, Gerhard; Hogenhuis, Harm; Killow, Christian; Perreur-Lloyd, Michael; Pijnenburg, Joep; Robertson, David; Schütte, Dirk; Schwarze, Thomas; Vogt, Malte; Wanner, Gudrun; Ward, Henry; Weise, Dennis; Danzmann, Karsten

33

Polarization Considerations for the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

34

Laser exposure analysis for a near-infrared ocular interferometer  

NASA Astrophysics Data System (ADS)

Ocular interferometry has potential value in a variety of ocular measurement applications, including measuring ocular thicknesses, topography of ocular surfaces or the wavefront of the eye. Of particular interest is using interferometry for characterizing corneal shape and irregular corneal features, making this technology attractive due to its inherent accuracy and spatial resolution. A particular challenge of designing an ocular interferometer is determining safe laser exposure levels to the eye, including both the retina and anterior segment. Described here are the laser exposure standards relevant in the interferometer design and the corresponding calculations and results. The results of this work can be used to aid in the design of similar laser-based systems for ocular evaluation.

Primeau, Brian C.; Goldstein, Goldie L.; Greivenkamp, John E.

2012-06-01

35

Michelson Interferometer characterisation of noise reduction in DFB fibre lasers  

NASA Astrophysics Data System (ADS)

A comparison is made between unpackaged and packaged distributed feedback (DFB) fibre lasers using the Michelson interferometer configuration for delayed self-heterodyne interferometery (MIDSHI) to ascertain the improvements to the external environmental noise, quantified by reductions in the Gaussian linewidth. Voigt fitting is used to extract and separate out the Lorentzian and Gaussian linewidth contributions and therefore the associated sources of noise. Significant improvements in the Gaussian linewidth were achieved as a result of significant reductions in the sensitivity of the DFB laser to external perturbations using packaging. However, a broadening of the laser Lorentzian linewidth was observed.

Canagasabey, Albert; Jones, David; Mann, David; Canning, John; Fleming, Simon; Holdsworth, John

2012-02-01

36

Research on beam splitting prism in laser heterodyne interferometer  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

37

A laser interferometer dilatometer for thermal expansion measurements of composites  

NASA Technical Reports Server (NTRS)

A high precision Fizeau type, laser interferometer dilatometer system has been developed for low expansion composite materials. The strain resolution is about 1 microstrain. The system is automated to operate over a large temperature range and record data during the test in real time. A technique has been developed to reduce the fringe data in real time to length changes. The dilatometer system is described and thermal expansion measurements for several fiber-reinforced and particle filled composites are presented.

Tompkins, S. S.; Bowles, D. E.; Kennedy, W. R.

1984-01-01

38

The GRACE Follow-On Laser Ranging Interferometer  

NASA Astrophysics Data System (ADS)

In the year 2017 a follow-on mission to the joint German / NASA mission GRACE (Gravity Recovery And Climate Experiment) will be launched. While a microwave ranging instrument has been used for the ranging measurement in GRACE, an additional laser ranging interferometer (LRI) will be implemented into the architecture of the GRACE Follow-On satellites as a technology demonstrator. An overview of the current status of the development of the LRI will be presented.

Görth, Alexander

2014-05-01

39

Reference laser source for the IASI interferometer  

Microsoft Academic Search

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

Laurence Pujol; Jacques Lizet; Olivier Sosnicki

2001-01-01

40

A laser unequal path interferometer for the optical shop.  

PubMed

The application of laser technology has been extended to optical shop testing by incorporating a cw, helium-neon gas laser in a package that houses a modified Twyman-Green interferometer. This modification provides for optical testing over large path differences with an auxiliary set of lenses used in the long path and a small reference flat used in the short path of the interferometer. With this technique, f/0.7 spherical mirrors have been tested (at the center of curvature) to an accuracy of 1/10 wavelength at the surface, and various other optical systems have been tested in both double pass and single pass. Two of the advantages of this testing method are (1) the capability of testing spherical concave surfaces without physically contacting the surface and (2) the ability to use small reference surfaces for large optical components or systems. The device known as a laser unequal path interferometer can be used with a set of null lenses to qualify aspheric surfaces. The unit is portable and capable of testing in any orientation under various environmental conditions. Several applications of this device are presented to illustrate its versatility. PMID:20062171

Houston, J B; Buccini, C J; O'Neill, P K

1967-07-01

41

Influence of laser frequency noise on scanning Fabry-Perot interferometer based laser Doppler velocimetry  

NASA Astrophysics Data System (ADS)

In this work, we study the performance of a scanning Fabry-Perot interferometer based laser Doppler velocimeter (sFPILDV) and compare two candidate 1.5 um single-frequency laser sources for the system - a fiber laser (FL) and a semiconductor laser (SL). We describe a straightforward calibration procedure for the sFPI-LDV and investigate the effect of different degrees of laser frequency noise between the FL and the SL on the velocimeter's performance.

Rodrigo, Peter John; Pedersen, Christian

2014-03-01

42

A simple pendulum laser interferometer for determining the gravitational constant.  

PubMed

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

Parks, Harold V; Faller, James E

2014-10-13

43

Antiresonant ring interferometer for laser cavity dumping, mode locking, and other applications  

NASA Technical Reports Server (NTRS)

Applications in lasers for antiresonant ring interferometer include coupled laser cavities, variable laser-output coupling, intercavity harmonic-output coupling, mode locking, cavity dumping, and pulse code modulation.

Siegman, A. E.

1975-01-01

44

Development of a heterodyne laser interferometer for very small high frequency displacements detection.  

National Technical Information Service (NTIS)

A heterodyne laser interferometer with detection electronics has been developed for measuring very small amplitude high frequency vibrations. A laser beam from HeNe-laser is focused and reflected in the vibrating surface and the generated phase shifts are...

P. Baarmann

1992-01-01

45

The Laser Interferometer Space Antenna (LISA)  

NASA Astrophysics Data System (ADS)

LISA is a joint NASA/ESA space mission designed to measure gravitational waves in the band from 0.1 mHz to 0.1 Hz, a band that is richly populated by strong sources of gravitational waves. Signals will come from a wide range of sources: massive black holes merging in galaxies; compact objects captured by massive black holes; ultra-compact Galactic binaries; and possibly other sources such as relics of the Big Bang. These sources convey detailed information addressing a wide range of physics and astrophysics: the history of galaxies and black holes in the universe; general relativity; measurements of luminosity distances; the physics of dense matter and stellar remnants; and possibly new physics associated with events in the very early universe. The LISA mission uses laser metrology between three spacecraft separated by 5 million km to detect gravitational wave sources with very high sensitivity. We will describe the LISA mission and summarize its current status, including technology development and the upcoming LISA Pathfinder mission.

Prince, Thomas Allen; LISA International Science Team

2011-01-01

46

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

PubMed Central

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

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

2014-01-01

47

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

PubMed

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

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

2014-01-01

48

Precision Pointing for the Laser Interferometer Space Antenna (LISA) Mission  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) mission is a planned NASA-ESA gravity wave detector consisting of three spacecraft in heliocentric orbit. Lasers are used to measure distance fluctuations between the proof masses aboard the spacecraft to the picometer level over the 5 million kilometer spacing. Each spacecraft and it's two laser transmit/receive telescopes must be held stable in pointing to less than 8 nanoradians per root Hertz in the frequency band 0.1 mHz to 0.1 Hz. This is accomplished by sensing the pointing error in the received beam and controlling the spacecraft attitude with a set of micronewton thrusters. Requirements, sensors, actuators, control design, and simulations are described in this paper.

Bauer, Frank H. (Technical Monitor); Hyde, T. Tupper; Maghami, P.

2003-01-01

49

VCSEL-based miniature laser-Doppler interferometer  

NASA Astrophysics Data System (ADS)

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.

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

2008-02-01

50

Explosive component acceptance tester using laser interferometer technology  

NASA Technical Reports Server (NTRS)

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.

Wickstrom, Richard D.; Tarbell, William W.

1993-01-01

51

Note: Measurement speed improvement of microchip Nd:YAG laser feedback interferometer  

NASA Astrophysics Data System (ADS)

We analyze the measurement speed limit of the quasi-common-path laser feedback interferometer and demonstrate a much improved measurement speed from 100 ?m/s to 60 mm/s owing to the optimized system parameters and a novel signal processing method. The performance is experimentally verified by comparing to an Agilent 5529A dual-frequency laser interferometer.

Zhang, Song; Tan, Yidong; Zhang, Shulian

2014-03-01

52

LIGO: The Laser Interferometer Gravitational-Wave Observatory  

E-print Network

The goal of the Laser Interferometric Gravitational-Wave Observatory (LIGO) is to detect and study gravitational waves of astrophysical origin. Direct detection of gravitational waves holds the promise of testing general relativity in the strong-field regime, of providing a new probe of exotic objects such as black hole 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 1 part in 1E21. With this unprecedented sensitivity, the data are being analyzed to detect or place limits on gravitational waves from a variety of potential astrophysical sources.

The LIGO Scientific Collaboration; B. Abbott

2007-11-19

53

Multicomponent wavefield characterization with a novel scanning laser interferometer  

SciTech Connect

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.

Blum, Thomas E.; Wijk, Kasper van [Department of Geosciences, Boise State University, 1910 University Drive, Boise, Idaho 83725 (United States); Pouet, Bruno; Wartelle, Alexis [Bossa Nova Technologies LLC, 606 Venice Blvd., Suite B, Venice, California 90291 (United States)

2010-07-15

54

Microkelvin thermal control system for the laser interferometer space antenna mission and beyond  

Microsoft Academic Search

The Laser Interferometer Space Antenna (LISA) mission aims to detect directly gravitational waves from massive black holes and galactic binaries. Through detecting gravitational waves, we can study blackholes and the origin of the universe, which is inaccessible from the electromagnetic wave spectrum. It will open a new window to the universe. LISA is essentially a Michelson interferometer placed in space

Sei Higuchi

2009-01-01

55

LASERS: Stable pulsed picosecond GSGG:Nd3+ laser with a resonator based on Sagnac interferometer  

NASA Astrophysics Data System (ADS)

An investigation was made of the characteristics of a laser with a new active medium in the form of neodymium-activated gadolinium scandium gallium garnet (GSGG:Nd3+), containing chromium and emitting ultrashort pulses in the case of passive mode locking. Statistical dependences of the duration, energy, and reproducibility of the output pulses on the position of a cell with a saturable absorber (dye 3274 in ethanol) in an interferometer and on the initial transmission of the cell were determined. A new resonator configuration with an asymmetric position of the active element inside an interferometer ring was used: it ensured simple emission of the lowest transverse mode without additional spatial selection. A comparison of the main parameters of the ultrashort pulses emitted by YAG and GSGG lasers demonstrated characteristic advantages of the new active medium in generation of picosecond pulses.

Prokhorenko, V. I.; Surovtsev, D. V.; Tikhonov, E. A.; Yatskiv, D. Ya

1990-03-01

56

Coherence measurements of a Nd-YAG laser by image processing of Michelson interferometer fringe patterns  

Microsoft Academic Search

To determine the coherence of a laser device, the concept of visibility is used and applied to the measured interference patterns produced by this laser light in a specific interferometer. In this case, to determine the coherence of a Diode Pumped Solid State Nd -YAG Laser, a digital image processing procedure was developed and applied to the fringe patterns obtained

Claudia Valdés; Efraín Solarte

2005-01-01

57

A Laser Interferometer for the Undergraduate Teaching Laboratory Demonstrating Picometer Sesitivity  

E-print Network

We describe a 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. 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.

Libbrecht, Kenneth G

2014-01-01

58

Laser Interferometer Space Antenna (LISA) Far Field Phase Patterns  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

59

Ultra-stable performance of an underground-based laser interferometer observatory for gravitational waves  

E-print Network

In order to detect the rare astrophysical events that generate gravitational wave (GW) radiation, sufficient stability is required for GW antennas to allow long-term observation. In practice, seismic excitation is one of the most common disturbances effecting stable operation of suspended-mirror laser interferometers. A straightforward means to allow more stable operation is therefore to locate the antenna, the ``observatory'', at a ``quiet'' site. A laser interferometer gravitational wave antenna with a baseline length of 20m (LISM) was developed at a site 1000m underground, near Kamioka, Japan. This project was a unique demonstration of a prototype laser interferometer for gravitational wave observation located underground. The extremely stable environment is the prime motivation for going underground. In this paper, the demonstrated ultra-stable operation of the interferometer and a well-maintained antenna sensitivity are reported.

S. Sato; S. Miyoki; S. Telada; D. Tatsumi; A. Araya; M. Ohashi; Y. Totsuka; M. Fukushima; M. -K. Fujimoto

2004-03-18

60

Pulse-shaping of gain-switched pulse from multimode laser diode using fiber Sagnac interferometer.  

PubMed

We propose a pulse-tail elimination and pulse shortening method using an optical interferometer, which is effective for picosecond chirped pulses from gain-switched multimode laser diodes. In a numerical simulation, when the delay distance between a chirped pulse and its replica in an optical interferometer matches two times the round-trip optical length of the laser cavity, the pulse-front and -rear tail parts are effectively eliminated from the input chirped pulse after passing through the optical interferometer. Using this method with a fiber Sagnac interferometer, a 33 ps pulse with a long-tail emitted from a gain-switched 1540 nm multimode laser diode was linearly transformed into a 20 ps pulse with a substantially reduced tail. PMID:19030074

Wada, Kenji; Takamatsu, Shuji; Watanebe, Hideyuki; Matsuyama, Tetsuya; Horinaka, Hiromichi

2008-11-24

61

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

PubMed

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. PMID:24089870

Hilbert, Vinzenz; Blinne, Alexander; Fuchs, Silvio; Feigl, Torsten; Kämpfer, Tino; Rödel, Christian; Uschmann, Ingo; Wünsche, Martin; Paulus, Gerhard G; Förster, Eckhart; Zastrau, Ulf

2013-09-01

62

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

SciTech Connect

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.

Hilbert, Vinzenz; Fuchs, Silvio; Paulus, Gerhard G.; Zastrau, Ulf [Institute of Optics and Quantum Electronics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany)] [Institute of Optics and Quantum Electronics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Blinne, Alexander [Institute for Theoretical Physics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany)] [Institute for Theoretical Physics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Feigl, Torsten [Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Straße 7, 07745 Jena (Germany)] [Fraunhofer Institute for Applied Optics and Precision Engineering, Albert-Einstein-Straße 7, 07745 Jena (Germany); Kämpfer, Tino; Rödel, Christian; Uschmann, Ingo; Wünsche, Martin; Förster, Eckhart [Institute of Optics and Quantum Electronics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany) [Institute of Optics and Quantum Electronics, Friedrich-Schiller University Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Helmholtz Institute, Fröbelstieg 3, 07743 Jena (Germany)

2013-09-15

63

Detection of low frequency hurricane emissions using a ring laser interferometer  

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

64

Pulse compression for gain-switched multimode laser diode using optical interferometer  

Microsoft Academic Search

We have proposed a pulse compression method using an optical interferometer, which is effective for gain-switched pulses from multimode laser diodes. Features of the method were examined numerically. Using this method, a picosecond pulse from a gain-switched 830-nm Fabry-Perot laser diode was compressed from 30 to 22 ps.

Kenji Wada; Shuji Takamatsu; Hideyuki Watanabe; Tetsuya Matsuyama; H. Horinaka

2007-01-01

65

A high-power tapered and cascaded active multimode interferometer semiconductor laser diode  

Microsoft Academic Search

A high power semiconductor laser diode with a tapered and cascaded active multimode interferometer (MMI) cavity was designed and demonstrated. An output power as high as 32 mW was obtained for the novel laser diode with a tapered and cascaded active MMI cavity, being much higher than the 9.8 mW output power of the conventional single ridge F---P laser with

Lai Weijiang; Cheng Yuanbing; Yao Chen; Zhou Daibing; Bian Jing; Zhao Lingjuan; Wu Jian

2011-01-01

66

Laser surface patterning using a Michelson interferometer and femtosecond laser radiation  

NASA Astrophysics Data System (ADS)

We report on a simple method to obtain surface gratings using a Michelson interferometer and femtosecond laser radiation. In the optical setup used, two parallel laser beams are generated using a beam splitter and then focused using the same focusing lens. An interference pattern is created in the focal plane of the focusing lens, which can be used to pattern the surface of materials. The main advantage of this method is that the optical paths difference of the interfering beams is independent of the distance between the beams. As a result, the fringes period can be varied without a need for major realignment of the optical system and the time coincidence between the interfering beams can be easily monitored. The potential of the method was demonstrated by patterning surface gratings with different periods on titanium surfaces in air.

Oliveira, V.; Polushkin, N. I.; Conde, O.; Vilar, R.

2012-10-01

67

Interferometer Interferometer  

E-print Network

by NASA as engineering testbed for Keck . Specifically designed with dual star mode for narrow�phased. #12; SPIEMarch 23, 1998 Palomar Testbed Interferometer JKW�15 Constant�TermMetrology . Measures difference in optical path between the two arms for each beam combiner -- difference in metrology measurments

68

Coherence length modulation of a multimode laser diode in a dual Michelson interferometer configuration.  

PubMed

The use of a multimode (compact-disk type) laser diode in a dual Michelson interferometer arrangement is investigated, both theoretically and experimentally, by using the technique of coherence length modulation. A reproducible way of shifting the interference regions is considered for the potential use of the technique in optical sensors, for flow or distance measurement. PMID:20720762

Ning, Y N; Grattan, K T; Palmer, A W; Meggitt, B T

1992-03-20

69

Coherence length modulation of a multimode laser diode in a dual Michelson interferometer configuration  

Microsoft Academic Search

The use of a multimode (compact-disk type) laser diode in a dual Michelson interferometer arrangement is investigated, both theoretically and experimentally, by using the technique of coherence length modulation. A reproducible way of shifting the interference regions is considered for the potential use of the technique in optical sensors, for flow or distance measurement.

Y. N. Ning; K. T. V. Grattan; A. W. Palmer; B. T. Meggitt

1992-01-01

70

Eleven-wavelength switchable fiber ring laser with a dispersion compensation fiber and a delayed interferometer  

Microsoft Academic Search

We demonstrate a fiber ring laser with a dispersion compensation fiber (DCF) and a delayed interferometer (DI) with temperature control, which is able to switch eleven wavelengths one by one. In ring cavity, DCF supplies different effective cavity lengths for different wavelengths, DI generates a wavelength comb corresponding to the ITU grid, a flat-gain erbium-doped fiber amplifier (EDFA) provides uniform

Fei Wang; Xin-Liang Zhang; Jian-Ji Dong; Yu Yu; Zheng Zhang

2008-01-01

71

Three mode interactions as a precision monitoring tool for advanced laser interferometers  

NASA Astrophysics Data System (ADS)

Many thousands of three mode opto-acoustic interactions are expected to be observable in the advanced laser interferometer gravitational wave detectors now under construction. Each interaction represents a high-Q acoustic resonance interacting with high order optical modes inside the interferometer. This paper shows that this huge set of signals between 10-100 kHz have high sensitivity to changes in the optical wavefronts within the interferometer and can be used to create a powerful probe of the entire interferometer. We show that 3MI signals can be used to monitor thermal distortions corresponding to wavefront changes ˜3 × 10-12 m. Observations can be used at low optical power to predict parametric instabilities that could occur at higher power. In addition, the observed mode amplitudes could be used to control the interferometer operating point against slow environmental perturbations. Data on 80 m cavities and modelling results are used to demonstrate the sensitivity of 3MI monitoring. Experimental observations on advanced interferometers are suggested as a means to turn 3MI monitoring into an effective tool.

Ju, L.; Zhao, C.; Blair, D. G.; Gras, S.; Susmithan, S.; Fang, Q.; Blair, C. D.

2014-09-01

72

Virgo: a laser interferometer to detect gravitational waves  

NASA Astrophysics Data System (ADS)

This paper presents a complete description of Virgo, the French-Italian gravitational wave detector. The detector, built at Cascina, near Pisa (Italy), is a very large Michelson interferometer, with 3 km-long arms. In this paper, following a presentation of the physics requirements, leading to the specifications for the construction of the detector, a detailed description of all its different elements is given. These include civil engineering infrastructures, a huge ultra-high vacuum (UHV) chamber (about 6000 cubic metres), all of the optical components, including high quality mirrors and their seismic isolating suspensions, all of the electronics required to control the interferometer and for signal detection. The expected performances of these different elements are given, leading to an overall sensitivity curve as a function of the incoming gravitational wave frequency. This description represents the detector as built and used in the first data-taking runs. Improvements in different parts have been and continue to be performed, leading to better sensitivities. These will be detailed in a forthcoming paper.

Accadia, T.; Acernese, F.; Alshourbagy, M.; Amico, P.; Antonucci, F.; Aoudia, S.; Arnaud, N.; Arnault, C.; Arun, K. G.; Astone, P.; Avino, S.; Babusci, D.; Ballardin, G.; Barone, F.; Barrand, G.; Barsotti, L.; Barsuglia, M.; Basti, A.; Bauer, Th S.; Beauville, F.; Bebronne, M.; Bejger, M.; Beker, M. G.; Bellachia, F.; Belletoile, A.; Beney, J. L.; Bernardini, M.; Bigotta, S.; Bilhaut, R.; Birindelli, S.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Boccara, C.; Boget, D.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouedo, T.; Bouhou, B.; Bozzi, A.; Bracci, L.; Braccini, S.; Bradaschia, C.; Branchesi, M.; Briant, T.; Brillet, A.; Brisson, V.; Brocco, L.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calamai, G.; Calloni, E.; Campagna, E.; Canuel, B.; Carbognani, F.; Carbone, L.; Cavalier, F.; Cavalieri, R.; Cecchi, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chatterji, S.; Chiche, R.; Chincarini, A.; Chiummo, A.; Christensen, N.; Clapson, A. C.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Conforto, G.; Corsi, A.; Cortese, S.; Cottone, F.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Daguin, G.; Dari, A.; Dattilo, V.; David, P. Y.; Davier, M.; Day, R.; Debreczeni, G.; De Carolis, G.; Dehamme, M.; Del Fabbro, R.; Del Pozzo, W.; del Prete, M.; Derome, L.; De Rosa, R.; DeSalvo, R.; Dialinas, M.; Di Fiore, L.; Di Lieto, A.; Emilio, M. Di Paolo; Di Virgilio, A.; Dietz, A.; Doets, M.; Dominici, P.; Dominjon, A.; Drago, M.; Drezen, C.; Dujardin, B.; Dulach, B.; Eder, C.; Eleuteri, A.; Enard, D.; Evans, M.; Fabbroni, L.; Fafone, V.; Fang, H.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Forest, D.; Forte, L. A.; Fournier, J.-D.; Fournier, L.; Franc, J.; Francois, O.; Frasca, S.; Frasconi, F.; Freise, A.; Gaddi, A.; Galimberti, M.; Gammaitoni, L.; Ganau, P.; Garnier, C.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Gennaro, G.; Giacobone, L.; Giazotto, A.; Giordano, G.; Giordano, L.; Girard, C.; Gouaty, R.; Grado, A.; Granata, M.; Granata, V.; Grave, X.; Greverie, C.; Groenstege, H.; Guidi, G. M.; Hamdani, S.; Hayau, J.-F.; Hebri, S.; Heidmann, A.; Heitmann, H.; Hello, P.; Hemming, G.; Hennes, E.; Hermel, R.; Heusse, P.; Holloway, L.; Huet, D.; Iannarelli, M.; Jaranowski, P.; Jehanno, D.; Journet, L.; Karkar, S.; Ketel, T.; Voet, H.; Kovalik, J.; Kowalska, I.; Kreckelbergh, S.; Krolak, A.; Lacotte, J. C.; Lagrange, B.; La Penna, P.; Laval, M.; Le Marec, J. C.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lieunard, B.; Liguori, N.; Lodygensky, O.; Lopez, B.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Loupias, M.; Mackowski, J. M.; Maiani, T.; Majorana, E.; Magazzù, C.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mancini, S.; Mansoux, B.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marin, P.; Marque, J.; Martelli, F.; Masserot, A.; Massonnet, L.; Matone, G.; Matone, L.; Mazzoni, M.; Menzinger, F.; Michel, C.; Milano, L.; Minenkov, Y.; Mitra, S.; Mohan, M.; Montorio, J.-L.; Morand, R.; Moreau, F.; Moreau, J.; Morgado, N.; Morgia, A.; Mosca, S.; Moscatelli, V.; Mours, B.; Mugnier, P.; Mul, F.-A.; Naticchioni, L.; Neri, I.; Nocera, F.; Pacaud, E.; Pagliaroli, G.; Pai, A.; Palladino, L.; Palomba, C.; Paoletti, F.; Paoletti, R.; Paoli, A.; Pardi, S.; Parguez, G.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Perciballi, M.; Perniola, B.; Persichetti, G.; Petit, S.; Pichot, M.; Piergiovanni, F.; Pietka, M.; Pignard, R.; Pinard, L.; Poggiani, R.; Popolizio, P.; Pradier, T.; Prato, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Qipiani, K.; Rabaste, O.; Rabeling, D. S.; Rácz, I.; Raffaelli, F.; Rapagnani, P.; Rapisarda, S.; Re, V.; Reboux, A.; Regimbau, T.; Reita, V.; Remilleux, A.; Ricci, F.; Ricciardi, I.; Richard, F.; Ripepe, M.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Rosi?ska, D.; Roudier, P.; Ruggi, P.; Russo, G.; Salconi, L.; Sannibale, V.; Sassolas, B.; Sentenac, D.; Solimeno, S.; Sottile, R.; Sperandio, L.; Stanga, R.; Sturani, R.; Swinkels, B.; Tacca, M.; Taddei, R.; Taffarello, L.; Tarallo, M.; Tissot, S.; Toncelli, A.; Tonelli, M.; Torre, O.; Tournefier, E.; Travasso, F.; Tremola, C.; Turri, E.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; Vasuth, M.; Vavoulidis, M.; Vedovato, G.; Verkindt, D.; Vetrano, F.; Véziant, O.; Viceré, A.; Vinet, J.-Y.; Vilalte, S.; Vitale, S.; Vocca, H.; Ward, R. L.; Was, M.; Yamamoto, K.; Yvert, M.; Zendri, J.-P.; Zhang, Z.

2012-03-01

73

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

PubMed

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

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

2010-05-28

74

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

NASA Astrophysics Data System (ADS)

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.

Mitryk, Shawn J.

75

Quadrature-quadrature phase-shift keying  

Microsoft Academic Search

Quadrature-quadrature phase-shift keying (Q2PSK) is a spectrally efficient modulation scheme which utilizes available signal space dimensions in a more efficient way than two-dimensional schemes such as QPSK and MSK (minimum-shift keying). It uses two date shaping pulses and two carriers, which are pairwise quadrature in phase, to create a four-dimensional signal space and increases the transmission rate by a factor

D. Saha; T. G. Birdsall

1989-01-01

76

Mirror thermal noise in laser interferometer gravitational wave detectors operating at room and cryogenic temperature  

E-print Network

Mirror thermal noise is and will remain one of the main limitations to the sensitivity of gravitational wave detectors based on laser interferometers. We report about projected mirror thermal noise due to losses in the mirror coatings and substrates. The evaluation includes all kind of thermal noises presently known. Several of the envisaged substrate and coating materials are considered. The results for mirrors operated at room temperature and at cryogenic temperature are reported.

Janyce Franc; Nazario Morgado; Raffaele Flaminio; Ronny Nawrodt; Iain Martin; Liam Cunningham; Alan Cumming; Sheila Rowan; James Hough

2009-12-01

77

Disturbance-free phase-shifting laser diode interferometer using adaptive feedback control  

SciTech Connect

A feedback-control-equipped phase-shifting laser diode interferometer that eliminates external disturbance is proposed. The feedback loop is stabilized by adaptive control of the polarity of the interference signal. Conventional phase-shifting interferometry can be used with the feedback control, resulting in simplified signal processing and accurate measurement. Several experiments confirm the stability of the feedback control with a measurement repeatability of 1.8 nm.

Suzuki, Takamasa; Takahashi, Tsutomu; Sasaki, Osami

2009-10-10

78

Characteristics of a multimode laser diode in a dual-interferometer configuration  

Microsoft Academic Search

The results of an experimental investigation of an interferometric sensor scheme using a Michelson interferometer in conjunction with a Fabry-Perot reference cavity, illuminated by light from a multimode compact-disk-type laser diode, are reported. The results are compared with the results of calculations using a simple theoretical model, and good agreement is seen. Potential applications to interferometric-based sensors are discussed.

Yanong Ning; Kenneth T. V. Grattan; Andrew W. Palmer; Beverley T. Meggitt

1990-01-01

79

Characteristics of a multimode laser diode in a dual-interferometer configuration  

Microsoft Academic Search

The results of an experimental investigation of an interferometric sensor scheme using a Michelson interferometer in conjunction with a Fabry-Perot reference cavity, illuminated by light from a multimode compact disk (CD)-type laser diode, are reported. The results are compared with the results of calculations using a simple theoretical model and good agreement is seen. Potential applications to interferometric-based sensors are

YANONG NING; KENNETH T. V. GRATTAN; ANDREW W. PALMER; BEVERLEY T. MEGGITT

1990-01-01

80

Real-time vibration measurement using a feedback type of laser diode interferometer with an optical fiber  

Microsoft Academic Search

A laser diode interferometer that uses an optical fiber is proposed. The laser diode simultaneously functions as a light source, a phase modulator, and a phase compensator. Detection of the vibration and reduction of external disturbance are carried out using a feedback control for the injection current of the laser diode. Thus it can measure vibration accurately in real time

Takamasa Suzuki; Takao Okada; Osami Sasaki; Takeo Maruyama

1997-01-01

81

Metrology source for high-resolution heterodyne interferometer laser gauges  

Microsoft Academic Search

We describe the development, functional performance, and space-qualification status of a Metrology Source suitable for implementation of space-based metrology systems with picometer-level relative displacement measurement and micron-level absolute displacement measurement resolution. The Metrology Source consists of the following components: lasers, frequency stabilization system, frequency shifters, and frequency modulators. All components are interconnected by polarization maintaining fibers to facilitate integration into

Serge Dubovitsky; David J. Seidel; Duncan T. Liu; Roman C. Gutierrez

1998-01-01

82

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

E-print Network

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, GEO600 and KAGRA.

Dooley, Katherine L; Dwyer, Sheila; Puppo, Paola

2014-01-01

83

Experiments with an 834 m2 ring laser interferometer  

NASA Astrophysics Data System (ADS)

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.

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

2009-06-01

84

Stroboscopic step height measurement with two-wavelength interferometer using single diode laser source  

NASA Astrophysics Data System (ADS)

We propose a two-wavelength interferometer that is used to a stroboscopic step height measurement. Different from most two-wavelength interferometers, in present experiment, two slightly different wavelengths are simultaneously oscillated by currently and thermally controlling a laser diode to work at mode hop region. By use of this two-wavelength laser source, a Twyman-Green interferometer, whose reference arm and object arm have known step height r and unknown step height h, respectively, is constructed. Three independent interference patterns corresponding to different OPDs are formed and they can be simultaneously taken by a CCD camera. Furthermore, tilting the reference, spatial frequencies are introduced into the interference patterns. Taking the Fourier transform of these patterns, three fringe amplitudes are obtained and their expressions can be solved for the unknown step height. As we can capture clear image of the interference patterns in a very short time by use of the high speed shutter function of the CCD camera, the error induced by the external disturbance is farthest reduced.

Zhao, Xuefeng; Suzuki, Takamasa; Sasaki, Osami

2004-02-01

85

Experimental investigation of sensitivity improvement of chaotic fiber ring laser sensing system with embedded Sagnac interferometer  

NASA Astrophysics Data System (ADS)

The sensitivity of optical fiber ring laser distributed sensing system based on the mechanism of chaotic system's sensitivity to initial conditions is low. Fiber interferometer distributed sensing system's sensitivity is high. In this paper, a distributed sensing system with the structure of chaotic fiber ring laser (CFRL) embedding a Sagnac loop interferometer is proposed by combining the property of zero order interference of chaotic light and reciprocity of Sagnac interferometer. It can be used to improve the sensitivity of CFRL sensing system. According to the changes of temporal waveforms, frequency spectrums and autocorrelation functions out of the systems under the same disturbance, the sensitivities are compared between the improved system and the original CFRL system. Experimental results show that the sensitivity of the proposed system is higher than that of the CFRL system. In addition, the response properties of the system under the same amplitude and different frequencies of disturbance signals are measured. The results show that the system can detect the disturbances in the frequency range from 10 kHz to 300 kHz and the responses are flat. The detection abilities to weak signals with different amplitudes are compared. With the rising of disturbance signals amplitudes under the same frequency, the autocorrelation amplitudes of the interference signals increase. In conclusion, the proposed system improves the sensitive to weak disturbance signals with different amplitudes and frequencies. The frequency and amplitude of the disturbance signals can be obtained by the frequency spectrum and autocorrelation function of the waveform of the system.

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

2014-07-01

86

CONTROL OF LASER RADIATION PARAMETERS: Device for enhancing the time contrast of utrashort laser pulses based on a polarisation Mach—Zehnder interferometer  

NASA Astrophysics Data System (ADS)

A polarisation Mach—Zehnder interferometer is considered containing identical cells with a nonlinear medium in different arms. A parallel wave beam propagates through one cell and a converging-diverging wave beam propagates through the other. It is shown that the interferometer transmission depends on the power of the laser pulse propagated through it. It is proposed to use this effect to enhance the time contrast of ultrashort and superhigh-power laser pulses, i.e. to suppress side (background) pulses.

Gitin, Andrey V.

2009-02-01

87

Quest for circular polarization of a gravitational wave background and orbits of laser interferometers in space  

SciTech Connect

We show that an isotropic component of circular polarization of a stochastic gravitational wave background can be explored by contriving configuration of multiple laser interferometers for correlation analysis. For the proposed BBO mission, the circular polarization degree {pi} can be measured down to {pi}{approx}0.08({omega}{sub GW}/10{sup -15}){sup -1}(SNR/5) with slightly ({approx}10%) sacrificing the detection limit for the total intensity {omega}{sub GW}. This might allow us to detect a signature of parity violation in the very early universe.

Seto, Naoki [Department of Physics and Astronomy, 4186 Frederick Reines Hall, University of California, Irvine, California 92697 (United States)

2007-03-15

88

Demonstration of detuned dual recycling at the Garching 30m laser interferometer  

E-print Network

Dual recycling is an advanced optical technique to enhance the signal-to-noise ratio of laser interferometric gravitational wave detectors in a limited bandwidth. To optimise the center of this band with respect to Fourier frequencies of expected gravitational wave signals detuned dual recycling has to be implemented. We demonstrated detuned dual recycling on a fully suspended 30m prototype interferometer. A control scheme that allows to tune the detector to different frequencies will be outlined. Good agreement between the experimental results and numerical simulations has been achieved.

A. Freise; G. Heinzel; K. A. Strain; J. Mizuno; K. D. Skeldon; H. Lueck; B. Willke; R. Schilling; A. Ruediger; W. Winkler; K. Danzmann

2000-06-07

89

Hohlraum glint and laser pre-pulse detector for NIF experiments using velocity interferometer system for any reflectora)  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

90

Fiber inline Michelson interferometer fabricated by CO2 laser irradiation for refractive index sensing  

NASA Astrophysics Data System (ADS)

A compact Michelson interferometer (MI) in a single-mode fiber (SMF) is successfully formed by CO2 laser irradiation to measure refractive index (RI) values. The fiber inline MI mainly consists of two parts: one is the waist region in fiber formed by CO2 laser irradiation and the other one is the fiber tip end facet with pure gold sputter coating. Based on the MI theory, the interference signal is generate between the core mode and the cladding mode excited by the core mode at the waist region. Reflective spectra at two different interference lengths of 5mm and 15mm are given and the calculated lengths based on theory are well verified. After the measurements of matching liquids with seven different refractive indices, the RI sensitivity of the MI sample is tested of -197.3+/-19.1nm/RIU (refractive index unit), which suggests well potential application in RI sensing.

Wu, Hongbin; Yuan, Lei; Zhao, Longjiang; Cao, Zhitao; Wang, Peng

2014-03-01

91

Characterization of preformed plasmas with an interferometer for ultra-short high-intensity laser-plasma interactions  

NASA Astrophysics Data System (ADS)

The evolution of an Al preformed plasma produced by a prepulse was observed before and after the arrival of the main pulse by an interferometer using a femtosecond probe pulse. A central density depression due to the ponderomotive force of the main laser pulse in the preformed plasma with a 100 ?m scale length was clearly visible after the main pulse irradiation at an intensity of 5×1016 W/cm2. The temporal profiles of the prepulse, characterized by a cross-correlation in conjunction with a precise density profile measurement by an interferometer, contribute to the better understanding of femtosecond laser-matter interactions.

Sagisaka, A.; Daido, H.; Ogura, K.; Orimo, S.; Hayashi, Y.; Nishiuchi, M.; Mori, M.; Matsukado, K.; Fukumi, A.; Li, Z.; Nakamura, S.; Takagaki, K.; Hazama, H.; Suzuki, M.; Utsumi, T.; Bulanov, S. V.; Esirkepov, T.

92

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

SciTech Connect

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.

Shu, D.

1985-02-01

93

Ground-based laser interferometers for GW detection: status and prospects for operations  

NASA Astrophysics Data System (ADS)

We are living in an exciting time for the maturing field of gravitational-wave (GW) physics. A world-wide network of advanced multi-kilometer long laser interferometers for GW detection is currently under construction in the United States, Europe, and Japan. Compared to the initial detectors which were in operation until 2011, the advanced detectors will be about 10 times more sensitive, resulting in a 1000-fold increase in observable volume. In only a couple years' time, we expect to make not only the first direct detection of GWs, but to start an era in which signals are routinely observed. We present a general overview of the advanced detectors and the status of their construction and commissioning.

Dooley, Katherine

94

Preliminary Optimal Orbit Design for the Laser Interferometer Space Antenna (LISA)  

NASA Technical Reports Server (NTRS)

In this paper we present a preliminary optimal orbit analysis for the Laser Interferometer Space Antenna (LISA). LISA is a NASA/ESA mission to study gravitational waves and test predictions of general relativity. The nominal formation consists of three spacecraft in heliocentric orbits at 1 AU and trailing the Earth by twenty degrees. This configuration was chosen as a trade off to reduce the noise sources that will affect the instrument and to reduce the fuel to achieve the final orbit. We present equations for the nominal orbit design and discuss several different measures of performance for the LISA formation. All of the measures directly relate the formation dynamics to science performance. Also, constraints on the formation dynamics due to spacecraft and instrument limitations are discussed. Using the nominal solution as an initial guess, the formation is optimized using Sequential Quadratic Programming to maximize the performance while satisfying a set of nonlinear constraints. Results are presented for each of the performance measures.

Hughes, Steven P.; Bauer, Frank H. (Technical Monitor)

2002-01-01

95

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

NASA Technical Reports Server (NTRS)

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.

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

1981-01-01

96

A stable pulsed picosecond GSGG:Nd(3+) laser with a resonator based on the Sagnac interferometer  

NASA Astrophysics Data System (ADS)

A study is made of a passively mode-locked laser based on chromium-doped gadolinium-scandium-gallium garnet operating in the ultrashort-pulse emission mode. Statistical expressions are presented which relate the width, energy, and repeatability of the generated pulses as a function of the position of a cell with a saturable absorbent (dye 3274 in ethanol) in the interferometer and its initial transmission. A new resonator scheme with asymmetric positioning of the active element with the interferometer ring is described which makes it possible to achieve stable generation at the lower transverse mode without additional spatial selection.

Prokhorenko, V. I.; Surovtsev, D. V.; Tikhonov, E. A.; Iatskiv, D. Ia.

1990-03-01

97

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

NASA Technical Reports Server (NTRS)

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.)

Monson, D. J.; Higuchi, H.

1981-01-01

98

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

DOEpatents

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).

Buchenauer, C. Jerald (Los Alamos, NM)

1984-01-01

99

Correlated quadratures of resonance fluorescence and the generalized uncertainty relation  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

100

Combination of a spectrometer-on-chip and an array of Young's interferometers for laser spectrum monitoring.  

PubMed

This Letter presents the design and experimental results for an on-chip photonic device for laser spectrum monitoring that combines a nanospectrometer and an array of Young's interferometers. The array of Young's interferometers and the spectrometer measure the width and wavelength of a spectrum in visible light, respectively. The accuracy of spectral width measurements is around 10% for FWHM higher than 2.5 pm. The spectrometer-on-chip is based on a digital planar hologram, and provides a resolution around 145 pm within the spectral range of 719-861 nm (142 nm bandwidth). The performance of the device is demonstrated for distinguishing between the single- and two-longitudinal mode operation of a fiber Bragg grating laser diode with 23 pm mode separation. PMID:25360949

Koshelev, A; Calafiore, G; Peroz, C; Dhuey, S; Cabrini, S; Sasorov, P; Goltsov, A; Yankov, V

2014-10-01

101

COMPONENTS OF LASER SYSTEMS AND STABILITY PROBLEMS: Integrated optical analogs of classical interferometers  

NASA Astrophysics Data System (ADS)

An analysis is made of the modulation and filtering properties of planar analogs of multistage Mach-Zehnder and Fabry-Perot interferometers. It is shown that the best parameters are exhibited by a modulator or a filter in the form of a series of planar Mach-Zehner interferometers with a nonlinear dependence of the phase of the control signal on the stage number. A planar Fabry-Perot interferometer is characterized by the smallest capacitance of the control plates.

Malyutin, A. A.

1988-08-01

102

Laser interferometer skin-friction measurements of crossing-shock-wave/turbulent-boundary-layer interactions  

NASA Astrophysics Data System (ADS)

Wall shear stress measurements beneath crossing-shock-wave/turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 deg at Mach 3 and 15 deg at Mach 3.85. The measurements were made using a laser interferometer skin-friction meter, a device that determines the wall 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 center line. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k-epsilon model, are compared with the experimental results for the Mach 3.85, 15-deg interaction case. Although the k-epsilon 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.

Garrison, T. J.; Settles, G. S.; Narayanswami, N.; Knight, D. D.

1994-06-01

103

The Performance Of Arm Locking In The Laser Interferometer Space Antenna  

NASA Astrophysics Data System (ADS)

For the laser interferometer space antenna (LISA) to reach its design sensitivity, the coupling of the free running laser frequency noise to the signal readout must be reduced by more than 14 orders of magnitude. The current LISA baseline design has three stages of frequency noise reduction: pre-stabilization to an optical cavity; stabilization to the LISA arms (arm locking); and cancellation in post processing by time delay interferometry (TDI). One challenging aspect of arm locking is maintaining control system stability in the presence of the 33 second light travel time of a LISA arm round trip. We provide results from a detailed study of arm locking implementation on LISA that includes: *Orbital effects (changing arm lengths and Doppler shifts) *A comparison of control system architectures (how to best combine the phase measurements) *A study of the significant noise sources, ultra-stable oscillator (clock) noise, spacecraft motion, and shot noise. We arrive at a detailed design of the control system and provide a high fidelity analysis of the expected performance. We explain the dependence of the arm locking sensor phase delay on the open loop gain of the control system. Exploiting this effect yields 10 times more noise suppression in the LISA science band (100uHz - 1Hz). We also propose a modification to the dual arm locking sensor to minimize low-frequency noise coupling. We find that the performance of arm locking is sufficient for the LISA sensitivity to be realized with arm locking and TDI only, without any form of pre-stabilization.

McKenzie, Kirk; Spero, R. E.; Shaddock, D. A.

2010-01-01

104

Temporally flat top pulse generation from gain switched semiconductor lasers based on a polarization interferometer with variable transfer function  

NASA Astrophysics Data System (ADS)

We propose the use of a polarization based interferometer with variable transfer function for the generation of temporally flat top pulses from gain switched single mode semiconductor lasers. The main advantage of the presented technique is its flexibility in terms of input pulse characteristics, as pulse duration, spectral bandwidth and operating wavelength. Theoretical predictions and experimental demonstrations are presented and the proposed technique is applied to two different semiconductor laser sources emitting in the 1550 nm region. Flat top pulses are successfully obtained with input seed pulses with duration ranging from 40 ps to 100 ps.

Consoli, Antonio; Esquivias, Ignacio

2014-10-01

105

Microkelvin thermal control system for the laser interferometer space antenna mission and beyond  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) mission aims to detect directly gravitational waves from massive black holes and galactic binaries. Through detecting gravitational waves, we can study blackholes and the origin of the universe, which is inaccessible from the electromagnetic wave spectrum. It will open a new window to the universe. LISA is essentially a Michelson interferometer placed in space with a third spacecraft added. Gravitational waves are time-varying strain in space-time, which is detectable as a fractional change in a proper distance. LISA will monitor fractional changes in the interferometer arms of a nominally 5 million km. The fractional change in the arm length can be as small as 1 x 10-21 m/(m · Hz ) even for powerful sources. LISA makes use of the gravitational reference sensors (GRS) for drag-free control and will achieve the required sensitivity through management of specific acceleration noise. The total acceleration disturbance to each proof mass, which floats at the center of each GRS, is required to be below 3 x 10-15 m/(s2 · Hz ). Thermal variations due to, for example, solar irradiation, or temperature gradients across the proof mass housing, are expected to be significant disturbance source to the LISA sensitivity requirements. Even a small temperature gradient can produce distortions in the housing structure, which results in a mass attraction force. In this thesis, I focus on developing a thermal control system that aims to achieve the temperature stability of 10 muK / Hz over 0.1 mHz to 1 Hz. We have chosen glass-bead thermistors as the temperature sensor for feedback temperature control of the GRS. First, we created a temperature sensor design program in MATLAB that provides an optimal values of resistances in the thermistor bridge circuit for the given application. The spectral stability of the sensor achieves as low as 20 muK/ Hz at 1 mHz with a DC excitation source. The LISA thermal requirement is met by employing AC excitation and phase sensitive demodulation. Second, a passive thermal isolation system with a specially designed multilayer thermal chamber has been developed. For ground testing, the thermal specification can be met fairly readily with a massive amount of thermal mass. However, for spacecraft the thermal mass is limited, which calls for active compensation particularly in the low frequency range. In order for our test facility to simulate in-flight conditions and to compensate for solar radiation and other thermal disturbance sources we have designed it be analogous to the spacecraft structure. The temperature requirement is met to a frequency as low as 10 mHz through passive thermal isolation. Finally, to overcome the limited bandwidth of passive designs to reduce the temperature variations below 10 mHz, a model predictive control (MPC) algorithm is developed for active disturbance temperature cancellation. The system attenuates low frequency variations as low as 2 mK/ Hz at 0.1 mHz.

Higuchi, Sei

2009-10-01

106

Quadrature, Interpolation and Observability  

NASA Technical Reports Server (NTRS)

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.

Hodges, Lucille McDaniel

1997-01-01

107

Atom Interferometers  

E-print Network

Interference with atomic and molecular matter waves is a rich branch of atomic physics and quantum optics. It started with atom diffraction from crystal surfaces and the separated oscillatory fields technique used in atomic clocks. Atom interferometry is now reaching maturity as a powerful art with many applications in modern science. In this review we first describe the basic tools for coherent atom optics including diffraction by nanostructures and laser light, three-grating interferometers, and double wells on AtomChips. Then we review scientific advances in a broad range of fields that have resulted from the application of atom interferometers. These are grouped in three categories: (1) fundamental quantum science, (2) precision metrology and (3) atomic and molecular physics. Although some experiments with Bose Einstein condensates are included, the focus of the review is on linear matter wave optics, i.e. phenomena where each single atom interferes with itself.

Alexander D. Cronin; Joerg Schmiedmayer; David E. Pritchard

2007-12-21

108

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

PubMed

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 × 10(17) 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. PMID:24089824

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

109

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

110

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

PubMed

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

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

2013-02-11

111

Carrier-envelope phase locking of multi-pulse lasers with an intra-cavity Mach-Zehnder interferometer.  

PubMed

We propose the use of an intra-cavity Mach Zehnder interferometer (MZI), for increasing the repetition rate at which carrier-envelope phase-locked pulses are generated in passively mode-locked fiber lasers. The attractive feature of the proposed scheme is that light escaping through the open output ports of the MZI can be used as a monitor signal feeding a servo loop that allows multiple pulses to co-exist in the cavity, while rigidly controlling their separation. The proposed scheme enables in principle a significant increase in the pulse-rate with no deterioration in the properties of the generated pulses. PMID:22109199

Shtaif, Mark; Menyuk, Curtis R; Dennis, Michael L; Gross, Michael C

2011-11-01

112

A double-interferometer laser system for cold 87Rb atom gyroscopes based on stimulated Raman transitions  

E-print Network

We proposed and implemented a double-interferometer laser system to manipulate cold 87Rb atoms to interfere. A frequency-modulated continuous-wave technique was applied to determine and compensate the optical path difference between the two Raman beams. With a coherent self-heterodyne method, the beat signal's FWHM linewidth was measured and the obtained linewidth of ~1Hz mainly limited by the resolution bandwidth of the spectrum analyzer indicates a good coherence degree of the two Raman beams, paving the way to realize a highly sensitive atom gyroscope.

Song, Ningfang; Li, Wei; Li, Yang; Liu, Jixun; Xu, Xiaobin; Pan, Xiong

2014-01-01

113

Multi-chord fiber-coupled interferometer with a long coherence length laser for the Plasma Liner Experiment  

E-print Network

This paper describes a 561 nm laser heterodyne interferometer that provides time-resolved measurements of line-integrated plasma electron density within the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the Plasma Liner Experiment (PLX), which aims to produce $\\mu$s-, cm-, and Mbar-scale plasmas through the merging of thirty plasma jets in a spherically convergent geometry. A long coherence length, 320 mW laser allows for a strong, sub-fringe phase-shift signal without the need for closely-matched probe and reference path lengths. Thus only one reference path is required for all eight probe paths, and an individual probe chord can be altered without altering the reference or other probe path lengths. Fiber-optic decoupling of the probe chord optics on the vacuum chamber from the rest of the system allows the probe paths to be easily altered to focus on different spatial regions of the plasma. We demonstrate that sub-fringe resolution capability allows the interferometer to operate dow...

Merritt, Elizabeth C; Gilmore, Mark A; Hsu, Scott C

2011-01-01

114

Digital coherent quadrature phase-shift-keying (QPSK)  

Microsoft Academic Search

Conventional coherent detection attempts to synchronize local lasers with transmit lasers indiscriminately without considering individual noise contributors. Handling each contributor properly, we proposed a novel approach for quadrature-phase-shift-keying to enable realization of coherent communication without need of synchronization

U. Koc; A. Leven; Y. ChenandN; N. Kaneda

2006-01-01

115

Digital quadrature phase detection  

DOEpatents

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.

Smith, James A. (Idaho Falls, ID); Johnson, John A. (Idaho Falls, ID)

1992-01-01

116

Dual surface interferometer  

DOEpatents

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.

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

1982-01-01

117

The Palomar Testbed Interferometer  

E-print Network

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 July 1995. 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 pair-wise to provide baselines to 110 m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 um 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.

M. M. Colavita; J. K. Wallace

1998-10-17

118

The Palomar Testbed Interferometer  

E-print Network

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 July 1995. 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 pair-wise to provide baselines to 110~m. The interferometer actively tracks the white-light fringe using an array detector at 2.2 um 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.

Colavita, M M

1999-01-01

119

2-?m switchable dual-wavelength fiber laser with cascaded filter structure based on dual-channel Mach-Zehnder interferometer and spatial mode beating effect  

NASA Astrophysics Data System (ADS)

We demonstrated a 2-?m switchable dual-wavelength fiber laser with cascaded filter structure based on dual-channel Mach-Zehnder interferometer and spatial mode beating effect. Few-mode fiber-embedded Sagnac ring configuration and a Mach-Zehnder interferometer are cascaded to form a multiwavelength filter for our previous 2-?m fiber laser. By adopting suitable fiber length and adjusting the polarization controller, we obtained a 2-?m dual-wavelength fiber laser with switchable wavelength interval. Experimental results revealed that the proposed laser shows higher quality and better stability compared with our previous work and it has potential applications in the fields of atmospheric propagation and microwave photonics.

Wang, Shun; Lu, Ping; Zhao, Shui; Liu, Deming; Yang, Wei; Zhang, Jiangshan

2014-06-01

120

Femtosecond laser fabrication of directional couplers and Mach-Zehnder interferometers  

E-print Network

The use of femtosecond lasers for photonic device fabrication in glass has become an active area of research in recent years. Since the first demonstration of laser modification of refractive index in glass, a variety of ...

Gu, Yu, S.M. Massachusetts Institute of Technology

2007-01-01

121

Fiber Fabry-Perot interferometer (FFPI) sensor using vertical cavity surface emitting laser (VCSEL)  

E-print Network

This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Modulation of the drive current causes thermal tuning of the laser light frequency...

Lee, Kyung-Woo

2006-10-30

122

Optimized quadrature surface coil designs  

PubMed Central

Background Quadrature surface MRI/MRS detectors comprised of circular loop and figure-8 or butterfly-shaped coils offer improved signal-to-noise-ratios (SNR) compared to single surface coils, and reduced power and specific absorption rates (SAR) when used for MRI excitation. While the radius of the optimum loop coil for performing MRI at depth d in a sample is known, the optimum geometry for figure-8 and butterfly coils is not. Materials and methods The geometries of figure-8 and square butterfly detector coils that deliver the optimum SNR are determined numerically by the electromagnetic method of moments. Figure-8 and loop detectors are then combined to create SNR-optimized quadrature detectors whose theoretical and experimental SNR performance are compared with a novel quadrature detector comprised of a strip and a loop, and with two overlapped loops optimized for the same depth at 3 T. The quadrature detection efficiency and local SAR during transmission for the three quadrature configurations are analyzed and compared. Results The SNR-optimized figure-8 detector has loop radius r8 ? 0.6d, so r8/r0 ? 1.3 in an optimized quadrature detector at 3 T. The optimized butterfly coil has side length ? d and crossover angle of ? 150° at the center. Conclusions These new design rules for figure-8 and butterfly coils optimize their performance as linear and quadrature detectors. PMID:18057975

Kumar, Ananda; Bottomley, Paul A.

2008-01-01

123

A high-quality Mach-Zehnder interferometer fiber sensor by femtosecond laser one-step processing.  

PubMed

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 10(4) nm/RIU, and the temperature sensitivity is 51.5 pm/°C at 200 ? 875 °C with a step of 25 °C. PMID:22346567

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

2011-01-01

124

Fiber Fizeau interferometer for remote passive sensing  

NASA Astrophysics Data System (ADS)

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.

Bush, Jeff; Suh, Kwang

2012-06-01

125

Electronic frequency modulation for the increase of maximum measurable velocity in a heterodyne laser interferometer  

SciTech Connect

A Zeeman-type He-Ne laser is frequently used as a heterodyne laser due to the simple construction and the small loss of a light. However, the low beat frequency of the Zeeman-type laser limits the maximum measurable velocity. In this article, an electronic frequency modulation algorithm is proposed to overcome the drawback of the low velocity measurement capability by increasing the beat frequency electronically. The brief analysis, the measurement scheme of the proposed algorithm, and the experimental results are presented. It is demonstrated that the proposed algorithm is proven to enhance the maximum measurable velocity.

Choi, Hyunseung; La, Jongpil; Park, Kyihwan [Intelligent Manufacturing Group, LG Production Engineering Research Institute, 19-1 Cheongho-Ri, Jinwuy-myun, Pyungtaik, Kyunggi-Do 451-713 (Korea, Republic of); Compressor Development Group, Samsung Gwangju Electronic Company, 1119 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Department of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of)

2006-10-15

126

Fiber optic interferometer with tuning diode laser for gravity field measuring  

Microsoft Academic Search

This paper discusses the remote sensing based on a GaAs diode laser with an external dispersive cavity (DL EDC). The scheme provides continuous generation on a single longitudinal mode of external cavity and the generation line-width less than 1 kHz or generation on a broad mode of internal laser cavity. This source of coherent radiation provided the work of fiber-optic

Igor G. Goncharov; Alexander P. Grachev; Constantin A. Scvorchevsky; Andrey Y. Beskurnikov

1996-01-01

127

Fiber ring interferometer  

Microsoft Academic Search

A ring interferometer rotation detector (gyroscope) using optical fiber waveguide is designed. The sensitivity of the device is enhanced via multiple traverses of counterrotating beams around an area, but restrictions on the optimum fiber length are imposed by the photon noise limit. A well-defined wavefront and efficient coupling of light into the fiber are required. Laser light divided by a

V. Vali; R. W. Shorthill

1976-01-01

128

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

129

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

NASA Astrophysics Data System (ADS)

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.

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

1993-07-01

130

Fiber laser strain sensor based in the measurement of a Sagnac interferometer optical power spectrum  

NASA Astrophysics Data System (ADS)

In this paper a linear cavity Erbium doped fiber (EDF) laser based in a fiber Bragg grating (FBG) and a fiber optical loop mirror with a high birefringence fiber in the loop (Hi-Bi FOLM) is used as a strain sensor. The Fabry-Perot cavity is formed by the FBG and the Hi-Bi FOLM, used as a measurement system of strain variations produced on the FBG, used as a strain sensor device. Usually, fiber laser sensor experimental setups determine the measured variable magnitude by using of an optical spectrum analyzer (OSA). Hi-Bi FOLM transmission spectrum wavelength displacement by fiber loop temperature variations measurement can be an attractive application exploiting the characteristics of FOLM transmission spectrum behavior due to Hi-Bi fiber loop temperature variations to determine the FBG strain applied through the maximal optical power monitoring by simple use of a photodetector and a temperature meter.

Durán Sánchez, M.; Álvarez Tamayo, R. I.; Pottiez, O.; Kuzin, E. A.; Ibarra-Escamilla, B.; Barcelata Pinzón, A.

2014-06-01

131

Phase modulated self-mixing interferometer of a fiber laser system  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

132

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

SciTech Connect

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{sup ?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.

Zheng, Mei C., E-mail: meizheng@princeton.edu; Gmachl, Claire F. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States)] [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Liu, Peter Q. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States) [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Institute of Quantum Electronics, ETH Zürich, 8093 Zürich (Switzerland); Wang, Xiaojun; Fan, Jen-Yu; Troccoli, Mariano [AdTech Optics, Inc., City of Industry, California 91748 (United States)] [AdTech Optics, Inc., City of Industry, California 91748 (United States)

2013-11-18

133

Basic Tools: Integration by Gaussian Quadrature.  

ERIC Educational Resources Information Center

Provides examples of nested subroutines, focusing on the Gaussian quadrature function and test program (program listings included). Nested subroutines, features of the Gaussian quadrature, and when not to use it are considered. (JN)

Thompson, H. Bradford; Tuttle, Caroline

1984-01-01

134

Fiber Sagnac interferometers with ultralong and random distributed feedback Raman laser amplification  

NASA Astrophysics Data System (ADS)

We numerically study and compare the performance limitations imposed by accumulated noise and nonlinear phase difference in various configurations of amplified fiber optic gyroscopes in which amplification is provided by stimulated Raman scattering, with a focus on ultralong and random distributed feedback Raman fiber lasers. We show that, even in the presence of pump power and signal instabilities, some of the proposed configurations have the potential to allow the use of up to 5 times longer spool lengths, with a corresponding 5-fold increase in sensitivity. The results could have direct application to the improvement of the detection of seismic rotational events.

Nuño, J.; Ania-Castañón, J. D.

2014-03-01

135

Keck Interferometer  

NASA Technical Reports Server (NTRS)

At the summit of Mauna Kea, Hawaii, NASA astronomers have linked the two 10-meter (33-foot) telescopes at the W. M. Keck Observatory. The linked telescopes, which together are called the Keck Interferometer, make up the world's most powerful optical telescope system. The Keck Interferometer will search for planets around nearby stars and study dust clouds around those stars that may hamper future space-based searches for habitable, Earthlike planets. The Keck Interferometer is part of NASA's Origins program, which seeks to answer two fundamental questions: How did we get here? Are we alone?

2003-01-01

136

Heterodyne Interferometer Angle Metrology  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

137

Least-Squares Estimation and Group Delay in Astrometric Interferometers  

E-print Network

-mail: lawson@huey.jpl.nasa.gov #12; As implemented at PTI, changes in c(t) are monitored with metrology Interferometer and other interferometers within NASA's Origins program. Astrometric interferometers estimate of imperfect mirror mounts and thermal drifts within the interferometer. PTI uses separate laser metrology

138

Quasimonochromatic white light fringe interferometer.  

PubMed

Quasimonochromatic light sources, such as laser diodes and high power LEDs, are investigated to determine their suitability for zero path difference determination using white light fringes in a Michelson interferometer. Fringe visibility curves are theoretically determined for various combinations of light sources and compared with experimental results when used in a Michelson interferometer with a 25-m path length. A resolution of 2-3 microm was obtained for a pair of multimode laser diodes and also for a single multimode laser diode operated as an LED. This is more than adequate for the calibration of survey baselines. PMID:20581948

Ward, B K; Seta, K

1991-01-01

139

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)

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.

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

1982-01-01

140

Relating gravitational wave constraints from primordial nucleosynthesis, pulsar timing, laser interferometers, and the CMB: Implications for the early universe  

SciTech Connect

We derive a general equation relating the gravitational-wave observables r and {omega}{sub 0}{sup gw}(f); or the observables {omega}{sub 0}{sup gw}(f{sub 1}) and {omega}{sub 0}{sup gw}(f{sub 2}). Here, r is the so-called 'tensor-to-scalar ratio', which is constrained by cosmic-microwave-background experiments; and {omega}{sub 0}{sup gw}(f) is the energy spectrum of primordial gravitational waves, which is constrained, e.g., by pulsar-timing measurements, laser-interferometer experiments, and the standard big bang nucleosynthesis bound. Differentiating this equation yields a new expression for the tilt dln{omega}{sub 0}{sup gw}(f)/dlnf of the present-day gravitational-wave spectrum. The relationship between r and {omega}{sub 0}{sup gw}(f) depends sensitively on the uncertain physics of the early universe, and we show that this uncertainty may be encapsulated (in a model-independent way) by two quantities: w-circumflex(f) and n-circumflex{sub t}(f), where n-circumflex{sub t}(f) is a certain logarithmic average over n{sub t}(k) (the primordial tensor spectral index); and w-circumflex(f) is a certain logarithmic average over w-tilde(a) (the effective equation-of-state parameter in the early universe, after horizon re-entry). Here, the effective equation-of-state parameter w-tilde(a) is a combination of the ordinary equation-of-state parameter w(a) and the bulk viscosity {zeta}(a). Thus, by comparing observational constraints on r and {omega}{sub 0}{sup gw}(f), one obtains (remarkably tight) constraints in the {l_brace}w-circumflex(f),n-circumflex{sub t}(f){r_brace} plane. In particular, this is the best way to constrain (or detect) the presence of a stiff energy component (with w>1/3) in the early universe, prior to big bang nucleosynthesis. (The discovery of such a component would be no more surprising than the discovery of a tiny cosmological constant at late times{exclamation_point}) Finally, although most of our analysis does not assume inflation, we point out that if cosmic-microwave-background experiments detect a nonzero value for r, then we will immediately obtain (as a free by-product) a new upper bound w-circumflex < or approx. 0.55 on the logarithmically averaged effective equation-of-state parameter during the 'primordial dark age' between the end of inflation and the start of big bang nucleosynthesis.

Boyle, Latham A. [Canadian Institute for Theoretical Astrophysics (CITA), University of Toronto, 60 St. George Street, Toronto, Ontario, M5S 3H8 (Canada); Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States); Buonanno, Alessandra [Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2008-08-15

141

In-fiber Bragg grating sensors using interferometric interrogations for passive quadrature signal processing  

Microsoft Academic Search

This letter describes a simple optically passive detection scheme for Bragg grating sensors. This detection scheme is based on two cavity lengths in Fabry-Perot read-out interferometers to produce two quadrature phase shifted signals from the Bragg grating sensor. Using the amplified spontaneous emission from an erbium-doped fiber amplifier as a low-coherence and high-power broad-band source, the passive detection technique is

Yu-Lung Lo

1998-01-01

142

Quadrature Component Analysis for interferometry  

NASA Astrophysics Data System (ADS)

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].

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

2013-05-01

143

Development of a Nomarski-type multi-frame interferometer as a time and space resolving diagnostics for the free electron density of laser-generated plasma  

SciTech Connect

This article reports on the development and set-up of a Nomarski-type multi-frame interferometer as a time and space resolving diagnostics of the free electron density in laser-generated plasma. The interferometer allows the recording of a series of 4 images within 6 ns of a single laser-plasma interaction. For the setup presented here, the minimal accessible free electron density is 5 x 10{sup 18} cm{sup -3}, the maximal one is 2 x 10{sup 20} cm{sup -3}. Furthermore, it provides a resolution of the electron density in space of 50 {mu}m and in time of 0.5 ns for one image with a customizable magnification in space for each of the 4 images. The electron density was evaluated from the interferograms using an Abel inversion algorithm. The functionality of the system was proven during first experiments and the experimental results are presented and discussed. A ray tracing procedure was realized to verify the interferometry pictures taken. In particular, the experimental results are compared to simulations and show excellent agreement, providing a conclusive picture of the evolution of the electron density distribution.

Boerner, M.; Frank, A.; Pelka, A.; Schaumann, G.; Schoekel, A.; Schumacher, D.; Roth, M. [Institut fuer Kernphysik, Technische Universitaet Darmstadt, Schlossgartenstrasse 9, 64289 Darmstadt (Germany); Fils, J.; Blazevic, A.; Hessling, T. [Helmholtzzentrum fuer Schwerionenforschung GSI, Planckstr. 1, 64291 Darmstadt (Germany); Basko, M. M. [ITEP, Moscow (Russian Federation); Maruhn, J.; Tauschwitz, An. [ITP, University of Frankfurt am Main (Germany)

2012-04-15

144

Fourier Transform Fringe-Pattern Analysis of an Absolute Distance Michelson Interferometer for Space-Based Laser Metrology  

Microsoft Academic Search

Future NASA proposals include the placement of optical interferometer systems in space for a wide variety of astrophysical studies including a vastly improved deflection test of general relativity, a precise and direct calibration of the Cepheid distance scale, and the determination of stellar masses (Reasenberg et al., 1988). There are also plans for placing large array telescopes on the moon

James Joseph Talamonti

1995-01-01

145

Synthetic quadrature phase detector/demodulator for Fourier transform spectrometers.  

PubMed

A method is developed to demodulate (velocity correct) Fourier transform spectrometer data that are 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 simple implementation make it an attractive alternative in space-based applications when compared to previous methods such as the Brault algorithm. PMID:19104542

Campbell, Joel

2008-12-20

146

Reducing ranking effects in parallel adaptive quadrature  

SciTech Connect

We develop parallel one-dimensional globally adaptive quadrature algorithms, building on NAG code D01AKF. Our most effective strategy replaces D01AKF`s error estimate ranking strategy by a tabulation approach. D01AKF uses 61-point Gauss-Kronrod (GK) quadrature. We also use the 21-point GK rule. A fuller discussion, with expanded results, is given in.

Napierala, M.A.; Gladwell, I. [Southern Methodist Univ., Dallas, TX (United States)

1995-12-01

147

Error Analysis of Quadrature Rules. Classroom Notes  

ERIC Educational Resources Information Center

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…

Glaister, P.

2004-01-01

148

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)

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.

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

2012-10-01

149

Measurement and control of the movable coil position of a joule balance with a system based on a laser heterodyne interferometer  

NASA Astrophysics Data System (ADS)

A system based on laser heterodyne interferometer is proposed in this paper to measure and control the movable coil position of a joule balance. A damping system is used to suppress the movement of the movable coil in the horizontal direction while a piezoelectric ceramic control unit with PID controller is used to inhibit the vibration and long term drift of the movable coil in the vertical direction. The effectiveness of the proposed method in measuring and controlling the movable coil position of a joule balance is proved through experiments. Experimental results indicate that the displacement of the movable coil in the vertical direction can be reduced from 400 to 50 nm while its drift is successfully inhibited.

Yang, Hongxing; Lu, Yunfeng; Hu, Pengcheng; Li, Zhengkun; Zeng, Tao; He, Qing; Zhang, Zhonghua; Tan, Jiubin

2014-06-01

150

Performance characteristics of the robust laser interferometer (RLI) with respect to health monitoring needs for civil, mechanical, and aerospace infrastructure elements  

NASA Astrophysics Data System (ADS)

Correct sensing provides the availability of information for health monitoring interests, including those associated with unit health, stress, diagnostics and prognostics. Data is presented from measurement projects employing a 'highly linear,' wideband (0 to hundreds of kilohertz), large dynamic range (over 180 dB demonstrated in both displacement and acceleration), non-contact, vibration and Acoustic Emissions (AE) measurement capability. The measurement capability is currently embodied in an Epoch Engineering, Inc. Research and Development (R&D) Robust Laser Interferometer (RLI). Existing data from previous measurement projects is assessed in terms of its potential to provide meaningful information for health monitoring needs in situations involving civil, mechanical and aerospace infrastructure elements. In addition to performance considerations, implementation alternatives, integration benefits, cost considerations and remaining work that would need to be accomplished for commercializing the RLI capability is presented.

Zarroli, John M.; Karchnak, Martin; Goodenow, Theodore C.

2004-07-01

151

Wavelength independent interferometer  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

152

Temperature compensated two-mode fiber interferometer  

E-print Network

In this thesis we propose an innovative approach of designing and implementing a temperature compensated two-mode optical fiber interferometer in a control system of stabilizing the wavelength of a laser. We give the procedure for designing...

Doma, Jagdish Ramchandra

2012-06-07

153

Michelson Interferometer  

NASA Technical Reports Server (NTRS)

The Michelson Interferometer is a device used in many applications, but here it was used to measure small differences in distance, in the milli-inch range, specifically for defects in the Orbiter windows. In this paper, the method of using the Michelson Interferometer for measuring small distances is explained as well as the mathematics of the system. The coherence length of several light sources was calculated in order to see just how small a defect could be measured. Since white light is a very broadband source, its coherence length is very short and thus can be used to measure small defects in glass. After finding the front and back reflections from a very thin glass slide with ease and calculating the thickness of it very accurately, it was concluded that this system could find and measure small defects on the Orbiter windows. This report also discusses a failed attempt for another use of this technology as well as describes an area of promise for further analysis. The latter of these areas has applications for finding possible defects in Orbiter windows without moving parts.

Rogers, Ryan

2007-01-01

154

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

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.

Goodenow, T.C.; Shipman, R.L.; Holland, H.M. [Epoch Engineering, Inc., Gaithersburg, MD (United States)

1995-06-01

155

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

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.

Goodenow, T.C.; Shipman, R.L.; Holland, H.M. [Epoch Engineering, Inc., Gaithersburg, MD (United States)

1995-06-01

156

Demodulators for optical fiber interferometers with (3 x 3) outputs  

Microsoft Academic Search

A highly sensitive optical fiber interferometer sensor comprising a laser light source, a (2 x 2) optical fiber coupler to split the beam in two, a differential transducer which converts a signal of interest into optical phase shift in the laser light transmitted through the two optical fibers in the interferometer and a (3 x 3) optical fiber complex which

Robert M. Keolian; Steven L. Garrett; Charles B. Cameron

1994-01-01

157

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

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

158

Dual-beam skin friction interferometer  

NASA Technical Reports Server (NTRS)

A portable dual-laser beam interferometer is described that nonintrusively measures skin friction by monitoring the thickness change of an oil film at two locations while said oil film is subjected to shear stress. An interferometer flat is utilized to develop the two beams. Light detectors sense the beam reflections from the oil film and the surface thereunder. The signals from the detectors are recorded so that the number of interference fringes produced over a given time span may be counted.

Monson, D. J. (inventor)

1981-01-01

159

Single and double superimposing interferometer systems  

DOEpatents

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.

Erskine, David J. (Oakland, CA)

2000-01-01

160

LIGO interferometer operating at design sensitivity with application to gravitational radiometry  

E-print Network

During the last decade the three interferometers of the Laser Interferometer Gravitational Wave Observatory (LIGO) were built and commissioned. In fall 2005 design sensitivity was achieved, corresponding to a strain ...

Ballmer, Stefan W. (Stefan Werner)

2006-01-01

161

Rotative quadrature phase-shift keying  

NASA Technical Reports Server (NTRS)

A rotative quadrature phase-shift keying (RQPSK) modulation scheme is proposed. By rotating the QPSK signal constellation by pi/2, either clockwise or anticlockwise, during a symbol duration, the conventional QPSK scheme can be modified to transmit 3 bits per symbol to achieve both power and bandwidth efficiency.

Liu, J.; Kim, J.; Kwatra, S. C.; Stevens, G. H.

1992-01-01

162

Mechanical properties of sensory hair bundles are reflected in their Brownian motion measured with a laser differential interferometer.  

PubMed Central

By optically probing with a focused, low-power laser beam, we measured the spontaneous deflection fluctuations of the sensory hair bundles on frog saccular hair cells with a sensitivity of about 1 pm/square root of Hz. The preparation was illuminated by two orthogonally polarized laser beams separated by only about 0.2 microns at their foci in the structure under investigation. Slight movement of the object from one beam toward the other caused a change of the phase difference between the transmitted beams and an intensity modulation at the detector where the beams interfered. Maintenance of the health of the cells and function of the transduction mechanism were occasionally confirmed by measuring the intracellular resting potential and the sensitivity of transduction. The root-mean-square (rms) displacement of approximately 3.5 nm at a hair bundle's tip suggests a stiffness of about 350 microN/m, in agreement with measurements made with a probe attached to a bundle's tip. The spectra resemble those of overdamped harmonic oscillators with roll-off frequencies between 200 and 800 Hz. Because the roll-off frequencies depended strongly on the viscosity of the bathing medium, we conclude that hair-bundle motion is mainly damped by the surrounding fluid. PMID:2787510

Denk, W; Webb, W W; Hudspeth, A J

1989-01-01

163

Trellis Coded Modulation Schemes Using A New Expanded 16-Dimensional Constant Envelope Quadrature-Quadrature Phase Shift Keying Constellation.  

E-print Network

??In this thesis, the author presents and analyzes two 4-dimensional Constant Envelope Quadrature-Quadrature Phase Shift Keying constellations. Optimal demodulators for the two constellations are presented,… (more)

Quinteros, Milton I.

2009-01-01

164

Differential detection in quadrature-quadrature phase shift keying (Q2PSK) systems  

Microsoft Academic Search

A generalized quadrature-quadrature phase shift keying (Q2 PSK) signaling format is considered for differential encoding and differential detection. Performance in the presence of additive white Gaussian noise (AWGN) is analyzed. Symbol error rate is found to be approximately twice the symbol error rate in a quaternary DPSK system operating at the same Eb\\/N0. However, the bandwidth efficiency of differential Q2PSK

Osama M. El-Ghandour; Debabrata Saha

1991-01-01

165

Geophysical fiber interferometer gyroscope  

Microsoft Academic Search

This report describes a development effort of the University of Utah Research Institute aimed at perfecting a North-seeking device based on the passive interferometer gyroscope concept. The rotation sensing mechanism of the interferometer is based on the Sagnac effect. The form of the interferometer is a fiber ring. The performance requirements of the device are developed in terms of desired

L. D. Weaver

1979-01-01

166

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

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.

Letunov, A. A.; Logvinenko, V. P. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Zav'yalov, V. V. [Russian Academy of Sciences, P.L. Kapitza Institute for Physical Problems (Russian Federation)

2008-03-15

167

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

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.

Letunov, A. A.; Logvinenko, V. P. [Russian Academy of Sciences, Prokhorov Institute of General Physics (Russian Federation); Zav'yalov, V. V. [Russian Academy of Sciences, P.L. Kapitza Institute for Physical Problems (Russian Federation)

2008-03-15

168

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

E-print Network

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.

John G. Baker; James Ira Thorpe

2012-01-26

169

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

NASA Technical Reports Server (NTRS)

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.

Baker, John G.

2012-01-01

170

Dispersion cancellation in a triple Laue interferometer  

NASA Astrophysics Data System (ADS)

The concept of dispersion cancellation has been established in light optics to improve the resolution of interferometric measurements on dispersive media. Odd order dispersion cancellation allows to measure phase shifts without defocusing the interferometer due to wave packet displacements, while even order dispersion cancellation allows to measure time lags without losing resolution due to wave packet spreading. We report that either type of dispersion cancellation can be realized very easily in a triple Laue interferometer. Such interferometers are Mach-Zehnder interferometers based on Bragg diffraction, and are commonly used for neutrons and x-rays. Although the first x-ray interferometer was built nearly five decades ago, the feature of dispersion cancellation hasn't been recognized so far because the concept was hardly known in the neutron and x-ray community. However, it explains right away the surprising decoupling of phase shift and spatial displacement that we have discovered recently in neutron interferometry (Lemmel and Wagh 2010 Phys. Rev. A 82 033626). Furthermore, this article might inspire the light optics community to consider whether a triple Laue interferometer for laser light would be useful and feasible. We explain how dispersion cancellation works in neutron interferometry, and we describe the setup rigorously by solving the Schrödinger equation and by calculating the path integral. We point out, that the latter has to be evaluated with special care since in our setup the beam trajectory moves with respect to the crystal lattice of the interferometer.

Lemmel, Hartmut

2014-10-01

171

Optomechanical design of the Micro-Arcsecond Metrology testbed interferometer  

Microsoft Academic Search

The Micro Arcsecond Metrology Testbed (MAM) is a laboratory- based, long baseline, white-light interferometer inside a vibration-isolated vacuum tank. The single baseline, high precision interferometer will be able to observe a translating, artificial star at a distance of 10.74 meters with 5 (mu) as accuracy. The MAM testbed consists of an artificial star, laser metrology and a high precision interferometer.

Andrew E. Carlson; Stuart B. Shaklan; Randall D. Bartos; Steve Azevedo

1998-01-01

172

Nulling at the Keck Interferometer  

NASA Technical Reports Server (NTRS)

The nulling mode of the Keck Interferometer is being commissioned at the Mauna Kea summit. The nuller combines the two Keck telescope apertures in a split-pupil mode to both cancel the on-axis starlight and to coherently detect the residual signal. The nuller, working at 10 um, is tightly integrated with the other interferometer subsystems including the fringe and angle trackers, the delay lines and laser metrology, and the real-time control system. Since first 10 um light in August 2004, the system integration is proceeding with increasing functionality and performance, leading to demonstration of a 100:1 on-sky null in 2005. That level of performance has now been extended to observations with longer coherent integration times. An overview of the overall system is presented, with emphasis on the observing sequence, phasing system, and differences with respect to the V2 system, along with a presentation of some recent engineering data.

Colavita, M. Mark; Serabyn, Gene; Wizinowich, Peter L.; Akeson, Rachel L.

2006-01-01

173

Phase shifting interferometer  

DOEpatents

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.

Sommargren, Gary E. (Santa Cruz, CA)

1999-01-01

174

A Novel Cavity-Based Atom Interferometer  

NASA Astrophysics Data System (ADS)

The world's leading atom interferometers are housed in bulky atomic fountains. They employ a variety of techniques to increase the spatial separation between atomic clouds including high order Bragg diffraction. The largest momentum transfer in a single Bragg beamsplitter has been limited to 24 k by laser power and beam quality. We present an atom interferometer in a 40 cm optical cavity to enhance the available laser power, minimize wavefront distortions, and control other systematic effects symptomatic to atomic fountains. We expect to achieve spatial separations between atomic trajectories comparable to larger scale fountains within a more compact device. We report on our progress in developing this new interferometer using cold Cs atoms and discuss its prospects for exploring large momentum transfer up to 100 k in a single Bragg diffraction process. The compact design will enable the first demonstration of the gravitostatic Aharonov-Bohm effect.

Brown, Justin; Estey, Brian; Müller, Holger

2012-06-01

175

Calibration of a high spatial resolution laser two-color heterodyne interferometer for density profile measurements in the TJ-II stellarator  

SciTech Connect

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.

Acedo, Pablo; Pedreira, P.; Criado, A. R.; Lamela, Horacio [Universidad Carlos III de Madrid, Avda. de la Universidad 30, Leganes, 28911 Madrid (Spain); Sanchez, Miguel; Sanchez, Joaquin [Laboratorio Nacional de Fusion por Confinamiento Magnetico-CIEMAT, Ciudad Universitaria s/n, 28040 Madrid (Spain)

2008-10-15

176

A polarization sensitive interferometer for Faraday rotation detection.  

E-print Network

??Time-resolved Faraday rotation (TRFR) is a pulsed laser pump/probe optical measurement used to characterize electron spin dynamics in semiconductor materials. A Mach-Zehnder type interferometer with… (more)

LaForge, Joshua Michael

2007-01-01

177

Coupled-Cavity Interferometer for the Optics Laboratory  

ERIC Educational Resources Information Center

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)

Peterson, R. W.

1975-01-01

178

Ramsey-Bordé interferometer for electrons  

NASA Astrophysics Data System (ADS)

A scheme to realize an electron interferometer using low-intensity, bichromatic laser pulses as beam splitter is proposed. The splitting process is based on a modification of the Kapitza-Dirac effect, which produces a momentum kick for electrons with a specific initial momentum. A full interferometric setup in Ramsey-Bordé configuration is theoretically analyzed.

Marzlin, Karl-Peter

2013-10-01

179

Surface profiling interferometer  

DOEpatents

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.

Takacs, Peter Z. (P.O. Box 385, Upton, NY 11973); Qian, Shi-Nan (Hefei Synchrotron Radiation Laboratory, University of Science and, Hefei, Anhui, CN)

1989-01-01

180

The AEI 10 m prototype interferometer  

NASA Astrophysics Data System (ADS)

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.

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

181

Dispersion interferometer using modulation amplitudes on LHD (invited)a)  

NASA Astrophysics Data System (ADS)

Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 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 × 1017 m-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 × 1020 m-3 can be overcome by a sufficient sampling rate of about 100 kHz.

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

2014-11-01

182

Analysis of spatial mode sensitivity of gravitational wave interferometer and targeted search for gravitational radiation from the Crab pulsar  

E-print Network

Over the last several years the Laser Interferometer Gravitational Wave Observatory (LIGO) has been making steady progress in improving the sensitivities of its three interferometers, two in Hanford, Washington, and one ...

Betzwieser, Joseph (Joseph Charles)

2008-01-01

183

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

PubMed

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

Pozar, Tomaz; Gregorcic, Peter; Mozina, Janez

2009-12-01

184

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

NASA Technical Reports Server (NTRS)

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.

Campbell, Joel

2008-01-01

185

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

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.

Turner, A. [Churchville-Chili High School, NY (United States)

1999-03-01

186

Full-field Fabry-Perot interferometer  

SciTech Connect

This paper describes the use of a Fabry-Perot interferometer for simultaneously measuring velocity at many points on the surface of a shock-loaded solid. The method is based upon work reported by S. Gidon and G. Behar in 1986, but the data analysis has been improved by the application of image-processing techniques. Light from a pulsed single-frequency laser is focused onto a moving target and the returned Doppler-shifted image passed through a Fabry-Perot interferometer. Output of the interferometer is a set of fringes that are formed for specific combinations of wavelength and light angle. These fringes are recorded on film for subsequent analysis. Fringe position determines the velocity for each point on the target that forms a fringe. A method for determining the velocity as a function of both position and time will also be discussed. 5 refs., 6 figs.

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

1991-01-01

187

A heterodyne interferometer for angle metrology.  

PubMed

We have developed a compact, high-resolution, angle measurement instrument based on a heterodyne interferometer. Common-path heterodyne interferometer metrology is used to measure displacements of a reflective target surface. In the interferometer set up, an optical mask is used to sample the laser beam reflecting back from four areas on a target surface. From the relative displacement measurements of the target surface areas, we can simultaneously determine angular rotations around two orthogonal axes in a plane perpendicular to the measurement beam propagation direction. The device is used in a testbed for a tracking telescope system where pitch and yaw angle measurements of a flat mirror are performed. Angle noise measurement of the device shows 0.1 nrad/square root of Hz at 1 Hz, at a working distance of 1 m. The operation range and nonlinearity of the device when used with a flat mirror is approximately +/-0.15 mrad, and 3 microrad rms, respectively. PMID:20441364

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

2010-04-01

188

A heterodyne interferometer for angle metrology  

SciTech Connect

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

Hahn, Inseob; Weilert, M.; Wang, X.; Goullioud, R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

2010-04-15

189

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

190

LASER RADIATION SCATTERING: Application of Young—Michelson and Brown—Twiss interferometers for determining geometric parameters of nonplanar rough objects  

NASA Astrophysics Data System (ADS)

The possibility of using Young—Michelson and Brown—Twiss interferometers for measuring the angular dimensions and parameters of the surface shape of remote passively scattering and self-luminous nonplanar rough objects by optical radiation propagating from them is substantiated. The analysis is based on the properties of approximate transverse functions of field coherence Bt and Bt' and intensity coherence Bti and Bti' formed by the time averaging of the products of fields and intensities taken at two points of a receiving aperture (the prime denotes self-luminous objects). The averaging time is set to be much longer than the coherence time of radiation propagating from an object. It is shown that for the radiation coherence length much smaller than the depth of the visible region of the object, the functions Bt and Bt' are proportional to the Fourier transform of the intensity distribution in the image of a remote object, which is the generalisation of the Van Cittert—Zernicke theorem to the case of a nonplanar object, while functions Bti and Bti' are proportional to the squares of the modulus of the Fourier transform of this distribution. It is also shown that the recording of functions Bt and Bt' with a Young—Michelson interferometer gives only the angular dimensions of the visible region of objects, whereas the recording of functions Bti and Bti' with a Brown—Twiss interferometer allows one to find these dimensions and the radius of curvature of the object surface.

Mandrosov, V. I.

2008-05-01

191

Phase shifting diffraction interferometer  

DOEpatents

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.

Sommargren, G.E.

1996-08-29

192

Phase shifting diffraction interferometer  

DOEpatents

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.

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

193

The May 1997 SOHO-Ulysses Quadrature  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

194

Furnace control apparatus using polarizing interferometer  

DOEpatents

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

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

1995-03-28

195

Heterodyne interferometer with angstrom-level periodic nonlinearity  

DOEpatents

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.

Schmitz, Tony L. (Gainesville, FL); Beckwith, John F. (Indialantic, FL)

2005-01-25

196

Path matched vibration insensitive Fizeau interferometer  

NASA Astrophysics Data System (ADS)

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. Microwave modulation of a high powered red laser diode is used to create a 15 mW laser source having a coherence length of 250 um with minimal sidelobe ringing. With a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. Additionally, stray light interference is substantially reduced due to the source's short coherence, allowing the measurement of thin transparent optics. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers. This work starts with a basic review of interferometry, phase shifting, and polarization as a lead in to a description of the theory and operation of the pixelated mask spatial carrier phase shifting technique. An analysis of the standard Fizeau Interferometer is then given. This is followed by detailed theoretical discussion of the path matched vibration insensitive (PMVI) Fizeau, which includes a theoretical model of the effects of multiple beam return from the test surface when measuring high value reflectors. The coherence properties of laser diodes are then discussed, a theoretical model for the effects of high frequency drive current is derived, and experimental results are given. Finally, the performance of the PMVI Fizeau is experimentally analyzed, potential error sources discussed, and suggestions for improvements provided.

Kimbrough, Bradley Trent

197

Hybrid photonic chip interferometer for embedded metrology  

NASA Astrophysics Data System (ADS)

Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the work piece. Providing closer integration of metrology upon the manufacturing platform can lead to the better control and increased throughput. In this work we present the development of a high precision hybrid optical chip interferometer metrology device. The complete metrology sensor system is structured into two parts; optical chip and optical probe. The hybrid optical chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. The key structure in the device is a tunable laser module based upon an external-cavity diode laser (ECDL). Within the cavity is a multi-layer thin film filter which is rotated to select the longitudinal mode at which the laser operates. An optical probe, which uses a blazed diffracting grating and collimating objective lens, focuses light of different wavelengths laterally over the measurand. Incident laser light is then tuned in wavelength time to effectively sweep an `optical stylus' over the surface. Wavelength scanning and rapid phase shifting can then retrieve the path length change and thus the surface height. We give an overview of the overall design of the final hybrid photonic chip interferometer, constituent components, device integration and packaging as well as experimental test results from the current version now under evaluation.

Kumar, P.; Martin, H.; Maxwell, G.; Jiang, X.

2014-03-01

198

A Comparison of three high-precision quadrature schemes  

SciTech Connect

The authors have implemented three numerical quadrature schemes, using the new Arbitrary Precision (ARPREC) software package, with the objective of seeking a completely ''automatic'' arbitrary precision quadrature facility, namely one that does not rely on a priori information of the function to be integrated. Such a facility is required, for example, to permit the experimental identification of definite integrals based on their numerical values. The performance and accuracy of these three quadrature schemes are compared using a suite of 15 integrals, ranging from continuous, well-behaved functions on finite intervals to functions with vertical derivatives and integrable singularities at endpoints, as well as several integrals on an infinite interval.

Bailey, David H.; Li, Xiaoye S.

2003-07-01

199

Novel double path shearing interferometer in corneal topography measurements  

NASA Astrophysics Data System (ADS)

The paper presents an approach for measurements of corneal topography by use of a patent pending double path shearing interferometer (DPSI). Laser light reflected from the surface of the cornea is divided and directed to the inputs of two interferometers. The interferometers use lateral shearing of wavefronts in two orthogonal directions. A tilt of one of the mirrors in each interferometric setup perpendicularly to the lateral shear introduces parallel carrier frequency fringes at the output of each interferometer. There is orthogonal linear polarization of the laser light used in two DPSI. Two images of fringe patters are recorded by a high resolution digital camera. The obtained fringe patterns are used for phase difference reconstruction. The phase of the wavefront was reconstructed by use of algorithms for a large grid based on discrete integration. The in vivo method can also be used for tear film stability measurement, artificial tears and contact lens tests.

Licznerski, Tomasz J.; Jaronski, Jaroslaw; Kosz, Dariusz

2005-09-01

200

Fiber in-line Michelson Interferometer for refractive index sensing  

NASA Astrophysics Data System (ADS)

A fiber in-line Michelson interferometer based on open micro-cavity is demonstrated, which is fabricated by femtosecond laser micromachining and thin film coating technique. In refractive index sensing, this interferometer operates in a reflection mode of detection, exhibits compact sensor head, good mechanical reliability, wide operation range and high sensitivity of 975nm/RIU (refractive index unit) at the refractive index value of 1.484.

Liao, C. R.; Wang, D. N.; Wang, Min; Yang, Minghong; Wang, Yiping

2013-09-01

201

Mariner 9 michelson interferometer.  

PubMed

The Michelson interferometer on Mariner 9 measures the thermal emission spectrum of Mars between 200 cm(-1) and 2000 cm(-1) (between 5 microm and 50 microm) with a spectral resolution of 2.4 cm(-1) in the apodized mode. A noise equivalent radiance of 0.5 x 10(-7) W cm(-2) sr(-1)/cm(-1) is deduced from data recorded in orbit around Mars. The Mariner interferometer deviates in design from the Nimbus 3 and 4 interferometers in several areas, notably, by a cesium iodide beam splitter and certain aspects of the digital information processing. Special attention has been given to the problem of external vibration. The instrument performance is demonstrated by calibration data and samples of Mars spectra. PMID:20119381

Hanel, R; Schlachman, B; Breihan, E; Bywaters, R; Chapman, F; Rhodes, M; Rodgers, D; Vanous, D

1972-11-01

202

PDX multichannel interferometer  

SciTech Connect

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.

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

1980-10-01

203

Wave Based Inversion and Imaging for the Optical Quadrature Microscope.  

National Technical Information Service (NTIS)

The Center for Subsurface Sensing & Imaging Systems (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, w...

S. K. Lehman

2005-01-01

204

Convergence acceleration of the Gauss-Laguerre quadrature formula  

Microsoft Academic Search

Asymptotic expansions have been obtained for the error of the Gauss-Laguerre quadrature formula for a large class of analytic integrands. Then, a theorem of convergence acceleration is given. Numerical examples are also given.

M. Kzaz

1999-01-01

205

On the Theory of Quadrature Oscillations Obtained Through Parallel VCOs  

Microsoft Academic Search

This paper presents a theory of parallel quadrature voltage-controlled oscillators, which are widely used to generate in-phase and quadrature signals in communication systems. The theory is developed without making any hypothesis on the circuit topology and allows us to thoroughly analyze the synchronized oscillations, as well as the effect of unavoidable parameter mismatches, by means of closed-form expressions for the

Antonio Buonomo; Alessandro Lo Schiavo

2010-01-01

206

Numerical Modelling of Water Hammer Using Differential Quadrature Method  

NASA Astrophysics Data System (ADS)

In this research, Incremental Differential Quadrature Method (IDQM) is applied for modelling of unsteady flow (water hammer) in pipeline systems. This is considered as the first application of differential quadrature in this area. The implementation of the IDQM to the governing equations along with some numerical studies are presented. The main attractive feature of the proposed method compared with existing numerical techniques is unconditional stability.

Hashemi, M. R.; Abedini, M. J.

2007-09-01

207

Mesoscopic Interferometers for Electron Waves  

SciTech Connect

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.

Rohrlich, D. [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)

2005-09-15

208

Dual differential interferometer  

NASA Technical Reports Server (NTRS)

A dual two-beam differential interferometer that measures both the amplitude and orientation of propagating, broadband surface acoustic waves is disclosed. Four beams are focused on a surface. The four reflected beams are separated into two pairs. The two pairs are detected to produce two signals that are used to compute amplitude and orientation.

Claus, R. O.; Turner, T. M. (inventors)

1985-01-01

209

Dual beam optical interferometer  

NASA Technical Reports Server (NTRS)

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.

Gutierrez, Roman C. (Inventor)

2003-01-01

210

Results of the calibration of interferometer transmission flats for the LIGO Pathfinder optics  

Microsoft Academic Search

To certify compliance with the exceptional surface figure requirements of the laser interferometer gravity observatory, Hughes Danbury Optical Systems developed a unique high-accuracy metrology capability consisting of a custom 12 inch phase-measuring interferometer and an absolute calibration algorithm. The interferometer was specifically designed to minimize systematic retrace, phase- modulation, and ghost reflection errors. The calibration algorithm extends existing three-flat methods

Robert P. Bourgeois; Joann Magner; H. Philip Stahl

1997-01-01

211

Interferometers and Decoherence Matrices  

E-print Network

It is shown that the Lorentz group is the natural language for two-beam interferometers if there are no decoherence effects. This aspect of the interferometer can be translated into six-parameter representations of the Lorentz group, as in the case of polarization optics where there are two orthogonal components of one light beam. It is shown that there are groups of transformations which leave the coherency or density matrix invariant, and this symmetry property is formulated within the framework of Wigner's little groups. An additional mathematical apparatus is needed for the transition from a pure state to an impure state. Decoherence matrices are constructed for this process, and their properties are studied in detail. Experimental tests of this symmetry property are possible.

D. Han; Y. S. Kim; Marilyn E. Noz

2000-03-13

212

One-element interferometer  

NASA Astrophysics Data System (ADS)

We apply the phase-switching method of Ryle to convert single dish radio telescopes to one-element interferometers and thereby accord them the benefit of correlation measurements, viz. to measure only the flux from the celestial sources avoiding contributions from the receiver and the atmosphere. This application has many uses: (a) enables single dishes to image the sky efficiently without the need to scan, measuring all sources, point, extended, spectral and continuum, with both bolometric and coherent receivers; (b) enables adding reliable short-spacing data to existing interferometers such as Atacama Large Millimetre-wave Array,, mitigating calibration issues; (c) enables ground-based NIR/MIR imaging to accurately remove atmospheric contributions; (d) can be adapted to provide an alternate surface measurement method for telescopes.

Balasubramanyam, Ramesh

2014-11-01

213

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Space interferometers consisting of several free flying telescopes, such as the planned Darwin mission, require a complex metrology system to make all the components operate as a single instrument. Our research focuses on one of its sub-systems that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy would be in the order of 10 µm over 250 meter. To measure this absolute distance, we are currently exploring the frequency sweeping interferometry technique. Its measurement principle is to first measure a phase in the interferometer, sweep a tunable laser over a known frequency interval and finally measure a second phase. By also counting the number of fringes during the sweep it is possible to determine the absolute path length difference without ambiguities. The wavelength at the endpoints of the sweep is stabilized on a Fabry-Perot cavity. In this way the unknown distance is directly referenced to the length of the Fabry-Perot cavity.

Swinkels, Bas L.; Wendrich, Thijs J.; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J.

2004-09-01

214

Multipulsed dynamic moire interferometer  

DOEpatents

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.

Deason, Vance A. (Idaho Falls, ID)

1991-01-01

215

Design of a phase-shifting interferometer in the extreme ultraviolet for high-precision metrology.  

PubMed

The design of a phase-shift interferometer in the extreme ultraviolet (EUV) is described. The interferometer is expected to achieve a significantly higher precision as compared with similar instruments that utilize lasers in the visible range. The interferometer's design is specifically adapted for its utilization with a table top pulsed capillary discharge EUV laser. The numerical model evaluates the errors in the interferograms and in the retrieved wavefront induced by the shot-to-shot fluctuations and pointing instabilities of the laser. PMID:24663354

Capeluto, María Gabriela; Marconi, Mario Carlos; Iemmi, Claudio Cesar

2014-03-01

216

The Keck Interferometer  

NASA Astrophysics Data System (ADS)

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 ?m), K (2.2 ?m), and L (3.8 ?m) bands, and nulling measurements at N band (10 ?m), 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.

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

217

Herriott Cell Interferometer for Density Measurements in Small-Scale Length Plasmas  

NASA Astrophysics Data System (ADS)

The introduction of a Herriott cell into a standard quadrature heterodyne interferometer is evaluated and demonstrated to increase the resolution of the system. Measurements of electron and neutral density during and after the current pulse are sought for modeling purposes for spacecraft contamination from Pulsed Plasma Thrusters. Testing is performed on the UIUC PPT-4, a coaxial electrothermal Pulsed Plasma Thruster pulsing at 20 J. Analytical and experimental analysis is conducted to determine the integrity of the phase front and the effect of multiple passes on the density measurements taken. The phase front quality is found to be acceptable for interferometric purposes and density measurements are taken for 2, 6, 14, and 18 passes in the Herriott cell. The advantage of the cell is obvious at late times when the external room vibrations induce an apparent phase shift in the same direction as neutral particles. Due to the same dependence on wavelength, 2 laser frequencies cannot be used to separate neutral and vibration contributions. The Herriott cell allows a density resolution increase linear with the number of passes that does not increase the vibrational component. Uncertainties from both vibrational sources and shot-to-shot variations of the thruster itself are investigated and characterized for this system. Due to variations in room vibrations on a day to day basis, the cell was unable to characterize the neutral density of the thruster. However, for single tests, neutral density measurements were acquired. The Herriott cell with 18 passes introduced a 9-fold increase in resolution over the standard 2-pass interferometric setup. At 200 microseconds for single tests at 14 and 18 passes (^20 shots averaged) neutral density at the exit plane was shown to be no more than 1*1016/cu cm. Peak electron density (4 microseconds) was shown to be 5.0*1015 +/- 1.1*1015/cu cm.

Antonsen, Erik; Burton, Rodney; Engelman, Scott; Spanjers, Greg

2000-06-01

218

The development of accurate and efficient methods of numerical quadrature  

NASA Technical Reports Server (NTRS)

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.

Feagin, T.

1973-01-01

219

Fringe Visibility Estimators for the Palomar Testbed Interferometer  

E-print Network

Visibility estimators and their performance are presented for use with the Palomar Testbed Interferometer (PTI). One operational mode of PTI is single-baseline visibility measurement using pathlength modulation with synchronous readout by a NICMOS-3 infrared array. Visibility is estimated from the fringe quadratures, either incoherently, or using source phase referencing to provide a longer coherent integration time. The visibility estimators differ those used with photon-counting detectors in order to account for biases attributable to detector offsets and read noise. The performance of these estimators is affected not only by photon noise, but also by the detector read noise and errors in estimating the bias corrections, which affect the incoherent and coherent estimators differently. Corrections for visibility loss in the coherent estimators using the measured tracking jitter are also presented.

M. M. Colavita

1998-10-28

220

SPIE March 23, 1998 Palomar Testbed Interferometer Palomar Testbed Interferometer  

E-print Network

March 23, 1998 Palomar Testbed Interferometer JKW-5 PTI History · Funded by NASA as engineering testbed March 23, 1998 Palomar Testbed Interferometer JKW-15 Constant-Term Metrology · Measures difference in optical path between the two arms for each beam combiner ­ difference in metrology measurments between

221

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Space interferometers consisting of several free flying telescopes, such as the planned Darwin mission, require a complex metrology system to make all the components operate as a single instrument. This metrology system consists of various sub-systems to monitor distances, angles and speeds. Our research focuses on one of these sub-systems that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy would be in the order of 10 ?m over 250 meter. To measure this absolute distance, we are currently building a frequency sweeping interferometer. It is operated by first measuring a phase in the interferometer, sweeping a tunable laser over a known frequency interval and finally measuring a second phase. By also counting the number of fringes during the sweep it is possible to determine the absolute path length difference without ambiguities. We plan on actively stabilizing the wavelength at the endpoints of the sweep on a Fabry-Perot cavity using the Pound-Drever-Hall technique. In this way the unknown distance is directly referenced to the length of the Fabry-Perot cavity.

Swinkels, B. L.; Wendrich, T. J.; Bhattacharya, N.; Wielders, A. A.; Braat, J. J. M.

2004-06-01

222

Differential heterodyne interferometer for measuring thickness of glass panels  

Microsoft Academic Search

Differential heterodyne interferometer is applied for measuring spatial thickness variations across glass panels of liquid-crystal displays. This system uses the Zeeman laser as a source of two-frequency shifted orthogonally linearly polarized probe waves, passing through the glass in two spatially separated points. These waves are then recombined in a single beam to produce the intermediate frequency signal with the phase

Vladimir Protopopov; Sunghoon Cho; Kwangso Kim; Sukwon Lee; Hyuk Kim

2007-01-01

223

Keck Interferometer status and plans  

NASA Astrophysics Data System (ADS)

Keck Interferometer is a NASA-funded project to combine the two 10 m Keck telescopes for high sensitivity near-infrared fringe visibility measurements, nulling interferometry at 10 ?m to measure the quantity of exozodiacal emission around nearby stars, and differential-phase measurements to detect "hot-Jupiters" by their direct emission. It is being developed by the Jet Propulsion Laboratory, the W. M. Keck Observatory, and the Michelson Science Center. Recent activity has included formal visibility mode commissioning, as well as science observations, and we briefly review some of the significant technical aspects and updates to the system. We have also completed laboratory development of the nuller. The nuller uses two modified Mach-Zehnder input nullers, a Michelson cross combiner, and a 10 ?m array camera to produce background-limited null measurements. To provide required temporal stability for the nuller, the system incorporates end-to-end laser metrology with phase referencing from two 2.2 ?m fringe trackers. The nuller recently completed its pre-ship review and is being installed on the summit. After nuller integration and test, the differential phase mode will be deployed, which will use a 2-5 ?m fringe detector in combination with a precision path length modulator and a vacuum delay line for dispersion control.

Colavita, M. M.; Wizinowich, Peter L.; Akeson, Rachel L.

2004-10-01

224

Convergence Acceleration of Gauss–Chebyshev Quadrature Formulae  

Microsoft Academic Search

The aim of this paper is to accelerate, via extrapolation methods, the convergence of the sequences generated by the Gauss–Chebyshev quadrature formula applied to functions holomorphic in ]-1,1[ and possessing, in the neighborhood of 1 or -1, an asymptotic expansion with log?(1±x)(1±x)a, (1±x)a, a>-1, as elementary elements.

M. Kzaz; M. Prévost

2003-01-01

225

Wave-Based Inversion & Imaging for the Optical Quadrature Microscope  

SciTech Connect

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.

Lehman, S K

2005-10-27

226

Archimedes Quadrature of the Parabola: A Mechanical View  

ERIC Educational Resources Information Center

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…

Oster, Thomas J.

2006-01-01

227

On Quadrature Methods for Highly Oscillatory Integrals and Their Implementation  

Microsoft Academic Search

The main theme of this paper is the construction of efficient, reliable and affordable error bounds for two families of quadrature methods for highly oscillatory integrals. We demonstrate, using asymptotic expansions, that the error can be bounded very precisely indeed at the cost of few extra derivative evaluations. Moreover, in place of derivatives it is possible to use finite difference

A. Iserles; S. P. NØrsett

2004-01-01

228

A 100 MHz MEMS SiBAR Phase Modulator for Quadrature Phase Shift Keying  

E-print Network

A 100 MHz MEMS SiBAR Phase Modulator for Quadrature Phase Shift Keying Logan Sorenson and Farrokh of a MEMS resonator to form the basic component of a switchless quadrature phase shift keying (QPSK) scheme modulator, such as for the popular quadrature phase shift keying (QPSK) scheme. Although a capacitively

Ayazi, Farrokh

229

Optical analysis and alignment applications using the infrared Smartt interferometer  

SciTech Connect

The possibility of using the infrared Smartt interferometer for optical analysis and alignment of infrared laser systems has been discussed previously. In this paper, optical analysis of the Gigawatt Test Facility at Los Alamos, as well as a deformable mirror manufactured by Rocketdyne, are discussed as examples of the technique. The possibility of optically characterizing, as well as aligning, pulsed high energy laser systems like Helios and Antares is discussed in some detail.

Viswanathan, V.K.; Bolen, P.D.; Liberman, I.; Seery, B.D.

1981-01-01

230

High intrinsic modulation bandwidth InGaAsP/InGaAsP 1.55 µm asymmetric active multimode interferometer laser diode by using split pump configuration  

NASA Astrophysics Data System (ADS)

1.55 µm InGaAsP/InGaAsP multiple quantum well (MQW) asymmetric active multimode laser diode (active MMI-LD) with split pumping scheme has been demonstrated. Asymmeric configuration ensures the singlewavelength output from the designed device. Moreover, the advantage of having large multimode active pumping section behind the splitted modulation section is the key contributor for having higher photon density in modulation section without increasing the device length. By utilizing the split pump configuration in the designed active MMI-LD, high intrinsic 3 dB modulation bandwidth of 24.6 GHz is achieved. To the best of our knowledge this is the highest reported intrinsic modulation bandwidth for active MMI-LD. Required photon density to achieve more than 40 GHz 3 dB bandwidth for direct modulation is also clarified.

Nasir Uddin, Mohammad; Kizu, Takaaki; Hinokuma, Yasuhiro; Hong, Bingzhou; Tajima, Akio; Kato, Kazutoshi; Hamamoto, Kiichi

2014-08-01

231

Fiber-optic extrinsic Fabry-Perot interferometer sensors with three-wavelength digital phase demodulation.  

PubMed

A three-wavelength-based passive quadrature digital phase-demodulation scheme has been developed for readout of fiber-optic extrinsic Fabry-Perot interferometer vibration, acoustic, and strain sensors. This scheme uses a superluminescent diode light source with interference filters in front of the photodiodes and real-time arctan calculation. Quasi-static strain and dynamic vibration sensing with up to an 80-kHz sampling rate is demonstrated. Periodic nonlinearities owing to dephasing with increasing fringe number are corrected for with a suitable algorithm, resulting in significant improvement of the linearity of the sensor characteristics. PMID:18073795

Schmidt, M; Fürstenau, N

1999-05-01

232

Rational choices for the wavelengths of a two color interferometer  

SciTech Connect

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.

Jobes, F.C.

1995-07-01

233

MIT's interferometer CST testbed  

NASA Astrophysics Data System (ADS)

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.

Hyde, Tupper; Kim, Ed; Anderson, Eric; Blackwood, Gary; Lublin, Leonard

1990-12-01

234

The Keck Interferometer Nuller  

NASA Astrophysics Data System (ADS)

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 (~order of magnitude) improvement in mid-infrared long-baseline fringe-visibility accuracies.

Serabyn, E.; Mennesson, B.; Colavita, M. M.; Koresko, C.; Kuchner, M. J.

2012-03-01

235

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Future space missions, among which the Darwin Space Interferometer, will consist of several free flying satellites. A complex metrology system is required to have all the components fly accurately in formation and have it operate as a single instrument. Our work focuses on a possible implementation of the sub-system that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy is on the order of 70 micrometer over a distance of 250 meter. We are exploring a technique called frequency sweeping interferometry, which involves interferometrically measuring a phase difference while sweeping the wavelength of a tunable laser. This phase difference is directly proportional to the absolute distance. A very high finesse Fabry-Perot cavity is used as a reference standard, to which the laser is locked at the end-points of the sweep. We will discuss our measurement scheme, our set-up and some first measurements.

Swinkels, Bas L.; Latoui, Abdelhalim; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J. M.

2005-08-01

236

Absolute distance metrology for space interferometers  

NASA Astrophysics Data System (ADS)

Future space missions, among which the Darwin Space Interferometer, will consist of several free flying satellites. A complex metrology system is required to have all the components fly accurately in formation and have it operate as a single instrument. Our work focuses on a possible implementation of the sub-system that measures the absolute distance between two satellites with high accuracy. For Darwin the required accuracy is on the order of 70 micrometer over a distance of 250 meter. We are exploring a technique called frequency sweeping interferometry, which involves interferometrically measuring a phase difference while sweeping the wavelength of a tunable laser. This phase difference is directly proportional to the absolute distance. A very high finesse Fabry-Perot cavity is used as a reference standard, to which the laser is locked end-points of the sweep. We will discuss the control system that drives the setup and show some first experimental results.

Swinkels, Bas L.; Bhattacharya, Nandini; Wielders, Arno A.; Braat, Joseph J. M.

2005-06-01

237

White light velocity interferometer  

DOEpatents

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.

Erskine, David J. (Oakland, CA)

1999-01-01

238

Simultaneous measurement of temperature and pressure with cascaded extrinsic Fabry-Perot interferometer and intrinsic Fabry-Perot interferometer sensors  

NASA Astrophysics Data System (ADS)

This paper presents an approach for simultaneous measurement of temperature and pressure using miniaturized fiber inline sensors. The approach utilizes the cascaded optical fiber inline intrinsic Fabry-Perot interferometer and extrinsic Fabry-Perot interferometer as temperature and pressure sensing elements, respectively. A CO2 laser was used to create a loss between them to balance their reflection power levels. The multiplexed signals were demodulated using a Fast Fourier transform-based wavelength tracking method. Experimental results showed that the sensing system could measure temperature and pressure unambiguously in a pressure range of 0 to 6.895×105 Pa and a temperature range from 20°C to 700°C.

Zhang, Yinan; Huang, Jie; Lan, Xinwei; Yuan, Lei; Xiao, Hai

2014-06-01

239

The high accuracy data processing system of laser interferometry signals based on MSP430  

NASA Astrophysics Data System (ADS)

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.

Qi, Yong-yue; Lin, Yu-chi; Zhao, Mei-rong

2009-07-01

240

TMO Progress Report 42-136 February 15, 1999 Trellis-Coded Quadrature-Phase-Shift Keying (QPSK)  

E-print Network

TMO Progress Report 42-136 February 15, 1999 Trellis-Coded Quadrature-Phase-Shift Keying (QPSK to that of uncoded quadrature-phase-shift keying (QPSK). I. Introduction Quadrature overlapped raised-cosine (QORC keying (MSK) and that of quadrature-phase-shift keying (QPSK) or offset2 QPSK (OQPSK) with identical

Arabshahi, Payman

241

Solar Wind Characteristics from SOHO-Sun-Ulysses Quadrature Observations  

NASA Technical Reports Server (NTRS)

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.

Poletto, Giannina; Suess, Steve T.; Six, N. Frank (Technical Monitor)

2002-01-01

242

Continuous phase quadrature phase shift keyed (CPQPSK) signaling technique  

NASA Technical Reports Server (NTRS)

A continuous-phase quadrature-phase-shift-keyed (CPQPSK) modulation technique is presented. This method uses a conventional QPSK-modulated signal and a phase trajectory converter to obtain nearly constant envelope amplitude and continuous-phase trajectories. A computer simulation program, MODEM, is used to simulate the CPQPSK signaling technique. It is concluded that this technique is particularly useful in building a high-data-rate transmitter for existing QPSK communication systems.

Kuh, Steve; Ryan, Carl

1988-01-01

243

Improving the performance of interferometers in metrological scanning probe microscopes  

NASA Astrophysics Data System (ADS)

The traceability of metrological scanning probe microscopes (MSPMs) is achieved in most cases by laser interferometers. Different means have been adopted to account for the nonlinearity of those interferometers. The thorough investigation of an existing MSPM shows the necessity of interferometrical position measurement with real time full-bandwidth nonlinearity correction. The paper demonstrates that the ellipse parameters of Heydemann nonlinearity correction are sufficiently stable and position independent. This is used in reducing the signal processing time by calculating the ellipse parameters in advance and fixing them during real time nonlinearity correction. As a result, a real time signal processing system with the ability of executing Heydemann correction in 0.32 µs and a complete demodulation in 2.2 µs is designed and implemented. It reduces the residual nonlinearity of interferometers from about 3.5 to <0.3 nm. Some measurement results of a flatness standard illustrate the effectiveness of this new method.

Dai, Gaoliang; Pohlenz, Frank; Danzebrink, Hans-Ulrich; Hasche, Klaus; Wilkening, Guenter

2004-02-01

244

New system of miniaturization online testing of spherical interferometer  

NASA Astrophysics Data System (ADS)

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.

Lin, Jian; Han, Zhenhua; Zhuo, Jinzhai; Wang, Min

2011-11-01

245

VISAR (Velocity Interferometer System for Any Reflector): Displacement-mode data reduction  

SciTech Connect

A Velocity Interferometer System for Any Reflector (VISAR) is a laboratory tool that measures high velocities by continuously measuring the Doppler shift of laser light reflected from a moving surface. It produces lower output frequencies than a displacement interferometer in which Doppler-shifted laser light from a moving target is mixed with unshifted laser light. To obtain lower frequencies, a VISAR employs a wide-angle Michelson interferometer with a time delay in one leg. Undelayed and delayed light rays are thus mixed to detect the relatively small difference between two Doppler shifts produced by accelerating motion at two slightly different velocities. In most VISAR data reduction programs, the velocity is assumed to be proportional to the interferometer fringe count at any instant. This yields velocity details that are inaccurate over the interferometer delay time. In the examples of this paper, the signal time resolution was shorter than the interferometer delay. The subject of this paper is a data reduction method that uses the displacement information in suitable VISAR signals to recover velocity features that occur during the interferometer delay. 9 refs., 8 figs.

Hemsing, W.F.

1990-01-01

246

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology  

NASA Technical Reports Server (NTRS)

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.

Decker, Arthur J.

2002-01-01

247

Balloon Exoplanet Nulling Interferometer (BENI)  

NASA Technical Reports Server (NTRS)

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.

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

248

Fiber Sagnac interferometer temperature sensor  

SciTech Connect

A modified Sagnac interferometer-based fiber temperature sensor is proposed. Polarization independent operation and high temperature sensitivity of this class of sensors make them cost effective instruments for temperature measurements. A comparison of the proposed sensor with Bragg grating and long-period grating fiber sensors is derived. A temperature-induced spectral displacement of 0.99 nm/K is demonstrated for an internal stress birefringent fiber-based Sagnac interferometer. {copyright} {ital 1997 American Institute of Physics.}

Starodumov, A.N.; Zenteno, L.A.; Monzon, D.; De La Rosa, E. [Centro de Investigaciones en Optica, 37150 Leon, Gto (Mexico)] [Centro de Investigaciones en Optica, 37150 Leon, Gto (Mexico)

1997-01-01

249

Michelson Interferometer (MINT)  

NASA Astrophysics Data System (ADS)

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.

Lacis, Andrew; Carlson, Barbara

1993-09-01

250

Michelson Interferometer (MINT)  

NASA Technical Reports Server (NTRS)

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.

Lacis, Andrew; Carlson, Barbara

1993-01-01

251

Lasers.  

ERIC Educational Resources Information Center

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)

Schewe, Phillip F.

1981-01-01

252

A robust sinusoidal signal processing method for interferometers  

NASA Astrophysics Data System (ADS)

Laser interferometers are widely used as a reference for length measurement. Reliable bidirectional optical fringe counting is normally obtained by using two orthogonally sinusoidal signals derived from the two outputs of an interferometer with path difference. These signals are subject to be disturbed by the geometrical errors of the moving target that causes the separation and shift of two interfering light spots on the detector. It results in typical Heydemann errors, including DC drift, amplitude variation and out-of-orthogonality of two sinusoidal signals that will seriously reduce the accuracy of fringe counting. This paper presents a robust sinusoidal signal processing method to correct the distorted waveforms by hardware. A corresponding circuit board has been designed. A linear stage equipped with a laser displacement interferometer and a height gauge equipped with a linear grating interferometer are used as the test beds. Experimental results show that, even with a seriously disturbed input waveform, the output Lissajous circle can always be stabilized after signal correction. This robust method increases the stability and reliability of the sinusoidal signals for data acquisition device to deal with pulse count and phase subdivision.

Wu, Xiang-long; Zhang, Hui; Tseng, Yang-Yu; Fan, Kuang-Chao

2013-10-01

253

A novel adaptive mismatch cancellation system for quadrature IF radio receivers  

Microsoft Academic Search

This paper investigates and resolves in-phase\\/quadrature phase (I\\/Q) imbalances between the input paths of quadrature IF receivers. These mismatches along the paths result in the image interference aliasing into the desired signal band, thus reducing the dynamic range and degrading the performance of the receivers. I\\/Q errors occur because of gain and phase imbalances between quadrature mixers. They are also

Li Yu; W. M. Snelgrove

1999-01-01

254

On deriving a locally corrected Nystrom scheme from a quadrature sampled moment method  

Microsoft Academic Search

A novel high-order method of moment procedure with quadrature point-based discretization is presented. The scheme is equivalent to a moment method employing smooth basis and testing functions applying a fixed-point numerical quadrature approximation for the outer integral. Mapping the current to the quadrature points then leads to a formulation that is equivalent to that derived via the locally corrected Nystrom

Stephen D. Gedney

2003-01-01

255

Sparse, adaptive Smolyak quadratures for Bayesian inverse problems  

NASA Astrophysics Data System (ADS)

Based on the parametric deterministic formulation of Bayesian inverse problems with unknown input parameter from infinite-dimensional, separable Banach spaces proposed in Schwab and Stuart (2012 Inverse Problems 28 045003), we develop a practical computational algorithm whose convergence rates are provably higher than those of Monte Carlo (MC) and Markov chain Monte Carlo methods, in terms of the number of solutions of the forward problem. In the formulation of Schwab and Stuart, the forward problems are parametric, deterministic elliptic partial differential equations, and the inverse problem is to determine the unknown diffusion coefficients from noisy observations comprising linear functionals of the system’s response. The sparsity of the generalized polynomial chaos representation of the posterior density being implied by sparsity assumptions on the class of the prior (Schwab and Stuart 2012), we design, analyze and implement a class of adaptive, deterministic sparse tensor Smolyak quadrature schemes for the efficient approximate numerical evaluation of expectations under the posterior, given data. The proposed, deterministic quadrature algorithm is based on a greedy, iterative identification of finite sets of most significant, ‘active’ chaos polynomials in the posterior density analogous to recently proposed algorithms for adaptive interpolation (Chkifa et al 2012 Report 2012-NN, 2013 Math. Modelling Numer. Anal. 47 253-80). Convergence rates for the quadrature approximation are shown, both theoretically and computationally, to depend only on the sparsity class of the unknown, but are bounded independently of the number of random variables activated by the adaptive algorithm. Numerical results for a model problem of coefficient identification with point measurements in a diffusion problem confirm the theoretical results.

Schillings, Claudia; Schwab, Christoph

2013-06-01

256

Achieving resonance in the Advanced LIGO gravitational-wave interferometer  

NASA Astrophysics Data System (ADS)

Interferometric gravitational-wave detectors are complex instruments comprised of a Michelson interferometer enhanced by multiple coupled cavities. Active feedback control is required to operate these instruments and keep the cavities locked on resonance. The optical response is highly nonlinear until a good operating point is reached. The linear operating range is between 0.01% and 1% of a fringe for each degree of freedom. The resonance lock has to be achieved in all five degrees of freedom simultaneously, making the acquisition difficult. Furthermore, the cavity linewidth seen by the laser is only ? 1 Hz, which is four orders of magnitude smaller than the linewidth of the free running laser. The arm length stabilization system is a new technique used for arm cavity locking in Advanced LIGO. Together with a modulation technique utilizing third harmonics to lock the central Michelson interferometer, the Advanced LIGO detector has been successfully locked and brought to an operating point where detecting gravitational-waves becomes feasible.

Staley, A.; Martynov, D.; Abbott, R.; Adhikari, R. X.; Arai, K.; Ballmer, S.; Barsotti, L.; Brooks, A. F.; DeRosa, R. T.; Dwyer, S.; Effler, A.; Evans, M.; Fritschel, P.; Frolov, V. V.; Gray, C.; Guido, C. J.; Gustafson, R.; Heintze, M.; Hoak, D.; Izumi, K.; Kawabe, K.; King, E. J.; Kissel, J. S.; Kokeyama, K.; Landry, M.; McClelland, D. E.; Miller, J.; Mullavey, A.; O?Reilly, B.; Rollins, J. G.; Sanders, J. R.; Schofield, R. M. S.; Sigg, D.; Slagmolen, B. J. J.; Smith-Lefebvre, N. D.; Vajente, G.; Ward, R. L.; Wipf, C.

2014-12-01

257

Bichromatic, phase compensating interferometer based on prism pair compressors  

NASA Astrophysics Data System (ADS)

We present a bichromatic prism pair interferometer (BPPI) for controlling the delay between laser pulses of two different frequencies propagating collinearly in a single beam. The BPPI is especially useful when working with ultrafast laser pulses because it intrinsically allows for independent control over the second-order dispersion experienced by the differently colored pulses. We use this control to demonstrate successful precompensation for blue (??390 nm) and UV (??260 nm) pulses that pass through 2.2 cm of dispersive material after the interferometer. The BPPI is extremely flexible and works with all frequencies from the UV to the near-infrared. We demonstrate this by describing measurements made with BPPIs configured for three different combinations of central frequencies.

Flickinger, Daniel A.; Coffee, Ryan N.; Gibson, George N.; Weinacht, Thomas C.

2006-08-01

258

Differential heterodyne interferometer for measuring thickness of glass panels.  

PubMed

Differential heterodyne interferometer is applied for measuring spatial thickness variations across glass panels of liquid-crystal displays. This system uses the Zeeman laser as a source of two-frequency shifted orthogonally linearly polarized probe waves, passing through the glass in two spatially separated points. These waves are then recombined in a single beam to produce the intermediate frequency signal with the phase proportional to the thickness gradient of a glass sample. The phase of the intermediate signal is measured against the laser reference by means of a lock-in amplifier, and finally real-time integration provides the thickness variation. Since spatial separation of the probe beams is only 1.35 mm good approximation for the thickness gradient is achieved. Detailed design of the interferometer and experimental results on real samples are presented. PMID:17672800

Protopopov, Vladimir; Cho, Sunghoon; Kim, Kwangso; Lee, Sukwon; Kim, Hyuk

2007-07-01

259

Differential heterodyne interferometer for measuring thickness of glass panels  

SciTech Connect

Differential heterodyne interferometer is applied for measuring spatial thickness variations across glass panels of liquid-crystal displays. This system uses the Zeeman laser as a source of two-frequency shifted orthogonally linearly polarized probe waves, passing through the glass in two spatially separated points. These waves are then recombined in a single beam to produce the intermediate frequency signal with the phase proportional to the thickness gradient of a glass sample. The phase of the intermediate signal is measured against the laser reference by means of a lock-in amplifier, and finally real-time integration provides the thickness variation. Since spatial separation of the probe beams is only 1.35 mm good approximation for the thickness gradient is achieved. Detailed design of the interferometer and experimental results on real samples are presented.

Protopopov, Vladimir; Cho, Sunghoon; Kim, Kwangso; Lee, Sukwon; Kim, Hyuk [Samsung Electronics, Mechatronics Center, 416 Maetan-3Dong, Yeongtong-Gu, Suwon-City, Gyeonggi-Do 442-600 (Korea, Republic of)

2007-07-15

260

Orbit analysis of a geostationary gravitational wave interferometer detector array  

E-print Network

We analyze the trajectories of three geostationary satellites forming the GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\\cite{tinto}, a space-based laser interferometer mission aiming to detect and study gravitational radiation in the ($10^{-4} - 10$) Hz band. The combined effects of the gravity fields of the Earth, the Sun and the Moon make the three satellites deviate from their nominally stationary, equatorial and equilateral configuration. Since changes in the satellites relative distances and orientations could negatively affect the precision of the laser heterodyne measurements, we have derived the time-dependence of the inter-satellite distances and velocities, the variations of the polar angles made by the constellation's three arms with respect to a chosen reference frame, and the time changes of the triangle's enclosed angles. We find that, during the time between two consecutive station-keeping maneuvers (about two weeks), the relative variations of the inter-satellite distances do not...

Tinto, Massimo; Kuga, Helio K; Alves, Marcio E S; Aguiar, Odylio D

2014-01-01

261

Exciton-polariton Josephson interferometer in a semiconductor microcavity  

NASA Astrophysics Data System (ADS)

We propose to construct an exciton-polariton Josephson interferometer in a planar semiconductor microcavity. For a single excitation laser, the time-independent Josephson currents appear, regardless of the excitation laser, energy differences, and interactions. Exciton polaritons can exist in the trap far away from the excitation area (several micrometres), although their lifetime is very short (several picoseconds). If there are two excitation sources, the constructive and destructive interferences can be modulated, and they are related to the condensate energies, densities, interactions, and hopping energy in the dc Josephson effect. The 0\\text-? transition is obtained by altering the condensate energies. A synchronized phase exists in the ac Josephson effect and keeps the system oscillating in the steady state. These results are useful to interpret the coherence in the driven-dissipative Josephson interferometer.

Zhang, Chuanyi; Zhang, Weifeng

2014-10-01

262

Mach-Zehnder interferometer for movement monitoring  

NASA Astrophysics Data System (ADS)

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.

Vasinek, Vladimir; Cubik, Jakub; Kepak, Stanislav; Doricak, Jan; Latal, Jan; Koudelka, Petr

2012-06-01

263

Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics  

NASA Technical Reports Server (NTRS)

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.

Griffin, DeVon W.; Marshall, Keneth L.

2002-01-01

264

Parametric generation of quadrature squeezing of mirrors in cavity optomechanics  

SciTech Connect

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.

Liao, Jie-Qiao; Law, C. K. [Department of Physics and Institute of Theoretical Physics, Chinese University of Hong Kong, Shatin, Hong Kong Special Administrative Region (Hong Kong)

2011-03-15

265

Quadrature-dependent Bogoliubov transformations and multiphoton squeezed states  

Microsoft Academic Search

We introduce a linear, canonical transformation of the fundamental\\u000asingle--mode field operators $a$ and $a^{\\\\dagger}$ that generalizes the linear\\u000aBogoliubov transformation familiar in the construction of the harmonic\\u000aoscillator squeezed states. This generalization is obtained by adding to the\\u000alinear transformation a nonlinear function of any of the fundamental quadrature\\u000aoperators $X_{1}$ and $X_{2}$, making the original Bogoliubov transformation\\u000aquadrature--dependent.

Silvio De Siena; Antonio Di Lisi; Fabrizio Illuminati

2001-01-01

266

Noise-cancelling quadrature magnetic position, speed and direction sensor  

DOEpatents

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.

Preston, Mark A. (Niskayuna, NY); King, Robert D. (Schenectady, NY)

1996-01-01

267

Vibration diagnosis and remediation design for an x-ray optics stitching interferometer system.  

SciTech Connect

The Advanced Photon Source (APS) x-ray optics Metrology Laboratory currently operates a small-aperture Wyko laser interferometer in a stitching configuration. While the stitching configuration allows for easier surface characterization of long x-ray substrates and mirrors, the addition of mechanical components for optic element translation can compromise the ultimate measurement performance of the interferometer. A program of experimental vibration measurements, quantifying the laboratory vibration environment and identifying interferometer support-system behavior, has been conducted. Insight gained from the ambient vibration assessment and modal analysis has guided the development of a remediation technique. Discussion of the problem diagnosis and possible solutions are presented in this paper.

Preissner, C.; Assoufid, L.; Shu, D.; Experimental Facilities Division (APS)

2004-01-01

268

Characterization of the frequency-modulated continuous wave subsystem of an angstrom-accuracy absolute interferometer  

NASA Astrophysics Data System (ADS)

An external cavity diode laser is used as source for a frequency modulated continuous wave (FMCW) interferometer intended to determine absolute optical path differences (OPD) of up to 3mm with a target accuracy of 0.3 microns. This interferometer will eventually be paired with a heterodyne interferometer to extend the accuracy of the system to 0.1nm. Rather than using injection current modulation for the FMCW subsystem, the frequency sweep is provided by moving a mirror of the external cavity with a piezo element. A noise source analysis for this particular setup is provided, and estimates of the maximum attainable accuracy are made.

Krieg, Lukas M.; Swinkels, Bas L.; Braat, Joseph J. M.

2002-06-01

269

Long-Term Stability of an Area-Reversible Atom-Interferometer Sagnac Gyroscope  

E-print Network

We report on a study of the long-term stability and absolute accuracy of an atom interferometer gyroscope. This study included the implementation of an electro-optical technique to reverse the vector area of the interferometer for reduced systematics and a careful study of systematic phase shifts. Our data strongly suggests that drifts less than 96 $\\mu$deg/hr are possible after empirically removing shifts due to measured changes in temperature, laser intensity, and several other experimental parameters.

D. S. Durfee; Y. K. Shaham; M. A. Kasevich

2005-10-27

270

A new method for determining the plasma electron density using three-color interferometer  

SciTech Connect

A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO{sub 2} laser. Short-time integrations of the fractional fringes enhance the reliability of this method.

Arakawa, Hiroyuki; Kawano, Yasunori; Itami, Kiyoshi [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-shi, Ibaraki 311-0193 (Japan)

2012-06-15

271

Anomalous dynamic backaction in interferometers  

NASA Astrophysics Data System (ADS)

We analyze the dynamic optomechanical backaction in signal-recycled Michelson and Michelson-Sagnac interferometers that are operated off the dark port. We show that in this case—and in contrast to the well-studied canonical form of dynamic backaction on the dark port—optical damping in a Michelson-Sagnac interferometer acquires a nonzero value on cavity resonance, and additional stability and instability regions on either side of the resonance, revealing additional regimes of cooling and heating of micromechanical oscillators. In a free-mass Michelson interferometer for a certain region of parameters we predict a stable single-carrier optical spring (positive spring and positive damping), which can be utilized for the reduction of quantum noise in future-generation gravitational-wave detectors.

Tarabrin, Sergey P.; Kaufer, Henning; Khalili, Farid Ya.; Schnabel, Roman; Hammerer, Klemens

2013-08-01

272

Phase-modulation interferometer for ICF-target characterization  

SciTech Connect

Characterization requirements for high gain laser fusion targets are severe. We are required to detect defects on the surfaces of opaque and transparent shells with an amplitude resolution of +- 5 nm and a spatial resolution of 1 to 10 ..mu..m. To achieve this we have developed a laser-illuminated phase-modulation interferometer. This instrument is based on a photoelastic polarization modulation technique which allows one to convert phase information into an intensity modulation which can be easily and sensitively measured using ac signal processing techniques. This interferometer has detected path length changes as small as 1 nm and the required spatial resolution is assured by using a microscope objective to focus the probe laser beam down to a small (approx. 1 ..mu..m) spot on the surface of a microballoon. The interferometer will soon be coupled to an LSI-11 controlled 4..pi.. sphere manipulator which will allow us to automatically inspect the entire surface area of a target sphere.

Cooper, D.E.

1981-01-01

273

Two-wavelength quadrature multipoint detection of partial discharge in power transformers using fiber Fabry-Perot acoustic sensors  

NASA Astrophysics Data System (ADS)

A reliable and low-cost two-wavelength quadrature interrogating method has been developed to demodulate optical signals from diaphragm-based Fabry-Perot interferometric fiber optic sensors for multipoint partial discharge detection in power transformers. Commercial available fused-silica parts (a wafer, a fiber ferrule, and a mating sleeve) and a cleaved optical single mode fiber were bonded together to form an extrinsic Fabry-Perot acoustic sensor. Two lasers with center wavelengths separated by a quarter of the period of sensor interference fringes were used to probe acousticwave- induced diaphragm vibration. A coarse wavelength-division multiplexing (CWDM) add/drop multiplexer was used to separate the reflected two wavelengths before two photo detectors. Optical couplers were used to distribute mixed laser light to each sensor-detector module for multiplexing purpose. Sensor structure, detection system design and experiment results are presented.

Dong, Bo; Han, Ming; Wang, Anbo

2012-06-01

274

Fast convolution quadrature for the wave equation in three dimensions  

NASA Astrophysics Data System (ADS)

This work addresses the numerical solution of time-domain boundary integral equations arising from acoustic and electromagnetic scattering in three dimensions. The semidiscretization of the time-domain boundary integral equations by Runge-Kutta convolution quadrature leads to a lower triangular Toeplitz system of size N. This system can be solved recursively in an almost linear time (O(Nlog2?N)), but requires the construction of O(N) dense spatial discretizations of the single layer boundary operator for the Helmholtz equation. This work introduces an improvement of this algorithm that allows to solve the scattering problem in an almost linear time. The new approach is based on two main ingredients: the near-field reuse and the application of data-sparse techniques. Exponential decay of Runge-Kutta convolution weights wnh(d) outside of a neighborhood of d?nh (where h is a time step) allows to avoid constructing the near-field (i.e. singular and near-singular integrals) for most of the discretizations of the single layer boundary operators (near-field reuse). The far-field of these matrices is compressed with the help of data-sparse techniques, namely, H-matrices and the high-frequency fast multipole method. Numerical experiments indicate the efficiency of the proposed approach compared to the conventional Runge-Kutta convolution quadrature algorithm.

Banjai, L.; Kachanovska, M.

2014-12-01

275

Automatic Alignment of Displacement-Measuring Interferometer  

NASA Technical Reports Server (NTRS)

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.

Halverson, Peter; Regehr, Martin; Spero, Robert; Alvarez-Salazar, Oscar; Loya, Frank; Logan, Jennifer

2006-01-01

276

Accurate wavelength measurement with Pohl interferometer through post detection processing  

NASA Astrophysics Data System (ADS)

We present a simple wavemeter setup based on Pohl Interferometer to measure wavelength using post detection processing of data using a simple circular averaging algorithm. Advantage of the same is its portability, ease of use with CW as well pulsed lasers, speed at which we can measure the wavelength to a good enough accuracy and above all no requirement of a reference laser. Resolution approaching 0.5 nm can be easily achieved using such setup which can be further enhanced using a fiber coupler to couple the unknown wavelength in addition to advanced signal processing methods.

Barthwal, Sachin; Ashoka V., S.

2014-10-01

277

AN ATOM INTERFEROMETER GYROSCOPE JAMES GREENBERG  

E-print Network

phase to determine the Earth's rotation rate as well as the orientation of our interferometer polarizability made in our apparatus. #12;4 TABLE OF CONTENTS CHAPTER 1 Introduction 5 CHAPTER 2 Contrast vs interferometer to measure the Earth's rotation rate as well as the orientation of our interferometer with respect

Cronin, Alex D.

278

Coupled fiber ring interferometer array: theory  

Microsoft Academic Search

A novel fiber-optic interferometer, the coupled fiber ring interferometer array (CFRIA) is proposed. The addition of one or more single-mode fiber directional couplers to the fiber ring interferometer results in a CFRIA. The theory based on the matrix method has been proposed for the calculation of the electric field intensity output of the CFRIA. Equations for calculating the transmittance are

An Wang; Haiming Xie

1991-01-01

279

White Light Extended Source Shearing Interferometer  

Microsoft Academic Search

A grating lateral shear interferometer is described that can be used with a white light source. The use of the interferometer with certain types of extended sources is also demonstrated. In a recent paper a simple double frequency grat- ing shearing interferometer, similar to a Ronchi in- terferometer, was described for use with a quasi- monochromatic point light source. l

J. C. Wyant

1974-01-01

280

A triangular path inverting interferometer  

Microsoft Academic Search

A triangular path inverting interferometer is described with application to the study of thermal 'schlieren'. This is practically free of any vibration and coherence troubles, and possesses the unique feature that either differential or total shear may be obtained only with proper positioning of the object; once aligned, the optical components need not be disturbed further. This simple and stable

D. Chakrabarti; S. P. Basu; M. De

1977-01-01

281

Spatial quadrature: a novel technique for multi-dimensional velocity estimation  

Microsoft Academic Search

Conventional ultrasonic motion or flow velocity estimation is limited to the axial velocity component. I present a novel technique, called “spatial quadrature”, for the simultaneous estimation of axial and lateral velocity components. This technique utilizes even and odd spatial weightings of the point spread function which have a quadrature relationship. These weightings produce modulation in the received echo which can

M. E. Anderson

1997-01-01

282

General n-dimensional quadrature transform and its application to interferogram demodulation.  

PubMed

Quadrature operators are useful for obtaining the modulating phase phi 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(phi) into -sin(phi) regardless of the frequency spectrum of the signal. With the quadrature of the phase-modulated signal, one can easily calculate the value of phi 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. PMID:12747439

Servin, Manuel; Quiroga, Juan Antonio; Marroquin, Jose Luis

2003-05-01

283

Direct quadrature phase shift keying modulator using six-port technology  

E-print Network

Direct quadrature phase shift keying modulator using six-port technology Y. Zhao, C. Viereck, J.F. Frigon, R.G. Bosisio and K. Wu A direct quadrature phase shift keying modulator based on six terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technol- ogy

Frigon, Jean-François

284

The Nature of the Nodes, Weights and Degree of Precision in Gaussian Quadrature Rules  

ERIC Educational Resources Information Center

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…

Prentice, J. S. C.

2011-01-01

285

Accurate computation of weights in classical Gauss-Christoffel quadrature rules  

SciTech Connect

For many classical Gauss-Christoffel quadrature rules there does not exist a method which guarantees a uniform level of accuracy for the Gaussian quadrature weights at all quadrature nodes unless the nodes are known exactly. More disturbing, some algebraic expressions for these weights exhibit an excessive sensitivity to even the smallest perturbations in the node location. This sensitivity rapidly increases with high order quadrature rules. Current uses of very high order quadratures are common with the advent of more powerful computers, and a loss of accuracy in the weights has become a problem and must be addressed. A simple but efficient and general method for improving the accuracy of the computation of the quadrature weights even though the nodes may carry a significant large error. In addition, a highly efficient root-finding iterative technique with superlinear converging rates for computing the nodes is developed. It uses solely the quadrature polynomials and their first derivatives. A comparison of this method with the eigenvalue method of Golub and Welsh implemented in most standard software libraries is made. The proposed method outperforms the latter from the point of view of both accuracy and efficiency. The Legendre, Lobatto, Radau, Hermite, and Laguerre quadrature rules are examined. 22 refs., 7 figs., 5 tabs.

Yakimiw, E. [Recherche en Prevision Numerique, Dorval, Quebec (Canada)] [Recherche en Prevision Numerique, Dorval, Quebec (Canada)

1996-12-01

286

A low phase noise and low power series coupled quadrature VCO using reconfigurable LC tank  

Microsoft Academic Search

To design a multi standard and a multi band transceiver, a quadrature voltage controlled oscillator (VCO), which has a wide tuning range, is essential, while providing low phase noise with low current consumption. In this paper, a dual band quadrature VCO in 0.18 mum CMOS process is presented. To accomplish dual band operation, reconfigurable LC tank is adopted. Series coupling

Cheol-Hoe Kim; Soo-Hwan Shin; Hyung-Joun Yoo

2008-01-01

287

Novel quadrature interferometric platform with application in optical coherence tomography  

NASA Astrophysics Data System (ADS)

Optical Coherence Tomography is an imaging technique for capturing three-dimensional images of weakly scattering sample1. At the core of this technique are an interferometer with low temporal coherence and an optical delay line for in depth movement of the coherent gate. The interferometeric setup has to be robust and with high signal-to-noise ratio. Fiber-optic implementation of the interferometer has the advantages of being rugged, compact and by using SM fiber yields minimal scattering into higher-order modes. On the other hand large bandwidth required for light sources cannot be accommodated by the fiber optic components usually design for a smaller bandwidth. The Michelson configuration is widely used as an interferometric platform with OCT application.

Flueraru, C.; Kumazaki, H.; Sherif, S.; Chang, S.

2006-09-01

288

Analysis and applications of quadrature hybrids as RF circulators  

SciTech Connect

The operation of a quadrature hybrid as a power combiner is analyzed. The analytical results are compared with data measured experimentally using a 211 MHz cavity. Graphical solution of the measured cases are in good agreement with analytical predictions. The use of the 90{degree}-hybrid as an RF circulator is also analyzed. The active operation of the harmonic cavity in the NSLS VUV-ring is used to demonstrate this application. This fourth-harmonic cavity is used to change the shape of the bucket potential to lengthen a stored bunch. Thus, a longer stored-beam lifetime can be achieved without compromising the high brightness of the VUV photon beam. If operated actively, the harmonic cavity would present a mismatched load to an RF generator. Thus, a need exists for a circulator. Similarities in operation between the 90{degree}-hybrid and a circulator are discussed.

Hanna, S.M.; Keane, J.

1993-12-31

289

Odd-bit symmetric QASK. [quadrature amplitude shift keyed signals  

NASA Technical Reports Server (NTRS)

Multiple-amplitude and phase-shift-keyed (MAPSK) signal set selection is influenced by factors such as average and/or peak signal-to-noise ratio for a given error probability, dynamic range of signal amplitudes, simplicity of generation and detection, and number of bit errors per adjacent symbol error. This paper compares two possible quadrature-amplitude-shift-keyed (QASK) signal sets for the case where the number of bits per symbol is odd (for the even-bit case, the square array is the only viable QASK choice). The symmetric QASK version out-performs the rectangular QASK set at a very modest implementation penalty. This permits symmetric QASK to be considered in future odd-bit system studies.

Smith, J. G.

1974-01-01

290

Geothermal modeling by Gauss-Legendre quadrature integration  

NASA Astrophysics Data System (ADS)

Bottom-hole temperature data and temperature dependent seismic, gravity, magnetic and other geological data are becoming increasingly available for improving our understanding of the geological structure and evolution of the Earth, aiding fossil energy exploration and CO2 sequestration efforts as well as for enhancing geothermal energy exploration. In assessing these growing data sets, there is a great need for developing methods to compute regional and local thermal fields from geologic models in spherical as well as Cartesian coordinates. We explore the utility of the elegant Gauss-Legendre quadrature formulation for numerically modeling the thermal effects (i.e., potential and field) of the spherical prism for heat productivity contrasts in radiogenic content and thermal conductivity. As an application, we investigate the potential, T, and heat flow, q, effects of real terrain on BHT observations and heat flow estimates in Ohio.

Leftwich, T. E.; von Frese, R. R.; Tost, B. C.

2011-12-01

291

Two-step greedy algorithm for reduced order quadratures  

E-print Network

We present an algorithm to generate application-specific, global reduced order quadratures (ROQ) for multiple fast evaluations of weighted inner products between parameterized functions. If a reduced basis (RB) or any other projection-based model reduction technique is applied, the dimensionality of integrands is reduced dramatically; however, the cost of evaluating the reduced integrals still scales as the size of the original problem. In contrast, using discrete empirical interpolation (DEIM) points as ROQ nodes leads to a computational cost which depends linearly on the dimension of the reduced space. Generation of a reduced basis via a greedy procedure requires a training set, which for products of functions can be very large. Since this direct approach can be impractical in many applications, we propose instead a two-step greedy targeted towards approximation of such products. We present numerical experiments demonstrating the accuracy and the efficiency of the two-step approach. The presented ROQ are ex...

Antil, Harbir; Herrmann, Frank; Nochetto, Ricardo H; Tiglio, Manuel

2012-01-01

292

On quadrature methods for refractory point process likelihoods.  

PubMed

Parametric models of the conditional intensity of a point process (e.g., generalized linear models) are popular in statistical neuroscience, as they allow us to characterize the variability in neural responses in terms of stimuli and spiking history. Parameter estimation in these models relies heavily on accurate evaluations of the log likelihood and its derivatives. Classical approaches use a discretized time version of the spiking process, and recent work has exploited the existence of a refractory period (during which the conditional intensity is zero following a spike) to obtain more accurate estimates of the likelihood. In this brief letter, we demonstrate that this method can be improved significantly by applying classical quadrature methods directly to the resulting continuous-time integral. PMID:25248082

Mena, Gonzalo; Paninski, Liam

2014-12-01

293

Two-step greedy algorithm for reduced order quadratures  

E-print Network

We present an algorithm to generate application-specific, global reduced order quadratures (ROQ) for multiple fast evaluations of weighted inner products between parameterized functions. If a reduced basis (RB) or any other projection-based model reduction technique is applied, the dimensionality of integrands is reduced dramatically; however, the cost of approximating the integrands by projection still scales as the size of the original problem. In contrast, using discrete empirical interpolation (DEIM) points as ROQ nodes leads to a computational cost which depends linearly on the dimension of the reduced space. Generation of a reduced basis via a greedy procedure requires a training set, which for products of functions can be very large. Since this direct approach can be impractical in many applications, we propose instead a two-step greedy targeted towards approximation of such products. We present numerical experiments demonstrating the accuracy and the efficiency of the two-step approach. The presented ROQ are expected to display very fast convergence whenever there is regularity with respect to parameter variation. We find that for the particular application here considered, one driven by gravitational wave physics, the two-step approach speeds up the offline computations to build the ROQ by more than two orders of magnitude. Furthermore, the resulting ROQ rule is found to converge exponentially with the number of nodes, and a factor of ~50 savings, without loss of accuracy, is observed in evaluations of inner products when ROQ are used as a downsampling strategy for equidistant samples using the trapezoidal rule. While the primary focus of this paper is on quadrature rules for inner products of parameterized functions, our method can be easily adapted to integrations of single parameterized functions, and some examples of this type are considered.

Harbir Antil; Scott E. Field; Frank Herrmann; Ricardo H. Nochetto; Manuel Tiglio

2012-10-01

294

Real-time Digital Carrier & Data Recovery for a Synchronous Optical Quadrature Phase Shift Keying Transmission System  

E-print Network

Real-time Digital Carrier & Data Recovery for a Synchronous Optical Quadrature Phase Shift Keying is presented which are required to realize a 10 Gbaud synchronous optical quadrature phase shift keying (QPSKQPSK ­ Key components for synchronous quadrature phase shift keying transmission", funded by the European

Noé, Reinhold

295

Static and (quasi)dynamic calibration of stroboscopic scanning white light interferometer  

NASA Astrophysics Data System (ADS)

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.

Seppä, Jeremias; Kassamakov, Ivan; Nolvi, Anton; Heikkinen, Ville; Paulin, Tor; Lassila, Antti; Hao, Ling; Hæggsröm, Edward

2013-04-01

296

Pointing Stability for the LIGO Seismic Platform Interferometer (Invited)  

NASA Astrophysics Data System (ADS)

The LIGO project aims to detect gravitational waves with the use of laser interferometers. The optics are suspended from structures mounted on seismic isolation platforms, and the angular motion of these platforms affect the readings of the interferometers. This set of experiments serves to find the noise floor of that angular motion. To do so, a basic light source-to-detector setup was used, and step by step different variables, including beam length and light source, were changed to see their effect on the angular noise of the setup. In the end, it was concluded that a longer beam length, a lower RIN ASE source, and a longer stabilization period helped reduce the noise of the setup, but the noise is still not within the requirements. Further research must be done to find out what is still limiting the angular noise.

Raju, A.; Lantz, B.; Allen, G.

2009-12-01

297

Frequency domain interferometer simulation with higher-order spatial modes  

E-print Network

FINESSE is a software simulation that allows to compute the optical properties of laser interferometers as they are used by the interferometric gravitational-wave detectors today. It provides a fast and versatile tool which has proven to be very useful during the design and the commissioning of gravitational-wave detectors. The basic algorithm of FINESSE numerically computes the light amplitudes inside an interferometer using Hermite-Gauss modes in the frequency domain. In addition, FINESSE provides a number of commands to easily generate and plot the most common signals like, for example, power enhancement, error or control signals, transfer functions and shot-noise-limited sensitivities. Among the various simulation tools available to the gravitational wave community today, FINESSE is the most advanced general optical simulation that uses the frequency domain. It has been designed to allow general analysis of user defined optical setups while being easy to install and easy to use.

A. Freise; G. Heinzel; H. Lueck; R. Schilling; B. Willke; K. Danzmann

2003-09-02

298

Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space  

NASA Technical Reports Server (NTRS)

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.

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

299

Optimisations for quadrature representations of finite element tensors through automated code generation  

E-print Network

-level code may be exceeded; and the run time performance deteriorates rapidly relative to a quadrature approach. Complicated forms are by no means exotic. Many common nonlinear equations, when linearised, result in forms which involve numerous function... to investigate the cross-over point at which the quadrature representation becomes the better representation in terms of run time performance. Exact quadrature is used for all examples. All tests were performed on an Intel Core 2 X6800 CPU at 2.93GHz with 3.2GB...

Oelgaard, Kristian B; Wells, G N

2009-07-20

300

Quadrature methods for periodic singular and weakly singular Fredholm integral equations  

NASA Technical Reports Server (NTRS)

High-accuracy numerical quadrature methods for integrals of singular periodic functions are proposed. These methods are based on the appropriate Euler-Maclaurin expansions of trapezoidal rule approximations and their extrapolations. They are subsequently used to obtain accurate quadrature methods for the solution of singular and weakly singular Fredholm integral equations. Throughout the development the periodic nature of the problem plays a crucial role. Such periodic equations are used in the solution of planar elliptic boundary value problems such as those that arise in elasticity, potential theory, conformal mapping, and free surface flows. The use of the quadrature methods is demonstrated with numerical examples.

Sidi, Avram; Israeli, Moshe

1988-01-01

301

Sensitivity and noise analysis of 4 km laser interferometric gravitational wave antennae  

E-print Network

Around the world, efforts are underway to commission several kilometer-scale laser interferometers to detect gravitational radiation. In the United States, there are two collocated interferometers in Hanford, Washington ...

Adhikari, Rana, 1974-

2004-01-01

302

Nonlocal polarization interferometer for entanglement detection  

NASA Astrophysics Data System (ADS)

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.

Williams, Brian P.; Humble, Travis S.; Grice, Warren P.

2014-10-01

303

Configurations of a new atomic interferometer for gravitational wave detection  

E-print Network

Recently, the configuration using atomic interferometers (AIs) had been suggested for the detection of gravitational waves. A new AI with some additional laser pulses for implementing large momentum transfer was also put forward, in order to improve the influence of shot noise and laser frequency noise. In the paper, we use the sensitivity function to analyze all possible configurations of the new AI and to distinguish how many momenta are transferred in a specific configuration. With the analysis for the new configuration, we explore the detection scheme of gravitational wave further, in particular, for the amelioration of the laser frequency noise. We find that the amelioration is definite in such scheme, but novelly, in some cases the frequency noise can be canceled completely by using a proper data processing method.

Biao Tang; Baocheng Zhang; Lin Zhou; Jin Wang; Mingsheng Zhan

2013-12-30

304

Reissner-Mindlin Legendre Spectral Finite Elements with Mixed Reduced Quadrature  

SciTech Connect

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.

Brito, K. D.; Sprague, M. A.

2012-10-01

305

Sparse aerosol models beyond the quadrature method of moments  

NASA Astrophysics Data System (ADS)

This study examines a class of sparse aerosol models derived from linear programming (LP). The widely used quadrature method of moments (QMOM) is shown to fall into this class. Here it is shown how other sparse aerosol models can be constructed, which are not based on moments of the particle size distribution. The new methods enable one to bound atmospheric aerosol physical and optical properties using arbitrary combinations of model parameters and measurements. Rigorous upper and lower bounds, e.g. on the number of aerosol particles that can activate to form cloud droplets, can be obtained this way from measurement constraints that may include total particle number concentration and size distribution moments. The new LP-based methods allow a much wider range of aerosol properties, such as light backscatter or extinction coefficient, which are not easily connected to particle size moments, to also be assimilated into a list of constraints. Finally, it is shown that many of these more general aerosol properties can be tracked directly in an aerosol dynamics simulation, using SAMs, in much the same way that moments are tracked directly in the QMOM.

McGraw, Robert

2013-05-01

306

Real-time implementation of lateral flow estimation using spatial quadrature  

Microsoft Academic Search

The first real-time implementation of lateral flow estimation using spatial quadrature is described and results of its application in flow-phantom experiments presented. Spatial quadrature (SQ) is a recently-introduced technique for two- or three-dimensional flow velocity estimation. In its most basic form, this technique interrogates the region of interest with a pair of point spread functions which have weightings in the

M. E. Anderson

1998-01-01

307

A Gaussian quadrature method for total energy analysis in electronic state calculations  

Microsoft Academic Search

This article reports studies by Fukushima and coworkers since 1980 concerning their highly accurate numerical integral method using Gaussian quadratures to evaluate the total energy in electronic state calculations. Gauss-Legendre and Gauss-Laguerre quadratures were used for integrals in the finite and infinite regions, respectively. Our previous article showed that, for diatomic molecules such as CO and FeO, elliptic coordinates efficiently

Kimichika Fukushima

2009-01-01

308

Method for compensation of thermally induced modal distortions in the input optical components of gravitational wave interferometers  

Microsoft Academic Search

The next generation of interferometric gravitational wave detectors will employ laser powers approaching 200 W to increase shot-noise limited sensitivity. Optical components that transmit the laser light will exhibit increased thermal lensing induced by bulk absorption and concomitant changes in the material refractive index, resulting in significant changes in the modal characteristics of the beam. Key interferometer components such as

Guido Mueller; Rupal S. Amin; Dave Guagliardo; Donovan McFeron; Ramsey Lundock; David H. Reitze; D. B. Tanner

2002-01-01

309

678 OPTICS LETTERS / Vol. 18, No. 9 / May 1, 1993 Spatially coherent white-light interferometer based on  

E-print Network

678 OPTICS LETTERS / Vol. 18, No. 9 / May 1, 1993 Spatially coherent white-light interferometer (temporally incoherent source or white light) is as good as ultrashort-pulse lasers for high-resolution linear-diode-laser-based white-light in- terferometer can be used for optical reflectometry with a resolution as great as 10 ,um

310

Imaging interferometers for analysis of Thomson scattered spectraa)  

NASA Astrophysics Data System (ADS)

Polarization interferometers have some potential efficiency advantages for imaging Thomson scattering spectral analysis. In this article we present a number of designs for high-efficiency imaging polarization interferometers for Thomson scattering spectral analysis. The use of high-efficiency crystal polarizing beamsplitters (both displacement and angle) results in low-loss complementary passbands (no edge losses), simple imaging systems, and wide field of view. The efficiency and relative merits of both multiple-filter and dispersive-type configurations are being assessed before installation on the JT-60U ruby-laser Thomson scattering system. Light is transferred from the viewing port via a linear array of optical fiber bundles which will be imaged through the interferometer onto the photocathode of an intensified charge coupled device camera. Because of the broadband nature of the Thomson light, the optical delays required to Fourier analyze the spectrum are quite small. This leads to compact multicolor or dispersive systems based on combinations of Wollaston and Savart splitters and traditional waveplates.

Howard, J.; Hatae, T.

2008-10-01

311

Simple Ultra-Low-Cost Undergraduate Holography Using a Modified Michelson Interferometer.  

ERIC Educational Resources Information Center

A technique is presented for producing holograms using equipment which is already in the possesion of the majority of college physics departments, which includes a slightly modified Michelson interferometer, a helium-neon laser, and a long focal-length lens. Production of high quality holograms has been achieved by inexperienced undergraduates…

Rudmin, J. W.; And Others

1980-01-01

312

In-line interferometer for direction-sensitive displacement measurements by optical feedback detection  

Microsoft Academic Search

We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object.

Alvarado Tarun; Julius Jecong; Caesar Saloma

2005-01-01

313

Hand held phase-shifting diffraction Moire interferometer  

DOEpatents

An interferometer is described in which a coherent beam of light is generated within a remote case and transmitted to a hand held unit tethered to said remote case, said hand held unit having optical elements for directing a pair of mutually coherent collimated laser beams at a diffraction grating. Data from the secondary or diffracted beams are then transmitted to a separate video and data acquisition system for recording and analysis for load induced deformation or for identification purposes. Means are also provided for shifting the phase of one incident beam relative to the other incident beam and being controlled from within said remote case. 4 figs.

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

1994-09-20

314

Interferometer for Space Station Windows  

NASA Technical Reports Server (NTRS)

Inspection of space station windows for micrometeorite damage would be a difficult task insitu using current inspection techniques. Commercially available optical profilometers and inspection systems are relatively large, about the size of a desktop computer tower, and require a stable platform to inspect the test object. Also, many devices currently available are designed for a laboratory or controlled environments requiring external computer control. This paper presents an approach using a highly developed optical interferometer to inspect the windows from inside the space station itself using a self- contained hand held device. The interferometer would be capable as a minimum of detecting damage as small as one ten thousands of an inch in diameter and depth while interrogating a relatively large area. The current developmental state of this device is still in the proof of concept stage. The background section of this paper will discuss the current state of the art of profilometers as well as the desired configuration of the self-contained, hand held device. Then, a discussion of the developments and findings that will allow the configuration change with suggested approaches appearing in the proof of concept section.

Hall, Gregory

2003-01-01

315

Sensitivity investigation of instantaneous complex conjugate resolved swept-source OCT using a Mach-Zehnder interferometer with a 3x3 fiber coupler  

NASA Astrophysics Data System (ADS)

We present an instantaneous complex conjugate resolved swept-source optical coherence tomography (SS-OCT) using a 3x3 optical fiber coupler. A dual-channel balanced (dual-balanced) detection with phase shifted signals was formed by a Mach-Zehnder interferometer (MZI) with a 3x3 and one or more 2x2 optical fiber couplers. Non-complementary phase components of the complex interferometric signals from the dual-balanced detector were converted to quadrature components by a simple trigonometric formula. A-scans with resolved complex conjugate artifact were obtained by inverse Fourier transformation. This approach provides a two times increase in the effective depth of image. Two configurations of the quadrature interferometers based on Mach-Zehnder interferometer (MZI) topology are investigated. The first configuration with one 3x3 and three 2x2 optical fiber couplers is arranged for DC signal removal, and the second configuration with one 3x3 and one 2x2 optical fiber couplers is organised for optical power optimisation. We focus on the comparison of the measured sensitivity and complex conjugate artifact suppression between the two configurations of the quadrature MZI SS-OCT system. The suppression of complex conjugate artifact of >25 dB for the second configuration, i.e. 3x3 SS-OCT with one 2x2 fiber couplers, was obtained, which is 6 dB higher than that for the first configuration, i.e. 3x3 SS-OCT with three 2x2 coupler. The reason for the performance of the second configuration over the first one is the optimisation of the optical power handling. In the second configuration, the DC components of the complex interferometric signal caused by unequal optical power level have been removed by the balanced detection and DC noise subtraction.

Mao, Youxin; Flueraru, Costel; Sherif, Sherif; Chang, Shoude; Murdock, E.

2007-06-01

316

Tunable semiconductor lasers  

NASA Technical Reports Server (NTRS)

Tunable semiconductor lasers are disclosed requiring minimized coupling regions. Multiple laser embodiments employ ring resonators or ring resonator pairs using only a single coupling region with the gain medium are detailed. Tuning can be performed by changing the phase of the coupling coefficient between the gain medium and a ring resonator of the laser. Another embodiment provides a tunable laser including two Mach-Zehnder interferometers in series and a reflector coupled to a gain medium.

Taghavi-Larigani, Shervin (Inventor); Vanzyl, Jakob J. (Inventor); Yariv, Amnon (Inventor)

2006-01-01

317

Quantum Noise in Differential-type Gravitational-wave Interferometer and Signal Recycling  

E-print Network

There exists the standard quantum limit (SQL), derived from Heisenberg's uncertainty relation, in the sensitivity of laser interferometer gravitational-wave detectors. However, in the context of a full quantum-mechanical approach, SQL can be overcome using the correlation of shot noise and radiation-pressure noise. So far, signal recycling, which is one of the methods to overcome SQL, is considered only in a recombined-type interferometer such as Advanced-LIGO, LCGT, and GEO600. In this paper, we investigated quantum noise and the possibility of signal recycling in a differential-type interferometer. As a result, we found that signal recycling is possible and creates at most three dips in the sensitivity curve of the detector. Then, taking advantage of the third additional dip and comparing the sensitivity of a differential-type interferometer with that of a next-generation Japanese GW interferometer, LCGT, we found that SNR of inspiral binary is improved by a factor of 1.43 for neutron star binary, 2.28 for 50 M_sun black hole binary, and 2.94 for 100 M_sun black hole binary. We also found that power recycling to increase laser power is possible in our signal-recycling configuration of a detector.

Atsushi Nishizawa; Seiji Kawamura; Masa-aki Sakagami

2007-05-31

318

A new method for determining the plasma electron density using optical frequency comb interferometer.  

PubMed

A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density. PMID:24784608

Arakawa, Hiroyuki; Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

2014-04-01

319

POINTS: a small low-cost spaceborne astrometric optical interferometer  

NASA Astrophysics Data System (ADS)

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometry from space. In a five-year mission, POINTS could yield, e.g., a 1% Cepheid distance scale, galactic mass distribution, knowledge of cluster dynamics, and stellar masses and luminosities. POINTS could also perform a deep search for other planetary systems. The search would have a reliable detection threshold that would reach Earth-like planets for a few of the stars and be less than an order higher for over 1000 stars. The detection of longer period planets would benefit from a ten-year mission. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. POINTS 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 two baselines. The nominal design has baselines of 2 m, subapertures of 35 cm, and targets separated by 87 to 93 deg. 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 accuracy. On each side of the interferometer, there are only three (interferometrically critical) optical surfaces preceding the beamsplitter or its fold flat. POINTS is small, agile, and mechanically simple. It would prove much of the technology for future spaceborne interferometers. The development of POINTS has been supported by the Smithsonian Institution, NASA, JPL, Itek, and TRW. Present address: USNO, Washington, DC - Present address: Ball Aerospace & Technologies Corp., Boulder, CO

Reasenberg, R. D.; Babcock, R. W.; Murison, M. A.; Noecker, M. C.; Phillips, J. D.; Schumaker, B. L.; Ulvestad, J. S.; McKinley, W.; Zielinski, R. J.; Lillie, C. F.

1995-12-01

320

CIST....CORRTEX interferometer simulation test  

SciTech Connect

Testing was performed in order to validate and cross calibrate an RF interferometer and the crush threshold of cable. Nitromethane was exploded (inside of PVC pipe). The explosion was used to crush the interferometer sensor cables which had been placed inside and outside the pipe. Results are described.

Heinle, R.A.

1994-12-01

321

Metrology and pointing for astronomical interferometers  

Microsoft Academic Search

Metrology and pointing will be enabling technologies for a new generation of astronomical missions having large and distributed apertures and delivering unprecedented performance. The UV interferometer Stellar Imager would study stellar dynamos by imaging magnetic activity on the disks of stars in our Galaxy. The X-ray interferometer Black Hole Imager would study strong gravity physics and the formation of jets

James D. Phillips; Kenneth G. Carpenter; Keith C. Gendreau; Margarita Karovska; Philip E. Kaaret; Robert D. Reasenberg

2004-01-01

322

Quadrature subunits in directionally selective simple cells: spatiotemporal interactions.  

PubMed

I explore here whether linear mechanisms can explain directional selectivity (DS) in simple cells of the cat's striate cortex, a question suggested by a recent upswing in popularity of linear DS models. I chose a simple cell with a space-time inseparable receptive field (RF), i.e. one that shows gradually shifting latency across space, as the RF type most likely to depend on linear mechanisms of DS. However, measured responses of the cell to a moving bar were less modulated, and extended over a larger spatial region than predicted by two different popular "linear" models. They also were more DS in exhibiting a higher ratio of total spikes for the preferred direction. Each of the two models used for comparison has a single "branch" with a single spatiotemporally inseparable linear filter followed by a threshold, hence, a- "1-branch" model. Nonlinear interactions between pairs of bars in a 2-bar linear superposition test of the cell also disagreed in time-course with those of the 1-branch models. The only model whose 1-bar and 2-bar predictions matched the measured cell (including a complete "4-branch" motion energy model that matches complex cells) has two branches that differ in phase by about 90 deg, i.e. in quadrature. Each branch has its own threshold that helps define the preceding spatiotemporal unit as a subunit even after the outputs of the two branches are summed. As subunit phases differ by only 90 deg, flashing bar responses of the 2-subunit model are similar to those of the 1-subunit model. Therefore, the number of subunits is hidden from view when testing with a conventional stationary bar. In summary, movement responses and nonlinear interactions between pairs of bars in the measured cell matched those of the 2-subunit model, while they disagreed with the popular 1-subunit model. Thus, multiple nonlinear subunits appear to be necessary for DS, even in simple cortical cells. PMID:9147487

Emerson, R C

1997-01-01

323

Extended Gaussian quadratures for functions with an end-point singularity of logarithmic type  

NASA Astrophysics Data System (ADS)

The extended Gaussian quadrature rules are shown to be an efficient tool for numerical integration of wide class of functions with singularities of logarithmic type. The quadratures are exact for the functions pol1n-1(x)+lnx pol2n-1(x), where pol1n-1(x) and pol2n-1(x) are two arbitrary polynomials of degree n-1 and n is the order of the quadrature formula. We present an implementation of numerical algorithm that calculates the nodes and the weights of the quadrature formulas, provide a Fortran code for numerical integration, and test the performance of different kinds of Gaussian quadratures for functions with logarithmic singularities. Catalogue identifier: AETP_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETP_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 2535 No. of bytes in distributed program, including test data, etc.: 39 963 Distribution format: tar.gz Programming language: Mathematica, Fortran. Computer: PCs or higher performance computers. Operating system: Linux, Windows, MacOS. RAM: Kilobytes. Classification: 4.11. Nature of problem: Quadrature formulas for numerical integration, effective for a wide class of functions with end-point singularities of logarithmic type. Solution method: The method of solution is based on the algorithm developed in Ref. [1] with some modifications. Running time: Milliseconds to minutes. J. Ma, V. Rokhlin, S. Wandzura, Generalized Gaussian quadrature rules for systems of arbitrary functions, Soc. Indust. Appl. Math. J. Numer. Anal. 33 (3) (1996) 971-996.

Pachucki, K.; Puchalski, M.; Yerokhin, V. A.

2014-11-01

324

Beam shuttering interferometer and method  

DOEpatents

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Deason, Vance A. (Idaho Falls, ID); Lassahn, Gordon D. (Idaho Falls, ID)

1993-01-01

325

Beam shuttering interferometer and method  

DOEpatents

A method and apparatus resulting in the simplification of phase shifting interferometry by eliminating the requirement to know the phase shift between interferograms or to keep the phase shift between interferograms constant. The present invention provides a simple, inexpensive means to shutter each independent beam of the interferometer in order to facilitate the data acquisition requirements for optical interferometry and phase shifting interferometry. By eliminating the requirement to know the phase shift between interferograms or to keep the phase shift constant, a simple, economical means and apparatus for performing the technique of phase shifting interferometry is provide which, by thermally expanding a fiber optical cable changes the optical path distance of one incident beam relative to another.

Deason, V.A.; Lassahn, G.D.

1993-07-27

326

Miniature interferometer for refractive index measurement in microfluidic chip  

NASA Astrophysics Data System (ADS)

The design and development of the miniaturized interferometer for measurement of the refractive index or concentration of sub-microliter volume aqueous solution in microfludic chip is presented. It is manifested by a successful measurement of the refractive index of sugar-water solution, by utilizing a laser diode for light source and the small robust instrumentation for practical implementation. Theoretically, the measurement principle and the feasibility of the system are analyzed. Experimental device is constructed with a diode laser, lens, two optical plate and a complementary metal oxide semiconductor (CMOS). Through measuring the positional changes of the interference fringes, the refractive index change are retrieved. A refractive index change of 10-4 is inferred from the measured image data. The entire system is approximately the size of half and a deck of cards and can operate on battery power for long time.

Chen, Minghui; Geiser, Martial; Truffer, Frederic; Song, Chengli

2012-12-01

327

Porous silicon integrated Mach-Zehnder interferometer waveguide for biological and chemical sensing.  

PubMed

Optical waveguides comprised of nanoporous materials are uniquely suited for on-chip sensing applications, because they allow for a target chemical or analyte to directly infiltrate the optical material that comprises the core of the waveguide. We describe here the fabrication and characterization of nanoporous waveguides, and demonstrate their usefulness in measuring small changes in refractive index when exposed to a test analyte. We use a process of electrochemical etching and laser oxidation to produce channel waveguides and integrated on-chip Mach-Zehnder structures, and we compare the responsivity and interferometric stability of the integrated sensor to that of a fiber-based interferometer. We quantify the detection capability by selectively applying isopropanol to a 200 ?m length waveguide segment in one arm of the interferometer, which produces a phase shift of 9.7 ?. The integrated interferometer is shown to provide a more stable response in comparison to a comparable fiber-based implementation. PMID:24105496

Kim, Kyowon; Murphy, Thomas E

2013-08-26

328

In-line interferometer for direction-sensitive displacement measurements by optical feedback detection  

SciTech Connect

We demonstrate a compact in-line interferometer for direction-sensitive displacement measurement by optical feedback detection with a semiconductor laser (SL) light source. Two reflected beams from a semitransparent reference mirror and a reflecting test object interfere in the SL medium, causing a variation in its output power. The reference mirror is located between the SL output facet and the test object. The performance of the interferometer is investigated numerically and experimentally to determine its optimal operating conditions. We have verified the operating conditions where the behavior of the SL output power profile could indicate accurately the displacement magnitude and direction of the moving test object. The profile behavior is robust against variations in optical feedback and scale of the interferometer configuration.

Tarun, Alvarado; Jecong, Julius; Saloma, Caesar

2005-12-01

329

Nonclassical correlations between photon number and quadrature components of the light field  

E-print Network

Finite resolution quantum nondemolition (QND) measurements allow a determination of light field properties while preserving some of the original quantum coherence of the input state. It is thus possible to measure correlations between the photon number and a quadrature component of the same light field mode. Nonclassical features emerge as photon number quantization is resolved. In particular, a strong anti-correlation of quantization and coherence is observable in QND measurements of photon number, and a correlation between measurement induced quantum jumps and quadrature component measurement results is obtained in QND measurements of quadrature fluctuations in the photon vacuum. Such nonclassical correlations represent fundamental quantum properties of the light field and may provide new insights into the nature of quantization itself.

Holger F. Hofmann

2000-04-19

330

Effect of angular quadrature on results of two-dimensional space power reactor shield calculations.  

NASA Technical Reports Server (NTRS)

Study of the effect of angular quadrature on the results of two-dimensional transport calculations made to evaluate radiation environment in the vicinity of a shielded space power reactor. The application considered is for a manned space-station; crew shielding must be provided within a 25 deg cone angle. The asymmetric shield layout is evaluated using the two-dimensional transport code DOT. Within the shield, an S sub 6 angular quadrature yields satisfactory results. For regions where the ray effect may occur it is not apparent that an S sub 10 quadrature is adequate. Anomalies in results due to transport of particles in a void and necessary geometric approximations were observed.

Connolley, D. J.; Lahti, G. P.

1971-01-01

331

Phase measurement device using inphase and quadrature components for phase estimation  

NASA Technical Reports Server (NTRS)

A phasemeter for estimating the phase of a signal. For multi-tone signals, multiple phase estimates may be provided. An embodiment includes components operating in the digital domain, where a sampled input signal is multiplied by cosine and sine terms to provide estimates of the inphase and quadrature components. The quadrature component provides an error signal that is provided to a feedback loop, the feedback loop providing a model phase that tends to track the phase of a tone in the input signal. The cosine and sine terms are generated from the model phase. The inphase and quadrature components are used to form a residual phase, which is added to the model phase to provide an estimate of the phase of the input signal. Other embodiments are described and claimed.

Halverson, Peter G. (Inventor); Ware, Brent (Inventor); Shaddock, Daniel A. (Inventor); Spero, Robert E. (Inventor)

2009-01-01

332

Low-Latitude Solar Wind During the Fall 1998 SOHO-Ulysses Quadrature  

NASA Technical Reports Server (NTRS)

Solar and Heliospheric Observatory (SOH0)-Ulysses quadratures occur when the SOHO-Sun-Ulysses-included angle is 90 deg. These offer the opportunity to directly compare properties of plasma parcels, observed by SOHO [Dorningo et al.] in the low corona, with properties of the same parcels measured, in due time, in situ, by Ulysses [ Wenzel et al]. We refer the reader to Suess et al. for an extended discussion of SOHO-Ulysses quadrature geometry. Here it suffices to recall that there are two quadratures per year, as SOHO makes its one-year revolution around the Sun. This, because SOHO is at the L1 Lagrangian point, in essentially the same place as the Earth, while Ulysses is in a near-polar -5-year solar orbit with a perihelion of 1.34 AU and aphelion of 5.4 AU.

Poletto, G.; Suess, S. T.; Biesecker, D. A.; Esser, R.; Gloeckler, G.; Ko, Y.-K.; Zurbuchen, T. H.

2002-01-01

333

Polarization mismatch errors in radio phase interferometers.  

NASA Technical Reports Server (NTRS)

An analysis is presented which deals with the effects of polarization mismatch errors on the accuracy of a phase interferometer used for position location of unknown emitters relative to known calibration emitters. Closed-form expressions for the induced phase difference between interferometer antennas are derived for several combinations of receiving and transmitting antenna polarizations. Errors contributed by mechanical misalignment between antennas, as well as effects of power loss attributable to polarization mismatch, are also considered. The analysis leads to the conclusion that circularly polarized interferometer and transmitter antennas are best suited for the position location application, if it is assumed that polarization tracking of the interferometer antennas is not available. It is shown that a reasonable amount of ellipticity can be tolerated before the phase error becomes significant.

Muehldorf, E. I.; Teichman, M. A.; Kramer, E.

1972-01-01

334

The effect of rotations on Michelson interferometers  

NASA Astrophysics Data System (ADS)

In the contest of the special theory of relativity, it is shown that uniform rotations induce a phase shift in Michelson interferometers. The effect is second order in the ratio of the interferometer's speed to the speed of light, further suppressed by the ratio of the interferometer's arms length to the radius of rotation and depends on the interferometer's position in the co-rotating frame. The magnitude of the phase shift is just beyond the sensitivity of turntable rotated optical resonators used in present tests of Lorentz invariance. It grows significantly large in Earth's rotated kilometer-scale Fabry-Perot enhanced interferometric gravitational-wave detectors where it appears as a constant bias. The effect can provide the means of sensing center and radius of rotations.

Maraner, Paolo

2014-11-01

335

Active noise cancellation in a suspended interferometer  

E-print Network

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 ...

Driggers, Jennifer C.

336

GRATING INTERFEROMETER THE FAR-INFRARED  

E-print Network

A LAMELLAR FOR GRATING INTERFEROMETER THE FAR-INFRARED R. L. HENRYand D. B. TANNER Department Of and Dowl- ing,(s) Nolt, Kirby, Lytle and Sievers,@' and Milward."' 163 #12;R. L. HENRY and D. B. TANNER Fig

Tanner, David B.

337

Quantum correlations in a noisy neutron interferometer  

E-print Network

We investigate quantum coherences in the presence of noise by entangling the spin and path degrees of freedom of the output neutron beam from a noisy three-blade perfect crystal neutron interferometer. We find that in the ...

Wood, Christopher J.

338

An overview of the IRAM interferometer  

Microsoft Academic Search

The general characteristics of the IRAM interferometer are described. The interferometer has three antennas movable on a quasi-T-shaped track and two front-ends per antenna on two orthogonal linear polarizations. The calibration system has 30 Hz chopping between sky and ambient load and LO reference and IF return on one single coaxial cable per station and per front end. The first

L. Weliachew

1985-01-01

339

Quantum theory of the nonlinear interferometer  

SciTech Connect

A full quantum theory of the Mach-Zehnder interferometer with nonlinear Kerr media in both arms is presented. The nonlinear operator equations can be integrated, and the result can be normal-ordered. This permits the evaluation of the factorial moments of the photon number to all orders of the nonlinearity. Various excitations and phase biases are studied. The degree of squeezing by the interferometer is determined.

Shirasaki, M.; Haus, H.A.; Wong, D.L.

1989-01-01

340

Interferometer for measuring the dynamic surface topography of a human tear film  

NASA Astrophysics Data System (ADS)

The anterior refracting surface of the eye is the thin tear film that forms on the surface of the cornea. Following a blink, the tear film quickly smoothes and starts to become irregular after 10 seconds. This irregularity can affect comfort and vision quality. An in vivo method of characterizing dynamic tear films has been designed based upon a near-infrared phase-shifting interferometer. This interferometer continuously measures light reflected from the tear film, allowing sub-micron analysis of the dynamic surface topography. Movies showing the tear film behavior can be generated along with quantitative metrics describing changes in the tear film surface. This tear film measurement allows analysis beyond capabilities of typical fluorescein visual inspection or corneal topography and provides better sensitivity and resolution than shearing interferometry methods. The interferometer design is capable of identifying features in the tear film much less than a micron in height with a spatial resolution of about ten microns over a 6 mm diameter. This paper presents the design of the tear film interferometer along with the considerations that must be taken when designing an interferometer for on-eye diagnostics. Discussions include eye movement, design of null optics for a range of ocular geometries, and laser emission limits for on-eye interferometry.

Primeau, Brian C.; Greivenkamp, John E.

2012-03-01

341

Design of a nonlinear, thin-film Mach-Zehnder interferometer  

NASA Technical Reports Server (NTRS)

A Mach-Zehnder interferometer consists of a 3 db splitter to create the two separate beams, an optical path difference to control the interference between the two beams and another 3 db coupler to reconstruct the output signal. The performance of each of its components has been investigated. Since an optical path difference is required for its function, the performance of a Mach-Zehnder interferometer is not very sensitive to construction parameters. In designing an interferometer for this work, the following considerations must be observed: the interferometer is to be made of phthalocyanine or polydiacetylene thin films; in order to avoid thermal effects which are slower, the wavelength chosen must not be absorbed in either one or two photon processes; the wavelength chosen must be easily generated (laser line); the spacing between the interferometer arms must be large enough to allow attachment of external electrodes; the vapor deposition apparatus can accept disks no larger than 0.9 inches; and the design must allow multiple layer coating in order to determine the optimum film thickness or to change to another substance.

Pearson, Earl F.

1996-01-01

342

Keck Interferometer Nuller science highlights  

NASA Astrophysics Data System (ADS)

We report here on some of the major astronomical observations obtained by the Keck Interferometer Nuller (KIN), the high dynamic range instrument recombining the Keck Telescopes at wavelengths of 8 to 13 microns. A few science targets were observed during the commissioning phase (2004-2007). These early observations aimed at demonstrating the KIN’s ability to spatially resolve and characterize circumstellar dust emission around a variety of targets, ranging from evolved stars to young debris disks. Science operations started then in 2008 with the more demanding KIN exozodi key science programs, augmented by observations of YSOs and hot debris disks between 2009 and 2011. The last KIN observations were gathered in 2011B, and the interpretation of some of the results depicted here is still preliminary (exo-zodi survey) or pending (complicated behavior observed in YSOs). We discuss in particular the initial results of the KIN’s exo-zodi observations, which targeted a total of 40 nearby main sequence single stars. We look for trends in this sample, searching for possible correlations between the measured KIN excesses and basic stellar properties such as spectral type or the presence of dust inferred from separate observations.

Mennesson, Bertrand; Millan-Gabet, Rafael; Colavita, M. M.; Serabyn, E.; Hinz, P.; Kuchner, M.; Liu, W.; Barry, R.; Stark, C.; Ragland, S.; Woillez, J.; Traub, W.; Absil, O.; Defrère, Denis; Augereau, J. C.; Lebreton, J.

2012-07-01

343

Optical Ramsey spectroscopy in a rotating frame: Sagnac effect in a matter-wave interferometer  

SciTech Connect

A calcium atomic beam excited in an optical Ramsey geometry was rotated about an axis perpendicular to the plane defined by the laser beams and the atomic beam. A frequency shift of the Ramsey fringes of several kHz has been measured which is proportional to the rotation frequency of the apparatus and to the distance between the laser beams. The results can be interpreted in three equivalent ways as the Sagnac effect in a calcium-atomic-beam interferometer: in the rotating frame of the laser beams either along straight paths or along the curved trajectories of the atoms, or in the inertial atomic frame.

Riehle, F.; Kisters, T.; Witte, A.; Helmcke, J. (Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-3300 Braunschweig, Germany (DE)); Borde, C.J. (Institut Henri Poincare, Universite Pierre et Marie Curie, Paris, France (FR) Laboratoire de Physique des Lasers, Universite Paris, Villetaneuse, France (FR))

1991-07-08

344

Apparatus and method for laser velocity interferometry  

DOEpatents

An apparatus and method for laser velocity interferometry employing a fixed interferometer cavity and delay element. The invention permits rapid construction of interferometers that may be operated by those non-skilled in the art, that have high image quality with no drift or loss of contrast, and that have long-term stability even without shock isolation of the cavity.

Stanton, Philip L. (Bernalillo County, NM); Sweatt, William C. (Albuquerque, NM); Crump, Jr., O. B. (Albuquerque, NM); Bonzon, Lloyd L. (Albuquerque, NM)

1993-09-14

345

A comparison of flow tracking techniques: spatial quadrature with phase-sensitive axial demodulation versus speckle tracking  

Microsoft Academic Search

Spatial quadrature and speckle tracking are both techniques which extend the estimation of flow velocity or tissue motion velocity to two or three dimensions. The authors applied both under similar experimental conditions to assess and compare their performance. They also describe a new spatial quadrature processor that obviates the need for axial alignment under conditions of mixed axial-lateral flow. This

M. E. Anderson; L. N. Bohs; S. C. Gebhart

1999-01-01

346

A thermally scanned all-fiber interferometer based on vanadium-doped fiber  

NASA Astrophysics Data System (ADS)

This paper presents an all-optically controlled, all-fiber optical path-length modulator. The presented system takes advantage of the heating effect induced within vanadium-doped fiber through laser excitation. It can be applied in various applications, for example in white-light interferometry. The system consists of a Michelson interferometer with vanadium-doped fiber in one arm, a 980 nm excitation high-power laser diode, and 1310/1550 nm signal sources or channels. Due to the spectral-absorption properties of vanadium ions in silica, the absorbed optical power emitted by the 980 nm source is mostly converted via a non-radiative relaxation process into heat within the vanadium-doped fiber. A rise of fiber core temperature causes the fiber core refractive index to change and consequently, a change in the optical path difference of the interferometer. The extinction laser diode operates in pulse mode for continuous scanning of the white-light interferometer. The vanadium-doped fiber is, therefore, periodically heated and self-cooled. The optical path difference of the scanning interferometer is simultaneously measured using a high-coherence source that provides the needed reference trace. The achieved modulated optical path is over 150 ?m, with a system time constant of below 1 s. This all-optical configuration of the scanning interferometer allows for the remote and electrically passive control of the optical path length differences in various fiber-optic systems. In particular, the proposed design would be suitable as an interrogation system for various sensors, where an absolute optical path length variation/measurement is required.

Matjašec, Žiga; ?ampelj, Stanislav; ?onlagi?, Denis

2012-04-01

347

Laser barometer  

DOEpatents

A pressure measuring instrument that utilizes the change of the refractive index of a gas as a function of pressure and the coherent nature of a laser light to determine the barometric pressure within an environment. As the gas pressure in a closed environment varies, the index of refraction of the gas changes. The amount of change is a function of the gas pressure. By illuminating the gas with a laser light source, causing the wavelength of the light to change, pressure can be quantified by measuring the shift in fringes (alternating light and dark bands produced when coherent light is mixed) in an interferometer.

Abercrombie, Kevin R. (Westminster, CO); Shiels, David (Thornton, CO); Rash, Tim (Aurora, CO)

2001-02-06

348

Use of a Radial Shear Interferometer as a Self Reference Interferometer in Adaptive Optics  

Microsoft Academic Search

A radial shear interferometer (rsi) is produced by the interference of two different sized images of the test wavefront. When the center of curvature of the wavefronts are at the same location, they produce a shear in the radial direction. The rsi has a unique attribute which distinguishes it from other wavefront shear interferometers. For sufficiently large shears S, where

R. Tansey; A. Phenis; K. Shu

2006-01-01

349

NUMERICAL APPROXIMATION OF SEMI-INTEGRALS AND SEMIDERIVATIVES BY PRODUCT QUADRATURE RULES  

EPA Science Inventory

This paper is concerned with the numerical calculation of the semi-integral and semiderivative of a function f, whose values f (xj) are known on a discrete set of abscissas 0 = x(1) < x(2) < ... < x(n). A family of product quadrature rules is developed to approximate the semi-int...

350

A broadband digital diode phase shifter using a matrix interconnection of quadrature hybrid couplers, phase 1  

Microsoft Academic Search

An analysis of 2-bit digital diode phase shifter using four PIN diodes and a matrix arrangement of four 3-db quadrature hybrids has been performed. The 0 degrees, 90 degrees, 180 degrees, and 270 degrees differential phase states were achieved by using the 90 degrees phase relationship of the hybrid coupler outputs and proper combinations of open circuits and short circuits

C. W. Young Jr.

1975-01-01

351

Implementation of the quadrature method of moments in CFD codes for aggregation–breakage problems  

Microsoft Academic Search

In this work the quadrature method of moments (QMOM) is implemented in a commercial computational fluid dynamics (CFD) code (FLUENT) for modeling simultaneous aggregation and breakage. Turbulent and Brownian aggregation kernels are considered in combination with different breakage kernels (power law and exponential) and various daughter distribution functions (symmetric, erosion, uniform). CFD predictions are compared with experimental data taken from

Daniele L. Marchisio; R. Dennis Vigil; Rodney O. Fox

2003-01-01

352

A high-pass detunable quadrature birdcage coil at high-field  

E-print Network

and quadrature mode loaded with saline, oil and CuSO4 phantom was measured on the bench and the scanner. The coil performance was compared to two other birdcage coils in the lab. It was found that the unshielded trombone coil that was 3 times smaller in volume...

Kampani, Vishal Virendra

2008-10-10

353

Denoising performance of modified dual-tree complex wavelet transform for processing quadrature embolic Doppler signals.  

PubMed

Quadrature signals are dual-channel signals obtained from the systems employing quadrature demodulation. Embolic Doppler ultrasound signals obtained from stroke-prone patients by using Doppler ultrasound systems are quadrature signals caused by emboli, which are particles bigger than red blood cells within circulatory system. Detection of emboli is an important step in diagnosing stroke. Most widely used parameter in detection of emboli is embolic signal-to-background signal ratio. Therefore, in order to increase this ratio, denoising techniques are employed in detection systems. Discrete wavelet transform has been used for denoising of embolic signals, but it lacks shift invariance property. Instead, dual-tree complex wavelet transform having near-shift invariance property can be used. However, it is computationally expensive as two wavelet trees are required. Recently proposed modified dual-tree complex wavelet transform, which reduces the computational complexity, can also be used. In this study, the denoising performance of this method is extensively evaluated and compared with the others by using simulated and real quadrature signals. The quantitative results demonstrated that the modified dual-tree-complex-wavelet-transform-based denoising outperforms the conventional discrete wavelet transform with the same level of computational complexity and exhibits almost equal performance to the dual-tree complex wavelet transform with almost half computational cost. PMID:24048958

Serbes, Gorkem; Aydin, Nizamettin

2014-01-01

354

Quadrature Subharmonic Coupled Oscillators for a 60GHz SiGe Scalable Phased Array  

E-print Network

Quadrature Subharmonic Coupled Oscillators for a 60GHz SiGe Scalable Phased Array James F, CA 91125 Abstract -- This paper describes an integrated coupled oscillator array in Si are tiled to form larger arrays. A 2x2 oscillator array for a 60GHz transmitter is designed with integrated

Hajimiri, Ali

355

IEEE TRANS. CIRCUITS AND SYSTEMS|I, FEBRUARY 2001 0 Quadrature Chaos Shift Keying  

E-print Network

performance as BPSK (Binary Phase Shift Keying) with the same bandwidth occupation, but double data rateIEEE TRANS. CIRCUITS AND SYSTEMS|I, FEBRUARY 2001 0 Quadrature Chaos Shift Keying: Theory propose a multilevel version of the Di#11;erential Chaos Shift Keying (DCSK) telecommunication system

Galias, Zbigniew

356

QUADRATURE CHAOS SHIFT KEYING Zbigniew Galias and Gian Mario Maggio y  

E-print Network

to the BPSK (binary phase shift keying) modulation scheme [1]. In BPSK one transmits a sin(#1;) function at the receiver. One of the modifications of BPSK is the QPSK (quadra­ ture phase shift keying) scheme, whichQUADRATURE CHAOS SHIFT KEYING Zbigniew Galias #3; and Gian Mario Maggio y Institute for Nonlinear

Galias, Zbigniew

357

VIBRATION ANALYSIS OF ELASTICALLY SUPPORTED TURBOMACHINERY BLADES BY THE MODIFIED DIFFERENTIAL QUADRATURE METHOD  

Microsoft Academic Search

The modified differential quadrature method (MDQM) is proposed for vibration analysis of elastically supported turbomachinery blades. A pre-twisted blade with varying cross-section is modelled as a Timoshenko beam. The blade is supported by two translational springs and three rotational springs at each end, and has a shroud that is modelled as a mass at the tip of the blade. The

S.-T. CHOI; Y.-T. CHOU

2001-01-01

358

Vibration Analysis of Elastically Supported Turbomachinery Blades by the Modified Differential Quadrature Method  

Microsoft Academic Search

The modified differential quadrature method (MDQM) is proposed for vibration analysis of elastically supported turbomachinery blades. A pre-twisted blade with varying cross-section is modelled as a Timoshenko beam. The blade is supported by two translational springs and three rotational springs at each end, and has a shroud that is modelled as a mass at the tip of the blade. The

S.-T. Choi; Y.-T. Chou

2001-01-01

359

Quadrature sampling phase detection John Howard and Hans-Peter Landgraf  

E-print Network

for a digitizing instrument that measures directly the in-phase and quadrature components of the modulation in many applications and areas of research. Numerous electronic methods for de- modulation of the carrier reference frequency signal using a tracking phase- locked loop (PLL) and binary counter. As shown in Sec. II

Howard, John

360

Symmetrical modified dual tree complex wavelet transform for processing quadrature Doppler ultrasound signals.  

PubMed

Dual-tree complex wavelet transform (DTCWT), which is a shift invariant transform with limited redundancy, is an improved version of discrete wavelet transform. Complex quadrature signals are dual channel signals obtained from the systems employing quadrature demodulation. An example of such signals is quadrature Doppler signal obtained from blood flow analysis systems. Prior to processing Doppler signals using the DTCWT, directional flow signals must be obtained and then two separate DTCWT applied, increasing the computational complexity. In this study, in order to decrease computational complexity, a symmetrical modified DTCWT algorithm is proposed (SMDTCWT). A comparison between the new transform and the symmetrical phasing-filter technique is presented. Additionally denoising performance of SMDTCWT is compared with the DWT and the DTCWT using simulated signals. The results show that the proposed method gives the same output as the symmetrical phasing-filter method, the computational complexity for processing quadrature signals using DTCWT is greatly reduced and finally the SMDTCWT based denoising outperforms conventional DWT with same computational complexity. PMID:22255416

Serbes, G; Aydin, N

2011-01-01

361

Convergence acceleration of Jacobi-Gauss quadrature formulae for analytic functions with poles  

Microsoft Academic Search

Let (Sn) be the sequence given by the Jacobi-Gauss quadrature method when the integrand is an analytic function with different kinds of poles located outside the interval of integration, and S its limit. We give an asymptotic representation of the errors S ? Sn and of Sn+1 ? Sn, which leads to build other sequences which give a better approximation

M. Kzaz

1995-01-01

362

A quadrature-based moment method for gas-particle flows  

E-print Network

A quadrature-based moment method for gas-particle flows Alberto Passalacqua, Rodney O. Fox - College Park Alberto Passalacqua (Iowa State University) QMOM for polydisperse gas-particle flows Annual-laden channel flow Alberto Passalacqua (Iowa State University) QMOM for polydisperse gas-particle flows Annual

Maryland at College Park, University of

363

Utilization of Mechanical Quadrature in Silicon MEMS Vibratory Gyroscope to Increase and  

E-print Network

Utilization of Mechanical Quadrature in Silicon MEMS Vibratory Gyroscope to Increase and Expand of the long term in-run bias stability of Coriolis vibratory gyroscopes. The approach is based on utilization of the mechanical quadra- ture error in gyroscopes to compensate for variation in system parameters. The proposed

Tang, William C

364

Violations of entropic Bell inequalities with coarse-grained quadrature measurements for continuous-variable states  

NASA Astrophysics Data System (ADS)

It is a long-standing belief, as pointed out by Bell in 1986, that it is impossible to use a two-mode Gaussian state possessing a positive-definite Wigner function to demonstrate nonlocality as the Wigner function itself provides a local hidden-variable model. In particular, when one performs continuous-variable (CV) quadrature measurements upon a routinely generated CV entanglement, namely, the two-mode squeezed vacuum (TMSV) state, the resulting Wigner function is positive-definite and as such, the TMSV state cannot violate any Bell inequality using CV quadrature measurements. We show here, however, that a Bell inequality for CV states in terms of entropies can be quantum mechanically violated by the TMSV state with two coarse-grained quadrature measurements per site within experimentally accessible parameter regime. The proposed CV entropic Bell inequality is advantageous for an experimental test, especially for a possible loophole-free test of nonlocality, as the quadrature measurements can be implemented with homodyne detections of nearly 100% detection efficiency under current technology.

Chen, Zeng-Bing; Fu, Yao; Zhao, Yu-Kang

2014-08-01

365

Violations of entropic Bell inequalities with coarse-grained quadrature measurements for continuous-variable states  

E-print Network

It is a long-standing belief, as pointed out by Bell in 1986, that it is impossible to use a two-mode Gaussian state possessing a positive-definite Wigner function to demonstrate nonlocality as the Wigner function itself provides a local hidden-variable model. In particular, when one performs continuous-variable (CV) quadrature measurements upon a routinely generated CV entanglement, namely, the two-mode squeezed vacuum (TMSV) state, the resulting Wigner function is positive-definite and as such, the TMSV state cannot violate any Bell inequality using CV quadrature measurements. We show here, however, that a Bell inequality for CV states in terms of entropies can be quantum mechanically violated by the TMSV state with two coarse-grained quadrature measurements per site within experimentally accessible parameter regime. The proposed CV entropic Bell inequality is advantageous for an experimental test, especially for a possible loophole-free test of nonlocality, as the quadrature measurements can be implemented with homodyne detections of nearly 100\\% detection efficiency under current technology.

Zeng-Bing Chen; Yao Fu; Yu-Kang Zhao

2014-09-01

366

SIX MYTHS OF POLYNOMIALSIX MYTHS OF POLYNOMIAL INTERPOLATION AND QUADRATUREINTERPOLATION AND QUADRATURE  

E-print Network

SIX MYTHS OF POLYNOMIALSIX MYTHS OF POLYNOMIAL INTERPOLATION AND QUADRATUREINTERPOLATION AND QUADRATURE Nick Trefethen Oxford University SIX MYTHS OF POLYNOMIALSIX MYTHS OF POLYNOMIAL INTERPOLATION interpolant. Equispaced pts: Newton-Cotes. Chebyshev pts: Clenshaw-Curtis. Legendre pts: Gauss. . . #12;MYTH 1

Trefethen, Nick

367

Towards a matter wave interferometer on a sounding rocket  

NASA Astrophysics Data System (ADS)

Applications of coherent matter waves are high resolution interferometers for measuring inertial and gravitational forces as well as testing fundamental physics, for which they may serve as a laser like source with mesoscopic quantum features. Out of possible applications, the test of the principle of equivalence in the quantum domain is selected as a target with the highest scientific interest on timescales of a microgravity experiment at the ISS or on a free flyer (ATV, FOTON or other satellites). The QUANTUS project demonstrated the technological feasibil-ity of coherent matter waves in microgravity. As a next step, the consortium will prepare and procure a sounding rocket mission to demonstrate technologies for matter wave interferome-try based on the broad experience of former developments with experiments in the droptower. Therefore, the experiment has to withstand strong requirements concerning environmental con-ditions (Temperature, shock, environmental pressure, etc.) and needs to be designed to fit in a 600 l volume (diameter 35 cm, length 160 cm). It is considered as an important step towards the technology required for the ISS and other platforms. These experiments will give further insights on the potential of inertial sensors based on atom interferometers and the technology is for example of interest for applications in earth observation and geodesy. They could replace classical techniques relying on test masses and promise a further improvement in the accuracy of such devices.

van Zoest, Tim; Peters, Achim; Ahlers, Holger; Wicht, Andreas; Vogel, Anika; Wenzlawski, Anderas; Deutsch, Christian; Kajari, Endre; Gaaloul, Naceur; Dittus, Hansjürg; Hartwig, Jonas; Herr, Waldemar; Herrmann, Sven; Reichel, Jakob; Bongs, Kai; Koenemann, Thorben; Laemmerzahl, Claus; Lewoczko-Adamczyk, Wojtek; Schiemangk, Max; Müntinga, Hauke; Meyer, Nadine; Rasel, Ernst Maria; Walser, Reinhold; Resch, Andreas; Rode, Christina; Seidel, Stephan; Sengstock, Klaus; Singh, Yeshpal; Schleich, Wolfgang; Ertmer, Wolfgang; Rosenbusch, Peter; Wilken, Tobias; Goeklue, Ertan

368

High resolution Fourier interferometer-spectrophotopolarimeter  

NASA Technical Reports Server (NTRS)

A high-resolution Fourier interferometer-spectrophotopolarimeter is provided using a single linear polarizer-analyzer the transmission axis azimuth of which is positioned successively in the three orientations of 0 deg, 45 deg, and 90 deg, in front of a detector; four flat mirrors, three of which are switchable to either of two positions to direct an incoming beam from an interferometer to the polarizer-analyzer around a sample cell transmitted through a medium in a cell and reflected by medium in the cell; and four fixed focussing lenses, all located in a sample chamber attached at the exit side of the interferometer. This arrangement can provide the distribution of energy and complete polarization state across the spectrum of the reference light entering from the interferometer; the same light after a fixed-angle reflection from the sample cell containing a medium to be analyzed; and the same light after direct transmission through the same sample cell, with the spectral resolution provided by the interferometer.

Fymat, A. L. (inventor)

1976-01-01

369

Quantum correlations in a noisy neutron interferometer  

NASA Astrophysics Data System (ADS)

We investigate quantum coherences in the presence of noise by entangling the spin and path degrees of freedom of the output neutron beam from a noisy three-blade perfect crystal neutron interferometer. We find that in the presence of dephasing noise on the path degree of freedom the entanglement of the output state reduces to 0, however the quantum discord remains nonzero for all noise values. Hence even in the presence of strong phase noise nonclassical correlations persist between the spin and the path of the neutron beam. This indicates that measurements performed on the spin of the neutron beam will induce a disturbance on the path state. We calculate the effect of the spin measurement by observing the changes in the observed contrast of the interferometer for an output beam postselected on a given spin state. In doing so we demonstrate that these measurements allow us to implement a quantum eraser and a which-way measurement of the path taken by the neutron through the interferometer. While strong phase noise removes the quantum eraser, the spin-filtered which-way measurement is robust to phase noise. We experimentally demonstrate this disturbance by comparing the contrasts of the output beam with and without spin measurements of three neutron interferometers with varying noise strengths. This demonstrates that even in the presence of noise that suppresses path coherence and spin-path entanglement, a neutron interferometer still exhibits uniquely quantum behavior.

Wood, Christopher J.; Abutaleb, Mohamed O.; Huber, Michael G.; Arif, Muhammad; Cory, David G.; Pushin, Dmitry A.

2014-09-01

370

AAAS 2010 Annual Meeting February 21, 2010 Extreme Optical Tools and Applications Quantum Noise Limited Lasers and  

E-print Network

Quantum Noise Limited Lasers and The Search for Gravitational Waves Robert L. Byer Department of Applied-time, gravitational waves, travel at the speed of light. Today the Laser Interferometer Gravitational Wave Observatory the Laser Interferometer in Space Antenna, LISA, project, joint between NASA and ESA, will hold its 8th

Byer, Robert L.

371

Mach-Zehnder fiber interferometer for people monitoring  

NASA Astrophysics Data System (ADS)

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 over 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%.

Vasinek, Vladimir; Latal, Jan; Koudelka, Petr; Siska, Petr; Vitasek, Jan; Skapa, Jan

2010-10-01

372

A double common-path heterodyne interferometer for the measurement of flying height modulation  

Microsoft Academic Search

A double common-path differential heterodyne interferometer is proposed to measure the flying height modulation (FHM) of a slider in a hard disk drive. A transverse Zeeman He-Ne laser is employed as the light source and high-speed phase measurement is applied for signal processing. The resolution and the sampling frequency of FH measurement are 0.1 nm and 500 kHz, respectively. According

Dejiao Lin; Zhaoyang Yue; Nanhai Song; Yonggang Meng; Chunyong Yin

2008-01-01

373

Optical image hiding with a modified Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

A method for optical image hiding in a Fresnel domain is proposed. In our modified Mach-Zehnder interferometer (MZI) architecture, an object beam is inserted into the object image to be hidden; the reference beam is produced by laser illumination through the phase plates and the host image. Afterwards, the reference beam is not only restricted to providing phase shifts in the hologram-recording process, but it can also add host image to engage the image hiding function. After two images experience Fresnel diffraction, the diffraction waves are registered as interference patterns on a CCD plane, which resembles a Fresnel diffraction pattern of the host image. The object image is embedded in the host image inside the Fresnel domain. Here, we present a theoretical analysis and preliminary experimental results for this method. It can be widely applied to secure image transmissions at a high speed over the internet and for image watermarking.

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

2014-04-01

374

Quadrature transmit array design using single-feed circularly polarized patch antenna for parallel transmission in MR imaging  

PubMed Central

Quadrature coils are often desired in MR applications because they can improve MR sensitivity and also reduce excitation power. In this work, we propose, for the first time, a quadrature array design strategy for parallel transmission at 298 MHz using single-feed circularly polarized (CP) patch antenna technique. Each array element is a nearly square ring microstrip antenna and is fed at a point on the diagonal of the antenna to generate quadrature magnetic fields. Compared with conventional quadrature coils, the single-feed structure is much simple and compact, making the quadrature coil array design practical. Numerical simulations demonstrate that the decoupling between elements is better than –35 dB for all the elements and the RF fields are homogeneous with deep penetration and quadrature behavior in the area of interest. Bloch equation simulation is also performed to simulate the excitation procedure by using an 8-element quadrature planar patch array to demonstrate its feasibility in parallel transmission at the ultrahigh field of 7 Tesla. PMID:24649430

Pang, Yong; Yu, Baiying; Vigneron, Daniel B.

2014-01-01

375

First results from the J-TEXT high-resolution three-wave polarimeter-interferometer.  

PubMed

A laser-based far-infrared polarimeter-interferometer system utilizing the three-wave technique has been implemented on the J-TEXT tokamak. The polarimeter determines the Faraday effect by measuring the phase difference between two collinear, counter-rotating, circularly polarized laser beams. The first results of the polarimeter-interferometer designed for J-TEXT have been obtained in the most recent J-TEXT experimental campaign. Simultaneous polarimetric and interferometric measurement is achieved, with phase resolution up to 0.1°, at bandwidth of 50 kHz. The temporal resolution, which is dependent on the laser's frequency offset, is ?1 ?s. Continual spatial measurement covering 45 cm (80% of the plasma cross-section) is realized by utilizing 1D parabolic beam expansion optics. Three initial test chords are installed and future plans call for expansion up to 30 chords with 1.5 cm chord spacing, providing high spatial resolution for measurement of electron density and current density profiles. Reliability of both polarimetric and interferometric measurement is confirmed by comparison with computation and data from a hydrocyanic acid (HCN) interferometer. With the high temporal and phase resolution, perturbations associated with the sawtooth cycle and MHD activity have been observed. PMID:23126966

Chen, J; Zhuang, G; Wang, Z J; Gao, L; Li, Q; Chen, W; Brower, D L; Ding, W X

2012-10-01

376

Observing NGC 4151 with the Keck Interferometer  

NASA Technical Reports Server (NTRS)

Observations of the nucleus of NGC 4151 at 2.2 microns using the two 10-meter Keck telescopes as an interferometer show a marginally resolved source less than or equal to 0.1 pc in diameter. These observations are the first measurement of an extragalactic source with an optical/IR interferometer. These observations represent a ten-fold improvement in angular resolution when compared to previous near-infrared measurements of AGN and make it possible to test the subparsecscale, near-infrared emission models of NGC 4151.

Swain, Mark R.

2004-01-01

377

Computer control of a far infrared interferometer  

NASA Technical Reports Server (NTRS)

A simple interface has been designed for the automatic control and data collection from a Grubb Parsons Mark III cube interferometer. A computer is used to automatically step the movable mirror on the interferometer. Data may be directly input into the computer for immediate transformation or stored for later analysis via a fast Fourier transformation. The interface is based on a commercial analog-to-digital converter having a parallel-to-serial data converter. The device can also display ASCII characters sent from the computer in parallel binary code. The system is applicable to recording interferograms having long time durations and to measuring multiple interferograms for statistical averaging.

Breecher, J.

1977-01-01

378

Polarized point diffraction interferometer for fringe stabilization  

NASA Astrophysics Data System (ADS)

We propose a new point diffraction interferometer using a polarizer with a pinholed for qualitative optical analysis. Diffraction from a polarizer with a pinholed makes reference and measurement waves. Interference fringe between diffracted-undiffracted measurement wave and undiffracted-diffracted reference wave is stabilized by common-path configuration. We examined the pinhole size and divergence angle of the diffracted wave for test optics with various numerical aperture. Optical parts comprising the interferometer can be assembled into a small monolithic component and embedded into an imaging target for easy alignment. Optical systems evaluating imaging performances such as modulation transfer function would benefit in aligning target objects.

Kihm, Hagyong; Lee, Yun-Woo

2010-08-01

379

Leggett-Garg inequality in electron interferometers  

NASA Astrophysics Data System (ADS)

We consider the violation of the Leggett-Garg inequality in electronic Mach-Zehnder inteferometers. This setup has two distinct advantages over earlier quantum-transport proposals: Firstly, the required correlation functions can be obtained without time-resolved measurements. Secondly, the geometry of an interferometer allows one to construct the correlation functions from ideal negative measurements, which addresses the noninvasiveness requirement of the Leggett-Garg inequality. We discuss two concrete realizations of these ideas: the first in quantum Hall edge-channels, the second in a double quantum dot interferometer.

Emary, Clive; Lambert, Neill; Nori, Franco

2012-12-01

380

A Fabry-Perot like two-photon interferometer for high-dimensional time-bin entanglement  

E-print Network

We generate high-dimensional time-bin entanglement using a mode-locked laser and analyze it with a 2-photon Fabry-Perot interferometer. The dimension of the entangled state is limited only by the phase coherence between subsequent pulses and is practically infinite. In our experiment a pico-second mode-locked laser at 532 nm pumps a non-linear potassium niobate crystal to produce photon pairs by spontaneous parametric down-conversion at 810 and 1550 nm.

Damien Stucki; Hugo Zbinden; Nicolas Gisin

2005-02-25

381

On the Potential of Large Ring Lasers  

E-print Network

We describe a new ring laser with area A = 833 m^2 and update performance statistics for several such machines. Anandan & Chaio 1982 judged ring lasers inferior to matter interferometers as possible detectors of gravitational waves. However, we note that geophysically interesting results have been obtained from large ring lasers and that there is still a lot of room for improvements.

G. E. Stedman; R. B. Hurst; K. U. Schreiber

2007-07-10

382

Using a Non-Product Quadrature Grid to Compute the Vibrational Spectrum of C2H4  

NASA Astrophysics Data System (ADS)

We present an accurate 12-D basis set calculation of the lowest 100 energy levels of the C2H4 molecule. A Smolyak non-product quadrature grid, a pruned product basis set, and the Lanczos algorithm are used. This scheme allows one to reduce the size of the basis set by almost 7 orders of magnitude (from 9× 1012 to 1.3× 106) and the size of the quadrature grid by almost 6 orders of magnitude (from 5.6× 1013 to 1.52 × 108). Basis pruning and the nonproduct quadrature grid therefore enable us to solve a problem, numerically exactly, that would be impossible without these tools.

Avila, Gustavo; Carrington, Tucker Carrington, Jr.

2011-06-01

383

Numerical quadrature methods for integrals of singular periodic functions and their application to singular and weakly singular integral equations  

NASA Technical Reports Server (NTRS)

High accuracy numerical quadrature methods for integrals of singular periodic functions are proposed. These methods are based on the appropriate Euler-Maclaurin expansions of trapezoidal rule approximations and their extrapolations. They are used to obtain accurate quadrature methods for the solution of singular and weakly singular Fredholm integral equations. Such periodic equations are used in the solution of planar elliptic boundary value problems, elasticity, potential theory, conformal mapping, boundary element methods, free surface flows, etc. The use of the quadrature methods is demonstrated with numerical examples.

Sidi, A.; Israeli, M.

1986-01-01

384

(presentation) Precision Mechanisms for Space Interferometers: A Tutorial  

NASA Technical Reports Server (NTRS)

To maximize salability, spaceborne interferometer designs must minimize actuator cost while maximizing science quality and quantity. Interferometer designers must have the knowledge to design a system with the simplist, most reliable, and least expensive actuators possible.

Agronin, Michael L.

1993-01-01

385

The Palomar Testbed Interferometer M. M. Colavita 1 , J. K. Wallace 1 , B. E. Hines 1 , Y. Gursel 1 , F. Malbet 1;3 D. L. Palmer 1 , X. P.  

E-print Network

with a range of \\Sigma38 m. Laser metrology of the delay lines allows for servo control, and laser metrology, for NASA as a testbed for interferometric techniques applicable to the Keck Interferometer. These include, including active fringe tracking, optical delay lines, laser metrology, and real­time control, is applicable

386

Photonic generation of a microwave signal by incorporating a delay interferometer and a saturable absorber.  

PubMed

A novel approach to generate microwave signals is presented by employing a dual-wavelength erbium-doped fiber ring laser. By using a delay interferometer as a comb filter cascaded with a tunable bandpass filter and a saturable absorber formed by an unpumped polarization-maintaining erbium-doped fiber, a stable wavelength-tunable dual-wavelength single longitudinal-mode laser is achieved. A microwave signal at 20.07 GHz with a linewidth of <25 kHz is demonstrated by beating the two wavelengths at a photodetector. PMID:18347707

Chen, Guojie; Huang, Dexiu; Zhang, Xinliang; Cao, Hui

2008-03-15

387

The Conceptual Design of the Magdalena Ridge Observatory Interferometer  

E-print Network

We describe the scientific motivation for and conceptual design of the Magdalena Ridge Observatory Interferometer, an imaging interferometer designed to operate at visible and near-infrared wavelengths. The rationale for the major technical decisions in the interferometer design is discussed, the success of the concept is appraised, and the implications of this analysis for the design of future arrays are drawn out.

Buscher, David F; Farris, Allen; Haniff, Christopher A; Young, John S

2013-01-01

388

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner the density profile of the plasma in LDX, we are constructing a multi-channel microwave interferometer be inverted to reconstruct a radially symmetric density profile. The microwave interferometer of LDX

389

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner design follows other microwave interferometers in the literature, in particular C.W. Domier et. al. Rev.Sci.Instrum. 59 [1988], 1588 · An RF beam of 60 GHz puts our interferometer in the microwave spectrum. · Our

390

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment A. Boxer, J. Kesner a multi-channel microwave interferometer. Such a device makes use the relationship between a plasma;Basic Design · An RF of 60 GHz puts our interferometer in the microwave spectrum. · The primary design

391

An electron Talbot-Lau interferometer and magnetic field sensing  

SciTech Connect

We present a demonstration of a three grating Talbot-Lau interferometer for electrons. As a proof of principle, the interferometer is used to measure magnetic fields. The device is similar to the classical Moiré deflectometer. The possibility to extend this work to build a scaled-up electron deflectometer or interferometer for sensitive magnetic field sensing is discussed.

Bach, Roger; Batelaan, Herman [Department of Physics and Astronomy, University of Nebraska-Lincoln, Theodore P. Jorgensen Hall, Lincoln, Nebraska 68588 (United States)] [Department of Physics and Astronomy, University of Nebraska-Lincoln, Theodore P. Jorgensen Hall, Lincoln, Nebraska 68588 (United States); Gronniger, Glen [The National Secure Manufacturing Center (NSMC), National Nuclear Security Administration's Kansas City Plant, National Security Campus, 14520 Botts Road, Kansas City, Missouri 64147 (United States)] [The National Secure Manufacturing Center (NSMC), National Nuclear Security Administration's Kansas City Plant, National Security Campus, 14520 Botts Road, Kansas City, Missouri 64147 (United States)

2013-12-16

392

A stellar interferometer on the Moon  

Microsoft Academic Search

The work I present in this document has been divided into two main parts, the first one related to the IOTA project and the second one related to the study on the lunar interferometer, and an introduction section. Each section can be read independently from the other, however they are presented following the logical order in which the research work

Irene Porro

1997-01-01

393

An overview of the Keck Interferometer Nuller  

NASA Technical Reports Server (NTRS)

The first high dynamic range interferometry mode planned to come on line at the Keck Observatory is mid-infrared nulling interferometry. In this paper, an overview is given of the goals and experimental configuration of the Keck Interferometer Nuller (KIN).

Serabyn, Eugen

2003-01-01

394

Pair of accelerated frames: a perfect interferometer  

E-print Network

The four Rindler quadrants of a pair of oppositely accelerated frames are identified as a (Lorentzian) Mach-Zehnder interferometer. The Rindler frequency dependence of the interference process is expressed by means of a (Lorentzian) differential cross section. The Rindler frequencies of the waves in the two acccelerated frames can be measured directly by means of a simple inertially moving detector.

Ulrich H. Gerlach

1999-11-01

395

Differential Phase Mode with the Keck Interferometer  

NASA Technical Reports Server (NTRS)

We describe the differential phase mode of the Keck Interferometer. The scientific goal of this mode is the direct detection and spectroscopic characterization of hot, Jupiter mass planets. We describe the differential phase effect, the basic observational mode, and the expected differential phase signatures for the extrasolar planets discovered through radial velocity searches.

Akeson, Rachel; Swain, Mark

2000-01-01

396

Development of the test interferometer for ALMA  

NASA Astrophysics Data System (ADS)

The ALMA Test Interferometer appeared as an infrastructure solution to increase both ALMA time availability for science activities and time availability for Software testing and Engineering activities at a reduced cost (<30000K USD) and a low setup time of less than 1 hour. The Test Interferometer could include up to 16 Antennas when used with only AOS resources and a possible maximum of 4 Antennas when configured using Correlator resources at OSF. A joined effort between ADC and ADE-IG took the challenge of generate the Test Interferometer from an already defined design for operations which imposed a lot of complex restrictions on how to implement it. Through and intensive design and evaluation work it was determined that is possible to make an initial implementation using the ACA Correlator and now it is also being tested the feasibility to implement the Testing Interferometer connecting the Test Array at AOS with Correlator equipment installed at the OSF, separated by 30 km. app. Lastly, efforts will be done to get interferometry between AOS and OSF Antennas with a baseline of approximately 24 km.

Olguin, R.; Shen, T.; Brito, R.; Saez, A.; Soto, R.; Asayama, S.; Follert, C.; Knee, L.; Quintana, A.; Rabanus, D.; Reynolds, E.; Saez, N.; Sepulveda, J.

2012-09-01

397

The StarLight Space Interferometer  

NASA Technical Reports Server (NTRS)

Two papers describe the StarLight space interferometer a Michelson interferometer that would be implemented by two spacecraft flying in formation. The StarLight formation flying interferometer project has been testing and demonstrating engineering concepts for a new generation of space interferometers that would be employed in a search for extrasolar planets and in astrophysical investigations. As described in the papers, the original StarLight concept called for three spacecraft, and the main innovation embodied is a modification that makes it possible to reduce complexity by eliminating the third spacecraft. The main features of the modification are (1) introduction of an optical delay line on one spacecraft and (2) controlling the flying formation such that the two spacecraft are located at two points along a specified parabola so as to define the required baseline of specified length (which could be varied up to 125 m) perpendicular to the axis of the parabola. One of the papers presents a detailed description of the optical layout and discusses computational modeling of the performance; the other paper presents an overview of the requirements for operation and design, the overall architecture, and subsystems.

Folkner, William; Shao, Michael; Gorham, Peter

2004-01-01

398

Path matched vibration insensitive Fizeau interferometer  

Microsoft Academic Search

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and

Bradley Trent Kimbrough

2006-01-01

399

Development of a multichannel integrated interferometer immunosensor  

Microsoft Academic Search

This report describes the design, realization and testing of a highly sensitive two-channel integrated optical (IO) Young interferometer (YI) as well as the design of a first multichannel YI. An integrated channel waveguide Y-splitter with two output parallel branches has been used as the basic optical component for building the YI. The generated interference pattern as result of the overlap

Aurel Ymeti; Johannes S. Kanger; Robert Wijn; Paul V. Lambeck; Jan Greve

2002-01-01

400

Smart photogalvanic running-grating interferometer  

NASA Astrophysics Data System (ADS)

Photogalvanic effect produces actuation of periodic motion of macroscopic LiNbO3 crystal. This effect was applied to the development of an all-optical moving-grating interferometer usable for optical trapping and transport of algae chlorella microorganisms diluted in water with a concentration of 27×104ml-1.

Kukhtarev, N. V.; Kukhtareva, T.; Edwards, M. E.; Jones, J.; Bayssie, M.; Wang, J.; Lyuksyutov, S. F.; Reagan, M. A.; Buchhave, P.

2005-03-01

401

A Microwave Interferometer on an Air Track.  

ERIC Educational Resources Information Center

Uses an air track and microwave transmitters and receivers to make a Michelson interferometer. Includes three experiments: (1) measuring the wavelength of microwaves, (2) measuring the wavelength of microwaves by using the Doppler Effect, and (3) measuring the Doppler shift. (MVL)

Polley, J. Patrick

1993-01-01

402

Kramers-Kronig relations for an interferometer.  

E-print Network

dependence of all the optical parameters, including the complex index of refraction, is properly taken the amplitude of light reflected from a Gires-Tournois interferometer are presented. 1 Introduction The Kramers of Preprint submitted to Elsevier Preprint 25 March 1999 #12;refraction. The real part of the index

Sprik, Rudolf

403

Theory of fractional quantum Hall interferometers  

NASA Astrophysics Data System (ADS)

Interference of fractionally charged quasiparticles is expected to lead to Aharonov-Bohm oscillations with periods larger than the flux quantum. However, according to the Byers-Yang theorem, observables of an electronic system are invariant under an adiabatic insertion of a quantum of singular flux. We resolve this seeming paradox by considering a microscopic model of electronic interferometers made from a quantum Hall liquid at filling factor 1/m with the shape of a Corbino disk. In such interferometers, the quantum Hall edge states are utilized in place of optical beams, the quantum point contacts play the role of beam splitters connecting different edge channels, and Ohmic contacts represent a source and drain of quasiparticle currents. Depending on the position of Ohmic contacts, one distinguishes interferometers of Fabry-Pérot (FP) and Mach-Zehnder (MZ) type. An approximate ground state of such interferometers is described by a Laughlin-type wave function, and low-energy excitations are incompressible deformations of this state. We construct a low-energy effective theory by restricting the microscopic Hamiltonian of electrons to the space of incompressible deformations and show that the theory of the quantum Hall edge so obtained is a generalization of a chiral conformal field theory. In our theory, a quasiparticle tunneling operator is found to be a single-valued function of tunneling point coordinates, and its phase depends on the topology determined by the positions of Ohmic contacts. We describe strong coupling of the edge states to Ohmic contacts and the resulting quasiparticle current through the interferometer with the help of a master equation. We find that the coherent contribution to the average quasiparticle current through MZ interferometers does not vanish after summation over quasiparticle degrees of freedom. However, it acquires oscillations with the electronic period, in agreement with the Byers-Yang theorem. Importantly, our theory does not rely on any ad hoc constructions, such as Klein factors, etc. When the magnetic flux through an FP interferometer is varied with a modulation gate, current oscillations have the quasiparticle periodicity, thus allowing for spectroscopy of quantum Hall edge states.

Levkivskyi, Ivan P.; Fröhlich, Jürg; Sukhorukov, Eugene V.

2012-12-01

404

Comparison of two quadrature-based moment methods for simulating dilute granular gases  

NASA Astrophysics Data System (ADS)

A dilute non-isothermal inelastic granular gas between two stationary Maxwellian walls is studied by means of numerical simulations of the Boltzmann kinetic equation with a hard-sphere collision kernel for mono-dispersed particles. Two types of quadrature-based moment methods with different orders of accuracy in terms of the moments of the distribution function are used with four different inelastic collision models. The models differ in the manner with which the moment equations are closed and in the number of moments that can be controlled for a given number of quadrature points. Results from the kinetic models are compared with the predictions of molecular dynamics simulations of a nearly equivalent system.

Fox, Rodney; Passalacqua, Alberto; Vedula, Prakash; Yuan, Jason

2009-11-01

405

High order quadratures to compute evolution of axis-symmetric interfacial Stokes flows  

NASA Astrophysics Data System (ADS)

Boundary integral methods have been used widely for the simulation of interfacial Stokes flows. These methods reduce the dimensionality of the problem by one since the fluid velocity reduces to an integral over the interface. In the case of axisymmetric interfaces it is difficult to approximate these integrals accurately. The integrands have singular behaviour at the symmetry axis and as a result, existing quadrature rules are, at best, of a limited second order accuracy. Furthermore, cancellation of large terms introduces large roundoff errors. In this work, we propose a new numerical approach to overcome these difficulties. The approach is based on analytic error corrections constructed from an asymptotic analysis of the integrands. We present quadratures that achieve a uniform accuracy of order five, apply them to compute the evolution of a drop, and demonstrate numerically their superior accuracy and efficiency.

Nitsche, Monika; Ceniceros, Hector; Karniala, Aino

2007-11-01

406

Observation of localized multi-spatial-mode quadrature squeezing in four-wave mixing  

E-print Network

Quantum states of light can improve imaging whenever the image quality and resolution are limited by the quantum noise of the illumination. In the case of a bright illumination, quantum enhancement is obtained for a light field composed of many squeezed transverse modes. A possible realization of such a multi-spatial-mode squeezed state is a field which contains a transverse plane in which the local electric field displays reduced quantum fluctuations at all locations, on any one quadrature. Using nondegenerate four-wave mixing in a hot vapor, we have generated a bichromatic multi-spatial-mode squeezed state and showed that it exhibits localised quadrature squeezing at any point of its transverse profile, in regions much smaller than its size. We observe 75 independently squeezed regions. This confirms the potential of this technique for producing illumination suitable for practical quantum imaging.

Embrey, C S; Petrov, P G; Boyer, V

2014-01-01

407

Interrogation of a remote elliptical-core dual-mode fiber strain sensor by using a tandem interferometer configuration.  

PubMed

We report on the interrogation of a lead-insensitive dual-mode fiber sensor using a white-light interferometric technique with a multimode laser-diode source. An elliptical-core dual-mode fiber acts as a remote-sensing interferometer, and a second dual-mode fiber acts as a receiver interferometer. We establish the sensor design for optimized performance and demonstrate the capability of accurate detection of periodic strain signals in the presence of, e.g., temperature-induced low-frequency phase drifts. PMID:19794601

Bohnert, K; de Wit, G; Nehring, J

1992-05-01

408

Use of Quadrature Filters for Detection of Stellate Lesions in Mammograms  

Microsoft Academic Search

\\u000a We propose a method for finding stellate lesions in digitized mammograms based on the use of both local phase and local orientation\\u000a information extracted from quadrature filter outputs. The local phase information allows efficient and fast separation between\\u000a edges and lines and the local orientation estimates are used to find areas circumscribed by edges and with radiating lines.\\u000a The method

Hans Bornefalk

2005-01-01

409

Semi-blind adaptive beamforming for high-throughput quadrature amplitude modulation systems  

Microsoft Academic Search

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude\\u000a modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna array’s elements, are\\u000a first utilised to provide a rough initial least squares estimate of the beamformer’s weight vector. A concurrent constant\\u000a modulus algorithm and soft decision-directed scheme is then applied

Sheng Chen; Wang Yao; Lajos Hanzo

2010-01-01

410

Optimum Receiver Filters in Digital Quadrature Phase-Shift-Keyed Systems with a Nonlinear Repeater  

Microsoft Academic Search

The effects of filter shaping and nonlinearity in a coherent quadrature phase-shift-keyed (QPSK) system are investigated. Optimization of the receiver filter with respect to the meansquare error (MSE) is considered. Optimization is performed under two different constraints, corresponding to implementation of the filter at intermediate frequency and baseband, respectively. As an example a channel with a typical traveling-wave tube (TWT)

STAFFAN A. FREDRICSSON

1975-01-01

411

Multiple bit differential detection of offset quadrature phase-shift-keying  

NASA Technical Reports Server (NTRS)

Analogous to multiple symbol differential detectionof quadrature phase-shift-keying (QPSK), a multiple bit differential detection scheme is described for offset QPSK that also exhibits continuous improvement in performance with increasing observation interval. Being derived from maximum-likelihood (ML) considerations, the proposed scheme is purported to be the most power efficient scheme for such a modulation and detection method. Extension of the results to shaped offset QPSK is also possible.

Simon, M.

2003-01-01

412

Coherent detection of optical quadrature phase-shift keying signals with carrier phase estimation  

Microsoft Academic Search

This paper describes a coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK) signals. At the receiver, a phase-diversity homodyne detection scheme is employed without locking the phase of the local oscillator (LO). To handle the carrier phase drift, the carrier phase is estimated with digital signal processing (DSP) on the homodyne-detected signal. Such a scheme presents the following

Dany-Sebastien Ly-Gagnon; Satoshi Tsukamoto; Kazuhiro Katoh; Kazuro Kikuchi

2006-01-01

413

A quadrature-free discontinuous Galerkin method for the level set equation  

NASA Astrophysics Data System (ADS)

A quadrature free, Runge-Kutta discontinuous Galerkin method (QF-RK-DGM) is developed to solve the level set equation written in a conservative form on two- and tri-dimensional unstructured grids. We show that the DGM implementation of the level set approach brings a lot of additional benefits as compared to traditional ENO level set realizations. Some examples of computations are provided that demonstrate the high order of accuracy and the computational efficiency of the method.

Marchandise, Emilie; Remacle, Jean-François; Chevaugeon, Nicolas

2006-02-01

414

A Gaussian quadrature method for total energy analysis in electronic state calculations  

NASA Astrophysics Data System (ADS)

This article reports studies by Fukushima and coworkers since 1980 concerning their highly accurate numerical integral method using Gaussian quadratures to evaluate the total energy in electronic state calculations. Gauss-Legendre and Gauss-Laguerre quadratures were used for integrals in the finite and infinite regions, respectively. Our previous article showed that, for diatomic molecules such as CO and FeO, elliptic coordinates efficiently achieved high numerical integral accuracy even with a numerical basis set including transition metal atomic orbitals. This article will generalize straightforward details for multiatomic systems with direct integrals in each decomposed elliptic coordinate determined from the nuclear positions of picked-up atom pairs. Sample calculations were performed for the molecules O3 and H2O. This article will also try to present, in another coordinate, a numerical integral by partially using the Becke's decomposition published in 1988, but without the Becke's fuzzy cell generated by the polynomials of internuclear distance between the pair atoms. Instead, simple nuclear weights comprising exponential functions around nuclei are used. The one-center integral is performed with a Gaussian quadrature pack in a spherical coordinate, included in the author's original program in around 1980. As for this decomposition into one-center integrals, sample calculations are carried out for Li2.

Fukushima, Kimichika

415

On the power spectral density of quadrature modulated signals. [satellite communication  

NASA Technical Reports Server (NTRS)

The conventional (no-offset) quadriphase modulation technique suffers from the fact that hardlimiting will restore the frequency sidelobes removed by proper filtering. Thus, offset keyed quadriphase modulation techniques are often proposed for satellite communication with bandpass hardlimiting. A unified theory is developed which is capable of describing the power spectral density before and after the hardlimiting process. Using the in-phase and the quadrature phase channel with arbitrary pulse shaping, analytical results are established for generalized quadriphase modulation. In particular MSK, OPSK or the recently introduced overlapped raised cosine keying all fall into this general category. It is shown that for a linear communication channel, the power spectral density of the modulated signal remains unchanged regardless of the offset delay. Furthermore, if the in phase and the quadrature phase channel have identical pulse shapes without offset, the spectrum after bandpass hardlimiting will be identical to that of the conventional QPSK modulation. Numerical examples are given for various modulation techniques. A case of different pulse shapes in the in phase and the quadrature phase channel is also considered.

Yan, T. Y.

1981-01-01

416

Laser interferometry for next generation satellite gravimetry  

NASA Astrophysics Data System (ADS)

The use of precision laser interferometry in the next generation of satellite gravity field missions, including inter-satellite ranging and laser gravity gradiometry, will be discussed. Much of the interferometer technology developed for the Laser Interferometer Space Antenna (LISA), a space-based gravitational wave detector and its technology demonstrator, LISA Pathfinder, is relevant to such a mission - for example laser based heterodyne interferometry for measuring the fluctuations of the distance between two satellites or between two test masses within a single satellite. The status of the development of interferometry for future satellite gravimetry missions, including laboratory experiments, at the Albert Einstein Institute Hannover will be presented.

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

2010-05-01

417

Trellis-Coded Quadrature-Phase-Shift Keying (QPSK) With Variable Overlapped Raised-Cosine Pulse Shaping  

Microsoft Academic Search

This article introduces the notion of uncoded, partially overlapped, staggered quadrature raised-cosine modulation (SQORC-P) as well as that of a trellis-coded form that is implemented as a speciflc embodiment of the recently introduced cross- correlated trellis-coded quadrature modulation (XTCQM). Consideration is given to the power spectral density (PSD) of the scheme over both linear and nonlinear chan- nels as well

M. K. Simon; P. Arabshahi; M. Srinivasan

1998-01-01

418

The Effect of Mismatches and Delay on the Quadrature Error of a Cross-Coupled Relaxation Oscillator  

Microsoft Academic Search

Cross-coupled relaxation oscillators can produce two highly accurate quadrature output signals (Verhoeven, 1992). We present a high-level model of these oscillators in terms of circuit parameters, from which we obtain explicit equations for duty-cycle, oscillation frequency, and quadrature error. They show the influence on the oscillator performance of component mismatches and other nonideal effects, such as delays. The results provide

Jorge R. Fernandes; Michiel H. L. Kouwenhoven; Chris van den Bos; Luis B. Oliveira; Chris J. M. Verhoeven

2007-01-01

419

Trade-off between quantum and thermal fluctuations in mirror coatings yields improved sensitivity of gravitational-wave interferometers  

E-print Network

We propose a simple way to improve the laser gravitational-wave detectors sensitivity by means of reduction of the number of reflective coating layers of the core optics mirrors. This effects in the proportional decrease of the coating thermal noise, the most notorious among the interferometers technical noise sources. The price for this is the increased quantum noise, as well as high requirements for the pump laser power and power at the beamsplitter. However, as far as these processes depend differently on the coating thickness, we demonstrate that a certain trade-off is possible, yielding a 20-30% gain (for diverse gravitational wave signal types and interferometer configurations), providing that feasible values of laser power and power on the beamsplitter are assumed.

N. V. Voronchev; S. L. Danilishin; F. Ya. Khalili

2012-02-29

420

Parallel multiplex laser feedback interferometry  

SciTech Connect

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian, E-mail: zsl-dpi@mail.tsinghua.edu.cn [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)] [State Key Laboratory of Precision Measurements, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)

2013-12-15

421

Parallel multiplex laser feedback interferometry  

NASA Astrophysics Data System (ADS)

We present a parallel multiplex laser feedback interferometer based on spatial multiplexing which avoids the signal crosstalk in the former feedback interferometer. The interferometer outputs two close parallel laser beams, whose frequencies are shifted by two acousto-optic modulators by 2? simultaneously. A static reference mirror is inserted into one of the optical paths as the reference optical path. The other beam impinges on the target as the measurement optical path. Phase variations of the two feedback laser beams are simultaneously measured through heterodyne demodulation with two different detectors. Their subtraction accurately reflects the target displacement. Under typical room conditions, experimental results show a resolution of 1.6 nm and accuracy of 7.8 nm within the range of 100 ?m.

Zhang, Song; Tan, Yidong; Zhang, Shulian

2013-12-01

422

Quantum metrology with parametric amplifier-based photon correlation interferometers.  

PubMed

Conventional interferometers usually utilize beam splitters for wave splitting and recombination. These interferometers are widely used for precision measurement. Their sensitivity for phase measurement is limited by the shot noise, which can be suppressed with squeezed states of light. Here we study a new type of interferometer in which the beam splitting and recombination elements are parametric amplifiers. We observe an improvement of 4.1±0.3?dB in signal-to-noise ratio compared with a conventional interferometer under the same operating condition, which is a 1.6-fold enhancement in rms phase measurement sensitivity beyond the shot noise limit. The improvement is due to signal enhancement. Combined with the squeezed state technique for shot noise suppression, this interferometer promises further improvement in sensitivity. Furthermore, because nonlinear processes are involved in this interferometer, we can couple a variety of different waves and form new types of hybrid interferometers, opening a door for many applications in metrology. PMID:24476950

Hudelist, F; Kong, Jia; Liu, Cunjin; Jing, Jietai; Ou, Z Y; Zhang, Weiping

2014-01-01

423

Quantum metrology with parametric amplifier-based photon correlation interferometers  

PubMed Central

Conventional interferometers usually utilize beam splitters for wave splitting and recombination. These interferometers are widely used for precision measurement. Their sensitivity for phase measurement is limited by the shot noise, which can be suppressed with squeezed states of light. Here we study a new type of interferometer in which the beam splitting and recombination elements are parametric amplifiers. We observe an improvement of 4.1±0.3?dB in signal-to-noise ratio compared with a conventional interferometer under the same operating condition, which is a 1.6-fold enhancement in rms phase measurement sensitivity beyond the shot noise limit. The improvement is due to signal enhancement. Combined with the squeezed state technique for shot noise suppression, this interferometer promises further improvement in sensitivity. Furthermore, because nonlinear processes are involved in this interferometer, we can couple a variety of different waves and form new types of hybrid interferometers, opening a door for many applications in metrology. PMID:24476950

Hudelist, F.; Kong, Jia; Liu, Cunjin; Jing, Jietai; Ou, Z.Y.; Zhang, Weiping

2014-01-01

424

Confocal Fabry-Perot interferometer based high spectral resolution lidar  

NASA Astrophysics Data System (ADS)

A high spectral resolution lidar (HSRL) instrument has been developed which utilizes the fundamental and second harmonic output from an injection seeded Nd:YAG laser as the laser transmitter. The light scattered in the atmosphere is collected using a commercial Schmidt-Cassegrain telescope. The second harmonic return signal is mode matched into a tunable confocal Fabry-Perot (CFP) interferometer with a free spectral range of 7.5 GHz and a finesse of 50.7 (312) at 532 nm (1064 nm) placed in the optical receiver for spectrally filtering the molecular and aerosol return signals. The light transmitted through the CFP is used to monitor the aerosol return signal while the light reflected from the CFP is used to monitor the molecular return signal. Data collected with the HSRL are presented and inversion results are compared to a co-located solar radiometer, demonstrating the successful operation of the instrument. The CFP-based filtering technique successfully employed by this HSRL instrument is novel, and is easily portable to other arbitrary wavelengths, thus allowing for the future development of multi-wavelength HSRL instruments.

Hoffman, David Swick

425

Demonstration of improved sensitivity of echo interferometers to gravitational acceleration  

NASA Astrophysics Data System (ADS)

We have developed two configurations of an echo interferometer that rely on standing-wave excitation of a laser-cooled sample of rubidium atoms. Both configurations can be used to measure acceleration a along the axis of excitation. For a two-pulse configuration, the signal from the interferometer is modulated at the recoil frequency and exhibits a sinusoidal frequency chirp as a function of pulse spacing. In comparison, for a three-pulse stimulated-echo configuration, the signal is observed without recoil modulation and exhibits a modulation at a single frequency as a function of pulse spacing. The three-pulse configuration is less sensitive to effects of vibrations and magnetic field curvature, leading to a longer experimental time scale. For both configurations of the atom interferometer (AI), we show that a measurement of acceleration with a statistical precision of 0.5% can be realized by analyzing the shape of the echo envelope that has a temporal duration of a few microseconds. Using the two-pulse AI, we obtain measurements of acceleration that are statistically precise to 6 parts per million (ppm) on a 25 ms time scale. In comparison, using the three-pulse AI, we obtain measurements of acceleration that are statistically precise to 0.4 ppm on a time scale of 50 ms. A further statistical enhancement is achieved by analyzing the data across the echo envelope so that the statistical error is reduced to 75 parts per billion (ppb). The inhomogeneous field of a magnetized vacuum chamber limited the experimental time scale and resulted in prominent systematic effects. Extended time scales and improved signal-to-noise ratio observed in recent echo experiments using a nonmagnetic vacuum chamber suggest that echo techniques are suitable for a high-precision measurement of gravitational acceleration g. We discuss methods for reducing systematic effects and improving the signal-to-noise ratio. Simulations of both AI configurations with a time scale of 300 ms suggest that an optimized experiment with improved vibration isolation and atoms selected in the mF=0 state can result in measurements of g statistically precise to 0.3 ppb for the two-pulse AI and 0.6 ppb for the three-pulse AI.

Mok, C.; Barrett, B.; Carew, A.; Berthiaume, R.; Beattie, S.; Kumarakrishnan, A.

2013-08-01

426

A simple laser system for atom interferometry  

NASA Astrophysics Data System (ADS)

We present here a simple laser system for a laser-cooled atom interferometer, where all functions (laser cooling, interferometry and detection) are realized using only two extended cavity laser diodes, amplified by a common tapered amplifier. One laser is locked by frequency modulation transfer spectroscopy, the other being phase locked with an offset frequency determined by an field-programmable gate array-controlled direct digital synthesizer, which allows for efficient and versatile tuning of the laser frequency. Raman lasers are obtained with a double pass acoustooptic modulator. We demonstrate a gravimeter using this laser system, with performances close to the state of the art.

Merlet, S.; Volodimer, L.; Lours, M.; Pereira Dos Santos, F.

2014-07-01

427

An imaging interferometer for compact sources  

NASA Astrophysics Data System (ADS)

This paper presents the results of a study designed to test the feasibility of imaging satellites in geostationary orbit from the ground. We argue that the instrument should be an interferometer consisting of > 30 telescopes mounted on a common, steerable boom. Light from the telescopes is fed to the beam combiner with optical fibers. The delays are equalized by steering the boom and stretching the fibers. The feed system and delay lines are replaced with single mode fibers. This system should be better throughput than the optical interferometers in use today and should be able to reach the sensitivity needed to image these targets with meter-scale telescopes. Calculations supporting this claim and a system design are presented.

Mozurkewich, D.; Armstrong, J. T.; Hindsley, R. B.; Jorgensen, A. M.; Restaino, S. R.; Schmitt, H. R.

2011-09-01

428

Bright solitonic matter-wave interferometer.  

PubMed

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud. PMID:25032924

McDonald, G D; Kuhn, C C N; Hardman, K S; Bennetts, S; Everitt, P J; Altin, P A; Debs, J E; Close, J D; Robins, N P

2014-07-01

429

Data Processing for Atmospheric Phase Interferometers  

NASA Technical Reports Server (NTRS)

This paper presents a detailed discussion of calibration procedures used to analyze data recorded from a two-element atmospheric phase interferometer (API) deployed at Goldstone, California. In addition, we describe the data products derived from those measurements that can be used for site intercomparison and atmospheric modeling. Simulated data is used to demonstrate the effectiveness of the proposed algorithm and as a means for validating our procedure. A study of the effect of block size filtering is presented to justify our process for isolating atmospheric fluctuation phenomena from other system-induced effects (e.g., satellite motion, thermal drift). A simulated 24 hr interferometer phase data time series is analyzed to illustrate the step-by-step calibration procedure and desired data products.

Acosta, Roberto J.; Nessel, James A.; Morabito, David D.

2009-01-01

430

GaAs/AlGaAs-based Mach-Zehnder interferometer as integrated optical immunosensor  

NASA Astrophysics Data System (ADS)

System miniaturization is a key issue in further development of integrated optical sensors. We present an integrated optical GaAs/AlGaAs-based Mach-Zehnder interferometer with a 2 mm long TiO2 on SiO2 embedded waveguide sensor pad and its performance as a bioaffinity sensor. Preliminary experiments to evaluate the performance of our Mach-Zehnder interferometer device were done by studying the binding of immunoglobulin (IgG) to protein A. The current resolution limit of IgG surface coverage is 3 pg/mm2, corresponding to less than 1/1600 of a saturated IgG monolayer. Since the design of the basic GaAs/AlGaAs waveguide structure is fully compatible with monolithic integration of lasers, modulators and detectors, improved performance can be expected from integration of these optoelectronic components on the same chip.

Maisenhoelder, Bernd; Zappe, Hans P.; Kunz, Rino E.; Riel, Peter; Moser, Michael; Duveneck, Gert L.

1996-11-01

431

Automatic Alignment for the first science run of the Virgo interferometer  

NASA Astrophysics Data System (ADS)

During the past few years a network of large-scale laser interferometers, including the Virgo detector, has been developed with the aim of detecting gravitational waves. To properly operate the detectors, the longitudinal and angular positions of the suspended detector test masses, the interferometer mirrors, must be kept within a small range from the operating point. The design of the Virgo angular control system, called Automatic Alignment is based on a modified version of the Anderson-Giordano technique, a wave-front sensing scheme which uses the modulation-demodulation technique. This paper will present the theoretical background of the Virgo Automatic Alignment system, the implementation issues and the performances observed during the first Virgo science run (VSR1). A total RMS of 4 × 10 -2 to 3 × 10 -3 ?rad for all angular degrees of freedom has been achieved.

Acernese, F.; Alshourbagy, M.; Antonucci, F.; Aoudia, S.; Arun, K. G.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Bauer, Th. S.; Bigotta, S.; Birindelli, S.; Bizouard, M. A.; Boccara, C.; Bondu, F.; Bonelli, L.; Bosi, L.; Braccini, S.; Bradaschia, C.; Brillet, A.; Brisson, V.; Bulten, H. J.; Buskulic, D.; Cagnoli, G.; Calloni, E.; Campagna, E.; Canuel, B.; Carbognani, F.; Carbone, L.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chatterji, S.; Cleva, F.; Coccia, E.; Colas, J.; Colombini, M.; Corda, C.; Corsi, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dari, A.; Dattilo, V.; Davier, M.; De Rosa, R.; Del Prete, M.; Di Fiore, L.; Di Lieto, A.; Di Paolo Emilio, M.; Di Virgilio, A.; Fafone, V.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Gammaitoni, L.; Garufi, F.; Genin, E.; Gennai, A.; Giazotto, A.; Granata, M.; Granata, V.; Greverie, C.; Guidi, G.; Heitmann, H.; Hello, P.; Hild, S.; Huet, D.; La Penna, P.; Laval, M.; Leroy, N.; Letendre, N.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Mackowski, J.-M.; Majorana, E.; Man, C. N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Masserot, A.; Menzinger, F.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Moreau, J.; Morgado, N.; Mosca, S.; Mours, B.; Neri, I.; Nocera, F.; Pagliaroli, G.; Palomba, C.; Paoletti, F.; Pardi, S.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Piergiovanni, F.; Pinard, L.; Poggiani, R.; Punturo, M.; Puppo, P.; Rabaste, O.; Rapagnani, P.; Regimbau, T.; Ricci, F.; Rocchi, A.; Rolland, L.; Romano, R.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Swinkels, B. L.; Terenzi, R.; Toncelli, A.; Tonelli, M.; Tournefier, E.; Travasso, F.; Trummer, J.; Vajente, G.; van den Brand, J. F. J.; van der Putten, S.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vocca, H.; Was, M.; Yvert, M.

2010-04-01

432

Coupled Mach-Zehnder interferometer memory element.  

PubMed

Two active Mach-Zehnder interferometers are integrated in a monolithic InP/InGaAsP photonic integrated circuit. Together they form a crucial component for optical signal processing: an optical memory element or set-reset flip-flop. The switching time for this initial device is approximately 200 ps. The photonic integrated circuit contains active and passive optical components, including electro-optic phase shifters. PMID:16075546

Hill, Martin T; Dorren, H J S; Leijtens, X J M; den Besten, J H; de Vries, T; van Zantvoort, J H C; Smalbrugge, E; Oei, Y S; Binsma, J J M; Khoe, G D; Smit, M K

2005-07-01

433

Modeling of a tilted pressure-tuned field-widened Michelson interferometer for application in high spectral resolution lidar  

NASA Astrophysics Data System (ADS)

High spectral resolution lidars (HSRLs) designed for aerosol and cloud remote sensing are increasingly being deployed on aircraft and called for on future space-based missions. The HSRL technique relies on spectral discrimination of the atmospheric backscatter signals to enable independent, unambiguous retrieval of aerosol extinction and backscatter. A compact, monolithic field-widened Michelson interferometer is being developed as the spectral discrimination filter for an HSRL system at NASA Langley Research Center. The Michelson interferometer consists of a cubic beam splitter, a solid glass arm, and an air arm. The spacer that connects the air arm mirror to the main part of the interferometer is designed to optimize thermal compensation such that the frequency of maximum interference can be tuned with great precision to the transmitted laser wavelength. In this paper, a comprehensive radiometric model for the field-widened Michelson interferometeric spectral filter is presented. The model incorporates the angular distribution and finite cross sectional area of the light source, reflectance of all surfaces, loss of absorption, and lack of parallelism between the airarm and solid arm, etc. The model can be used to assess the performance of the interferometer and thus it is a useful tool to evaluate performance budgets and to set optical specifications for new designs of the same basic interferometer type.

Liu, Dong; Hostetler, Chris; Miller, Ian; Cook, Anthony; Hair, Jonathan

2011-10-01

434

Low frequency noise distributed-feedback ytterbium fibre laser  

SciTech Connect

We report a single-frequency 1-W fibre laser source emitting at 1093 nm, composed of a distributed-feedback ytterbium fibre laser and fibre-optic amplifier. The laser frequency was stabilised by side-locking to a transmission peak of a Fabry - Perot interferometer, and the residual frequency noise spectrum of the laser was measured. Our results indicate that the laser linewidth can be narrowed down below 1 kHz. (lasers)

Nikulin, M A; Babin, S A; Kablukov, S I [Novosibirsk State University, Novosibirsk (Russian Federation); Dmitriev, Aleksandr K; Dychkov, Aleksandr S; Lugovoy, Aleksei A [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Pecherskii, Yu Ya [Rzhanov Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk (Russian Federation)

2009-10-31

435

A Study of Imaging Interferometer Simulators  

NASA Technical Reports Server (NTRS)

Several new space science mission concepts under development at NASA-GSFC for astronomy are intended to carry out synthetic imaging using Michelson interferometers or direct (Fizeau) imaging with sparse apertures. Examples of these mission concepts include the Stellar Imager (SI), the Space Infrared Interferometric Telescope (SPIRIT), the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and the Fourier-Kelvin Stellar Interferometer (FKSI). We have been developing computer-based simulators for these missions. These simulators are aimed at providing a quantitative evaluation of the imaging capabilities of the mission by modelling the performance on different realistic targets in terms of sensitivity, angular resolution, and dynamic range. Both Fizeau and Michelson modes of operation can be considered. Our work is based on adapting a computer simulator called imSIM, which was initially written for the Space Interferometer Mission in order to simulate the imaging mode of new missions such as those listed. In a recent GSFC-funded study we have successfully written a preliminary version of a simulator SISIM for the Stellar Imager and carried out some preliminary studies with it. In a separately funded study we have also been applying these methods to SPECS/SPIRIT.

Allen, Ronald J.

2002-01-01

436

Stabilization and calibration of an ECDL system with a Michelson interferometer  

NASA Astrophysics Data System (ADS)

The experimental setup developed to stabilize a red diode laser using a mode-locking technique with a reference gas cell is presented. This system has an external cavity diode laser (ECDL) in a Littrow configuration and is used to calibrate gauge blocks. The electronic controller limits the bandwidth of the laser and does not allow the setup to establish the wavelength of the tuned iodine transition, which is needed to calculate the gauge block values. To solve this limitation, we have set up a laser wavemeter based on a two-beam scanning Michelson interferometer. The unknown wavelength is determined from the ratio of the number of fringes obtained by the He-Ne reference laser and our ECDL. This technique measures the laser wavelength with an accuracy of 1ppm. As the resolution of the system is influenced by the optical path length, the stability of the reference laser and the phase ratio of both lasers, an electronic Vernier counter is used to improve the accuracy of these values below 1ppm. The uncertainty evaluation is also presented.

Outumuro, I.; Valencia, J. L.; Diz-Bugarin, J.; Estevez-Caride, I.; Blanco, J.; Dorrío, B. V.

2013-11-01

437

Ultraviolet-excimer laser-based incoherent Doppler lidar system  

NASA Technical Reports Server (NTRS)

The topics covered include the following: principles of Doppler measurements, laser backscatter, eye safety, demonstration concepts, the wavelength-meter, the interferometer detector, return signal model, and comparison of incoherent and coherent lidars.

Mcdermid, I. Stuart; Laudenslager, James B.; Rees, David

1985-01-01

438

Interchannel Nonlinearities in Coherent Polarization-Division-Multiplexed Quadrature-Phase-Shift- Keying Systems  

Microsoft Academic Search

We study with simulations interchannel nonlinear effects on a 42.8-Gb\\/s coherent polarization-division-multiplexed quadrature-phase-shift-keying (PDM-QPSK) system with and without dispersion management. We find that interchannel cross-phase-modulation induced nonlinear polarization scattering can severely degrade the performance of a dispersion-managed PDM-QPSK system. We demonstrate that the time-interleaved return-to-zero PDM-QPSK, where the symbols of the two polarizations are shifted by half a symbol in

Chongjin Xie

2009-01-01

439

Solutions of radiative heat transfer in nonhomogeneous participating media using the quadrature method  

SciTech Connect

This work considers radiative heat transfer in a three-dimensional, rectangular, scattering medium exposed to diffuse radiation. Applying the quadrature method with singularity subtraction to the exact integral equations in terms of the moments of intensity can generate highly accurate solutions, and so the method is adopted in this work. The example solutions provided are for radiative equilibrium in homogeneous absorbing-emitting media, and for radiative transfer in nonhomogeneous absorbing-scattering (isotropic and linearly anisotropic) media with non-reflecting surfaces. To validate the solutions, the present results are compared with the solutions obtained by the YIX method and other methods.

Wu, S.H.; Wu, C.Y. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Mechanical Engineering; Hsu, P. [Florida Inst. of Tech., Melbourne, FL (United States). Mechanical and Aerospace Engineering Programs

1996-12-31

440

Quadrature-Free Implementation of the Discontinuous Galerkin Method for Hyperbolic Equations  

NASA Technical Reports Server (NTRS)

A discontinuous Galerkin formulation that avoids the use of discrete quadrature formulas is described and applied to linear and nonlinear test problems in one and two space dimensions. This approach requires less computational time and storage than conventional implementations but preserves the compactness and robustness inherent to the discontinuous Galerkin method. Test problems include both linear and nonlinear one-dimensional scalar advection of botH smooth and discontinuous initial value problems, two-dimensional scalar advection of smooth initial value problems discretized by using unstructured grids with varying degrees of smoothness and regularity, and two-dimensional linear Euler solutions on unstructured grids.

Atkins, H. L.; Shu, Chi-Wang

1996-01-01

441

Design and analysis of an ultra-low-power LC quadrature VCO  

Microsoft Academic Search

This paper presents the design of an ultra-low-power LC quadrature VCO (QVCO). It is designed in a single-poly seven-metal\\u000a 65-nm CMOS process. Several aspects of state-of-the-art QVCO design are addressed, for example tank design and circuit topologies\\u000a in nano-meter CMOS technology. To minimize power dissipation, an inductor with a high LQ product of 188 nH at 2.4 GHz, and a self-resonant frequency

Kin Keung Lee; Carl Bryant; Markus Törmänen; Henrik Sjöland

2011-01-01

442

Adaptive multicarrier quadrature division modulation for long-distance continuous-variable quantum key distribution  

NASA Astrophysics Data System (ADS)

We propose the adaptive multicarrier quadrature division (AMQD) modulation technique for continuous-variable quantum key distribution (CVQKD). The method granulates the Gaussian random input into Gaussian subcarrier continuous variables in the encoding phase, which are then decoded by a continuous unitary transformation. The subcarrier coherent variables formulate Gaussian sub-channels from the physical link with strongly diverse transmission capabilities, which leads to significantly improved transmission efficiency, higher tolerable loss, and excess noise. We also investigate a modulation-variance adaption technique within the AMQD scheme, which provides optimal capacityachieving communication over the sub-channels in the presence of a Gaussian noise.

Gyongyosi, L.; Imre, S.

2014-05-01

443

Development of highly sensitive monolithic interferometer for infrared planet search  

Microsoft Academic Search

We present the design, fabrication and testing of a highly sensitive monolithic interferometer for InfraRed Exoplanet Tracker (IR-ET). This interferometer is field-compensated, thermal-stable for working in the wavelength range between 0.8 and 1.35 mum. Two arms of the interferometer creates a fixed delay of 18.0 mm, which is optimized to have the best sensitivity for radial velocity measurements of slow-rotating

J. Wang; J. Ge; X. Wan; P. Jiang; B. Lee

2011-01-01

444

Special topics in infrared interferometry. [Michelson interferometer development  

NASA Technical Reports Server (NTRS)

Topics in IR interferometry related to the development of a Michelson interferometer are treated. The selection and reading of the signal from the detector to the analog to digital converter is explained. The requirements for the Michelson interferometer advance speed are deduced. The effects of intensity modulation on the interferogram are discussed. Wavelength and intensity calibration of the interferometer are explained. Noise sources (Nyquist or Johnson noise, phonon noise), definitions of measuring methods of noise, and noise measurements are presented.

Hanel, R. A.

1985-01-01

445

Detecting Fulde-Ferrell superconductors by an Andreev interferometer  

NASA Astrophysics Data System (ADS)

We propose an Andreev interferometer, based on a branched Y-junction, to detect the finite momentum pairing in Fulde-Ferrell (FF) superconductors. In this interferometer, the oscillation of subgap conductance is a unique function of phase difference between the two channels of the Y-junction, which is determined by the phase modulation of the order parameter in the FF superconductors. This interferometer has the potential not only to determine the magnitude but also the direction of the momentum of Cooper pairs in the FF superconductor. The possible applications of the interferometer in the identification of the finite momentum pairing in non-centrosymmetric superconductors are also discussed.

Chen, Wei; Gong, Ming; Shen, R.; Xing, D. Y.

2014-08-01

446

CONFOCAL FABRY-PEROT INTERFEROMETER BASED HIGH SPECTRAL RESOLUTION LIDAR  

E-print Network

CONFOCAL FABRY-PEROT INTERFEROMETER BASED HIGH SPECTRAL RESOLUTION LIDAR by David Swick Hoffman....................................................................................3 Lidar............................................................................................................4 High Spectral Resolution Lidar

Lawrence, Rick L.

447

Combined shearing interferometer and hartmann wavefront sensor  

SciTech Connect

A sensitive wavefront sensor combining attributes of both a Hartmann type of wavefront sensor and an AC shearing interferometer type of wavefront sensor. An incident wavefront, the slope of which is to be detected, is focussed to first and second focal points at which first and second diffraction gratings are positioned to shear and modulate the wavefront, which then diverges therefrom. The diffraction patterns of the first and second gratings are positioned substantially orthogonal to each other to shear the wavefront in two directions to produce two dimensional wavefront slope data for the AC shearing interferometer portion of the wavefront sensor. First and second dividing optical systems are positioned in the two diverging wavefronts to divide the sheared wavefront into an array of subapertures and also to focus the wavefront in each subaperture to a focal point. A quadrant detector is provided for each subaperture to detect the position of the focal point therein, which provides a first indication, in the manner of a Hartmann wavefront sensor, of the local wavefront slope in each subaperture. The total radiation in each subaperture, as modulated by the diffraction grating, is also detected by the quadrant detector which produces a modulated output signal representative thereof, the phase of which relative to modulation by the diffraction grating provides a second indication of the local wavefront slope in each subaperture, in the manner of an AC shearing interferometer wavefront sensor. The data from both types of sensors is then combined by long term averaging thereof to provide an extremely sensitive wavefront sensor.

Hutchin, R. A.

1985-05-21

448

Low-Noise Piezoelectric Driver for External Cavity Diode Lasers Physics 492R Capstone  

E-print Network

I built a piezoelectric amplifier for a laser system used in a matter-wave interferometer. The piezoelectric driver is an essential part of each laser feedback system that controls the lock of each laser in the matter-wave interferometer. The lasers that we are building require extremely stable laser locks, therefore the piezoelectric amplifier I built must also be very quiet. I built this piezoelectric driver to be a lot less expensive and quieter than commercial units. 2.1 Background-In our research group we are building a matter-wave interferometer. The interferometer requires lasers to cool strontium atoms in a magneto optical trap, to ionize a stream of slow strontium atoms, and to provide pi and half pi pulses used in the

unknown authors

2012-01-01

449

Interferometer observations of RS Canum Venaticorum binaries  

NASA Astrophysics Data System (ADS)

We present radio flux measurements at 5 GHz for a sample of RS CVn-type chromospherically active binary systems made from 1988 to 1992 using the Nuffield Radio Astronomy Laboratories (NRAL) broad-band interferometer (BBI). The derived radio luminosities are consistent with previous observations but show that radio flaring is a common feature which will effect the results of rotation-activity studies. The mean brightness temperature for our sample, assuming a radio source size equal to twice the radius of the active stellar component, is consistent with a gyrosynchrotron emission process from mildly relativistic electrons.

Gunn, A. G.; Spencer, R. E.; Abdul Aziz, H.; Doyle, J. G.; Davis, R. J.; Pavelin, P. E.

1994-11-01

450

Micro-Precision Interferometer: Pointing Control System  

NASA Technical Reports Server (NTRS)

This paper describes the development of the wavefront tilt (pointing) control system for the JPL Micro-Precision Interferometer (MPI). This control system employs piezo-electric actuators and a digital imaging sensor with feedback compensation to reject errors in instrument pointing. Stringent performance goals require large feedback, however, several characteristics of the plant tend to restrict the available bandwidth. A robust 7th-order wavefront tilt control system was successfully implemented on the MPI instrument, providing sufficient disturbance rejection performance to satisfy the established interference fringe visibility.

O'Brien, John

1995-01-01

451

Commissioning status of the Virgo interferometer  

NASA Astrophysics Data System (ADS)

The Virgo interferometer is one of the big observatories aimed at detecting gravitational waves. This paper will describe the Virgo + upgrades and the commissioning work performed between the first Virgo science run (VSR1) and the second Virgo science run (VSR2). Some first results of VSR2 will be discussed, which was recently started with a good duty cycle and an inspiral range for the detection of binary neutron-star inspirals of 10 Mpc. To conclude, an outlook will be given on some future upgrades of the detector.

Accadia, T.; Swinkels, B. L.; Virgo Collaboration

2010-04-01

452

The Virgo Interferometer for Gravitational Wave Detection  

NASA Astrophysics Data System (ADS)

The Virgo interferometer for gravitational wave detection is described. During the commissioning phase that followed the first scientific data taking run an unprecedented sensitivity was obtained in the range 10-60 Hz. Since then an upgrade program has begun, with the aim of increasing the sensitivity, mainly through the introduction of fused silica wires to suspend mirrors and by increasing the Finesse of the Fabry-Perot cavities. Plans until the shutdown for the construction of the Advanced Virgo detector are given as well as the status of the upgrade.

Accadia, T.; Acernese, F.; Antonucci, F.; Astone, P.; Ballardin, G.; Barone, F.; Barsuglia, M.; Bauer, Th. S.; Beker, M. G.; Belletoile, A.; Birindelli, S.; Bitossi, M.; Bizouard, M. A.; Blom, M.; Boccara, C.; Bondu, F.; Bonelli, L.; Bonnand, R.; Boschi, V.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brillet, A.; Brisson, V.; Budzy?ski, R.; Bulik, T.; Bulten, H. J.; Buskulic, D.; Buy, C.; Cagnoli, G.; Calloni, E.; Campagna, E.; Canuel, B.; Carbognani, F.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cesarini, E.; Chassande-Mottin, E.; Chincarini, A.; Cleva, F.; Coccia, E.; Colacino, C. N.; Colas, J.; Colla, A.; Colombini, M.; Corsi, A.; Coulon, J.-P.; Cuoco, E.; D'Antonio, S.; Dattilo, V.; Davier, M.; Day, R.; Rosa, R. De; Debreczeni, G.; Del Prete, M.; di Fiore, L.; di Lieto, A.; di Paolo Emilio, M.; di Virgilio, A.; Dietz, A.; Dietz, A.; Drago, M.; Fafone, V.; Ferrante, I.; Fidecaro, F.; Fiori, I.; Flaminio, R.; Fournier, J.-D.; Franc, J.; Frasca, S.; Frasconi, F.; Freise, A.; Galimberti, M.; Gammaitoni, L.; Garufi, F.; Gáspár, M. E.; Gemme, G.; Genin, E.; Gennai, A.; Giazotto, A.; Gouaty, R.; Granata, M.; Greverie, C.; Guidi, G. M.; Hayau, J.-F.; Heitmann, H.; Hello, P.; Hild, S.; Huet, D.; Jaranowski, P.; Kowalska, I.; Królak, A.; Leroy, N.; Letendre, N.; Li, T. G. F.; Lorenzini, M.; Loriette, V.; Losurdo, G.; Majorana, E.; Maksimovic, I.; Man, N.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marque, J.; Martelli, F.; Masserot, A.; Michel, C.; Milano, L.; Minenkov, Y.; Mohan, M.; Moreau, J.; Morgado, N.; Morgia, A.; Mosca, S.; Moscatelli, V.; Mours, B.; Neri, I.; Nocera, F.; Pagliaroli, G.; Palladino, L.; Palomba, C.; Paoletti, F.; Pardi, S.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Persichetti, G.; Pichot, M.; Piergiovanni, F.; Pietka, M.; Pinard, L.; Poggiani, R.; Prato, M.; Prodi, G. A.; Punturo, M.; Puppo, P.; Rabeling, D. S.; Rácz, I.; Rapagnani, P.; Re, V.; Regimbau, T.; Ricci, F.; Robinet, F.; Rocchi, A.; Rolland, L.; Romano, R.; Rosi?ska, D.; Ruggi, P.; Sassolas, B.; Sentenac, D.; Sperandio, L.; Sturani, R.; Swinkels, B.; Toncelli, A.; Tonelli, M.; Torre, O.; Tournefier, E.; Travasso, F.; Vajente, G.; van den Brand, J. F. J.; van der Putten, S.; Vasuth, M.; Vavoulidis, M.; Vedovato, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinet, J.-Y.; Vocca, H.; Was, M.; Yvert, M.

453

'EXTREME ULTRAVIOLET WAVES' ARE WAVES: FIRST QUADRATURE OBSERVATIONS OF AN EXTREME ULTRAVIOLET WAVE FROM STEREO  

SciTech Connect

The nature of coronal mass ejection (CME)-associated low corona propagating disturbances, 'extreme ultraviolet (EUV) waves', has been controversial since their discovery by EIT on SOHO. The low-cadence, single-viewpoint EUV images and the lack of simultaneous inner corona white-light observations have hindered the resolution of the debate on whether they are true waves or just projections of the expanding CME. The operation of the twin EUV imagers and inner corona coronagraphs aboard STEREO has improved the situation dramatically. During early 2009, the STEREO Ahead (STA) and Behind (STB) spacecrafts observed the Sun in quadrature having a {approx}90 deg. angular separation. An EUV wave and CME erupted from active region 11012, on February 13, when the region was exactly at the limb for STA and hence at disk center for STB. The STEREO observations capture the development of a CME and its accompanying EUV wave not only with high cadence but also in quadrature. The resulting unprecedented data set allowed us to separate the CME structures from the EUV wave signatures and to determine without doubt the true nature of the wave. It is a fast-mode MHD wave after all.

Patsourakos, Spiros [George Mason University, Fairfax, VA 22030 (United States); Vourlidas, Angelos [Code 7663, Naval Research Laboratory, Washington, DC 20375 (United States)], E-mail: spiros.patsourakos@nrl.navy.mil, E-mail: vourlidas@nrl.navy.mil

2009-08-01

454

Application of Quadrature Methods for Re-Weighting in Lattice QCD  

SciTech Connect

Re-weighting is a useful tool that has been employed in Lattice QCD in different contexts including, tuning the strange quark mass, approaching the light quark mass regime, and simulating electromagnetic fields on top of QCD gauge configurations. In case of re-weighting the sea quark mass, the re-weighting factor is given by the ratio of the determinants of two Dirac operators D{sub a} and D{sub b}. A popular approach for computing this ratio is to use a pseudofermion representation of the determinant of the composite operator {Omega} = D{sub a}(D{sub b}{sup {dagger}}D{sub b}){sup -1} D{sub a}{sup {dagger}}. Here, we study using quadrature methods together with noise vectors to compute the ratio of determinants. We show that, with quadrature methods each determinant can be computed separately using the operators {Omega}{sub a} = D{sub a}{sup {dagger}}D{sub a} and {Omega}{sub b} = D{sub b}{sup {dagger}} D{sub b}. We also discuss using bootstrap re-sampling to remove the bias from the determinant estimator.

Abdou Abdel-Rehim, William Detmold, Kostas Orginos

2011-12-01

455

Highly precise nonlinear error calibrating system based on Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

Nanometer measurement has become more and more important in the development of metrology, material science, microelectronics and biology. Heterodyne Fabry-Perot interferometer can be used in the nonlinear error calibration with an accuracy of nanometer and sub-nanometer order. We can get very high resolution by using heterodyne Fabry-Perot interferometer frequency locking technique in theory. However, the measure uncertainty and the stability of results are worse than the expectation's. In this paper, in order to solve the problems of air refrective index change and temperature excursion, we designed the vacuum system that adjusts the interference light path and built it based on NIM's heterodyne Fabry-Perot interferometer. The key in our design is to reduce the thermic balance time and to ensure reliable hermetization of movable components. The influnce of the change of air refractive index to the measured precision was studied, and the approximate formula of vacuum degree that the system requires was concluded. It has been proved in the experiment that the system works steadily. The system's ability of anti-jamming has been improved, and the demand of the measure surroundings has been lowered. Comparing with capacitance displacement measurement instrument, we conclude that the nonlinear degree of this system in the range of 0.35um, which is longer than half of the wavelength of the laser, is better than 3.9nm.

Ma, Jichi; Li, Yan; Yin, Chunyong

2008-03-01

456

Linear diffraction grating interferometer with high alignment tolerance and high accuracy  

SciTech Connect

We present an innovative structure of a linear diffraction grating interferometer as a long stroke and nanometer resolution displacement sensor for any linear stage. The principle of this diffractive interferometer is based on the phase information encoded by the {+-}1st order beams diffracted by a holographic grating. Properly interfering these two beams leads to modulation similar to a Doppler frequency shift that can be translated to displacement measurements via phase decoding. A self-compensation structure is developed to improve the alignment tolerance. LightTool analysis shows that this new structure is completely immune to alignment errors of offset, standoff, yaw, and roll. The tolerance of the pitch is also acceptable for most installation conditions. In order to compact the structure and improve the signal quality, a new optical bonding technology by mechanical fixture is presented so that the miniature optics can be permanently bonded together without an air gap in between. For the output waveform signals, a software module is developed for fast real-time pulse counting and phase subdivision. A laser interferometer HP5529A is employed to test the repeatability of the whole system. Experimental data show that within 15 mm travel length, the repeatability is within 15 nm.

Cheng Fang; Fan, Kuang-Chao