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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

A precise and wide-dynamic-range displacement-measuring homodyne quadrature laser interferometer  

NASA Astrophysics Data System (ADS)

We present a fast, displacement-measuring, single-pass, two-detector homodyne quadrature laser interferometer and compare its performance with an arm-compensated, proportional, integral-derivative-controlled Michelson interferometer. Special attention is given to the extension of the dynamic range. The wide dynamic range is achieved by an accurate fringe subdivision based on an enhanced ellipse-specific fitting of the scattered Lissajous curve and by increasing the total displacement using the quadrature-detection technique. The common periodic deviations, i.e., the unequal AC amplitudes, the DC offsets, and the lack of quadrature are determined and reduced by data processing based on an ellipse-specific, least-squares fitting to obtain nanometric accuracy. The performance of the described interferometer is demonstrated through the measurement of high-amplitude and high-frequency laser-induced ultrasound.

Požar, T.; Gregor?i?, P.; Možina, J.

2011-11-01

3

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

4

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

NASA Astrophysics Data System (ADS)

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

Požar, T.; Možina, J.

2011-08-01

5

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.

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

2013-01-01

6

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

7

Measurement of the Ti X ion density in a theta-pinch plasma by a laser heterodyne quadrature interferometer  

SciTech Connect

The increase in the radial line integral of the electron density in the National Bureau of Standards theta-pinch plasma due to the ionization of the titanium impurity has been measured with the use of a He-Ne laser heterodyne quadrature interferometer. Titanium is injected as an impurity into the base gas of hydrogen with the use of a coaxial gun discharge between titanium electrodes. The Ti X ion density at its peak abundance in the plasma is deduced in each discharge from the measured increase in electron density by knowing the temporal charge-state distribution of Ti ions with the use of spectroscopy and assuming charge neutrality.

Datla, R.U.

1985-04-01

8

Spheromak Plasma Density Measurement Using a Quadrature Phase Interferometer  

NASA Astrophysics Data System (ADS)

A quadrature phase homodyne interferometer has been developed in double-pass Michelson geometry to measure the density of plasma produced in the Caltech spheromak experiment. The design is specially suited for large vacuum chambers (˜1.5m in diameter) and for experiments with time scales (˜10 ?s) much less than the time scale of acoustic vibrations. Quadrature phase information is generated by the interference of a linearly polarized scene beam and a circularly polarized reference beam. Path length difference between the two beams is approximately 3m. To compensate for this large difference, we utilize a non-fundamental longitudinal mode of the HeNe laser. This ensures a greatly simplified optical alignment procedure. The interferometer detected very high densities (˜10^22/m^3) of the central plasma jet column. The high densities have been corroborated by Stark broadening measurements. Motivated by the results of the homodyne interferometer, a prototype heterodyne interferometer is also being developed. It is expected to have much better signal to noise ratio.

Kumar, Deepak

2005-10-01

9

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

10

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

11

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

12

Phase-shift error in quadrature-detection-based interferometers  

NASA Astrophysics Data System (ADS)

This contribution investigates the influence of phase shift on the measured displacement error in interferometers based on quadrature detection. This error was experimentally investigated using a two-detector homodyne quadrature laser interferometer (HQLI) with two orthogonally polarized signals. Here, the phase shift can be continuously varied by rotating a wave plate. However, the rotation of the wave plate also produces unequal signal amplitudes and different zero offsets, both of which can be corrected with an appropriate signal processing. 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. For the robust realization of a HQLI, a slight deviation from the aligned angle of the wave plate should not shift the phase significantly from the ideal 90°. This may pose a problem if an additional phase shift originates from the polarization-sensitive light reflections, such as the reflection at the nonpolarizing beam splitter.

Gregorcic, Peter; Požar, Tomaž; Mozina, Janez

2010-04-01

13

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

14

Fourier domain--optical coherence tomography based on a quadrature Mach-Zehnder interferometer.  

PubMed

A quadrature Mach-Zehnder interferometer based on a 3 x 3 fiber coupler is presented. This novel interferometric platform is used in a homodyne configuration within an optical coherence tomography system. A fast swept laser source is used as light source. The complex interferometric signal is reconstructed so the complex conjugate ambiguity is removed. The features of this novel setup are discussed. PMID:18002538

Flueraru, C; Mao, Y; Sherif, S; Chang, S

2007-01-01

15

Nonlinear errors of passive homodyne polarized laser interferometer  

NASA Astrophysics Data System (ADS)

Based on Jones matrices theory, the paper researches the error source and action mechanism of the polarized interferometer in nanometer level measurement. It opens the door for selecting optical component, adjusting light set-up and compensating error. According to the theoretical analysis, the main reason that causes error is degeneration of polarization that the imperfect performance of optical components and imperfect adjusting bring. Especially the different delay angle happens more obviously. The characteristic of the passive homodyne laser interferometer based on the polarized phase-shift is that the output of interferometer is four-channel signals in quadrature. Using this characteristic, through strict selecting and fine adjusting components and differential signal processing, the interferometer can perform nanometer measurement.

Yang, Jun; Wu, Bing; Liu, Zhi-hai; Yuan, Li-bo

2007-03-01

16

The dynamic compensation of nonlinearity in a homodyne laser interferometer  

NASA Astrophysics Data System (ADS)

This paper presents a simple system for the dynamic compensation of nonlinearity in a homodyne laser interferometer that can be used for high-precision length measurement. The computer collects two phase-quadrature signals, and calculates the DC offsets, the AC amplitudes and the difference from the phase-quadrature by the elliptical fitting with a least-squares method. The control signals for adjusting these ellipse parameters are fed into the automatic control circuit through the D/A converters so that the offsets are zero, the amplitudes are same and the phase difference is 90°. As a result, the nonlinearity is eliminated electronically. The system can be used in applications requiring the real-time compensation of nonlinearity. Experimental results demonstrate that the nonlinearity of the homodyne interferometer can be reduced to sub-nanometre over the measuring range of 100 mm.

Eom, Tae Bong; Kim, Jong Yun; Jeong, Kyuwon

2001-10-01

17

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

18

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).

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

2012-01-01

19

Detection of interference phase by digital computation of quadrature signals in homodyne laser interferometry.  

PubMed

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

20

Michelson interferometer for laser wavelength  

NASA Astrophysics Data System (ADS)

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

Wang, Liqiang; Ren, Wenjie

2005-12-01

21

Quantum noise in laser-interferometer gravitational-wave detectors with a heterodyne readout scheme  

NASA Astrophysics Data System (ADS)

We analyze and discuss the quantum noise in signal-recycled laser interferometer gravitational-wave detectors, such as Advanced LIGO, using a heterodyne readout scheme and taking into account the optomechanical dynamics. Contrary to homodyne detection, a heterodyne readout scheme can simultaneously measure more than one quadrature of the output field, providing an additional way of optimizing the interferometer sensitivity, but at the price of additional noise. Our analysis provides the framework needed to evaluate whether a homodyne or heterodyne readout scheme is more optimal for second generation interferometers from an astrophysical point of view. As a more theoretical outcome of our analysis, we show that as a consequence of the Heisenberg uncertainty principle the heterodyne scheme cannot convert conventional interferometers into (broadband) quantum non-demolition interferometers.

Buonanno, Alessandra; Chen, Yanbei; Mavalvala, Nergis

2003-06-01

22

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

23

A Laser Interferometer for Measuring Linear Vibration.  

National Technical Information Service (NTIS)

A reference-beam type interferometer for the measurement of vibration is described. In the technique used, laser light reflected from a vibrating object is shifted in frequency (Doppler shift) because of the velocity of the object. The reflected light is ...

D. G. Simpson D. G. S. Lamb

1978-01-01

24

Lattice interferometer for laser-cooled atoms.  

PubMed

We demonstrate an atom interferometer in which atoms are laser cooled into a 1D optical lattice, suddenly released, and later subjected to a pulsed optical lattice. For short pulses, a simple analytical theory predicts the signal. We investigate both short and longer pulses where the analytical theory fails. Longer pulses yield higher precision and larger signals, and we observe a coherent signal at times that can differ significantly from the expected echo time. The interferometer has potential for precision measurements of variant Planck's/m(A), and can probe the dynamics of atoms in an optical lattice. PMID:19792621

Andersen, Mikkel F; Sleator, Tycho

2009-08-14

25

Lattice Interferometer for Laser-Cooled Atoms  

SciTech Connect

We demonstrate an atom interferometer in which atoms are laser cooled into a 1D optical lattice, suddenly released, and later subjected to a pulsed optical lattice. For short pulses, a simple analytical theory predicts the signal. We investigate both short and longer pulses where the analytical theory fails. Longer pulses yield higher precision and larger signals, and we observe a coherent signal at times that can differ significantly from the expected echo time. The interferometer has potential for precision measurements of (Planck constant/2pi)/m{sub A}, and can probe the dynamics of atoms in an optical lattice.

Andersen, Mikkel F.; Sleator, Tycho [Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8424 (United States) and Jack Dodd Center for Quantum Technology, Department of Physics, University of Otago (New Zealand); Department of Physics, New York University, 4 Washington Place, New York, New York 10003 (United States)

2009-08-14

26

An improved phase quadrature correction method by fitting the pesudo quadrature phase difference  

NASA Astrophysics Data System (ADS)

A novel type of homodyne interferometer with a real time nonlinearity tracking and compensation algorithm is presented. This interferometer measures the displacement motion of an object with a single measuring laser beam and two photodiodes with ?/2 phase difference. A novel nonlinearity correction method is derived based on minimizing pseudo phase difference between the quadrature channels. Experiment results shows that this method could correct not only the quadrature error caused by imperfection and misalignment of polarization optics, but also the variation of interference intensity related to laser power variation.

Liang, Chao-Wen; Tsai, Yung-Sheng

2009-08-01

27

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

28

Experimental generation of broadband quadrature entanglement using laser pulses  

NASA Astrophysics Data System (ADS)

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 ??2(Xa+Xb)?+??2(Ya-Yb)?=1.28<2 .

Zhang, Yun; Furuta, Tatsuya; Okubo, Ryuhi; Takahashi, Kosuke; Hirano, Takuya

2007-07-01

29

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

30

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

31

Control of the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

The detection of gravity waves will open a new window of observation on the universe. Unlike typical observatories, which detect electromagnetic waves traveling through space-time, the Laser Interferometer Space Antenna (LISA) will detect ripples in space-time itself. Science targets include galactic binaries, merging supermassive black holes, intermediate-mass/seed black holes, and cosmological backgrounds. Gravity waves are detected by measuring the strain in space, i.e. the change in distance between a set of masses (test masses or proof masses) separated by a great distance. Ground based detection of gravity waves by Laser Interferometer Gravitational Wave Observatory (LIGO) and other observatories are possible with laser interferometry; hut the relatively short arm length (4 km) and seismic noise limit the measurement band to above 10 Hz on Earth. LISA also uses laser interferometric measurement of the change in distance between test masses, but does it in space. Each LISA spacecraft embodies two test masses. Space allows very long arm lengths (5 million km for LISA) and a very quiet acceleration environment (3.5x10(exp -15) meters per second squared/Hertz (sup 0.5) for LISA), which allows for the detection of gravity wave strains to a best sensitivity of 3x10(exp -24) strain/Hertz (sup 0.5) over the measurement band of 10(exp -4) to 10(exp -1) Hertz for a one-year observation. The LISA mission consists of three spacecraft in heliocentric orbit. The orbits are chosen so that the three spacecraft form a roughly equilateral triangle with its center located at a radius of 1 AU and 20 degrees behind the Earth, as shown. Requirements are placed on the rotational and translational dynamics of each spacecraft to ensure that the proper sensitivity for science measurements can be achieved.

Maghami, Peiman; Hyde, T. Tupper

2003-01-01

32

Gravitational wave detection with single-laser atom interferometers  

Microsoft Academic Search

We present a new general design approach of a broad-band detector of gravitational radiation that relies on two atom interferometers\\u000a separated by a distance L. In this scheme, only one arm and one laser will be used for operating the two atom interferometers. We consider atoms in\\u000a the atom interferometers not only as perfect inertial reference sensors, but also as

Nan Yu; Massimo Tinto

2011-01-01

33

Mission analysis for the Laser Interferometer Space Antenna (LISA) mission  

Microsoft Academic Search

The interplanetary orbits of three pairs of spacecraft, forming three laser interferometers, are designed such that their separations, i.e. the lengths of the interferometer arms, remain nearly constant. Each spacecraft pair is located near the vertex of a rotating equilateral triangle formed by the individual orbits of the spacecraft about the Sun. Feasible spacecraft masses are computed for a scenario

F. Hechler; W. M. Folkner

2003-01-01

34

Homodyne interferometry with quadrature fringe detection for absolute gravimeter.  

PubMed

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

Svitlov, Sergiy; Araya, Akito

2014-06-01

35

Gravitational wave detectors based on matter wave interferometers (MIGO) are no better than laser interferometers (LIGO)  

Microsoft Academic Search

We show that a recent claim that matter wave interferometers have a much\\u000ahigher sensitivity than laser interferometers for a comparable physical setup\\u000ais unfounded. We point out where the mistake in the earlier analysis is made.\\u000aWe also disprove the claim that only a description based on the geodesic\\u000adeviation equation can produce the correct physical result. The equations

Albert Roura; Dieter R. Brill; B. L. Hu; Charles W. Misner; William D. Phillips

2006-01-01

36

Gauge block interferometer using three frequency-stabilized lasers  

NASA Astrophysics Data System (ADS)

We have developed a gauge block measurement system that uses three frequency-stabilized lasers. The stabilized lasers are as follows: an I2 stabilized offset locked He-Ne laser, an I2-stabilized Nd:YAG laser, and a Rb-stabilized diode laser. The I2-stabilized offset locked He-Ne laser is commercially available and its relative wavelength uncertainty is 2.5 X 10-11. An I2-stabilized Nd:YAG laser and a Rb-stabilized diode laser was developed in our institute and their relative wavelength uncertainties are 5 X 10-12 and 1 X 10-9, respectively. In the measurement system, laser beams were introduced to the interferometer using an optical multimode fiber. An interferometer fringe pattern was taken using a CCD camera and the excess fraction parts were calculated from the fringe pattern using the Fourier transform method. The excess fraction part obtained from the Rb-stabilized semiconductor laser was used only to determine the integer part of the fringe order, because the accuracy and stability of the wavelength were not sufficient for the long gauge block measurements. This interferometer can measure gauge blocks of up to 1000 nm long and the standard uncertainty of the interferometer is about 75 nm for a 1000 mm long gauge block.

Bitou, Youichi; Hirai, Akiko; Yoshimori, Hideaki; Hong, Feng-Lei; Zhang, Yun; Onae, Atsushi; Seta, Katuo

2001-10-01

37

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

NASA Astrophysics Data System (ADS)

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

Büttner, Lars; Czarske, Jürgen

2003-07-01

38

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

PubMed

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

Büttner, Lars; Czarske, Jürgen

2003-07-01

39

A CO2 laser interferometer insensitive to vibrations  

NASA Astrophysics Data System (ADS)

A dispersion interferometer has two optical channels with the same geometrical path but separate wavelengths. The key advantage of the dispersion interferometer--low sensitivity to vibrations--derives from this optical layout. A dispersion interferometer based on a CO2 laser has been developed for the the Gas Dynamic Trap (GDT) experiment. The sensitivity for measurements of line plasma density is ˜1x10^13 cm-2, temporal resolution ˜50 microseconds, and spatial resolution ˜1 cm. A ZnGeP2 nonlinear crystal is used as a frequency doubler to produce the two wavelengths that propagate through the plasma. The interferometer does not require specific vibration isolation structure and can be mounted directly on the working chamber of the plasma device.

Bagryansky, P. A.; Khilchenko, A. D.; Lizunov, A. A.; Maximov, V. V.; Voskoboynikov, R. V.; Solomahin, A. L.

2004-11-01

40

Confocal Fabry-Perot interferometer for frequency stabilization of laser  

NASA Astrophysics Data System (ADS)

The frequency shift of laser source of Doppler lidar is required in the range of a few megahertzs. To satisfy this demand, a confocal Fabry-Perot (F-P) interferometer was manufactured as the frequency standard for frequency stabilization. After analyzing and contrasting the center frequency shift of confocal Fabry-Perot interferometers that are made of three different types of material with the change of temperature, the zerodur material was selected to fabricate the interferometer, and the cavity mirrors were optically contacted onto the end of spacer. The confocal Fabry-Perot interferometer was situated within a double-walled chamber, and the change of temperature in the chamber was less than 0.01 K. The experimental results indicate that the free spectral range is 500 MHz, the full-width at half maximum is 3.33 MHz, and the finesse is 150.

Pan, H.-J.; Ruan, P.; Wang, H.-W.; Li, F.

2011-02-01

41

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

42

Explosive component acceptance tester using laser interferometer technology  

Microsoft Academic Search

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

Richard D. Wickstrom; William W. Tarbell

1993-01-01

43

Errors in the Measurement of Angle with a Laser Interferometer.  

National Technical Information Service (NTIS)

It is shown that when a laser interferometer is used for general angle measurement, including the calibration of angle measuring instruments such as rotary tables, errors of 30 inches or more can occur unless great care is taken in the optical alignment. ...

L. M. Ramsay D. B. Prowse

1979-01-01

44

Lithium atom interferometer using laser diffraction: description and experiments  

Microsoft Academic Search

We have built and operated an atom interferometer of the Mach-Zehnder type. The atomic wave is a supersonic beam of lithium seeded in argon and the mirrors and beam-splitters for the atomic wave are based on elastic Bragg diffraction on laser standing waves at ? = 671 nm. We give here a detailed description of our experimental setup and of

A. Miffre; M. Jacquey; M. Buchner; G. Trenec; J. Vigue

45

Dual-probe laser interferometer for structural health monitoring.  

PubMed

In this note we present the development of a dual-probe laser interferometer that uses the filtering properties of a polarized beamsplitter to enable two independent (uncoupled) detection probes. The robustness of this system is demonstrated by making broadband, noncontact, high fidelity measurements of Lamb waves in an aluminum plate. PMID:16642800

Hurlebaus, Stefan; Jacobs, Laurence J

2006-04-01

46

Long gauge block interferometer using two frequency-stabilized lasers  

NASA Astrophysics Data System (ADS)

The design and construction of a laser interferometer using the method of exact fractions for high-accuracy calibration of gauge blocks up to about one meter in length, are described. The interferometer is based on the classical Michelson arrangement. A two-mode stabilized He-Ne laser emitting light at a wavelength of 633 nm is the primary wavelength reference for the interferometric length measurement, since its frequency is calibrated by heterodyne measurement with an iodine-stabilized He-Ne laser at 633 nm which is used to maintain the national meter standard. A second two-mode stabilized He-Ne laser, at a wavelength of 543 nm, is used in order define the absolute length. The estimated standard uncertainty for interferometric length measurements is about 50 nm for a 1 meter gauge block. Results from trial measurements made on various gauge blocks, including a bilateral comparison, are reported.

Frennberg, Mikael; Johansson, M.; Kaellberg, Stefan; Karn, U.; Pendrill, Leslie R.

1998-09-01

47

Sinusoidal phase modulating laser diode interferometer using an additive operating type of integrating bucket method  

NASA Astrophysics Data System (ADS)

We propose a sinusoidal phase modulating laser diode interferometer using an additive operating type of integrating bucket method. In previous integrating bucket method, four images, which are integrated values of the interference pattern detected by a CCD image sensor, are required. According to additive and subtractive operations in a calculator, the quadrature signals can be calculated from these images. While these operations are associated with the technical computing software, such as MATLAB, in a personal computer, it is quite fast, even if the images possess large size. In a standard-alone system with a CPU, however, this kind of operation expends unbearable time. To lighten the burden of the calculator, we tried to simplify the operation. That is, on the basis of integrating bucket method, the subtraction in the signal processing is transformed to the addition by use of the phase shifting technique. All additive operations are achieved with the CCD image sensor. In this interferometer, not only the calculating quantity is reduced, but also the number of required images is reduced. The surface profile of a diamond-turned aluminum disk was measured. The repeatability in the measurements was 5.93 nm rms.

Zhao, Xuefeng; Suzuki, Takamasa; Sasaki, Osami

2002-09-01

48

Transverse modes in laser cavities terminating in reflective multipass interferometers  

NASA Astrophysics Data System (ADS)

The effect of reflective multipass interferometers on the transverse modes of laser cavities equipped with these devices is investigated. We demonstrate, both theoretically and experimentally in a pulsed CO2 laser, how information on the characteristics of these modes can be directly derived by simply describing these cavities in terms of suitable equivalent geometric parameters. We also discuss and explain the transverse-mode selective properties of these multimirror cavities.

Nichelatti, E.; Salvetti, G.

1995-05-01

49

Arm Locking for the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

50

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

51

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

52

Calcium-atom interferometer comprised of four copropagating traveling laser beams  

Microsoft Academic Search

Four laser beams traveling in the same direction that split and reflect a thermal calcium atomic beam compose an atomic interferometer like the Mach-Zehnder optical interferometer. The interference performance of the atomic interferometer was examined by changing the phase of the induced dipole moment in the atomic wave due to the laser beams, or the phase of atomic ``wavepacket'' in

Atsuo Morinaga; Yasushi Ohuchi

1995-01-01

53

A lunar gravitational wave antenna using a laser interferometer  

NASA Astrophysics Data System (ADS)

A moon-based laser interferometer for detecting gravitational radiation could detect signals in the band 0.1 - 10,000 Hz. A preliminary evaluation of the noise budget for an optimistic antenna design is reported here and compared to that for other planned gravitational wave interferometers. Over most of the frequency range, the sensitivity is controlled by the thermal noise in the test mass suspensions. From roughly 3 to a few hundred Hertz, it is about the same as the sensitivity expected in terrestrial antennas of the same construction, which will have been operating for at least a decade. Below 0.3 Hz, a proposed space-based interferometer, designed for operation down to 10 exp -5 Hz, would have better sensitivity.

Stebbins, R. T.; Bender, P. L.

1990-03-01

54

Measuring large amplitudes of mechanical vibrations with laser interferometers  

NASA Astrophysics Data System (ADS)

Heterodyne methods of laser interferometry are the most promising methods of measuring large mechanical vibrations, their main advantages being that they are contactless and remote operational, and their main features being high accuracy and reproducibility of readings. However, use of a square-law photodetector and a frequency detector with a laser interferometer requires conversion to single-frequency laser radiation to two-frequency one. An attendant problem is to provide a stable and efficient wideband heterodyne with wide dynamic range for a reference signal with a Doppler frequency shift sufficiently large relative to the frequency of the probing signal. One known method of such interferometry which meets these requirements involves use of an oscillograph and an electronic-counter frequency meter. The principle of this method is outlined on the example of one mirror of a two-beam interferometer, assuming that its vibrations are harmonic. The interferometer for this application consists of a light splitter, a reference mirror, and a movable mirror with a Teflon membrane controlled by a sine-wave generator. The light source is an LG-79/1 He-Ne laser. The photodetector is an FD-21 KP photodiode with a time constant of 6 ns. Vibrations are measured with a Ch3-34A frequency meter.

Bondarenko, A. N.; Trotsenko, V. P.

1984-09-01

55

Novel laser grating interferometer (LES) for industrial applications  

NASA Astrophysics Data System (ADS)

The concept, optomechanical design and principles of operation of novel laser grating interferometer are described. The system works in on-line, local strain measurement mode and off-line full-field, in-plane displacement/strain measurement mode. The extensometer is fully automatic and integrated with standard loading machine. Its applicability for solving various experimental mechanics and industrial problems is shown at numerous examples.

Kujawinska, Malgorzata; Salbut, Leszek A.

2001-10-01

56

Lithium atom interferometer using laser diffraction: description and experiments  

Microsoft Academic Search

.  We have built and operated an atom interferometer of the\\u000aMach-Zehnder type. The atomic wave is a supersonic beam of lithium\\u000aseeded in argon and the mirrors and beam-splitters for the atomic\\u000awave are based on elastic Bragg diffraction on laser standing\\u000awaves at =671 nm. We give here a detailed description of\\u000aour experimental set-up and of the procedures used

Alain Miffre; Marion Jacquey; M. Büchner; G. Trénec; J. Vigué

2005-01-01

57

Four-level atom interferometer with trichromatic laser fields  

SciTech Connect

A four-level atom interferometer comprised of three excited states and one ground state with trichromatic fields coupled between them is investigated using Zeeman sublevels of {sup 3}P{sub 1} and {sup 1}S{sub 0} states of a calcium atom. A theoretical description of the interaction of four-level atoms with trichromatic laser fields is presented and compared with the experimental results of the interference fringes which are generated by the three excited states.

Honda, Kazuhito; Kobayashi, Yoshiyuki; Morinaga, Atsuo [Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)

2007-02-15

58

Modulated laser interferometer with picometer resolution for piezoelectric characterization  

SciTech Connect

A modified double-beam interferometric measurement system is established and tested for displacement measurement of ferroelectric lead zirconate titanate bulk samples. To overcome the optical path-length drift or laser intensity instability, a modulation technique is introduced, and desired resolution (down to several picometers) and reliability are achieved without the complicated close loop servo system. This modified interferometer provides us a powerful yet easily accessible tool for piezoelectric thin/thick film characterizati0008.

Chao Chen; Wang Zhihong; Zhu Weiguang [Microelectronics Center, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798 Singapore (Singapore)

2004-11-01

59

Three-level atom interferometer with bichromatic laser fields  

SciTech Connect

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the visibility were derived and calculated for several types of the three-level atom interferometers with bichromatic fields. Optimum excitation conditions were evaluated. Next, several types of three-level atom interferometers were demonstrated experimentally using a thermal calcium atomic beam with two Zeeman substates of m=1 and m=-1 in the long-lived excited state coupled with bichromatic resonant fields between the ground state and the excited states. The behaviors of the interference fringes were compared among them along with the calculated results. The three-level atom interferometer excited by two bichromatic laser beams separated in space was found to produce the largest visibility among them when the excitation power of each frequency component was the same.

Honda, Kazuhito; Yanagimachi, Shinya; Morinaga, Atsuo [Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)

2003-10-01

60

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.

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

2014-01-01

61

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

62

Interferometer  

NASA Technical Reports Server (NTRS)

An interferometer of relatively simple design which is tilt compensated, and which facilitates adjustment of the path lengths of split light beams is described. The interferometer includes a pair of plate-like elements with a dielectric coating and an oil film between them, that forms a beamsplitter interface, and with a pair of reflector surfaces at the ends of the plates. A pair of retroreflectors are positioned so that each split beam component is directed by a retroreflector onto one of the reflector surfaces and is then returned to the beamsplitter interface, so that the reflector surfaces tilt in a direction and amount that compensates for tilting of the beamsplitter interface.

Breckinridge, J. B. (inventor)

1981-01-01

63

An Acquisition Control for the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna (LISA) mission is a planned gravitational wave detector consisting of three spacecraft in heliocentric orbit. Laser interferometry is used to measure distance fluctuations between test masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Each spacecraft has two incoming and two outgoing laser beams for a total of six laser links. These links will have to be established sequentially at the start of the mission, and the spacecraft control systems must aim their lasers at each other with pointing motions less than 8 nanoradians per root Hertz in the frequency band 0.1-100 mHz. This paper presents a strategy for the laser acquisition process. The outgoing beam on one spacecraft is spoiled to provide a wide beam that encompasses the accuracy (noise and mounting bias) of the star tracker. The control system then takes advantage of an array of sensors with increasing sensitivity to quiet the receiving spacecraft and lock the laser. This process is carried out for each of the six links of LISA. A complete analysis and simulation of the acquisition process are presented.

Maghami, Peiman G.; Hyde, T. Tupper; Kim, Jinho

2004-01-01

64

Quadrature frequency conversion  

Microsoft Academic Search

A technique for frequency conversion of high-power lasers is described which uses two crystals for each conversion step rather than one. The two crystals are oriented so that the waves generated in them are orthogonally polarized. The conversion efficiency of these quadrature arrangements is much less sensitive to laser pulse nonuniformities than that in single-crystal methods. Consequently, very high conversion

David Eimerl

1987-01-01

65

Ronchi-like laser interferometer for large spectral region-from extreme UV to far infrared  

Microsoft Academic Search

Proposed interferometer is a combination of well known Ronchi optical tester and a special designed laser interferometer for large spectral region: from extreme ultraviolet to far infrared. This apparatus consists of the coherent point light source (it is possible also to use parallel coherent point light beam, for example of laser), two off-axis mirrors, forming two point sources of light,

G. M. Popov; E. G. Popov

2003-01-01

66

Method for continuous end standard measurement utilizing laser interferometer  

NASA Astrophysics Data System (ADS)

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

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

2004-08-01

67

A stable 657nm laser for a Ca atom interferometer  

NASA Astrophysics Data System (ADS)

We will present an extremely stable laser to be used in an atom interferometer. A 657nm grating-stabilized diode laser is locked to a high-finesse cavity using the Pound-Drever-Hall method. Utilizing a feedback circuit with a bandwidth of 5 MHz we see a laser linewidth less than one kHz. In addition to a relatively high bandwidth, our circuit design allows for mode-hop-free scanning over a large range. We are also working on several improvements which should further reduce our linewidth; we are improving passive mechanical and thermal stability of the laser and the optical cavity and plan to change to a higher finesse cavity, we have designed and are testing a more stable current driver based on an updated Hall-Libbrecht design, and we calculating an optimized multiple-input feedback transfer function for our system. We will also present the measurement of the resonances of our optical cavity relative to the Ca intercombination line using a high-temperature vapor cell.

Neyenhuis, Brian; Erickson, Christopher; Tang, Rebecca; Doermann, Greg; van Zijll, Marshall; Durfee, Dallin

2006-05-01

68

Laser Stabilization and Material Studies for the Laser Interferometer Space Antenna (LISA)  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) is a joint NASA/ESA project designed to detect gravitational waves. The University of Florida (UF) LISA laboratory is currently implementing and testing much of the instrumentation of the LISA interferometer measurement system to ensure the success of the upcoming LISA mission. LISA will consist of three spacecraft (SC) orbiting the sun in an equilateral triangular formation with an arm length of 5 Gm. Each SC will house two free floating proof-masses, two laser interferometer benches and two telescopes to transmit the laser light between SC. The constellation will trail the earth by 20° and be tilted by 60° with respect to the ecliptic. LISA is designed to detect low frequency gravitational waves (GWs) in the frequency band of .1mHz to 1 Hz with optimal strain sensitivity of 10^-21/sqrt(Hz) at 3 mHz corresponding to sources such as galactic binaries and black hole mergers. The dimensional stability of all optical paths within each interferometer arm is imperative for the success of LISA. Changes larger than a pm/sqrt(Hz) in the distance between optical components in the interferometer would limit the sensitivity of LISA. The UF LISA lab is testing materials with low thermal expansion coefficients which could be used as spacer materials for the telescopes or as the base material for the optical benches. Together with the LISA group at Goddard Space Flight Center we currently also test the dimensional stability of a silicon carbide telescope structure for LISA. The most demanding requirement on material stability is the requirement for the optical reference cavity which is used as the frequency reference for the lasers. We currently test different sensing schemes for the laser frequency stabilization system of LISA and will also report about these experiments. This work is supported by NASA Contract #00078244 and NASA Grant NNX08AG75G.

Cordes, Amanda; Mueller, G.; Tanner, D. B.; Arsenovic, P.; Livas, J.; Preston, A.; Sanjuan, J.; Reza, S. A.; Mitryk, S.; Eichholz, J.; Spector, A.; Donelan, D.; Spannagel, R.; Korytov, D.

2011-05-01

69

Thermal Noise in Laser Interferometer Gravitational Wave Detectors  

NASA Astrophysics Data System (ADS)

Thermal noise is one of the major limitations to the sensitivity of present and future laser interferometers devoted to gravitational wave detection. According to the fluctuation-dissipation theorem any mechanical oscillator is affected by a motion of thermal origin directly related to its thermodynamic temperature. The mirrors and their suspensions that are used in gravitational wave detectors such as Virgo or LIGO are examples of such mechanical oscillators. As a consequence their position is affected by this thermal vibration and the sensitivity of the gravitational wave detector is thermal noise limited over a wide range of frequencies. After recalling briefly the fluctuation-dissipation theorem and its origins, this chapter describes the main types of thermal noise affecting gravitational wave detectors. In the last part of the chapter a special emphasis is given to the thermal noise due to dissipation in the mirrors optical coatings.

Flaminio, Raffaele

70

LIGO - The Laser Interferometer Gravitational-Wave Observatory  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

71

LIGO: the Laser Interferometer Gravitational-Wave Observatory  

NASA Astrophysics Data System (ADS)

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

Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arain, M. A.; Araya, M.; Armandula, H.; Armor, P.; Aso, Y.; Aston, S.; Aufmuth, P.; Aulbert, C.; Babak, S.; Baker, P.; Ballmer, S.; Barker, C.; Barker, D.; Barr, B.; Barriga, P.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Behnke, B.; Benacquista, M.; Betzwieser, J.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Biswas, R.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bodiya, T. P.; Bogue, L.; Bork, R.; Boschi, V.; Bose, S.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Bridges, D. O.; Brinkmann, M.; Brooks, A. F.; Brown, D. A.; Brummit, A.; Brunet, G.; Bullington, A.; Buonanno, A.; Burmeister, O.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Cannizzo, J.; Cannon, K. C.; Cao, J.; Cardenas, L.; Caride, S.; Castaldi, G.; Caudill, S.; Cavaglià, M.; Cepeda, C.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chatterji, S.; Chelkowski, S.; Chen, Y.; Christensen, N.; Chung, C. T. Y.; Clark, D.; Clark, J.; Clayton, J. H.; Cokelaer, T.; Colacino, C. N.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Coward, D.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Culter, R. M.; Cumming, A.; Cunningham, L.; Danilishin, S. L.; Danzmann, K.; Daudert, B.; Davies, G.; Daw, E. J.; DeBra, D.; Degallaix, J.; Dergachev, V.; Desai, S.; DeSalvo, R.; Dhurandhar, S.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doomes, E. E.; Drever, R. W. P.; Dueck, J.; Duke, I.; Dumas, J.-C.; Dwyer, J. G.; Echols, C.; Edgar, M.; Effler, A.; Ehrens, P.; Espinoza, E.; Etzel, T.; Evans, M.; Evans, T.; Fairhurst, S.; Faltas, Y.; Fan, Y.; Fazi, D.; Fehrmenn, H.; Finn, L. S.; Flasch, K.; Foley, S.; Forrest, C.; Fotopoulos, N.; Franzen, A.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T.; Fritschel, P.; Frolov, V. V.; Fyffe, M.; Galdi, V.; Garofoli, J. A.; Gholami, I.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Goda, K.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Grant, A.; Gras, S.; Gray, C.; Gray, M.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Grimaldi, F.; Grosso, R.; Grote, H.; Grunewald, S.; Guenther, M.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G. D.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Haughian, K.; Hayama, K.; Heefner, J.; Heng, I. S.; Heptonstall, A.; Hewitson, M.; Hild, S.; Hirose, E.; Hoak, D.; Hodge, K. A.; Holt, K.; Hosken, D. J.; Hough, J.; Hoyland, D.; Hughey, B.; Huttner, S. H.; Ingram, D. R.; Isogai, T.; Ito, M.; Ivanov, A.; Johnson, B.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J.; Kasprzyk, D.; Katsavounidis, E.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khan, R.; Khazanov, E.; King, P.; Kissel, J. S.; Klimenko, S.; Kokeyama, K.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Kozak, D.; Krishnan, B.; Kumar, R.; Kwee, P.; Lam, P. K.; Landry, M.; Lantz, B.; Lazzarini, A.; Lei, H.; Lei, M.; Leindecker, N.; Leonor, I.; Li, C.; Lin, H.; Lindquist, P. E.; Littenberg, T. B.; Lockerbie, N. A.; Lodhia, D.; Longo, M.; Lormand, M.; Lu, P.; Lubi?ski, M.; Lucianetti, A.; Lück, H.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Mandel, I.; Mandic, V.; Márka, S.; Márka, Z.; Markosyan, A.; Markowitz, J.; Maros, E.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McHugh, M.; McIntyre, G.; McKechan, D. J. A.; McKenzie, K.; Mehmet, M.; Melatos, A.; Melissinos, A. C.; Menéndez, D. F.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miller, J.; Minelli, J.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Mohanty, S. D.; Mohapatra, S. R. P.; Moreno, G.; Morioka, T.; Mors, K.; Mossavi, K.; Mow Lowry, C.; Mueller, G.; Müller-Ebhardt, H.; Muhammad, D.; Mukherjee, S.; Mukhopadhyay, H.; Mullavey, A.; Munch, J.; Murray, P. G.; Myers, E.; Myers, J.; Nash, T.; Nelson, J.; Newton, G.; Nishizawa, A.; Numata, K.; O'Dell, J.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; Ogin, G. H.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pan, Y.; Pankow, C.; Papa, M. A.; Parameshwaraiah, V.; Patel, P.; Pedraza, M.; Penn, S.; Perraca, A.; Pierro, V.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Postiglione, F.; Principe, M.; Prix, R.; Prokhorov, L.; Punken, O.; Quetschke, V.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raics, Z.; Rainer, N.; Rakhmanov, M.; Raymond, V.; Reed, C. M.; Reed, T.; Rehbein, H.; Reid, S.

2009-07-01

72

Digital Phase Meter for a Laser Heterodyne Interferometer  

NASA Technical Reports Server (NTRS)

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

Loya, Frank

2008-01-01

73

Influence of lasers propagation delay on the sensitivity of atom interferometers  

Microsoft Academic Search

.  In atom interferometers based on two photon transitions,\\u000a the delay induced by the difference of the laser beams paths makes\\u000a the interferometer sensitive to the fluctuations of the frequency\\u000a of the lasers. We first study, in the general case, how the laser\\u000a frequency noise affects the performance of the interferometer\\u000a measurement. Our calculations are compared with the measurements\\u000a performed on

J. Le Gouët; P. Cheinet; J. Kim; D. Holleville; A. Clairon; A. Landragin; F. Pereira Dos Santos

2007-01-01

74

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

75

Highly Sensitive Three Dimensional Measurement Using Ultrashort Pulse Fiber Laser and Fiber Interferometer  

Microsoft Academic Search

Three dimensional measurement system with high sensitivity of 99 dB and high longitudinal resolution of 10 ?m is demonstrated using ultrashort pulse fiber laser and fiber interferometer. Precise image is obtained from 1.5 m distance.

N. Nishizawa; T. Ohta; T. Goto

2005-01-01

76

Relative Power Losses at the Mirrors of an Asymmetric, Confocal, Laser Interferometer.  

National Technical Information Service (NTIS)

The asymmetric, confocal, laser interferometer with output apertures is considered. The diffraction losses at the two mirrors are shown to be equal, regardless of differences in mirror sizes or the existence of coupling apertures in one or both mirrors. (...

G. T. McNice V. E. Derr

1970-01-01

77

A laser interferometer for sub-nanometre measurements in the cochlea.  

PubMed

A modification of a light microscope is described here which allows measurement of nanometre movements along the optical axis of the microscope. The light path is reflected off 10-microns-diametre small glass beads which are individually imaged with the microscope objective. The interferometer is under computer control to allow it to remain in quadrature and so maximise sensitivity. The algorithm is described. Although the techniques are applied to detection of movements of the cochlear partition, they can be used to measure sub-micron movements of any reflecting structures accessible to microscopy. PMID:8544491

Mammano, F; Ashmore, J F

1995-08-01

78

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

79

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

80

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

81

Hyperfine structure measurement of rubidium atom and tunable diode laser stabilization by using Sagnac interferometer.  

PubMed

The Rubidium saturated absorption spectra for D2 transition lines are used to measure the Fabry-Perot interferometer free spectral range (FSR). The scale linearity of the laser frequency tuning is determined. The Sagnac interferometer has been used for the laser stabilization. The result shows that the laser frequency is stabilized upto sub-mega Herz level. Also the hyperfine structure [5(2)S(1/2) F = 3 --> F' = 2, 3, 4 5(2)P(3/2) 85Rb] of the rubidium atom has been measured by using the tilt locking method, which shows the same result as the conventional saturation spectroscopy. PMID:17252811

Kim, Jin-Tae; Zhen, Liu; Kapitanov, Venedikt; Kim, Hyun Su; Park, Jong Rak; Park, Si-Hyun

2006-11-01

82

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

83

Diagnosis of Laser-Induced Shock Waves in Brass Foil Using a Fiber-Optic Interferometer  

NASA Astrophysics Data System (ADS)

A fiber-optic interferometer is developed to investigate shock waves in brass foil impacted by a Neodymium:Yttrium-Aluminium-Garnet (Nd:YAG) laser at a wavelength of 1064 nm and pulse width (FWHM) of 7 ns. Because of introduction of an optical transceiver module, the interferometer is compact and reliable. Appreciable signals due to shock waves have been detected using this interferometer. The shock-wave velocity is deduced from the measured arrival times of shock waves in brass foils with different thicknesses (0.200 and 0.300 mm), and is found to be 8.33 km/s.

Zhang, Ping; Bian, Bao-Min; Li, Zhen-Hua

2005-06-01

84

Passive switches for femtosecond lasers based on a nonlinear Fabry - Perot interferometer with a semiconductor absorber  

SciTech Connect

An analytic model for the description of the generation of ultrashort pulses in solid-state lasers having passive switches based on semiconductor absorbers, considered as nonlinear Fabry - Perot interferometers, is proposed. The possibilities of controlling the parameters of ultrashort pulses by varying the switch parameters are demonstrated. The stability of the solutions obtained is investigated. (control of laser radiation parameters)

Poloiko, I G; Kalashnikov, V L; Mikhailov, V P [International Laser Center, Belarus State Technical University, Minsk (Belarus)

1999-05-31

85

Sensing and control in dual-recycling laser interferometer gravitational-wave detectors.  

PubMed

We introduce length-sensing and control schemes for the dual-recycled cavity-enhanced Michelson interferometer configuration proposed for the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). We discuss the principles of this scheme and show methods that allow sensing and control signals to be derived. Experimental verification was carried out in three benchtop experiments that are introduced. We present the implications of the results from these experiments for Advanced LIGO and other future interferometric gravitational-wave detectors. PMID:12638882

Strain, Kenneth A; Müller, Guido; Delker, Tom; Reitze, David H; Tanner, David B; Mason, James E; Willems, Phil A; Shaddock, Daniel A; Gray, Malcolm B; Mow-Lowry, Conor; McClelland, David E

2003-03-01

86

Miniaturized optical fiber Fabry-Perot interferometer fabricated by femtosecond laser irradiation and selective chemical etching  

NASA Astrophysics Data System (ADS)

A U-shaped optical fiber inline microchannel was fabricated by femtosecond laser irradiation and subsequent selective chemical wet etching. A high quality micro-cavity embedded inside the channel was obtained to construct a Fabry-Perot interferometer (FPI). A fringe visibility of 20 dB in spectrum domain was achieved. High temperature survivability of this micro device was also demonstrated. The proposed assembly-free optical fiber inline interferometer is attractive for sensing applications in high-temperature harsh environments.

Yuan, Lei; Lan, Xinwei; Huang, Jie; Wang, Hanzheng; Cheng, Baokai; Liu, Jie; Xiao, Hai

2014-03-01

87

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

Microsoft Academic Search

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J\\/pulse produced explosive laser heating in atmospheric air. Results show that the peak

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

2011-01-01

88

Gravitational Wave Science with Laser Interferometers and Pulsar Timing  

NASA Astrophysics Data System (ADS)

Within this decade, gravitational wave detection will open a new observational window on the Universe. Advanced ground-based interferometers covering the kilohertz frequency range will be online by 2016, and the announcement of a first detection within 5 years is foreseeable. At the same time, a worldwide effort for detecting low-frequency waves (in the nanohertz regime) by timing ultra-precise millisecond pulsars is rapidly growing, possibly leading to a positive detection within this decade. The millihertz regime, bridging these two windows, is the realm of space-based interferometers, which might be launched in the late 1920s. I provide here a short overview of the scientific payouts of gravitational wave astronomy, focusing the discussion on the low-frequency regime (pulsar timing and space-based interferometry). A detailed discussion of advanced ground-based interferometer can be found in Patrick Brady's contribution to this proceeding series.

Sesana, Alberto

2013-12-01

89

Microscopy of non-birefringent transmissive phase samples using Sagnac laser interferometer.  

PubMed

A cyclic interferometer, appropriately combined with a long working distance microscope objective, is adapted for quantitative phase microscopy. In such an arrangement, the sample information, in terms of the diffracted orders emerging from the sample, is carried by both the counter propagating beams within the cyclic interferometer. However, positioning the sample close to the input/output cube beam splitter and use of a suitably converging laser beam of light as the input to the interferometer ensure that only one of the counter propagating beams carries the object information to the objective while the other beam, which serves as the reference, allows only the undiffracted component to contribute to the process of image formation. Use of suitable polarization optics renders the interferometer its polarization phase shifting property. Using the proposed arrangement, the experimental results showing the quantitative 3D phase rendering of polystyrene microspheres and micro-wells etched in glass are presented. PMID:25080276

Sarkar, Sanjukta; Bhattacharya, K

2014-11-01

90

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

PubMed

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

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

2014-05-01

91

Performance comparison of robust laser interferometer (RLI) and contact accelerometer technology in aviation health monitoring  

Microsoft Academic Search

Accelerometer systems are commonly employed in aviation health and usage monitoring systems (HUMS) and other aviation diagnostic and prognostic system approaches. Over the past decade, an research and development (R&D) robust laser interferometer (RLI) has been employed in a variety of aviation component health measurement situations, and in a variety of functional measurement situations of potential significance for aviation system

Theodore Goodenow; Martin Karchnak; Robert Shipman

2004-01-01

92

New Speckle Analysing Interferometer for the Measurement of Double Exposure Laser Speckle Records.  

National Technical Information Service (NTIS)

A new speckle analyzing interferometer has been devised for the measurement of double exposure laser speckle records. The advantage is that it displays simultaneously side-by-side on a screen the fringe pattern, and an incoherent record of the speckle neg...

J. M. Webster

1985-01-01

93

Visualization of radiation from a high-power terahertz free electron laser with a thermosensitive interferometer  

Microsoft Academic Search

A thermosensitive interferometer based on a plane-parallel glass plate is used for visualization of a high-power terahertz radiation. The plane wavefront of visible radiation emitted by a semiconductor laser is reflected from the two surfaces of the plate and forms on a screen an interference pattern recorded by a digital video camera. Terahertz radiation being measured is incident on the

N. A. Vinokurov; B. A. Knyazev; G. N. Kulipanov; A. N. Matveenko; V. M. Popik; V. S. Cherkassky; M. A. Shcheglov

2007-01-01

94

Optimization of an autodyne laser interferometer for high-speed confocal imaging.  

PubMed

In autodyne interferometry, the beating between the reference beam and the signal beam takes place inside the laser cavity and therefore the laser fulfills simultaneously the roles of the emitter and the detector of photons. In these conditions, the laser relaxation oscillations play a leading role, both in the laser quantum noise that determines the signal-to-noise ratio (SNR) and also in the laser dynamics that determine the response time of the interferometer. In the present study, we have theoretically analyzed the SNR and the response time of a laser optical feedback imaging (LOFI) setup based on an autodyne interferometer. More precisely, we have compared the image quality of two lasers having the same output power and the same relaxation frequency, but having two different values of the LOFI gain induced by two different values of the laser response time. From this study, we have finally determined the best laser dynamical parameters and the best experimental conditions for high-speed imaging at the shot-noise limit. Finally, we conclude that a laser diode with a very short response time (in the nanosecond range) seems to be an interesting candidate compared to solid-state microchip laser with a response time of several tens of microseconds. Analytical predictions are confirmed by numerical simulations. PMID:23456002

Lacot, Eric; Glastre, Wilfried; Jacquin, Olivier; Hugon, Olivier; Guillet de Chatellus, Hugues

2013-01-01

95

Three-level atom interferometer with bichromatic laser fields  

Microsoft Academic Search

We have developed a three-level atom interferometer using three-level atoms coupled with bichromatic fields in order to investigate the phase information between two excited states. First, we presented a theoretical description of the interaction of three-level atoms with bichromatic fields based on single-transition operators. Using the time evolution of a wave function, the equations of the interference fringes and the

Kazuhito Honda; Shinya Yanagimachi; Atsuo Morinaga

2003-01-01

96

A Fourier optics model of two-beam scanning laser interferometers  

Microsoft Academic Search

:   The article illustrates the use of Fourier optics to describe the operation of two-beam scanning laser interferometers. It\\u000a deals with the effect of diffraction on the spatial periodicity of a monochromatic and coherent beam. Particular attention\\u000a is given to the analysis of systematic errors in high-accuracy laser metrology. The article reviews the special case of plane\\u000a wave and Gaussian

A. Bergamin; G. Cavagnero; L. Cordiali; G. Mana

1999-01-01

97

Two-dimensional interferogram of an exploding selenium foil using a soft X-ray laser interferometer  

Microsoft Academic Search

We have developed a soft X-ray interferometer capable of probing large high-density plasmas with micron spatial resolutions. A neon-like yttrium X-ray laser operating at 155 Å was combined with the Mach-Zehnder interferometer to obtain electron density profiles of a laser-produced exploding selenium foil plasma. The plasma was produced with one Nova laser beam using a 120-?m line focus, the same

L. B. Da Silva; R. Cauble; P. Celliers; D. Ciarlo; S. Libby; R. A. London; D. Matthews; S. Mrowka; J. C. Moreno; D. Ress; J. E. Trebes; A. S. Wan; F. Weber

1996-01-01

98

High spectral resolution Fourier transform imaging spectroscopy in a Michelson interferometer with homodyne laser metrology control  

NASA Astrophysics Data System (ADS)

High spectral resolution Fourier transform imaging spectroscopy has been demonstrated at the Lockheed Martin Advanced Technology Center. A testbed was built using a Michelson interferometer with a two-stage end-mirror control system. Homodyne laser metrology was used to sense relative tip, tilt and piston in the interferometer, and a 3-degree of freedom fast steering mirror in conjunction with a linear actuator stage provided sub-nanometer actuation control over 20 millimeters of piston range. The range of piston over which signal was present allowed for spectral resolution at the nanometer level in the visible / near infrared (VNIR) band for every pixel in the reconstructed image.

Ni, Mel; Feller, Greg; Irwin, J. Wes; Mason, James; Mudge, Jason

2009-08-01

99

A compact dual atom interferometer gyroscope based on laser-cooled rubidium  

Microsoft Academic Search

We present a compact and transportable inertial sensor for\\u000a precision sensing of rotations and accelerations. The sensor consists\\u000a of a dual atom interferometer operated with laser-cooled 87Rb.\\u000a Raman processes are employed to coherently manipulate the matter\\u000a waves. We describe and characterize the experimental apparatus. A\\u000a method for passing from a compact geometry to an extended\\u000a interferometer with three independent atom-light

T. Müller; M. Gilowski; M. Zaiser; P. Berg; Ch. Schubert; T. Wendrich; W. Ertmer; E. M. Rasel

2009-01-01

100

Dispersion interferometer based on a CO2 laser for TEXTOR and burning plasma experiments  

NASA Astrophysics Data System (ADS)

A dispersion interferometer based on a continuous-wave CO2 laser source (?=9.57 ?m) with double plasma passage for measurements of the line-integrated electron density in the TEXTOR tokamak and the GDT linear system has been developed and tested in experiments. A sensitivity of min=2×1017 m-2 and a temporal resolution of 1 ms have been achieved. The interferometer does not need any rigid frame for vibration insulation. Its basic components are installed compactly on an optical bench placed on a stable support outside of the torus. The possibility for the development of a multichannel dispersion interferometer for the next generation of fusion devices (e.g., W7-X, ITER) is discussed.

Bagryansky, P. A.; Khilchenko, A. D.; Kvashnin, A. N.; Lizunov, A. A.; Voskoboynikov, R. V.; Solomakhin, A. L.; Koslowski, H. R.

2006-05-01

101

Phase shift induced from the dc Stark effect in an atom interferometer comprised of four copropagating laser beams  

Microsoft Academic Search

We observed the phase shift of the atomic wave function induced from the dc Stark effect using an atom interferometer comprised of four copropagating traveling laser beams. We calculated the interference signal for the interferometer in the case of a thermal atomic beam. By comparing the observed interference fringes with the calculated ones, the difference between the polarizabilities of the

A. Morinaga; M. Nakamura; T. Kurosu; N. Ito

1996-01-01

102

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

SciTech Connect

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

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

1996-06-27

103

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

104

Pulse shortening of gain switched single mode semiconductor lasers using a variable delay interferometer.  

PubMed

We propose a pulse shaping and shortening technique for pulses generated from gain switched single mode semiconductor lasers, based on a Mach Zehnder interferometer with variable delay. The spectral and temporal characteristics of the pulses obtained with the proposed technique are investigated with numerical simulations. Experiments are performed with a Distributed Feedback laser and a Vertical Cavity Surface Emitting Laser, emitting at 1.5 µm, obtaining pulse duration reduction of 25-30%. The main asset of the proposed technique is that it can be applied to different devices and pulses, taking advantage of the flexibility of the gain switching technique. PMID:23037397

Consoli, Antonio; Esquivias, Ignacio

2012-09-24

105

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.

106

Laser-matter interaction studies using X-ray laser and double Lloyd's mirror interferometer  

NASA Astrophysics Data System (ADS)

Inertial confinement fusion (ICF) is one of the promising approaches how to get a new resource of energy. In order to model ICF implosions reliably, the measurements of the mass ablation rates are needed. Such a measurement was performed at PALS; using the Ne-like Zn X-ray laser (XRL) as a probe beam and the Double Lloyd's mirror interferometer as the main diagnostic. The Parylene N foil (200nm and 350nm) was heated by 250-ps pulse of 3? iodine laser with nominal energy of 1J. The size of the focal spot was ~300?m then the maximum resulting intensity was ~1012W/cm2. The plasma probed by XRL was imaged by Mo:Si spherical mirror to CCD detector with magnification 8. The expected phase shift for the chosen thicknesses, which corresponds to reasonable fringe visibility, was from ? to 2?. The recorded interferograms were taken for different time delays between the heating pulse and the probe.

Kozlová, M.; Nejdl, J.; Rus, B.; Sawicka, M.; Polan, J.; Gartside, L.; Rossall, A.; Tallents, G.

107

Laser scanning heterodyne-interferometer for micro-components  

Microsoft Academic Search

Laser Doppler vibrometry is a well-established technique for non-contact vibration measurement. The necessity to monitor the vibration of the whole surface rather than a single point leads to the appearance of laser scanning vibrometer. However, current scanning vibrometers are applied only to larger structures. Scanning vibrometer for micro-components whose feature size is in region of millimeters and microns is still

B. K. A Ngoi; K. Venkatakrishnan; B. Tan

2000-01-01

108

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

109

Visualization of radiation from a high-power terahertz free electron laser with a thermosensitive interferometer  

Microsoft Academic Search

A thermosensitive interferometer based on a plane-parallel glass plate is used for visualization of a high-power terahertz\\u000a radiation. The plane wavefront of visible radiation emitted by a semiconductor laser is reflected from the two surfaces of\\u000a the plate and forms on a screen an interference pattern recorded by a digital video camera. Terahertz radiation being measured\\u000a is incident on the

N. A. Vinokurov; B. A. Knyazev; G. N. Kulipanov; A. N. Matveenko; V. M. Popik; V. S. Cherkassky; M. A. Shcheglov

2007-01-01

110

Demonstration of Displacement- and Frequency-Noise-Free Laser Interferometry Using Bidirectional Mach-Zehnder Interferometers  

SciTech Connect

We have demonstrated displacement- and frequency-noise-free laser interferometry (DFI) by partially implementing a recently proposed optical configuration using bidirectional Mach-Zehnder interferometers (MZIs). This partial implementation, the minimum necessary to be called DFI, has confirmed the essential feature of DFI: the combination of two MZI signals can be carried out in a way that cancels displacement noise of the mirrors while maintaining gravitational-wave signals. The attained maximum displacement-noise suppression was 45 dB.

Sato, Shuichi; Kawamura, Seiji [TAMA project, National Astronomical Observatory of Japan, 2-21-1, Mitaka, Osawa, Tokyo 181-8588 (Japan); Kokeyama, Keiko [Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610 (Japan); Ward, Robert L. [LIGO Project 18-34, California Institute of Technology, Pasadena, California 91125 (United States); Chen Yanbei; Pai, Archana; Somiya, Kentaro [Max-Planck-Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany)

2007-04-06

111

TECHNICAL DESIGN NOTE: High-precision, low-coherence Fizeau interferometer using a pulsed laser diode for measurement of transparent plates  

NASA Astrophysics Data System (ADS)

A high-precision, low-coherence Fizeau interferometer system using a pulsed laser diode has been developed for the measurement of the flatness of transparent plates. A pulsed laser diode with a wavelength of around 633 nm was used as the low-coherence light source. A Twyman-Green interferometer with the pulsed laser diode was connected to the Fizeau interferometer. By adjusting the optical path differences in both interferometers, the interference fringe pattern due only to the reference and measurement surfaces could be observed. The accuracy of the measurements was found to be similar to that of a conventional Fizeau interferometer.

Bitou, Youichi; Ueki, Nobuaki

2010-07-01

112

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

NASA Technical Reports Server (NTRS)

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

Notari, Anthony; Gentry, Bruce M.

1992-01-01

113

Compact I2-Stabilized Frequency-Doubled Nd:YAG Laser for Long Gauge Block Interferometer  

NASA Astrophysics Data System (ADS)

A compact I2-stabilized frequency-doubled Nd:YAG laser has been developed for a long gauge block interferometer. The laser frequency stabilization is realized by the third-harmonic technique, where a fast frequency modulation (20 kHz) is applied to the piezoelectric transducer attached on the laser crystal. The relative uncertainty of the laser frequency has reached 3.6× 10-12 for a 0.01-s averaging time. It is theoretically indicated that the phase error in the interferometric measurement due to the optical frequency modulation is sufficiently small to measure the long gauge block up to 1000 mm. Long gauge block measurement up to 1000 mm was successfully demonstrated with the developed I2-stabilized frequency-doubled Nd:YAG laser.

Bitou, Youichi; Sasaki, Kaoru; Iwasaki, Shigeo; Hong, Feng-Lei

2003-05-01

114

Two-dimensional interferogram of an exploding selenium foil using a soft X-ray laser interferometer  

SciTech Connect

The authors have developed a soft X-ray interferometer capable of probing large high-density plasmas with micron spatial resolutions. A neon-like yttrium X-ray laser operating at 155 {angstrom} was combined with the Mach-Zehnder interferometer to obtain electron density profiles of a laser-produced exploding selenium foil plasma. The plasma was produced with one Nova laser beam using a 120-{micro}m line focus, the same conditions used to create a selenium X-ray laser. The interferogram of the selenium plasma was obtained from an end-on perspective.

Da Silva, L.B.; Cauble, R.; Barbee, T.W. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1996-02-01

115

Two-color CO{sub 2}/HeNe laser interferometer for C-2 experiment  

SciTech Connect

A six-channel two-color interferometer has been developed for plasma electron density measurements in the C-2 field reversed configuration experiment. A CO{sub 2} laser is utilized as the main probe beams, while copropagating visible HeNe laser beams are mainly sensitive to vibration. Density measurements in C-2 plasmas have shown that this is a reliable turn-key system. The maximum residual phase noise after vibration compensation is less than {+-}5 deg., corresponding to a line integral density of 3x10{sup 18} m{sup -2}. The time resolution for routine operation is 2 {mu}s.

Gornostaeva, O.; Deng, B. H.; Garate, E.; Gota, H.; Kinley, J.; Schroeder, J.; Tuszewski, M. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States)

2010-10-15

116

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

PubMed

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

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

2010-10-01

117

Searching for a stochastic background of gravitational waves with the laser interferometer gravitational-wave observatory  

Microsoft Academic Search

The Laser Interferometer Gravitational-Wave Observatory\\u000a\\u0009\\u0009 (LIGO) has performed the fourth science run, S4, with\\u000a\\u0009\\u0009 significantly improved interferometer sensitivities with\\u000a\\u0009\\u0009 respect to previous runs. Using data acquired during this\\u000a\\u0009\\u0009 science run, we place a limit on the amplitude of a\\u000a\\u0009\\u0009 stochastic background of gravitational waves. For a\\u000a\\u0009\\u0009 frequency independent spectrum, the new Bayesian 90\\\\% upper\\u000a\\u0009\\u0009 limit is Omega(GW) x {[}H-0\\/72 km

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

2007-01-01

118

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

119

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

120

Atomic Interferometers  

Microsoft Academic Search

We examine the role of laser phase in multiphoton excitation of atomic transitions. Closed loops in excitation linkages create interfering channels which depend on atomic and laser phases. Such phase-dependent dynamics suggest the use of these transition linkages as atomic interferometers in which states can be decoupled (and population trapped). We show how phase and amplitude measurements are possible in

S. J. Buckle; S. M. Barnett; P. L. Knight; M. A. Lauder; D. T. Pegg

1986-01-01

121

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

NASA Technical Reports Server (NTRS)

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

Byer, R. L.

1990-01-01

122

Prototyping of two-beam laser interferometer for measurement of optical turbulence along extended paths. Master's thesis  

SciTech Connect

This thesis demonstrates a proof-of-concept experimental validation of a prototype two-beam, division of wavefront laser interferometer that provides real-time measurement of the optical path difference, and subsequent phase distortion, caused by atmospheric turbulence along an extended horizontal path. Prototype's signal processing incorporates use of specialized phase comparator circuit developed by author's advisor, D.S. Davis. Photographs and results cited of the prototype receiver's output offer proof of the validity of the basic design. Further research of this technology is expected to support future laser/adaptive optics long range weapon applications....Two-beam laser interferometer, Optical turbulence, Adaptive optics, Phase comparator.

Barbour, C.S.

1992-12-01

123

LIGO: the Laser Interferometer Gravitational-Wave Observatory  

Microsoft Academic Search

The goal of the Laser Interferometric Gravitational-Wave\\u000a\\u0009\\u0009 Observatory (LIGO) is to detect and study gravitational\\u000a\\u0009\\u0009 waves (GWs) of astrophysical origin. Direct detection of\\u000a\\u0009\\u0009 GWs holds the promise of testing general relativity in the\\u000a\\u0009\\u0009 strong-field regime, of providing a new probe of exotic\\u000a\\u0009\\u0009 objects such as black holes and neutron stars and of\\u000a\\u0009\\u0009 uncovering unanticipated new astrophysics. {LIGO}, a joint\\u000a\\u0009\\u0009 Caltech-MIT

B. P. Abbott; R. Abbott; R. Adhikari; P. Ajith; B. Allen; G. Allen; R. S. Amin; S. B. Anderson; W. G. Anderson; M. A. Arain; M. Araya; H. Armandula; P. Armor; Y. Aso; S. Aston; P. Aufmuth; C. Aulbert; S. Babak; P. Baker; S. Ballmer; C. Barker; D. Barker; B. Barr; P. Barriga; L. Barsotti; M. A. Barton; I. Bartos; R. Bassiri; M. Bastarrika; B. Behnke; M. Benacquista; J. Betzwieser; P. T. Beyersdorf; I. A. Bilenko; G. Billingsley; R. Biswas; E. Black; J. K. Blackburn; L. Blackburn; D. Blair; B. Bland; T. P. Bodiya; L. Bogue; R. Bork; V. Boschi; S. Bose; P. R. Brady; V. B. Braginsky; J. E. Brau; D. O. Bridges; M. Brinkmann; A. F. Brooks; D. A. Brown; A. Brummit; G. Brunet; A. Bullington; A. Buonanno; O. Burmeister; R. L. Byer; L. Cadonati; J. B. Camp; J. Cannizzo; K. C. Cannon; J. Cao; L. Cardenas; S. Caride; G. Castaldi; S. Caudill; M. Cavaglià; C. Cepeda; T. Chalermsongsak; E. Chalkley; P. Charlton; S. Chatterji; S. Chelkowski; Y. Chen; N. Christensen; C. T. Y. Chung; D. Clark; J. Clark; J. H. Clayton; T. Cokelaer; C. N. Colacino; R. Conte; D. Cook; T. R. C. Corbitt; N. Cornish; D. Coward; D. C. Coyne; J. D. E. Creighton; T. D. Creighton; A. M. Cruise; R. M. Culter; A. Cumming; L. Cunningham; S. L. Danilishin; K. Danzmann; B. Daudert; G. Davies; E. J. Daw; D. DeBra; J. Degallaix; V. Dergachev; S. Desai; R. DeSalvo; S. Dhurandhar; M. Díaz; A. Dietz; F. Donovan; K. L. Dooley; E. E. Doomes; R. W. P. Drever; J. Dueck; I. Duke; J-C Dumas; J. G. Dwyer; C. Echols; M. Edgar; A. Effler; P. Ehrens; E. Espinoza; T. Etzel; M. Evans; T. Evans; S. Fairhurst; Y. Faltas; Y. Fan; D. Fazi; H. Fehrmenn; Lee Samuel Finn; K. Flasch; S. Foley; C. Forrest; N. Fotopoulos; A. Franzen; M. Frede; M. Frei; Z. Frei; A. Freise; R. Frey; T. Fricke; P. Fritschel; V. V. Frolov; M. Fyffe; V. Galdi; J. A. Garofoli; I. Gholami; J. A. Giaime; S. Giampanis; K. D. Giardina; K. Goda; E. Goetz; L. M. Goggin; G. González; M. L. Gorodetsky; S. Goßler; R. Gouaty; A. Grant; S. Gras; C. Gray; M. Gray; R. J. S. Greenhalgh; A. M. Gretarsson; F. Grimaldi; R. Grosso; H. Grote; S. Grunewald; M. Guenther; E. K. Gustafson; R. Gustafson; B. Hage; J. M. Hallam; D. Hammer; G. D. Hammond; C. Hanna; J. Hanson; J. Harms; G. M. Harry; I. W. Harry; E. D. Harstad; K. Haughian; K. Hayama; J. Heefner; I. S. Heng; A. Heptonstall; M. Hewitson; S. Hild; E. Hirose; D. Hoak; K. A. Hodge; K. Holt; D. J. Hosken; J. Hough; D. Hoyland; B. Hughey; S. H. Huttner; D. R. Ingram; T. Isogai; M. Ito; A. Ivanov; B. Johnson; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; S. Kandhasamy; J. Kanner; D. Kasprzyk; E. Katsavounidis; K. Kawabe; S. Kawamura; F. Kawazoe; W. Kells; D. G. Keppel; A. Khalaidovski; F. Y. Khalili; R. Khan; E. Khazanov; P. King; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; R. Kopparapu; S. Koranda; D. Kozak; B. Krishnan; R. Kumar; P. Kwee; P. K. Lam; M. Landry; B. Lantz; A. Lazzarini; H. Lei; M. Lei; N. Leindecker; I. Leonor; C. Li; H. Lin; P. E. Lindquist; T. B. Littenberg; N. A. Lockerbie; D. Lodhia; M. Longo; M. Lormand; P. Lu; M. Lubinski; A. Lucianetti; H. Lück; B. Machenschalk; M. MacInnis; M. Mageswaran; K. Mailand; I. Mandel; V. Mandic; S. Márka; Z. Márka; A. Markosyan; J. Markowitz; E. Maros; I. W. Martin; R. M. Martin; J. N. Marx; K. Mason; F. Matichard; L. Matone; R. A. Matzner; N. Mavalvala; R. McCarthy; D. E. McClelland; S. C. McGuire; M. McHugh; G. McIntyre; D. J. A. McKechan; K. McKenzie; M. Mehmet; A. Melatos; A. C. Melissinos; D. F. Menendez; G. Mendell; R. A. Mercer; S. Meshkov; C. Messenger; M. S. Meyer; J. Miller; J. Minelli; Y. Mino; V. P. Mitrofanov; G. Mitselmakher; R. Mittleman; O. Miyakawa; B. Moe; S. D. Mohanty; S. R. P. Mohapatra; G. Moreno; T. Morioka; K. Mors; K. Mossavi; C. Mow Lowry; G. Mueller; H. Müller-Ebhardt; D. Muhammad; S. Mukherjee; H. Mukhopadhyay; A. Mullavey; J. Munch; P. G. Murray; E. Myers; J. Myers; T. Nash; J. Nelson; G. Newton; A. Nishizawa; K. Numata; J. O'Dell; B. O'Reilly; R. O'Shaughnessy; E. Ochsner; G. H. Ogin; D. J. Ottaway; R. S. Ottens; H. Overmier; B. J. Owen; Y. Pan; C. Pankow; M. A. Papa; V. Parameshwaraiah; P. Patel; M. Pedraza; S. Penn; A. Perraca; V. Pierro; I. M. Pinto; M. Pitkin; H. J. Pletsch; M. V. Plissi; F. Postiglione; M. Principe; R. Prix; L. Prokhorov; O. Punken; V. Quetschke; F. J. Raab; D. S. Rabeling; H. Radkins; P. Raffai; Z. Raics; N. Rainer; M. Rakhmanov; V. Raymond; C. M. Reed; T. Reed; H. Rehbein; S. Reid; D. H. Reitze; R. Riesen; K. Riles; B. Rivera; P. Roberts; N. A. Robertson; C. Robinson; E. L. Robinson; S. Roddy; C. Röver; J. Rollins; J. D. Romano; J. H. Romie; S. Rowan; A. Rüdiger; P. Russell; K. Ryan; S. Sakata; L. Sancho de la Jordana; V. Sandberg; V. Sannibale; L. Santamaría; S. Saraf; P. Sarin; B. S. Sathyaprakash; S. Sato; M. Satterthwaite; P. R. Saulson; R. Savage; P. Savov; M. Scanlan; R. Schilling

2009-01-01

124

Compressive imaging and dual moire laser interferometer as metrology tools  

NASA Astrophysics Data System (ADS)

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

Abolbashari, Mehrdad

125

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

PubMed

The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference Z(S) between the probe and reference beam optical path lengths and the spectral separation k(S) between the center of the laser gain profile and the nearest laser mode of higher frequency. k(S) has a significant effect on V for a given Z(S). This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying Z(S) (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in k(S) for a given Z(S) is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 ?m HeNe lasers with similar specifications. In the first case, the function W(Z(S)) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of Z(S)values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto-optically upshifted by that amount, while k(S) spontaneously varies on an acoustic time scale. A single high-bandwidth waveform record for each Z(S), therefore, provides all the information needed to determine W. Despite the second laser's gain profile apparently differing in detail, qualitative agreement is achieved between the two methods sufficient to validate the technique. PMID:24182097

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

2013-10-01

126

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

127

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

128

Four-level atomic interferometer driven by shaped ultrafast laser pulses  

NASA Astrophysics Data System (ADS)

We analyze the behavior of a four-state, two-path atomic interferometer driven by shaped ultrafast laser pulses. The laser pulses interact with atomic rubidium, exciting the atoms to the 5D state via two intermediate resonances (the 5P1/2 and 5P3/2). The relative phase of the two paths can be modified by applying a varying spectral phase at the wavelength corresponding to one of the resonant transitions for each pathway. We trace out the behavior of the system from the simplest case of weak-field excitation with resonant fields to strong-field excitation with a broadband source. Our measurements and analysis reveal that while interference is observed for all field strengths and spectral widths, the character of the interference changes substantially.

Clow, Stephen; Weinacht, Thomas

2010-08-01

129

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

NASA Astrophysics Data System (ADS)

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

Dooley, Katherine Laird

130

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

SciTech Connect

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

Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya [Department of Advanced Energy, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8561 (Japan); Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro [Department of Aeronautics and Astronautics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan)

2011-04-15

131

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

NASA Astrophysics Data System (ADS)

Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density ne and the electron temperature Te profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO2 laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of ne and Te were, respectively, about 2 × 1024 m-3 and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured ne at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

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

2011-04-01

132

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

NASA Technical Reports Server (NTRS)

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

Martino, Anthony J.; Cornwell, Donald M.

1998-01-01

133

Gauge block calibration by using a high speed phase shifting interferometer comprising two frequency scanning diode lasers  

NASA Astrophysics Data System (ADS)

We developed a gauge block interferometer which utilizes the frequency tunable laser diodes as both light sources and phase shifters of a phase shifting interferometer. By using a confocal Fabry-Perot cavity made of ultra low expansion glass, and linearly modulating the laser diode current, the laser frequency could be injection locked to the resonant modes of the Fabry-Perot cavity consecutively. These equal spaced frequencies produce equally phase shifted interferometric images which are ideal to be analyzed by the Carré algorithm. Two frequency scanning lasers at the wavelengths of 636 nm and 657 nm are used as light sources for the gauge block interferometer. The system takes only 10 ms for a single measurement which acquires two sets of four equally phase shifted images with 640×480 pixels in size. Central lengths of gauge blocks are measured by using the phase shifting interferometry and exact fraction method. The performance of the high speed interferometer could be checked by comparing the measurement results on the same gauge block made by two different methods. Two results agreed well within the measurement uncertainty.

Kim, Jae Wan; Kim, Jong-Ahn; Jang, Roma; Kang, Chu-Shik

2009-06-01

134

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

Microsoft Academic Search

We are incorporating a novel self-referencing Mach-Zehnder interferometer into a large scale laser system as a real time, interactive diagnostic tool for wavefront measurement. The instrument is capable of absolute wavefront measurements accurate to better than λ\\/10 pv over a wavelength range > 300 nm without readjustment of the optical components. This performance is achieved through the design of both

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

1991-01-01

135

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

PubMed

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

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

2012-07-01

136

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

137

Digital Quadrature Modulation.  

National Technical Information Service (NTIS)

Two methods of modulation, analog quadrature and amplitude-phase, are being considered for the near term implementation of clutter and extended targets. Due to the practical non-linearities and imbalances of the physical devices implementing these modulat...

I. P. Bottlik

1978-01-01

138

Interferometer Configurations  

NASA Astrophysics Data System (ADS)

Gravitational waves induce a differential strain between free-falling test masses. The most sensitive instruments to measure this kind of effect are laser interferometers. This chapter introduces the working principles of the different optical configuration that were and will be used in gravitational wave detectors: Michelson interferometer, Fabry-Perot resonant cavity, power and signal recycling techniques. Advanced detectors will feature high power levels, therefore the important issue of radiation pressure effects is addressed. Finally, a brief introduction to the topic of diffraction limited beams and high order transverse electromagnetic modes is included.

Vajente, Gabriele

139

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

140

Optical fiber Fabry-Perot interferometer cavity fabricated by femtosecond laser micromachining and fusion splicing for refractive index sensing.  

PubMed

We demonstrate a fiber in-line Fabry-Perot interferometer cavity sensor for refractive index measurement. The interferometer cavity is formed by drilling a micro-hole at the cleaved fiber end facet, followed by fusion splicing. A micro-channel is inscribed by femtosecond laser micromachining to vertically cross the cavity to allow liquid to flow in. The refractive index sensitivity obtained is ~994 nm/RIU (refractive index unit). Such a device is simple in configuration, easy for fabrication and reliable in operation due to extremely low temperature cross sensitivity of ~4.8 × 10(-6) RIU/°C. PMID:23037431

Liao, C R; Hu, T Y; Wang, D N

2012-09-24

141

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

142

Quadrature Homodyne Detection in Doppler LIDAR.  

NASA Astrophysics Data System (ADS)

Coherent laser radars have the potential to provide complete information on the returned signal, including magnitude and phase. However, because optical detectors are insensitive to phase, obtaining complete information requires some effort. Often, only one quadrature of the signal is measured, for example in a Doppler lidar used to measure wind velocity when the sign is known from a priori information. In this case, the lidar determines only the magnitude of the velocity. Alternatively, the reference beam can be offset in frequency by using a Bragg cell or second laser. This offset allows the in-phase and quadrature components of the signal to be obtained electronically. In the present work, an alternative is presented, in which a standard technique of microwave radar, quadrature detection, is applied to laser radar. Two reference beams in quadrature phase, with orthogonal polarizations are mixed with the signal. The result is a simpler system, with lower cost and greater reliability. In this work, the theory is developed and experimental results presented. Practical implementation details are also discussed. To place the work in context, an extensive background in coherent laser radar is also presented.

Dimarzio, Charles Albert

143

Thermal calcium atom interferometer with a phase resolution of a few milliradians based on a narrow-linewidth diode laser  

NASA Astrophysics Data System (ADS)

A symmetrical atom interferometer with a thermal calcium atom beam has been developed using a narrow linewidth diode laser stabilized to the resonance of a high-finesse cavity. The linewidth of the diode laser was estimated to be less than 1 Hz relative to the cavity resonance in noise measurement over the range of 100 Hz to 1 MHz, and the phase instability of the interference fringes obtained from the Allan deviation was improved to 2 mrad at an integration time of 300 s. Using this atom interferometer, the ac Stark phase shift between the 1S0 and 3P1 states of a Ca atom was measured as a function of a laser power near the resonance of the 1S0-1P1 transition at a wavelength of 423 nm. The decay rate of the 1P1 state was determined to be ?=1.91(33)×108 s-1.

Akatsuka, Tomoya; Mori, Yoshihiro; Sone, Nobuhiko; Ohtake, Yurie; Machiya, Mamoru; Morinaga, Atsuo

2011-08-01

144

Phase measurement of various commercial heterodyne He-Ne-laser interferometers with stability in the picometer regime  

NASA Astrophysics Data System (ADS)

In order to be able to resolve displacements of a picometer with widely used commercially available heterodyne interferometers, an advanced phase meter was developed at PTB. Key to this level of accuracy is the use of a state-of-the-art analogue-to-digital converter (ADC) board enabling the implementation of a phase-evaluation method by using embedded field programmable gate arrays. Experimental results obtained with commercially available heterodyne laser interferometer components prove that the proposed phase-evaluation procedure is capable of interpolating an optical fringe down into the picometer regime. The phase evaluation was moreover extended to track simultaneously two heterodyne beat frequencies with only two photodetectors and ADCs. Potential limitations of the long-term stability of heterodyne interferometers are discussed. The phase meter was tested, has been readily applied, can be easily adapted and is therefore to be used in a wide field of applications.

Köchert, P.; Flügge, J.; Weichert, Ch; Köning, R.; Manske, E.

2012-07-01

145

Investigation of plasma evolution in a high power electron-beam diode using a two-frame laser shearing interferometer  

Microsoft Academic Search

Summary form only given. A two-frame laser shearing interferometer (LSI) was used to study the plasma evolution in a 140-kV, 220-kA electron-beam diode with a current pulse rise time of 40 ns. LSI used a 150-ps, 100-mJ, 532-nm, 10-cm-diameter, linearly-polarized laser beam. The p- and s-polarized components of the laser were split and re-combined with the s-component delayed by a

N. Qi; J. Goyer; B. H. Failor; S. K. Lam; J. C. Riordan; B. Whitton; H. Sze; D. Lojewski; A. Verma

2008-01-01

146

Quadrature Mixer LO Leakage Suppression Through Quadrature DC Bias.  

National Technical Information Service (NTIS)

A new concept has been developed which allows direct-to-RF conversion of digitally synthesized waveforms. The concept named Quadrature Error Corrected Digital Waveform Synthesis (QECDWS) employs quadrature amplitude and phase predistortion to the complex ...

J. G. Baldwin D. F. Dubbert

2002-01-01

147

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

148

Visualization of radiation from a high-power terahertz free electron laser with a thermosensitive interferometer  

NASA Astrophysics Data System (ADS)

A thermosensitive interferometer based on a plane-parallel glass plate is used for visualization of a high-power terahertz radiation. The plane wavefront of visible radiation emitted by a semiconductor laser is reflected from the two surfaces of the plate and forms on a screen an interference pattern recorded by a digital video camera. Terahertz radiation being measured is incident on the outer surface of the plate and heats a thin surface layer, which causes a shift of interference fringes. For K8 glass, a shift by one fringe corresponds to an absorbed energy of 5.1 J/cm2. The problem of determining the sign of the phase shift was solved by comparing the interference patterns with the images obtained with an infrared imager sensitive to near IR radiation. The processing of interference patterns makes it possible to determine the power density distribution over the beam cross section of the Novosibirsk free electron laser. In these measurements, the absolute value of the beam power determined by integrating over the cross section was 65 ± 7 W for a 130-?m wavelength. Visualization of the complex image with a spatial resolution no worse than 1 mm and a frame repetition rate of 25 Hz is demonstrated.

Vinokurov, N. A.; Knyazev, B. A.; Kulipanov, G. N.; Matveenko, A. N.; Popik, V. M.; Cherkassky, V. S.; Shcheglov, M. A.

2007-07-01

149

Modeling of optical quadrature microscopy for imaging mouse embryos  

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

150

Gaussian quadrature for sums  

NASA Astrophysics Data System (ADS)

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

Monien, H.

2010-04-01

151

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

152

Measurement of the wavefront of a laser diode system for intersatellite communication by a Jamin double-shearing interferometer  

NASA Astrophysics Data System (ADS)

The frame of a laser diode transmitter for intersatellite communication is concisely introduced. A simple, novel and visual method for measuring the diffraction-limited wavefront of the transmitter by a Jamin double-shearing interferometer is proposed. To verify the validity of the measurement, the far-field divergence of beam is additionally rigorously analysed in terms of the Fraunhofer diffraction. The measurement, the necessary analyses and discussion are given in detail. By directly measuring the fringe widths and quantitatively interpreting the interference fringes, the minimum detectable wavefront height (DWH) of the wavefront is only 0.2? (the distance between the perfect plane wavefront and the actual wavefront at the transmitting aperture) and the corresponding divergence is only 65.84 µrad. This indicates that the wavefront approaches the diffraction-limited condition. The results show that this interferometer is a powerful tool for testing the semiconductor laser beam's wavefront, especially the diffraction-limited wavefront.

Liu, Hongzhan; Liu, Liren; Xu, Rongwei; Zhang, Lei

2005-03-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

154

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

SciTech Connect

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

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

1987-07-01

155

Dynamic calibration of the positioning accuracy of machine tools and coordinate measuring machines using a laser interferometer  

Microsoft Academic Search

This paper describes a method for evaluating the positioning accuracy of machine tools and coordinate measuring machines (CMM) under dynamic conditions. It is based on the Hewlett Packard 5519A laser interferometer which is capable of performing dynamic calibration. Such method uses the A-quad-B pulses from the machine encoder as the position trigger signals, thus enabling to make measurements “on-the-fly”. A

H. F. F Castro; M Burdekin

2003-01-01

156

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

157

Expected Coalescence Rates of Ns-Ns Binaries for Laser Beam Interferometers  

NASA Astrophysics Data System (ADS)

The coalescence rate of two neutron stars (NS) is revisited. To estimate the number of bound NS-NS and the probability of their coalescence in a time scale ?, the galactic star formation history, directly derived from observations, and the evolution of massive stars are considered. The newly established galactic merging rate is (1.7±1.0) × 10-5 yr-1, while the local merging rate, including the contribution of elliptical galaxies, is about a factor of two higher, 3.4 × 10-5 yr-1. Using the present data basis on galaxy distribution in the local universe and the expected sensitivity of the first generation of laser beam interferometers, we estimate that one event should occur every 125 years for LIGO and one event each 148 years for VIRGO. The situation is considerably improved for advanced-LIGO, since we predict that 6 events per year should be detected whereas for a recently proposed VIRGO new configuration, the event rate might increase up to 3 events every two years.

de Freitas Pacheco, J. A.; Regimbau, T.; Vincent, S.; Spallicci, A.

158

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

NASA Technical Reports Server (NTRS)

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.

1994-01-01

159

Multichord laser interferometer for the magnetized target fusion program's field reverse configuration  

Microsoft Academic Search

AFRL's Directed Energy Directorate has built a multiple chord 6328 nm interferometer to diagnose a Field Reversed Configuration (FRC) being developed for LANL and AFRL's collaborative Magnetized Target Fusion (MTF) program. The FRC is intended for compression to near thermonuclear fusion conditions by AFRL's Shiva Star capacitor bank. The interferometer is designed to measure the density integral along eight chords

Edward Ruden; Francis Analla; Shouyin Zhang

2002-01-01

160

Second generation instruments for the Laser Interferometer Gravitational Wave Observatory (LIGO)  

Microsoft Academic Search

The interferometers being planned for second generation LIGO promise an order of magnitude increase in broadband strain sensitivity-with the corresponding cubic increase in detection volume-and an extension of the observation band to lower frequencies. In addition, one of the interferometers may be designed for narrowband performance, giving further improved sensitivity over roughly an octave band above a few hundred Hertz.

Peter Fritschel

2003-01-01

161

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

NASA Astrophysics Data System (ADS)

Self-generated magnetic fields produced in laser plasmas at moderate laser intensities have been measured using a three-channel polaro-interferometer. The main elements of this device are two birefringent calcite wedges placed between two crossed polarizers. Using this device, the spatial profiles of (a) the rotation angle (polarometry), (b) the electron density (interferometry), and (c) the transmitted probe beam intensity (shadowgraphy) are recorded simultaneously using a digital camera with a large format CCD in a single laser shot. Magnetic fields of 2-4 MG had been estimated in aluminum plasma at laser intensities ~1013 W/cm2. It is also possible to use this device in other configurations to get time resolved information.

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

2011-12-01

162

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

163

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

SciTech Connect

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

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

1990-01-01

164

Generation of transform-limited picosecond pulses from active mode-locked laser diodes with an external Fabry-Perot interferometer  

Microsoft Academic Search

Experiments on mode selection and active mode-locking in laser diodes with an external Fabry-Perot (FP) interferometer are reported for the first time. The static and dynamic single internal-mode operation have been realized successfully by using a PZT to adjust the interval of the FP interferometer. The nearly transform-limited Gaussian pulses with the repetition rate of 656MHz, the pulsewidth of 13ps

Jianhua Xu; Xingze Lu; Kui Han; Guangpeng Zhou; Weizai Zhang; Fu-Xi Gan

1996-01-01

165

Optical Thin Film Phase Quadrature Interferometry.  

NASA Astrophysics Data System (ADS)

An achromatic, fast time resolution, Michelson Doppler interferometric technique that is based on optical thin films and requires no scanning mechanisms has been developed. This was motivated by the pursuit to improve the time resolution of wide angle Michelson Doppler imaging interferometers for studies of the Earth's upper atmospheric winds and temperatures. The technique revolves around a mosaic of four metal-dielectric optical thin film multilayers, called Phase Quadrature Multilayers (PQMs), with relative values of phase change on reaction, Psi_ {R}, that differ by 90^ circ over a wavelength range covering ~350 nm in the visible spectrum. This is the first time that optical multilayers have been successfully designed and produced to meet specified Psi _{R} values over such a broad wavelength region; two orders of magnitude larger than produced before, and one order of magnitude larger than previously designed for. Experimental results with ZnS and Na_3 AlF_6 multilayers in a mica Fabry-Perot interferometer agreed with theory, validating the concept of the PQMs. Practical SiO_2 and Nb_2O_5 multilayers were then used in a Michelson interferometer and results also agreed with theory. The feasibility of the Phase Quadrature Interferometer (PQI) was experimentally investigated with that prototype instrument. The generalized phase algorithm can be used to compensate for the departures of Psi_{R} from 90^circ. Various Psi_{R} characterization schemes were investigated since the limiting accuracy of the method is determined by ones ability to know the relative phases between the PQMs. If the suggested stabilization, numerical and experimental techniques are employed, (extensions of the ones tried in the thesis), the PQI should be able to achieve the same accuracy of present Doppler interferometers (10 m/s of wind speed). The PQM concept is not restricted to studies of the Earth's atmosphere but could be used for other fields such as Solar or planetary studies. The spectral coverage can likely be extended to the ultraviolet and infrared regions.

McCall, Susan H. C. P.

166

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

PubMed Central

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

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

2011-01-01

167

Quadrature identities and the schottky double  

Microsoft Academic Search

By using Riemann surface theory we obtain results on quadrature domains and identities for analytic functions, e.g., existence of multiply-connected quadrature domains, descriptions of their algebraic boundaries and results on the multitude of quadrature domains associated to a fixed quadrature identity. The main idea is to characterize quadrature domains in terms of meromorphic functions and differentials on Riemann surfaces conformally

Björn Gustafsson

1983-01-01

168

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

169

CO{sub 2} laser-based dispersion interferometer utilizing orientation-patterned gallium arsenide for plasma density measurements  

SciTech Connect

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{sup 17} m{sup ?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.

Bamford, D. J.; Cummings, E. A.; Panasenko, D. [Physical Sciences Inc., 6652 Owens Drive, Pleasanton, California 94588 (United States)] [Physical Sciences Inc., 6652 Owens Drive, Pleasanton, California 94588 (United States); Fenner, D. B.; Hensley, J. M. [Physical Sciences Inc., 20 New England Business Center, Andover, Massachusetts 01810 (United States)] [Physical Sciences Inc., 20 New England Business Center, Andover, Massachusetts 01810 (United States); Boivin, R. L.; Carlstrom, T. N.; Van Zeeland, M. A. [General Atomics, P.O. Box 85608, San Diego, California 92186 (United States)] [General Atomics, P.O. Box 85608, San Diego, California 92186 (United States)

2013-09-15

170

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

171

Double resonant quadrature birdcage.  

PubMed

The combined acquisition of proton images and localized spectra is considered essential to the application of NMR techniques to human and animal research. The ideal imaging/spectroscopy coil for our purposes would be one that provides the highest possible signal-to-noise, high homogeneity, and operation on two or more frequencies without retuning requirements or cable changes. To address these needs we have developed a quadrature double-tuned birdcage. We have incorporated our earlier work on the transformer coupled double-tuned surface coil into the birdcage structure by placing two birdcages in a coaxial configuration. This structure resonates at 34.6 MHz (phosphorus resonance at 2.0 T) and 85.5 MHz (proton resonance at 2.0 T). The quadrature performance of this coil for phosphorus was excellent, with a signal-to-noise that was 133% of our linear reference. The proton performance was less efficient, with a signal to noise that was 67% of our linear reference, but still quite sufficient for imaging. A phosphorus spectra and proton image of a rat abdomen are shown. PMID:8396709

Fitzsimmons, J R; Beck, B L; Brooker, H R

1993-07-01

172

Hybrid Gauss-Trapezoidal Quadrature Rules.  

National Technical Information Service (NTIS)

A new class of quadrature rules for the integration of both regular and singular functions is constructed and analyzed. For each rule the quadrature weights are positive and the class includes rules of arbitrarily high order convergence. The quadratures r...

B. K. Alpert

1996-01-01

173

New quadrature mirror filter structures  

Microsoft Academic Search

This paper introduces new quadrature mirror filter (QMF) structures for the frequency domain analysis and synthesis of digital signals. The conventional QMF technique is first extended to cover complex quadrature mirror filters (CQMF) in which a digital signal is split into N adjacent complex subbands where the real and imaginary parts are subsampled by 1\\/2N with respect to the original

C. Galand; H. Nussbaumer

1984-01-01

174

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

SciTech Connect

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

Sato, Shuichi; Kawamura, Seiji; Kokeyama, Keiko; Kawazoe, Fumiko; Somiya, Kentaro [TAMA project, National Astronomical Observatory of Japan, 2-21-1, Mitaka, Osawa, Tokyo 181-8588 (Japan); The Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610 (Japan); Max-Planck-Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany)

2007-04-15

175

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

PubMed

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

Seto, Naoki; Taruya, Atsushi

2007-09-21

176

Interferometers Characterization  

NASA Technical Reports Server (NTRS)

Procedure and characterization result for two vibration insensitive phase shifting interferometers will be presented. Typical applications of the vibration insensitive interferometers include the testing of large astronomical primary mirrors with long radii of curvature in a severe vibration environment. The procedure list the steps for characterizing the two interferometers. The characterization compares the two interferometers and compares to its own specification.

Eng, Ron; Bardine, Robert (Technical Monitor)

2001-01-01

177

Thermal noise in the test mass suspensions of a laser interferometer gravitational-wave detector prototype  

Microsoft Academic Search

The thermal noise of the test mass suspensions of a prototype gravitational-wave interferometer was calculated and found to be in agreement with the measured noise near the resonant frequencies of the suspensions. The damping mechanism of the suspension modes was characterized and found to be nearly independent of frequency.

A. Gillespie; F. Raab

1993-01-01

178

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

179

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.

Kumar, Ananda; Bottomley, Paul A.

2008-01-01

180

The Palomar Testbed Interferometer  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

181

Quadrature interferometry for nonequilbrium ultracold atoms in optical lattices  

NASA Astrophysics Data System (ADS)

We propose an interaction-based interferometric technique for making time-resolved measurements of quadrature operators of nonequilibrium ultracold atoms in optical lattices. The technique creates two subsystems of magnetic atoms in different spin states and lattice sites--the arms of the interferometer. A Feshbach resonance turns off atom-atom interactions in one spin subsystem, making it a well-characterized reference state, while atoms in the other subsystem undergo nonequilibrium many-body dynamics for a variable hold time. The nonequilibrium evolution can involve a variety of Hamiltonians, including systems with tunneling and spin-orbit couplings using artificial gauge fields. Interfering the subsystems via a second beam-splitting operation, time-resolved quadrature measurements are directly obtained by detecting relative spin populations. Analyzing a simple application of the interferometer, we obtain analytic predictions for quadratures for deep optical lattices with negligible tunneling. As a second, distinct application, we show that atom-atom interaction strengths can in principle be determined with super-Heisenberg scaling n-3/2 in the mean number of atoms per lattice site n, making it possible to test the physics of interaction-based quantum metrology.

Johnson, Philip; Tiesinga, Eite

2013-03-01

182

On use of ghost-less beam splitter in reversal shear interferometer for measurement of spatial coherence of large cross-section laser beam  

Microsoft Academic Search

A configuration of reversal shear interferometer suitable for measurement of spatial coherence of high average power, large cross-section laser beam has been discussed. Ghost-less beam splitters in which unwanted multiple reflections from the surfaces have been suppressed by total internal reflection are used for beam splitting and re-combination. Advantages and drawbacks of this configuration have been discussed.

Sanjib Chatterjee; O. Prakash

2003-01-01

183

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

184

Scenario Machine: fast radio bursts, short gamma-ray burst, dark energy and Laser Interferometer Gravitational-wave Observatory silence  

NASA Astrophysics Data System (ADS)

We discuss the recently reported discovery of fast radio bursts (FRBs) in the framework of the neutron star-neutron star (NS+NS) or neutron star-black hole (NS+BH) binary merger model. We concentrate on what we consider to be an issue of greatest importance: what is the NS merger rate given that the FRB rate (1/1000 yr-1 per galaxy) is inconsistent with gamma-ray burst rate as discussed by Thornton and should be significantly higher. We show that there is no discrepancy between NS merger rate and observed FRB rates in the framework of the Scenario Machine population synthesis - for a kick velocity of 100-150 km s-1 an average NS merger rate is 1/500-1/2000 yr-1 per galaxy up to z = 0.5-1. Based on the Scenario Machine NS merger rate estimates, we discuss the lack of positive detections on the ground-based interferometers, considering the Laser Interferometer Gravitational-wave Observatory.

Lipunov, V. M.; Pruzhinskaya, M. V.

2014-05-01

185

Implementation of Digital Quadrature Modulation.  

National Technical Information Service (NTIS)

Two basic methods of implementing digital quadrature modulation have been proposed. Although the multiplying D/A implementation appears at first look to be simpler than the digital multiplier implementation, a more detailed analysis favors the digital mul...

I. P. Bottlik

1978-01-01

186

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

187

Atom interferometers  

Microsoft Academic Search

Atom interferometers have opened up new areas of fundamental and applied research. As well known from photon optics, multiple-beam interferometers offer an increased sensitivity on the relative phases between interfering waves. Very recently, first atomic multiple-beam interferometers were realized. These concepts are based on an atomic beam that is spatially split into coherent partial de Broglie waves, where the number

J. Lone; K. Sengstock; W. Ertmer

1998-01-01

188

Correlation of terrestrial surface oscillations and ionosphere disturbances during the earthquakes according to laser interferometer and GPS data  

NASA Astrophysics Data System (ADS)

Process of earthquakes preparation occupies, as a rule, the significant period of time and consequently demands carrying out the long observations above the possible earthquake focus. The existing network of ground navigating stations allows performing such observations in the ionosphere state. It also enables to determine the ionospheric effects of earthquakes based on the analysis of an electron density of F2 layer. The navigating systems GPS and Glonass despite the complexity of detecting ionospheric variations caused by seismic effects can be adapted in the best way to the realization of the ionosphere monitoring. Large-scale spatial and temporal disturbances of the earth strain and the total electron contents (TEC) in the ionospheric F2 layer have been recently detected by our underground laser strainmeters and microwave ionospheric profile-meter based on the GPS data [1]. Here the technique of long-base laser interferometry measurements and dual frequency GPS data acquisition are presented and new results of data analysis are discussed. We have compared the strain-barometric variations recorded by the laser interferometers of 100 m and 300 m length at the IRE RAS testing site (Moscow region), and TEC drifts according to the local (distance up to 100-200 km) and remote (being 2000-7000 km apart) GPS stations. The utmost sensitivity of laser interferometers was dL/L=10(-11) to the earth strain and dP=10(-4) mbar to the barometric variations. The ionospheric data have been calculated with radio translucence algorithms application. The connection of undulating strain-barometric oscillations of a surface and atmospheric pressure in 1-10 mHz frequency band and synchronously recorded TEC variations was found during earthquakes (Japan 25.09.03, Ms=8.4 and Altai 27.09.03 Ms=7.3 - 6.7) and the velocities of the disturbances propagation have been determined. [1] M.N. Dubrov and V.M. Smirnov, IUGG2003, 30.06-11.07.2003, Sapporo, Japan, JSA02.

Dubrov, M. N.; Smirnov, V. M.

2008-09-01

189

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

Microsoft Academic Search

We demonstrate a laser system consisting of a >1.6 Wtitanium:sapphire laser that is phase locked to another free-running titanium:sapphire laser at a wavelength of 852 nm with a phase noise of -138 dBc\\/Hz at 1 MHz from the carrier, using an intracavity electro-optic phase modulator. The residual phase variance is 2.5×10-8 rad2 integrated from 1 Hz to 10 kHz. This

Holger Müller; Sheng-Wey Chiow; Quan Long; Steven Chu

2006-01-01

190

Differential-quadrature-phase-shift quantum key distribution  

NASA Astrophysics Data System (ADS)

This paper presents a quantum key distribution (QKD) protocol named differential-quadrature-phase-shift (DQPS) QKD. A transmitter sends a coherent pulse train in which each pulse is phase modulated by {0,?} {?/2,3?/2} , and a receiver measures it with either one of two asymmetric Mach-Zehnder interferometers having phase biases of 0 and ?/2 , respectively. This scheme is devised such that the idea of the conventional Bennett-Brassard 1984 protocol (BB84) is introduced to differential-phase-shift (DPS) QKD. Simulations show that the proposed scheme is robust against a sequential attack that is crucial eavesdropping to DPS-QKD.

Inoue, Kyo; Iwai, Yuuki

2009-02-01

191

Ring interferometers with unit transmittance  

NASA Astrophysics Data System (ADS)

The phenomenon of lossless ring interferometers may be explained by recourse to a formalism in which the numerator and denominator are complex conjugates, constituting the optical analog of loss-free systems in electrical network theory. In the ring interferometer presently employed to demonstrate the property of unit transmittance, an He-Ne laser is used as a light source.

van de Stadt, H.

1985-08-01

192

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

PubMed

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

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

2011-12-01

193

A neural network approach to correcting nonlinearity in optical interferometers  

NASA Astrophysics Data System (ADS)

Real interferometers with phase quadrature detecting subsystems usually demonstrate nonlinearity with length measurements. Conventional nonlinearity correction techniques based on elliptical fittings are reviewed and their limitation is investigated using computer simulations. A new approach based on neural networks (NNs) for correcting nonlinearity in optical interferometers for length and displacement measurements is introduced, the principle of which is given (including the architecture of the NN) and its training method. An experimental setup was developed based on a differential plane-mirror interferometer for testing the proposed method. The experimental results show that this new approach is successfully applicable to real, noisy interferometer signals.

Li, Zhi; Herrmann, Konrad; Pohlenz, Frank

2003-03-01

194

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

195

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

196

Understanding Quadrature Formulas for Planar Regions.  

National Technical Information Service (NTIS)

Quadrature formulas for double integrals are described. Examples are used to given an idea of what should be proven about quadrature formulas. Proofs are simple and cover formulas of third- and fifth-degree polygonal accuracy. Several problems are provide...

C. B. Huelsman

1973-01-01

197

Vectorized Adaptive Quadrature in Matlab  

Microsoft Academic Search

Adaptive quadrature codes process a collection of subintervals one at a time. We show how to process them all simultaneously and so exploit vectorization and the use of fast built-in functions and array operations that are so important to e-cient computation in Matlab. Using algebraic transformations we have made it just as easy for users to solve problems on inflnite

L. F. Shampine

2006-01-01

198

Interferometers adaptations to lidars  

NASA Technical Reports Server (NTRS)

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

Porteneuve, J.

1992-01-01

199

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

200

Calibration of a Standard Transducer Using a Laser Interferometer (TTCP Calibration Round-Robin).  

National Technical Information Service (NTIS)

A 10-MHz piezoelectric transducer with a half-inch diameter element and square gold target of 4.0 mm on a side was used in an interlaboratory project which consisted of measuring the amplitude of vibration of a standard transducer using a laser interferom...

A. Moreau

1992-01-01

201

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

202

Quadrature interferometry for nonequilibrium ultracold atoms in optical lattices  

NASA Astrophysics Data System (ADS)

We develop an interferometric technique for making time-resolved measurements of field-quadrature operators for nonequilibrium ultracold bosons in optical lattices. The technique exploits the internal state structure of magnetic atoms to create two subsystems of atoms in different spin states and lattice sites. A Feshbach resonance turns off atom-atom interactions in one spin subsystem, making it a well-characterized reference state, while atoms in the other subsystem undergo nonequilibrium dynamics for a variable hold time. Interfering the subsystems via a second beam-splitting operation, time-resolved quadrature measurements on the interacting atoms are obtained by detecting relative spin populations. The technique can provide quadrature measurements for a variety of Hamiltonians and lattice geometries (e.g., cubic, honeycomb, superlattices), including systems with tunneling, spin-orbit couplings using artificial gauge fields, and higher-band effects. Analyzing the special case of a deep lattice with negligible tunneling, we obtain the time evolution of both quadrature observables and their fluctuations. As a second application, we show that the interferometer can be used to measure atom-atom interaction strengths with super-Heisenberg scaling n¯-3/2 in the mean number of atoms per lattice site, and standard quantum limit scaling M-1/2 in the number of lattice sites. In our analysis, we require M?1 and for realistic systems n¯ is small, and therefore the scaling in total atom number N=n¯M is below the Heisenberg limit; nevertheless, measurements testing the scaling behaviors for interaction-based quantum metrologies should be possible in this system.

Tiesinga, E.; Johnson, P. R.

2013-01-01

203

The in-line-quadrature bioCD  

Microsoft Academic Search

The biological compact disc (BioCD) is a sensitive detection platform that detects immobilized biomolecules on the surface of a spinning disc by quadrature laser interferometry. Spinning-disc interferometry (SDI) has the advantage of operating faraway from the 1\\/f system noise which has a 40 dB per octave slope, thus reducing the detection noise floor by more than 50 dB compared to

Ming Zhao; Xuefeng Wang; David Nolte

2007-01-01

204

Searches for gravitational waves from binary black hole coalescences with ground-based laser interferometers across a wide parameter space  

NASA Astrophysics Data System (ADS)

This is an exciting time for Gravitational Wave (GW) theory and observations. From a theoretical standpoint, the grand-challenge problem of the full evolution of a Binary Black Hole (BBH) system has been solved numerically, and a variety of source simulations are made available steadfastly. On the observational side, the first generation of state-of-the-art GW detectors, LIGO and Virgo, have achieved their design goal, collected data and provided astrophysically meaningful limits. The second generation of detectors are expected to start running by 2015. Inspired by this zeitgeist, this thesis focuses on the detection of potential GW signatures from the coalescence of BBH in ground-based laser interferometers. The LIGO Scientific Collaboration has implemented different algorithms to search for transient GW signatures, targeting different portions of the BBH coalescence waveform. This thesis has used the existing algorithms to study the detection potential of GW from colliding BBH in LIGO in a wide range of source parameters, such as mass and spin of the black holes, using a sample of data from the last two months of the S5 LIGO science run (14 Aug 2007 to 30 Sept 2007). This thesis also uses numerical relativity waveforms made available via the Numerical INJection Analysis project (NINJA). Methods such as the Chirplet based analysis and the use of multivariate classifiers to optimize burst search algorithms have been introduced in this thesis. These performance studies over a wide parameter space were designed to optimize the discovery potential of ground-based GW detectors and defining strategies for the search of BBH signatures in advanced LIGO data, as a step towards the realization of GW astronomy.

Ray Pitambar Mohapatra, Satyanarayan

205

Compact portable diffraction moire interferometer  

DOEpatents

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

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

1988-05-23

206

A Thermal-beam Calcium Interferometer  

NASA Astrophysics Data System (ADS)

We report on the construction of a next-generation atom interferometer. Our research includes developing passive stabilization techniques, low-noise laser current drivers, high-speed scan-balancing lock circuits, and high-speed low-noise photo-detecting units. Our efforts have lead to developing an extremely stable laser locked to an ultra-high finesse optical cavity for use in a Ramsey-Bord'e interferometer scheme. The interferometer itself is based on a thermal calcium beam and will be upgraded in the future to a dual species Ca/Sr interferometer sensitive enough to improve measurements of possible time variance of the fine structure constant.

Erickson, Christopher; van Zjill, Marshall; Washburn, Matthew; Archibald, James; Christensen, Dan; Birrell, Jeremiah; Burdett, Adam; Durfee, Dallin

2007-06-01

207

Improved skin friction interferometer  

Microsoft Academic Search

An improved system for measuring aerodynamic skin friction which uses a dual-laser-beam oil-film interferometer was developed. Improvements in the optical hardware provided equal signal characteristics for each beam and reduced the cost and complexity of the system by replacing polarization rotation by a mirrored prism for separation of the two signals. An automated, objective, data-reduction procedure was implemented to eliminate

R. V. Westphal; W. D. Bachalo; M. H. Houser

1986-01-01

208

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

209

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

PubMed

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

Berger, J; Lovberg, R H

1970-10-16

210

A Martin-Puplett cartridge FIR interferometer  

SciTech Connect

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

Smith, Roger J.; Penniman, Edwin E.; Jarboe, Thomas R. [University of Washington, Seattle, Washington 98195 (United States); Ball Aerospace and Technologies Corporation, Boulder, Colorado 80301 (United States); University of Washington, Seattle, Washington 98195 (United States)

2004-10-01

211

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

212

Self-coherent complex field reconstruction with in-phase and quadrature delay detection without a direct-detection branch.  

PubMed

Self-coherent detection with interferometric field reconstruction aims at retrieving the complex-valued optical field (amplitude and phase) by digitally processing delay interferometer (DI) measurements, in order to realize a differential direct detection receiver with capabilities akin to that of a fully coherent receiver with polarization multiplexing, albeit without requiring a local oscillator laser in the receiver. Here we introduce a novel digital recursive algorithm capable of accurately reconstructing the optical complex field (both amplitude and phase) solely from the quadrature DI outputs, eliminating the AM photo-detector branch. We analyze a key impairment namely the accumulation of errors and fluctuations in the reconstructed amplitude and phase due to ADC quantization noise, recirculating in the recursion. We introduce signal processing measures to effectively mitigate this noise impairment leading to a potentially practical self-coherent receiver, demonstrated in this paper for a single polarization. We also investigate the range of applicability of self-coherent detection concluding that it is most suitable to relatively low baud-rate systems such as passive optical networks, for which application the self-coherent receiver outperforms the coherent homodyne receiver due to its improved laser noise tolerance, obtained due to the removal of the optical local oscillator. PMID:22772241

Tselniker, Igor; Nazarathy, Moshe; Ezra, Shalva-Ben; Li, Jingshi; Leuthold, Juerg

2012-07-01

213

On Ignoring the Singularity in Numerical Quadrature.  

National Technical Information Service (NTIS)

Recent papers of P. Davis and P. Rabinowitz and of P. Rabinowitz study the problem of 'ignoring the singularity' in numerical quadrature of singular integrands. Among the other things they show that for certain quadratures if the singularity occurs at an ...

R. K. Miller

1969-01-01

214

Quadrature drift of dynamically adjustable gyroscopes  

NASA Astrophysics Data System (ADS)

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

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

215

A Compensation Method for Quadrature Modulation.  

National Technical Information Service (NTIS)

Two methods of modulation, quadrature and amplitude-phase, are being considered for the near-term implementation of clutter or extended targets. A test of quadrature modulation has been made with fairly good results (44 dB suppression for single-sided Gau...

I. P. Bottlik

1977-01-01

216

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

217

High Resolution, Real-Time Interferometer for Coherent Beam Combination  

NASA Astrophysics Data System (ADS)

Piston errors introduced during the pumping of high energy amplifiers in the laser chains are estimated to produce significant distortion and dramatically reduce the intensity of the combined beam resulted from the Coherent Beam Combination (CBC) of ultra intense short pulses. For monitoring the phase and optical path shift, we developed a high resolution real time interferometer. Based on the code counting method, the device is suitable for high speed/real time measurements and is immune to vibrations which might appear in the laser system. The device consists of an analog stage which generates the counting code, later processed by the microprocessor unit (CPU). The analog stage ensures 20 nm resolution, 2 m/s optical path variation speed measurements and has low sensitivity to variations of quadrature signals amplitude. The CPU is based on a complex programmable logic device (CPLD), with 8 ns processing time of the signals. The algorithm provides simultaneously measurements with increasing speed for lower resolution (20 nm at 2 m/s, 40 nm at 4 m/s and 80 nm at 8 m/s), making the system fault tolerant at high speed fluctuations of the optical path. The device contains also a digital-to-analog converter stage, making the instrument suitable for implementation of closed loop control.

Simion, Sandel; Blanaru, Constantin; Ursescu, Daniel

2010-04-01

218

Tunable 360° photonic radio frequency phase shifter based on optical quadrature double-sideband modulation and differential detection.  

PubMed

We propose a novel structure of a photonic RF phase shifter based on the vector-sum principle. The optical signal with quadrature double-sideband modulation passes through a dual-output Mach-Zehnder interferometer (MZI), and the two outputs are differentially detected. Two phase-quadrature RF terms are generated, and their amplitudes can be controlled in a triangularly complementary way by changing the phase of the MZI. A full tuning range of 0°-360° at 14?GHz is demonstrated experimentally accompanied by nearly constant RF amplitude. The validity of using our scheme in all-optical RF phase modulation is also verified. PMID:22139269

Xue, Xiaoxiao; Zheng, Xiaoping; Zhang, Hanyi; Zhou, Bingkun

2011-12-01

219

Gravimetry using atom interferometers: Some systematic effects  

Microsoft Academic Search

We present a theoretical investigation of some systematic effects in atom interferometers that have been used to measure the acceleration of gravity, g. We derive an explicit expression for the interferometer phase difference that differs from previously obtained results by a number of correction terms. These terms result from a rigorous treatment of the variation of the laser frequencies necessary

Peter Wolf; Philippe Tourrenc

1999-01-01

220

Liquid-Crystal Point-Diffraction Interferometer  

NASA Technical Reports Server (NTRS)

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

Mercer, Carolyn R.

1996-01-01

221

Effects of undesired external reflections on a laser diode feedback interferometer for measurement of displacements without ambiguity  

Microsoft Academic Search

When a small fraction of the power emitted from a single frequency laser is allowed to reenter the laser cavity, as in the case of a remote surface either reflective or diffusive illuminated by the laser spot, an injection modulation of the cavity field is generated, both in amplitude and frequency. By means of this technique known as laser diode

J. L. Arce-Diego; G. Giuliani; R. M. Cepeda-Echevarria; D. Pereda-Cubian; L. A. Fernandez-Fernandez

2001-01-01

222

Stable Operation of a 300-m Laser Interferometer with Sufficient Sensitivity to Detect Gravitational-Wave Events within Our Galaxy  

Microsoft Academic Search

TAMA300, an interferometric gravitational-wave detector with 300-m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations; the interferometer was operated for over 10 hours stably and continuously. With a strain-equivalent noise level of h~5×10-21\\/Hz, a signal-to-noise ratio of 30 is expected for gravitational waves generated by a

Masaki Ando; Koji Arai; Ryutaro Takahashi; Gerhard Heinzel; Seiji Kawamura; Daisuke Tatsumi; Nobuyuki Kanda; Hideyuki Tagoshi; Akito Araya; Hideki Asada; Youich Aso; Mark A. Barton; Masa-Katsu Fujimoto; Mitsuhiro Fukushima; Toshifumi Futamase; Kazuhiro Hayama; Gen'ichi Horikoshi; Hideki Ishizuka; Norihiko Kamikubota; Keita Kawabe; Nobuki Kawashima; Yoshinori Kobayashi; Yasufumi Kojima; Kazuhiro Kondo; Yoshihide Kozai; Kazuaki Kuroda; Namio Matsuda; Norikatsu Mio; Kazuyuki Miura; Osamu Miyakawa; Shoken M. Miyama; Shinji Miyoki; Shigenori Moriwaki; Mitsuru Musha; Shigeo Nagano; Ken-Ichi Nakagawa; Takashi Nakamura; Ken-Ichi Nakao; Kenji Numata; Yujiro Ogawa; Masatake Ohashi; Naoko Ohishi; Satoshi Okutomi; Ken-Ichi Oohara; Shigemi Otsuka; Yoshio Saito; Misao Sasaki; Shuichi Sato; Atsushi Sekiya; Masaru Shibata; Kentaro Somiya; Toshikazu Suzuki; Akiteru Takamori; Takahiro Tanaka; Shinsuke Taniguchi; Souichi Telada; Kuniharu Tochikubo; Takayuki Tomaru; Kimio Tsubono; Nobuhiro Tsuda; Takashi Uchiyama; Akitoshi Ueda; Ken-Ichi Ueda; Koichi Waseda; Yuko Watanabe; Hiromi Yakura; Kazuhiro Yamamoto; Toshitaka Yamazaki

2001-01-01

223

Achromatic self-referencing interferometer  

Microsoft Academic Search

A self-referencing Mach-Zehnder interferometer for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and registers the

1994-01-01

224

Achromatic self-referencing interferometer  

Microsoft Academic Search

A self-referencing Mach-Zehnder interferometer is described for accurately measuring laser wavefronts over a broad wavelength range (for example, 600 nm to 900 nm). The apparatus directs a reference portion of an input beam to a reference arm and a measurement portion of the input beam to a measurement arm, recombines the output beams from the reference and measurement arms, and

1994-01-01

225

Diffraction phases in atom interferometers  

Microsoft Academic Search

Diffraction of atoms by lasers is a very important tool for matter wave optics. Although the process is well understood, the phase shifts induced by this diffraction process are not well known. In this paper, we make analytical calculations of these phase shifts in some simple cases and use these results to model the contrast interferometer recently built by Pritchard

M. Buechner; R. Delhuille; A. Miffre; Cecile Robilliard; J. Vigué; C. Champenois

2003-01-01

226

Three-beam atom interferometer  

Microsoft Academic Search

We present an atom interferometer based on the interference of three partial matter waves in three different internal and external states. Coherent laser excitation acts as a beamsplitter to create a superposition state of the ground state and two Zeeman sublevels of the metastable state of magnesium atoms. The interference pattern of the output ports shows high contrast and the

H. Hinderthür; A. Pautz; V. Rieger; F. Ruschewitz; J. L. Peng; K. Sengstock; W. Ertmer

1997-01-01

227

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

228

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

229

Vibration Free Interferometer Mirror  

NASA Astrophysics Data System (ADS)

Optic tables may be an obstacle for the interferometric studies when they are exposed to mechanical vibrations in the particular frequency range. To reduce the mechanical noise, a moveable mirror of the FTIR spectrometer was used as an interferometer mirror. The vibration response of this mirror was investigated with a fiber optic Fabry-Perot interferometer that was built in our laboratory. The moveable mirror is mounted on a coil that is located between the permanent magnets. When the proper current is applied to the coil, the mirror becomes magnetically suspended and resistant to the mechanical vibrations. This work presents a non-contact vibration-monitoring technique with the extrinsic Fabry-Perot interferometric displacement sensor implemented using 4/125 ?m single-mode fiber with 3 dB fiber optic coupler. This device is based on a low finesse Fabry-Perot cavity which is formed by the end of a sensing optical fiber (fiber probe) and the magnetically-suspended mirror. The incoming light is emitted by a 660 nm laser diode. During the vibration test an ADC (NI 6070E) and a Labview software program were used. This technique helps to reduce the mechanical noise and to improve the stability of the interferometer.

Yaltkaya, S.

2007-04-01

230

Improved Skin Friction Interferometer  

NASA Technical Reports Server (NTRS)

An improved system for measuring aerodynamic skin friction which uses a dual-laser-beam oil-film interferometer was developed. Improvements in the optical hardware provided equal signal characteristics for each beam and reduced the cost and complexity of the system by replacing polarization rotation by a mirrored prism for separation of the two signals. An automated, objective, data-reduction procedure was implemented to eliminate tedious manual manipulation of the interferometry data records. The present system was intended for use in two-dimensional, incompressible flows over a smooth, level surface without pressure gradient, but the improvements discussed are not limited to this application.

Westphal, R. V.; Bachalo, W. D.; Houser, M. H.

1986-01-01

231

Atom Wave Interferometer.  

National Technical Information Service (NTIS)

The biggest accomplishment during the current grant period was the demonstration of a three grating interferometer for atoms--the first true atom interferometer reported in the literature. Our interferometer consists of three equally spaced transmission d...

D. E. Pritchard

1991-01-01

232

IR interferometers using modern cameras  

NASA Astrophysics Data System (ADS)

Laser interferometers have been used widely in the optics and disk drive industries. Often the surface of the sample is either too curved to resolve the fringes or too rough to reflect the incident beam back into the interferometer. Illuminating at a graze incident angle effectively increases the equivalent wavelength, and hence the reflectivity, but the image of a circular aperture becomes elliptical. Lasers with a long IR wavelength seem to be the solution. However,the spatial resolution of the vidicon cameras is usually poor, and the image lag is often too long. These limit the accuracy of an IR phase-shifting interferometer. Recently, we have designed tow types of interferometers for 3.39 micrometers and 10.6 micrometers using an InSb array and a micro- bolometer array, respectively. These modern cameras have a high resolution and hence greatly extend the range of measurable material from a blank to a finished optics. Because the refractive index of the optical material at the IR wavelength is usually very high, the anti-reflection coating of the optics at IR is more critical than that at a visible wavelength. The interferometer's design, the resolution, the dependence of the fringe contrast on the sample roughness, and the measurement results of various samples are presented.

Ai, Chiayu

1997-10-01

233

Photon-number statistics from the phase-averaged quadrature-field distribution: Theory and ultrafast measurement  

NASA Astrophysics Data System (ADS)

We prove that the photon-number distribution of an arbitrary single-mode optical state can be calculated directly from the phase-averaged quadrature amplitude distribution, measured using optical homodyne detection. We experimentally demonstrate the application of this result by measuring the ultrafast (subpicosecond), time-resolved photon-number statistics of a weak field from a pulsed diode laser. Also presented is a numerical calculation of the photon-number distribution of a quadrature-squeezed vacuum state.

Munroe, M.; Boggavarapu, D.; Anderson, M. E.; Raymer, M. G.

1995-08-01

234

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

PubMed

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

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

2011-12-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

236

Unequal-Arms Michelson Interferometers  

NASA Technical Reports Server (NTRS)

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

Tinto, Massimo; Armstrong, J. W.

1999-01-01

237

Unequal-Arms Michelson Interferometers  

NASA Technical Reports Server (NTRS)

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

Tinto, Massimo; Armstrong, J. W.

2000-01-01

238

Past and Future SOHO-Ulysses Quadratures  

NASA Technical Reports Server (NTRS)

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

Suess, Steven; Poletto, G.

2006-01-01

239

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

240

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

241

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

242

Quadrature formulae for problems in mechanics  

NASA Astrophysics Data System (ADS)

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

Milovanovi?, Gradimir V.; Igi?, Tomislav; Ton?ev, Novica

2012-09-01

243

102?k large area atom interferometers.  

PubMed

We demonstrate atom interferometers utilizing a novel beam splitter based on sequential multiphoton Bragg diffractions. With this sequential Bragg large momentum transfer (SB-LMT) beam splitter, we achieve high contrast atom interferometers with momentum splittings of up to 102 photon recoil momenta (102?k). To our knowledge, this is the highest momentum splitting achieved in any atom interferometer, advancing the state-of-the-art by an order of magnitude. We also demonstrate strong noise correlation between two simultaneous SB-LMT interferometers, which alleviates the need for ultralow noise lasers and ultrastable inertial environments in some future applications. Our method is intrinsically scalable and can be used to dramatically increase the sensitivity of atom interferometers in a wide range of applications, including inertial sensing, measuring the fine structure constant, and detecting gravitational waves. PMID:22026831

Chiow, Sheng-wey; Kovachy, Tim; Chien, Hui-Chun; Kasevich, Mark A

2011-09-23

244

Quadrature rules based on partial fraction expansions  

NASA Astrophysics Data System (ADS)

Quadrature rules are typically derived by requiring that all polynomials of a certain degree be integrated exactly. The nonstandard issue discussed here is the requirement that, in addition to the polynomials, the rule also integrates a set of prescribed rational functions exactly. Recurrence formulas for computing such quadrature rules are derived. In addition, Fejr's first rule, which is based on polynomial interpolation at Chebyshev nodes, is extended to integrate also rational functions with pre-assigned poles exactly. Numerical results, showing a favorable comparison with similar rules that have been proposed in the literature, are presented. An error analysis of a representative test problem is given.

Weideman, J. A. C.; Laurie, D. P.

2000-08-01

245

Composite Gauss-Legendre Quadrature with Error Control  

ERIC Educational Resources Information Center

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

Prentice, J. S. C.

2011-01-01

246

Control of the laser frequency of the Virgo gravitational wave interferometer with an in-loop relative frequency stability of 1.0 × 10?21 on a 100 ms time scale  

Microsoft Academic Search

The measurement of the space-time structure variations induced by strong cosmic events (supernovae, coalescing binaries of neutron stars, etc.) requires an oscillator with a relative stability of 10-21 on time scales typically ap100 ms. We demonstrate that the Virgo interferometer with a wavelength of 1.064 degm has a laser frequency with an in-loop stability of 1.0 times 10-21 on a

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

2009-01-01

247

Quadrature mixture LO suppression via DSW DAC noise dither  

Microsoft Academic Search

A Quadrature Error Corrected Digital Waveform Synthesizer (QECDWS) employs frequency dependent phase error corrections to, in effect, pre-distort the phase characteristic of the chirp to compensate for the frequency dependent phase nonlinearity of the RF and microwave subsystem. In addition, the QECDWS can employ frequency dependent correction vectors to the quadrature amplitude and phase of the synthesized output. The quadrature

Dale F. Dubbert; Peter A. Dudley

2007-01-01

248

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

249

Interferometer-type structures for guided atoms.  

PubMed

We experimentally demonstrate interferometer-type guiding structures for neutral atoms based on dipole potentials created by microfabricated optical systems. As a central element we use an array of atom waveguides being formed by focusing a red-detuned laser beam with an array of cylindrical microlenses. Combining two of these arrays, we realize X-shaped beam splitters and more complex systems like the geometries for Mach-Zehnder and Michelson-type interferometers for atoms. PMID:12485053

Dumke, R; Müther, T; Volk, M; Ertmer, W; Birkl, G

2002-11-25

250

Quadrature Compressive Sampling for Radar Signals  

NASA Astrophysics Data System (ADS)

Quadrature sampling has been widely applied in coherent radar systems to extract in-phase and quadrature (I and Q) components in the received radar signal. However, the sampling is inefficient because the received signal contains only a small number of significant target signals. This paper incorporates the compressive sampling (CS) theory into the design of the quadrature sampling system, and develops a quadrature compressive sampling (QuadCS) system to acquire the I and Q components with low sampling rate. The QuadCS system first randomly projects the received signal into a compressive bandpass signal and then utilizes the quadrature sampling to output compressive I and Q components. The compressive outputs are used to reconstruct the I and Q components. To understand the system performance, we establish the frequency domain representation of the QuadCS system. With the waveform-matched dictionary, we prove that the QuadCS system satisfies the restricted isometry property with overwhelming probability. For K target signals in the observation interval T, simulations show that the QuadCS requires just O(Klog(BT/K)) samples to stably reconstruct the signal, where B is the signal bandwidth. The reconstructed signal-to-noise ratio decreases by 3dB for every octave increase in the target number K and increases by 3dB for every octave increase in the compressive bandwidth. Theoretical analyses and simulations verify that the proposed QuadCS is a valid system to acquire the I and Q components in the received radar signals.

Xi, Feng; Chen, Shengyao; Liu, Zhong

2014-06-01

251

Optical Interferometer Testbed.  

National Technical Information Service (NTIS)

Viewgraphs on optical interferometer testbed presented at the MIT Space Research Engineering Center 3rd Annual Symposium are included. Topics covered include: space-based optical interferometer; optical metrology; sensors and actuators; real time control ...

G. H. Blackwood

1991-01-01

252

Special relativity and interferometers  

NASA Technical Reports Server (NTRS)

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

Han, D.; Kim, Y. S.

1988-01-01

253

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

254

Multisite EPR Oximetry from Multiple Quadrature Harmonics  

PubMed Central

Multisite continuous wave (CW) electron paramagnetic resonance (EPR) oximetry using multiple quadrature field modulation harmonics is presented. First, a recently developed digital receiver is used to extract multiple harmonics of field modulated projection data. Second, a forward model is presented that relates the projection data to unknown parameters, including linewidth at each site. Third, a maximum likelihood estimator of unknown parameters is reported using an iterative algorithm capable of jointly processing multiple quadrature harmonics. The data modeling and processing are applicable for parametric lineshapes under nonsaturating conditions. Joint processing of multiple harmonics leads to 2-3 fold acceleration of EPR data acquisition. For demonstration in two spatial dimensions, both simulations and phantom studies on an L-band system are reported.

Ahmad, R.; Som, S.; Johnson, D.H.; Zweier, J.L.; Kuppusamy, P.; Potter, L.C.

2011-01-01

255

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

256

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

257

An electron Talbot interferometer  

NASA Astrophysics Data System (ADS)

We report the first demonstration of a Talbot interferometer for electrons. The interferometer was used to image the Talbot carpet behind a nano-fabricated material grating. The Talbot interferometer design uses two identical gratings, and is particularly sensitive to distortions of the incident wavefronts. To illustrate this we used our interferometer to measure the curvature of concave wavefronts in a weakly focused electron beam. We describe how this wavefront curvature demagnified the Talbot revivals, and we discuss further applications for electron Talbot interferometers.

McMorran, Benjamin J.; Cronin, Alexander D.

2009-03-01

258

Active noise cancellation in a suspended interferometer.  

PubMed

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

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

2012-02-01

259

Interferometers for Displacement-Noise-Free Gravitational-Wave Detection  

SciTech Connect

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

Chen, Yanbei; Pai, Archana; Somiya, Kentaro; Kawamura, Seiji; Sato, Shuichi; Kokeyama, Keiko; Ward, Robert L.; Goda, Keisuke; Mikhailov, Eugeniy E. [Max-Planck Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany); TAMA project, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo, 112-8610 (Japan); LIGO Project 18-34, California Institute of Technology, Pasadena, California 91125 (United States); LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2006-10-13

260

JET polari-interferometer  

SciTech Connect

A multichannel far-infrared interferometer used on the Joint European Torus (JET) is described. The light source is a 195-{mu}m DCN laser. The instrument is of the Mach--Zehnder type, with a heterodyne detection system. The modulation frequency (100 kHz) is produced by diffraction from a rotating grating. There are six vertical and two oblique channels. The latter rely on retroreflection from mirrors mounted on the vessel wall. Their vibration is compensated by a second wavelength interferometer at 118.8 {mu}m. The various subsystems are described, with emphasis on features necessitated by (a) large path lengths, (b) remote handling requirements, (c) fluctuations in atmospheric humidity, and (d) unmanned automatic operation. Typical measurements, along with real-time and off-line data analysis, are presented. The phase-shift measurement is made with an accuracy of (1)/(20) of a fringe, corresponding to a line-integrated electron density of 5{times}10{sup 17} m{sup {minus}2}. Comparison with other electron density diagnostics are shown. The introduction of additional optics allows measurements of the Faraday effect and a determination of the poloidal magnetic field distribution. The signal processing and data analysis are described. Errors introduced by the calibration procedure, birefringence of the probing beams, toroidal field pickup, the flux geometry, and the density profile are considered. The Faraday angle is measured with an accuracy of 5% and a time resolution of 1--10 ms. The poloidal magnetic field is deduced with an accuracy of {plus minus}15%.

Braithwaite, G.; Gottardi, N.; Magyar, G.; O'Rourke, J.; Ryan, J.; Veron, D. (JET Joint Undertaking, Abingdon, Oxon OX14 3EA, United Kingdom (GB))

1989-09-01

261

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

262

Simulation of Fabry-Perot cavities in a Michelson interferometer  

Microsoft Academic Search

The Laser Interferometer Gravitational-Wave Observatory (LIGO) has designed to detect Gravitational Waves (GW); its system of detection is based on the Michelson interferometer configuration. When a GW hit on it, the optical elements are disturbed inducing a change in the optical path difference (OPD). The arms length in the detector should be of hundreds of kilometers, due to the small

Lina Aguilar-Lobo; Claudia Moreno; Guillermo Garcia-Torales

2009-01-01

263

Scalar-type gravitational wave emission from gravitational collapse in Brans-Dicke theory: Detectability by a laser interferometer  

NASA Astrophysics Data System (ADS)

To investigate the possibility of obtaining evidence for scalar-tensor theories of gravity by laser interferometric gravitational wave observatories (e.g., LIGO), we perform numerical simulations of the gravitational collapse of a spherically symmetric dust fluid and investigate the waveform and amplitude of scalar-type gravitational waves (SGW's) in the Brans-Dicke theory, which is one of the simplest scalar-tensor theories. We find that in the case of the dust collapse of mass ~10Msolar and initial radius ~100-1000 km, the emitted SGW's have a maximum amplitude ~10-22(500/?)(10 Mpc/R) and a characteristic frequency ~40-1000 Hz. This means that if the gravity theory is the Brans-Dicke theory with ?<~ several thousands, the advanced LIGO may detect a signal of SGW's from a supernova at the Virgo cluster. And, if we happen to find a supernova in our Galaxy, we may detect SGW's even if ? is as large as ~106. Concerning cosmic censorship, we also investigate the fate of a collapsed object. Our numerical results suggest that the final product of a collapsed object is a black hole in the Brans-Dicke theory like in the Einstein theory, and outside the black hole, the Brans-Dicke scalar field seems to become constant. These results support the cosmic censorship conjecture.

Shibata, Masaru; Nakao, Kenichi; Nakamura, Takashi

1994-12-01

264

A 0.5–20GHz quadrature downconverter  

Microsoft Academic Search

A quadrature downconverter with 4 GHz IF bandwidth and working over the 0.5-20 GHz RF frequency range has been designed, fabricated, and tested. The downconverter uses a frequency doubling and dividing scheme to generate quadrature local oscillator signals from 0.5-17 GHz and a pair of Gilbert-cell mixers to perform downconversion. When the IF outputs are combined with a commercial quadrature

Joseph C. Bardin; Sander Weinreb

2008-01-01

265

Improved sensitivity in a gravitational wave interferometer and implications for LIGO  

Microsoft Academic Search

Sensitivity enhancements in the laser interferometer gravitational wave observatory (LIGO) project's 40 m interferometer have been achieved through two major instrumental improvements. Improved vibration isolation has reduced the noise due to ground motion. New test masses with less mechanical dissipation were installed to lower the thermal noise associated with mirror vibrations. The minimum interferometer noise (square root of the spectral

A. Abramovici; W. Althouse; J. Camp; D. Durance; J. A. Giaime; A. Gillespie; S. Kawamura; A. Kuhnert; T. Lyons; F. J. Raab; R. L. Savage; D. Shoemaker; L. Sievers; R. Spero; R. Vogt; R. Weiss; S. Whitcomb; M. Zucker

1996-01-01

266

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) [Santa Cruz, CA

1999-01-01

267

The Offner imaging spectrometer in quadrature.  

PubMed

This is a proposal and description of a new configuration for an Offner imaging spectrometer based on the theory of aberrations of off-plane classical-ruled spherical diffraction gratings. This new spectrometer comprises a concave mirror used in double reflection and a convex reflection grating operating in quadrature, in a concentric layout. A very simple procedure obtains designs that are anastigmatic for a given point on the entrance slit and a given wavelength. Specific examples show that the performance of this type of system improves the performance of analogous conventional in-plane systems, when compactness and/or high spectral resolution is of fundamental importance. PMID:20588404

Prieto-Blanco, Xesús; Montero-Orille, Carlos; González-Nuñez, Héctor; Mouriz, María Dolores; Lago, Elena López; de la Fuente, Raúl

2010-06-01

268

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

269

Large infrared light polari-interferometer for JET.  

National Technical Information Service (NTIS)

The multichannel polari-interferometer installed on JET is feeded by the 195(mu)m radiation of a DCN laser. It has been operated for several years with 98% availability and a reduced maintenance. (ERA citation 15:054263)

D. Veron G. Braithwaite N. Gottardi G. Magyar J. O'Rourke

1989-01-01

270

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

271

Stepping optical path difference in an interferometer  

NASA Technical Reports Server (NTRS)

Stepping method permits higher amplitude modulation of secondary mirror of Fourier interferometer. Amplitude of mirror motion is limited only by available voltage drive on error-correcting actuator. Closed-loop controller provides servo error voltage linearly proportional to offset from proper null position. Bidirectional counter serves to count number of reference laser fringes offset from null position.

Schindler, R. A.

1976-01-01

272

Microwave Interferometer for Non-Destructive Testing  

NASA Astrophysics Data System (ADS)

A K-band microwave interferometer for non-destructive sensing of high frequency low amplitude (nm) vibration is demonstrated. This sensor uses direct-conversion receiver architecture with a phase shifter to adjust its sensitivity while varying the target distance. Detection of nanoscale vibration and laser-generated ultrasound waves through thin aluminum plate are measured and then compared with the theoretical results.

Choi, J.; Breugnot, S.; Itoh, T.

2010-02-01

273

Diffraction phases in atom interferometers  

SciTech Connect

Diffraction of atoms by lasers is a very important tool for matter wave optics. Although the process is well understood, the phase shifts induced by this diffraction process are not well known. In this paper, we make analytical calculations of these phase shifts in some simple cases and use these results to model the contrast interferometer recently built by Pritchard and co-workers. We thus show that the values of the diffraction phases are large and that they probably contribute to the phase noise observed in this experiment.

Buechner, M.; Delhuille, R.; Miffre, A.; Robilliard, C.; Vigue, J.; Champenois, C. [Laboratoire Collisions Agregats Reactivite-IRSAMC, Universite Paul Sabatier and CNRS UMR 5589, 118, Route de Narbonne, 31062 Toulouse Cedex, (France); PIIM, Universite de Provence and CNRS UMR 6633, Centre de Saint Jerome Case C21, 13397 Marseille Cedex 20, (France)

2003-07-01

274

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

275

Squeezing of optomechanical modes in detuned Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

We carry out analysis of optomechanical system formed by movable mirror of Fabry-Perot cavity pumped by detuned laser. Optical spring arising from detuned pump creates in the system several eigen modes which could be treated as high-Q oscillators. Modulation of laser power results in parametric modulation of oscillators spring constants thus allowing to squeeze noise in quadratures of the modes. Evidence of the squeezing could be found in the light reflected from the cavity.

Rakhubovsky, Andrey A.; Vyatchanin, Sergey P.

2013-08-01

276

Spectral sensitivity of LINC transmitters to quadrature modulator misalignments  

Microsoft Academic Search

The effects of misalignments in quadrature modulators on the LINC transmitter performance are studied by means of analysis and simulation. Ideally, each branch in the LINC system carries a constant amplitude signal allowing nonlinear high efficiency amplifiers to be used without generating intermodulation distortion (IMD). Misalignments in the quadrature modulators, however, introduce amplitude modulation on the branch signals and consequently

L. Sundstrom

2000-01-01

277

Polynomial interpolation and Gaussian quadrature for matrix-valued functions  

Microsoft Academic Search

The techniques for polynomial interpolation and Gaussian quadrature are\\u000ageneralized to matrix-valued functions. It is shown how the zeros and\\u000arootvectors of matrix orthonormal polynomials can be used to get a quadrature\\u000aformula with the highest degree of precision.

Ann Sinap

1994-01-01

278

Tomographic readout of an opto-mechanical interferometer  

NASA Astrophysics Data System (ADS)

The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. Full information of the state of light can only be gathered by a tomographic measurement. Here we demonstrate a tomographic interferometer readout by measuring arbitrary quadratures of the light field exiting a Michelson-Sagnac interferometer that contains a thermally excited high-quality silicon nitride membrane. A readout noise of 1.9 × 10-16 m Hz-1/2 around the membrane's fundamental oscillation mode at 133 kHz has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.

Kaufer, Henning; Sawadsky, Andreas; Westphal, Tobias; Friedrich, Daniel; Schnabel, Roman

2012-09-01

279

Analytic unit quadrature signals with nonlinear phase  

NASA Astrophysics Data System (ADS)

The notion of intrinsic mode functions (IMFs) in the algorithm of Hilbert-Huang transform (HHT) [N.E. Huang, Z. Shen, S.R. Long, M.C. Wu, H.H. Shih, Q. Zheng, N.-C. Yen, C.C. Tung, H.H. Liu, The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis, Proc. R. Soc. London A 454 (1998) 903-995] is essentially an engineering description in relation to mono-components of nonlinear and non-stationary signals. In this note we prove a version of Bedrosian’s theorem on the unit circle. We give a sufficient condition together with an example for nonlinear phases ?(t) that make the unit quadrature signals e to be analytic. We also establish a corresponding relationship between the periodic and non-periodic signals on the whole time range.

Qian, Tao; Chen, Qiuhui; Li, Luoqing

2005-04-01

280

Simultaneous quadrature detection of suppressed-carrier weak-coherent-states using a homodyne optical Costas loop receiver  

NASA Astrophysics Data System (ADS)

Weak coherent states (WCS) are being extensively employed in quantum communications and cryptography at telecommunications wavelengths. For these low-photon-number applications, simultaneous field quadrature measurements are frequently required, such as in the detection of multilevel modulations in the communications scenario or in cryptographic applications employing continuous variables. For this task multiport balanced homodyne detection (BHD) structures are employed, based on the splitting of the received field into its (non-commutating) in-phase (I) and quadrature (Q) components and their separate beating with a local oscillator (LO) in two BHD. This allows the simultaneous measurements of the 2 quadratures at the price of an additional noise due to the vacuum fields that leak via the unused ports. These schemes require the proper optical phase synchronization between the LO and the incoming field, which constitutes a challenge for WCS reception, especially for suppressed carrier modulations that are required for power economy. For this task, a Costas loop is implemented for low photon number WCS, with the design of an optimum feedback scheme considering the phase diffusion of WCS generated by semiconductor lasers. We implemented an optical Costas loop at 1550 nm based on polarization splitting of the laser field to detect I and Q quadratures simultaneously. We present results on the performance in phase error and bit error rate and compare with corresponding quantum limit.

López, J. A.; García, E.; Mendieta, F. J.; Arvizu, A.; Gallion, Phillipe

2011-09-01

281

Power flow control using quadrature boosters  

NASA Astrophysics Data System (ADS)

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

Sadanandan, Sandeep N.

282

Interferometrically Tuned Multi-Atmosphere CO2 Laser.  

National Technical Information Service (NTIS)

The patent application discloses a tunable infrared laser that employs a Fabry-Perot interferometer as a dispersive element inside the laser cavity. Laser oscillations occur at those frequencies which have the highest transmission through the interferomet...

F. J. O'Neill W. Whitney

1975-01-01

283

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

284

Miniature Angle Measuring Interferometer (MIAMI)  

NASA Astrophysics Data System (ADS)

The miniature Angle Measuring Interferometer (MIAMI) is a compact laser interferometer that was developed by Ball to satisfy the sensor needs of various pointing and tracking applications. These include: (1) attitude sensing for fast-steering mirrors and other optical elements, (2) structural monitoring and control for optical benches and other structures requiring micro-positioning, and (3) high-precision encoders for use in measuring the angular position of gimballed payloads and drives. MIAMI is constructed from off-the-shelf optical elements, using the inherent precision of the optical faces for alignment when feasible. In the present configuration, the laser light makes eight passes between the sensor head and the retroreflective target, amplifying the sensitivity of this device by a factor of eight. The interference of the two laser beams create fringe patterns, and the separation between fringes is equivalent to one wavelength of laser light (0.6328 micrometers). MIAMI uses interpolation to further subdivide each fringe spacing by a factor of 8 or 16, depending on configuration. MIAMI exhibits excellent performance characteristics, Its angular resolution is 175 nanoradians, and it achieves this with incremental data rates exceeding 5 MHz. MIAMI can accommodate rapid slew rates (greater than 50 deg/sec) and large angular travel (greater than +/- 20 deg). When used as a linear calibration sensor, MIAMI is capable of approxiamtely 10 nanometer linear resolution. The compact design (approximately 5 cubic in.) and light weight (approximately 8 oz) for the sensor head optics make it a very attractive candidate for space sensor applications.

Bauer, Robert J.

285

Sub-Aperture Interferometers  

NASA Technical Reports Server (NTRS)

Sub-aperture interferometers -- also called wavefront-split interferometers -- have been developed for simultaneously measuring displacements of multiple targets. The terms "sub-aperture" and "wavefront-split" signify that the original measurement light beam in an interferometer is split into multiple sub-beams derived from non-overlapping portions of the original measurement-beam aperture. Each measurement sub-beam is aimed at a retroreflector mounted on one of the targets. The splitting of the measurement beam is accomplished by use of truncated mirrors and masks, as shown in the example below

Zhao, Feng

2010-01-01

286

New harmonic materials: index engineering. Thin-thick quadrature frequency conversion  

SciTech Connect

The quadrature conversion scheme is a method of generating the second harmonic. The scheme, which uses two crystals in series, has several advantages over single-crystal or other two crystal schemes. The most important is that it is capable of high conversion efficiency over a large dynamic range of drive intensity and detuning angle. Consider a pair of KDP crystals cut for type-II phase matching. In the quadrature scheme, the optic axes of the crystals are arranged so that the plans containing the direction of the laser beam and their optic axes (the kz planes) are mutually perpendicular. This arrangement has two important properties. First, in type-II phase matching, the incident wave is polarized at 45 deg to the kz plane of the crystal. This, in the quadrature scheme, if the incident wave is correctly polarized for efficient conversion in the first crystal, it is also correctly polarized for efficient conversion in the second crystal. Both crystals can therefore convert efficiently.

Eimerl, D.

1985-02-07

287

Ultrastable heterodyne interferometer system using a CMOS modulated light camera.  

PubMed

A novel ultrastable widefield interferometer is presented. This uses a modulated light camera (MLC) to capture and stabilise the interferogram in the widefield heterodyne interferometer. This system eliminates the contribution of piston phase to the interferogram without the need for common path optics and results in a highly stable widefield interferometer. The MLC uses quadrature demodulation circuitry built into each pixel to demodulate the light signal and extract phase information using an electronic reference signal. In contrast to the work previously presented [Opt. Express 19, 24546 (2011)], the reference signal is derived from one of the pixels on board the MLC rather than an external source. This local reference signal tracks the instantaneous modulation frequency detected by the other pixels and eliminates the contribution of piston phase to the interferogram, substantially removing the contributions of unwanted vibrations and microphonics to the interferogram. Interferograms taken using the ultrastable system are presented with one of the interferometer mirrors moving at up to 85 mm s(-1) over a variety of frequencies from 18 Hz to 20 kHz (giving a variation in optical path length of 220 ?m, or 350 wavelengths at 62 Hz). This limit was the result of complex motion in the mirror mount rather than the stability limit of the system. The system is shown to be insensitive to pure piston phase variations equivalent to an object velocity of over 3 m s(-1). PMID:23038324

Patel, Rikesh; Achamfuo-Yeboah, Samuel; Light, Roger; Clark, Matt

2012-07-30

288

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

289

Process control system using polarizing interferometer  

DOEpatents

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

Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

1994-01-01

290

Furnace control apparatus using polarizing interferometer  

DOEpatents

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

Schultz, Thomas J. (Maumee, OH); Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

1995-01-01

291

Process control system 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.

1994-02-15

292

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

293

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

294

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

295

Michelson and His Interferometer  

ERIC Educational Resources Information Center

Presents a brief historical account of Michelson's invention of his interferometer with some subsequent ingenious applications of its capabilities for precise measurement discussed in details, including the experiment on detrmination of the diameters for heavenly bodies. (CC)

Shankland, Robert S.

1974-01-01

296

Atom Wave Interferometers.  

National Technical Information Service (NTIS)

Atom interferometers have proven to be versatile tools, applicable in many different scientific and technical arenas. We have concentrated our efforts in the three major areas of precision measurements of important quantities in atomic physics, basic rese...

D. E. Pritchard

1998-01-01

297

Atom Wave Interferometers.  

National Technical Information Service (NTIS)

Matter wave interferometers, in which de Broglie waves are coherently split and then recombined to produce interference fringes, have opened exciting new possibilities for precision and fundamental measurements with complex particles. The aim of our resea...

D. E. Pritchard

1999-01-01

298

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) [Santa Cruz, CA

1996-01-01

299

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

Microsoft Academic Search

This paper describes a Velocity Interferometer System for Any Reflector (VISAR) technique that extends velocity measurements from single points to a line. Single-frequency argon laser light was focused through a cylindrical lens to illuminate a line on a surface. The initially stationary, flat surface was accelerated unevenly during the experiment. Motion produced a Doppler-shift of light reflected from the surface

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

1990-01-01

300

Zone plate interferometer  

NASA Technical Reports Server (NTRS)

A developed form of the Fresner zone-plate interferometer is described. Three basic configurations are distinguished, associated with the real and virtual first order foci of a zone plate. Related versions and higher order variants are also educed. Compensated phase zone plates used in this application are found to produce uniform amplitude wavefronts. The properties of the interferometer in this form are discussed and an example given of its high-quality performance.

Smartt, R. N.

1974-01-01

301

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

302

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

303

Collisional decoherence in trapped-atom interferometers that use nondegenerate sources  

NASA Astrophysics Data System (ADS)

The coherence time, and thus sensitivity, of trapped-atom interferometers that use nondegenerate gases are limited by the collisions between the atoms. An analytic model that describes the effects of collisions between atoms in an interferometer is developed. It is then applied to an interferometer using a harmonically trapped nondegenerate atomic gas that is manipulated with a single set of standing wave laser pulses. The model is used to find the optimal operating conditions of the interferometer and direct Monte Carlo simulation of the interferometer is used to verify the analytic model.

Stickney, James A.; Squires, Matthew B.; Scoville, James; Baker, Paul; Miller, Steven

2009-01-01

304

Implementation of a modified Sag-Szekeres quadrature method.  

National Technical Information Service (NTIS)

The authors describe a modified Sag-Szekeres multidimensional quadrature algorithm and discuss its implementation as a general-purpose library procedure on serial and parallel architectures. Examples illustrate its effectiveness for both smooth and singul...

J. N. Lyness L. M. Delves

1997-01-01

305

Gaussian Quadrature Rules with Simple Node-Weight Relations  

NASA Astrophysics Data System (ADS)

In this paper, we consider the symmetric Gaussian and L-Gaussian quadrature rules associated with twin periodic recurrence relations with possible variations in the initial coefficient. We show that the weights of the associated Gaussian quadrature rules can be given as rational functions in terms of the corresponding nodes where the numerators and denominators are polynomials of degree at most 4. We also show that the weights of the associated L-Gaussian quadrature rules can be given as rational functions in terms of the corresponding nodes where the numerators and denominators are polynomials of degree at most 5. Special cases of these quadrature rules are givenE Finally, an easy to implement procedure for the evaluation of the nodes is described.

de Andrade, E. X. L.; Bracciali, C. F.; Sri Ranga, A.

2001-05-01

306

Residual Distribution Schemes for Conservation Laws Via Adaptive Quadrature.  

National Technical Information Service (NTIS)

This paper considers a family of nonconservative numerical discretizations for conservation laws which retains the correct weak solution behavior in the limit of mesh refinement whenever sufficient order numerical quadrature is used. Our analysis of 2-D d...

T. Barth R. Abgrall

2000-01-01

307

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

308

Is Gauss Quadrature Better than Clenshaw–Curtis?  

Microsoft Academic Search

We compare the convergence behavior of Gauss quadrature with that of its younger brother, Clenshaw{Curtis. Seven-line MATLAB codes are presented that implement both methods, and experiments show that the supposed factor-of-2 advantage of Gauss quadrature is rarely realized. Theorems are given to explain this eect. First, following O'Hara and Smith in the 1960s, the phenomenon is explained as a consequence

Lloyd N. Trefethen

2008-01-01

309

Lock acquisition of a gravitational-wave interferometer.  

PubMed

Interferometric gravitational-wave detectors, such as the Laser Interferometer Gravitational Wave Observatory (LIGO) detectors currently under construction, are based on kilometer-scale Michelson interferometers, with sensitivity that is enhanced by addition of multiple coupled optical resonators. Reducing the relative optic motions to bring the system to the resonant operating point is a significant challenge. We present a new approach to lock acquisition, used to lock a LIGO interferometer, whereby the sensor transformation matrix is dynamically calculated to sequentially bring the cavities into resonance. PMID:18007874

Evans, M; Mavalvala, N; Fritschel, P; Bork, R; Bhawal, B; Gustafson, R; Kells, W; Landry, M; Sigg, D; Weiss, R; Whitcomb, S; Yamamoto, H

2002-04-15

310

Inhomogeneity measurement at oblique incidence by phase measuring interferometers.  

PubMed

The huge power solid-state lasers require large optical materials with high quality. The inhomogeneity must be required to be measured. Inhomogeneity measurement is often done at normal incidence by interferometer, while the size of large blanks is limited to the interferometer aperture. A five-step method to measure refractive index inhomogeneity over the interferometer aperture is proposed in this paper. The variation of the refractive index inhomogeneity of the glass blank is directly calculated using five interferograms measured at oblique incidence. The high repeatability of the results is given. The reliability of the method is further verified by comparing the same part measured at normal incidence. PMID:24103946

Zhu, Luan

2013-09-01

311

Quadrature mixture LO suppression via DSW DAC noise dither  

DOEpatents

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

Dubbert, Dale F. (Cedar Crest, NM); Dudley, Peter A. (Albuquerque, NM)

2007-08-21

312

Bose-Einstein-condensate interferometer with macroscopic arm separation  

SciTech Connect

A Michelson interferometer using Bose-Einstein condensates is demonstrated with coherence times of up to 44 ms and arm separations up to 180 {mu}m. This arm separation is larger than that observed for any previous atom interferometer. The device uses atoms weakly confined in a magnetic guide and the atomic motion is controlled using Bragg interactions with an off-resonant standing-wave laser beam.

Garcia, O.; Deissler, B.; Hughes, K. J.; Reeves, J. M.; Sackett, C. A. [Physics Department, University of Virginia, Charlottesville, Virginia 22904 (United States)

2006-09-15

313

CO2 interferometer operation in Doublet III  

NASA Astrophysics Data System (ADS)

A CO2 laser interferometer is used for measuring the average free electron density along a vertical path in Doublet III, a large fusion research tokamak. The CO2 laser is used together with a collinear HeNe laser to form a two-wavelength interferometer capable of measuring plasma fringe shifts which are much less than the fringe shifts due to mechanical vibrations. This diagnostic has been shown to be able to resolve plasma electron fringe shifts smaller than 1/17 of a fringe during the pulsed operation which causes mechanical motion resulting in as many as 10 fringe shifts. The interferometer is operated in the Michelson configuration with a total double path length through the plasma of 6 m. The density resolution then is better than 2 x 10 to the 12th per cu cm. A density resolution of about 0.5 x 10 to the 12th per cu cm has been achieved during relatively quiet operation.

Baker, D. R.

1980-10-01

314

Results from a Prototype Second Harmonic Interferometer  

NASA Astrophysics Data System (ADS)

A tabletop second harmonic interferometer operating at 1.06 and 0.53 ?m has been built to test its sensitivity for use on tokamaks. This type of interferometer is insensitive to vibrations. The prototype uses a pulsed, 35 mJ, 10 Hz multimode, Nd:YAG laser, LiB_3O5 non-critically phase matched doublers, a retro-reflector, and a CCD camera detector. This interferometer has beam diameters of a few millimeters and spatial resolution of a few centimeters. Commercial lasers and CCD arrays are available which can scale this design to 20kHz. Tokamak applications typically require a sensitivity of 10-3 fringes and maximum changes of 1 fringe. The sensitivity of the prototype system has been investigated along with technical limitations on elements of the optical system relevant to its use on tokamaks. In particular, methods of normalizing shot-to-shot and spatial mode variations in the laser intensity are examined. A gas cell whose pressure can be varied has been used as a dispersive medium for calibrating and testing the instrumental sensitivity. The use of visible and near visible components allows a compact optical design and efficient use of port space.

Humensky, B.; Bretz, N.; Jobes, F.

1996-11-01

315

Sub-atomic dimensional metrology: developments in the control of x-ray interferometers  

NASA Astrophysics Data System (ADS)

Within the European Metrology Research Programme funded project NANOTRACE, the nonlinearity of the next generation of optical interferometers has been measured using x-ray interferometry. The x-ray interferometer can be regarded as a ruler or translation stage whose graduations or displacement steps are based on the lattice spacing of the crystallographic planes from which the x-rays are diffracted: in this case the graduations are every 192 pm corresponding to the spacing between the (2?2?0) planes in silicon. Precise displacement of the x-ray interferometer's monolithic translation stage in steps corresponding to discrete numbers of x-ray fringes requires servo positioning capability at the picometre level. To achieve this very fine control, a digital control system has been developed which has opened up the potential for advances in metrology using x-ray interferometry that include quadrature counting of x-ray fringes.

Yacoot, Andrew; Kuetgens, Ulrich

2012-07-01

316

Interferometer. [high resolution  

NASA Technical Reports Server (NTRS)

A high resolution interferometer is described. The interferometer is insensitive to slight misalignment of its elements, avoids channeling in the spectrum, generates a maximum equal path fringe contrast, produces an even two sided interferogram without critical matching of the wedge angles of the beamsplitter and compensator wedges, and is optically phase tunable. The interferometer includes a mirror along the path of each beam component produced by the beamsplitter, for reflecting the beam component from the beamsplitter, for reflecting the beam component from the beamsplitter to a corresponding retroreflector and for reflecting the beam returned by the retroreflector back to the beamsplitter. A wedge located along each beam component path, is large enough to cover the retroreflector, so that each beam component passes through the wedge during movement towards the retroreflector and away therefrom.

Breckinridge, J. B.; Norton, R. H.; Schindler, R. A. (inventors)

1981-01-01

317

Keck interferometer autoaligner  

NASA Astrophysics Data System (ADS)

A key thrust of NASA's Origins program is the development of astronomical interferometers. Pursuing this goal in a cost-effective and expedient manner from the ground has led NASA to develop the Keck Interferometer, which saw first fringes between the twin 10m Keck telescopes in March of 2001. In order to enhance the imaging potential of this facility, and to add astrometric capabilities for the detection of giant planets about nearby stars, four 1.8 m 'outrigger' telescopes may be added to the interferometer. Robust performance of the multi-aperture instrument will require precise alignment of the large number of optical elements found in the six optical beamtrains spread about the observatory site. The requirement for timely and reliable alignments dictated the development of an automatic alignment system for the Keck Interferometer. The autoaligner consists of swing-arm actuators that insert light-emitting diodes on the optical axis at the location of each optical element, which are viewed by a simple fixed-focus CCD camera at the end of the beamtrain. Sub-pixel centroiding is performed upon the slightly out-of-focus target spots using images provided by a frame grabber, providing steering information to the two-axis actuated optical elements. Resulting mirror-to-mirror alignments are good to within 2 arcseconds, and trimming the alignment of a full beamtrain is designed to take place between observations, within a telescope repointing time. The interactions of the autoaligner with the interferometer delay lines and coude trains are discussed in detail. The overall design of the interferometer's autoaligner system is presented, examining the design philosophy, system sequencing, optical element actuation, and subsystem co-alignment, within the context of satisfying performance requirements and cost constraints.

van Belle, Gerard T.; Colavita, M. Mark; Ligon, Edgar R., III; Moore, James D.; Palmer, Dean L.; Reder, Leonard J.; Smythe, Robert F.

2003-02-01

318

Optical interferometer testbed  

NASA Technical Reports Server (NTRS)

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

Blackwood, Gary H.

1991-01-01

319

Optical interferometer testbed  

NASA Astrophysics Data System (ADS)

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

Blackwood, Gary H.

1991-07-01

320

Displacement measurement with over-determined interferometer  

NASA Astrophysics Data System (ADS)

We present a concept combining traditional displacement incremental interferometry with a tracking refractometer following the fluctuations of the refractive index of air. This concept is represented by an interferometric system of three Michelson-type interferometers where two are arranged in a counter-measuring configuration and the third one is set to measure the changes of the fixed length, here the measuring range of the overall displacement. In this configuration the two counter-measuring interferometers have identical beam paths with proportional parts of the overall one. The fixed interferometer with its geometrical length of the measuring beam linked to a mechanical reference made of a high thermal-stability material (Zerodur) operates as a tracking refractometer monitoring the atmospheric refractive index directly in the beam path of the displacement measuring interferometers. This principle has been demonstrated experimentally through a set of measurements in a temperature controlled environment under slowly changing refractive index of air in comparison with its indirect measurement through Edlen formula. With locking of the laser optical frequency to fixed value of the overall optical length the concept can operate as an interferometric system with compensation of the fluctuations of the refractive index of air.

Lazar, Josef; Holá, Miroslava; Hrabina, Jan; Buchta, Zden?k.; ?íp, Ond?ej; Oulehla, Jind?ich

2012-01-01

321

Phase-Shifting Shearing Interferometer  

NASA Technical Reports Server (NTRS)

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

Griffin, DeVon W.

2001-01-01

322

The interferometer in radio astronomy  

Microsoft Academic Search

A theory is developed for the response of a two-element radio interferometer to a partially coherent field, without restriction as to bandwidth or antenna properties. It is shown that for a completely incoherent source the narrow-band interferometer output is a component of the Fourier transform of the source brightness, which can therefore be mapped by repeated interferometer observations. A partially

N. C. Mathur

1968-01-01

323

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

324

Multiple Beam Atomic Interferometer  

Microsoft Academic Search

We have demonstrated a multiple beam atom interferometer. Atoms in a cesium atomic beam are optically pumped into a spatially separating nonabsorbing superposition state consisting of five partial beams in different Zeeman sublevels separated by a momentum of two photon recoils each. When the partial waves are spatially recombined, we observe an interference signal which shows the sharply peaked Airy

M. Weitz; T. Heupel; T. W. Hänsch

1996-01-01

325

Bicrystal pi-interferometers  

Microsoft Academic Search

Experimental results for DC interferometers of asymmetric topology with high-Tc bicrystal Josephson junctions are reported. Model of the tilted bicrystal junctions is discussed. As a model, parallel array of alternating `0' and `?' contacts was studied numerically. It has been shown that the array can act as either 0- or ?-junction. Both the array characteristics and the critical current dependence

V. K Kornev; G. A Ovsyannikov; P. B Mozhaev; I. V Borisenko; N. F Pedersen

2002-01-01

326

Measurement of the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame by means of a laser-based interferometer technique  

NASA Astrophysics Data System (ADS)

With a view to measuring the structure coefficient of refractive index fluctuations in a turbulent premixed butane-air flame, a thin laser beam is sent into the flame perpendicular to the flow direction. The laser beam generally undergoes fluctuations of direction, phase, and amplitude. Only the random deflections of the laser beam may be taken into account. After having traversed the flame, the perturbed laser beam enters into an interferometric system. Materials and experimental procedure are described. In the unperturbed interference pattern, the zones only sensitive to fluctuations of the angle-of-arrival of the laser beam are detected. From the random displacements of the central bright fringe, the structure coefficient of refractive index fluctuations in the flame is measured. To prove that the method of measurement is satisfactory, the result obtained is applied for computing the power spectral density of the angle-of-arrival of the laser beam from the formula of correlations of the laser beam deflection angles which we have demonstrated in previous works. This computed power spectral density is compared to that measured from the effective position of the detector. A good agreement is observed between the two results.

Ngo Nyobe, Elisabeth; Pemha, Elkana; Hona, Jacques; Bilong, Jean; Lamara, Maurice

2014-08-01

327

Parametric oscillatory instability in a signal-recycled LIGO interferometer  

SciTech Connect

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

Vyatchanin, S P; Strigin, S E [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation)

2007-12-31

328

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

329

An Algorithm to Evaluate Imbalances of Quadrature Mixers  

NASA Astrophysics Data System (ADS)

It is essential, as bandwidths of wireless communications get wider, to evaluate the imbalances among quadrature mixer ports, in terms of carrier phase offset, IQ gain imbalance, and IQ skew. Because it is time consuming to separate skew, gain imbalance and carrier phase offset evaluation during test is often performed using a composite value, without separation of the imbalance factors. This paper describes an algorithm for enabling separation among quadrature mixer gain imbalance, carrier phase offset, and skew. Since the test time is reduced by the proposed method, it can be applied during high volume production testing.

Asami, Koji; Arai, Michiaki

330

Achromatic self-referencing interferometer  

DOEpatents

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

Feldman, Mark (Pleasanton, CA) [Pleasanton, CA

1994-01-01

331

Achromatic self-referencing interferometer  

DOEpatents

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

Feldman, M.

1994-04-19

332

Analysis of a free oscillation atom interferometer  

SciTech Connect

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

Kafle, Rudra P.; Zozulya, Alex A. [Department of Physics, Worcester Polytechnic Institute, 100 Institute Road, Worcester, Massachusetts 01609 (United States); Anderson, Dana Z. [Department of Physics and JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)

2011-09-15

333

Line-imaging Fabry-Perot interferometer  

SciTech Connect

A method for measuring the velocity history of a line element on a shock-loaded solid has been demonstrated. Light from single-frequency laser is focused through a cylindrical lens to a line on a moving target. The return Doppler-shifted image is passed through a Fabry-Perot interferometer. Because only specific combinations of incident light angle and frequency can pass through the interferometer the output is an incomplete image of the moving target appearing as a set of fringes. This image is focused onto an electronic streak camera and swept in time. The fringe pattern changes with time as the target surface moves, allowing determination of velocity for each point on the target that forms a fringe. Because the velocity can only be measured at the fringe positions, it is necessary to use an interpolating polynomial to obtain a continuous function of time and velocity along the sampled lien. 9 refs., 7 figs.

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

1990-01-01

334

Interferometers and decoherence matrices  

PubMed

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. PMID:11031652

Han; Kim; Noz

2000-05-01

335

The Antarctic Planet Interferometer  

NASA Technical Reports Server (NTRS)

The Antarctic Planet Interferometer is an instrument concept designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

Swain, Mark R.; Walker, Christopher K.; Traub, Wesley A.; Storey, John W.; CoudeduForesto, Vincent; Fossat, Eric; Vakili, Farrok; Stark, Anthony A.; Lloyd, James P.; Lawson, Peter R.; Burrows, Adam S.; Ireland, Michael; Millan-Gabet, Rafael; vanBelle, Gerard T.; Lane, Benjamin; Vasisht, Gautam; Travouillon, Tony

2004-01-01

336

The Antarctic Planet Interferometer  

NASA Astrophysics Data System (ADS)

The Antarctic Planet Interferometer is a concept designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on Earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperatures found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

Swain, M.; Lloyd, J.; Traub, W.; Walker, C.; Stark, A.; Lawson, P.; Storey, J.; Coudé du Foresto, V.; Fossat, E.; Ireland, M.; Burrows, A.; Vakili, F.

2003-12-01

337

Tolerance of laser frequency offset in optical minimum-shift keying transmission systems  

NASA Astrophysics Data System (ADS)

A mismatch between laser frequency and delay interferometer (DI) phase is found to be the most critical impairment for the receiver performance in a practical phase-modulated (PM) system. This paper investigates the receiver performance degradation caused by frequency offset between optical signal and DI in a 10 Gb/s minimum-shift keying (MSK) system, and compares it with the conventional PM formats, optical differential-phase-shift keying (DPSK) and differential-quadrature-phase-shift keying (DQPSK), which are nonreturn-to-zero (NRZ) and 50% duty cycle return-to-zero (RZ). Results show that the MSK system is about double times and six times more robust to frequency offset than the DPSK and DQPSK systems operating at the same bit rate, respectively.

Chen, Han; Dong, Yi; He, Hao; Hu, Weisheng; Li, Lemin

2009-07-01

338

Theoretical analysis of a single- and double-reflection atom interferometer in a weakly confining magnetic trap  

NASA Astrophysics Data System (ADS)

The operation of a BEC based atom interferometer, where the atoms are held in a weakly confining magnetic trap and manipulated with counterpropagating laser beams, is analyzed. A simple analytic model is developed to describe the dynamics of the interferometer. It is used to find the regions of parameter space with high and low contrast of the interference fringes for both single and double reflection interferometers. We demonstrate that for a double reflection interferometer the coherence time can be increased by shifting the recombination time. The theory is compared with recent experimental realizations of these interferometers.

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

2008-04-01

339

The University of Florida LISA interferometer simulator  

NASA Astrophysics Data System (ADS)

Interferometric gravitational wave detectors such as LISA are built around two major subsys-tems. Gravitational reference sensors (GRS) consist of several freely-falling proof masses which follow variations in space time caused by passing gravitational waves. Spurious accelerations of the proof masses caused by technical or environmental forces have to be below the fN/rtHz level in the frequency band of interest. Interferometer measurement systems (IMS) measure the changes in the distances between the proof masses with sufficient sensitivity. The GRS-system for LISA has been developed over the last ten years and will be tested in a dedicated test mission, the LISA Test Package (LTP), scheduled for launch in 2012. The IMS of LISA is one of the most dynamic and longest interferometers ever envisioned. It consists of many subsystems which depend on the long light-travel times, the changes in the light-travel times and the induced Doppler shifts. The signals of the IMS are beat tones taken between vari-ous lasers at various locations on the three spacecraft. The phase evolution of each signal is measured against on-board clocks, after which linear combinations between appropriately time-shifted signals are formed to cancel about 10 orders of magnitude of laser frequency noise and thereby reach LISA sensitivity. Achieving 10 orders of magnitude of common mode rejection is already a daunting task for a small static interferometer in an optical laboratory. LISA is a very large and highly dynamic interferometer with constantly changing arms which for exam-ple requires to adapt permanently the noise cancelling linear combinations to the current arm lengths and spacecraft velocities while continuously monitoring the relative noise between the three independent on-board clocks. The University of Florida LISA Interferometer Simulator (UFLIS) is a hardware-in-the-loop simulator which includes multiple lasers, LISA-like signal travel-times and LISA-like Doppler shifts. UFLIS generates signals that currently are the most LISA-like signals in the world; these can be used to develop, test, and verify various techniques and algorithms proposed to achieve the required LISA performance. In this presentation I will discuss the core elements of UFLIS and how these elements are used to generate LISA-like signals. I will present results from tests we have performed and discuss our future test plans. This work is supported by NASA grants NNX08AG75G and NNX09AF99G

Mueller, Guido; Hochman, Steven; Mitryk, Shawn; Sanjuan Munoz, Jose; Preston, Alix; Sweeney, Dylan; Yu, Yinan; Tanner, David B.; Mueller, Guido

340

A 900 MHz low phase noise CMOS quadrature oscillator  

Microsoft Academic Search

A novel method for designing quadrature oscillators is presented. The technique is based on differential coupling at the second harmonic frequency of two separate oscillators. The desired coupling is obtained using an integrated transformer which is attached to the common-mode nodes of two differential oscillators. A 900 MHz prototype has been implemented in a 0.35 ?m CMOS process. The oscillator

Josk Cabanillas; Laurent Dussopt; J. M. Lopez-Villegas; G. M. Rebeiz

2002-01-01

341

Thermodynamics of quadrature trajectories in open quantum systems  

NASA Astrophysics Data System (ADS)

We apply a large-deviation method to study the diffusive trajectories of the quadratures of light emitted from open quantum systems. We formulate the study of quadrature trajectories in terms of characteristic operators and show that, in the long-time limit, the statistics of such trajectories obey a large-deviation principle. We take our motivation from homodyne detection schemes which allow the statistics of light quadratures to be measured. We illustrate our approach with four examples of increasing complexity: a driven two-level system, a “blinking” three-level system, a pair of weakly coupled two-level driven systems, and the micromaser. We discuss how quadrature operators can serve as alternative order parameters for the classification of dynamical phases, which is particularly useful in cases where the statistics of quantum jumps cannot distinguish such phases. The formalism we introduce also allows us to analyze the properties of the light emitted in quantum-jump trajectories which deviate far from the typical dynamics.

Hickey, James M.; Genway, Sam; Lesanovsky, Igor; Garrahan, Juan P.

2012-12-01

342

Recursive quadrature mirror filters--Criteria specification and design method  

Microsoft Academic Search

Criteria are found for a pair of recursive infinite impluse response (IIR) filters which have mirror image amplitude responses and whose outputs are in phase quadrature at all frequencies. A method is suggested for designing filters with these characteristics, and their performance and processing requirements are compared with a typical nonrecursive finite impluse response (FIR) realization. A particular filter is

P. Millar

1985-01-01

343

Quadrature mirror filter design in the time domain  

Microsoft Academic Search

A new technique for designing quadrature mirror filters is described. The formulation, carried out in the time domain, is shown to result in an optimization problem requiring minimization of a quartic multinomial. An iterative solution is suggested which involves (computation of) the eigenvector of a matrix with a dimensionality equal to one half the number of filter taps. Our experiments

V. K. Jain; RONALD E. CROCHIERE

1984-01-01

344

An analytical formula for the design of quadrature mirror filters  

Microsoft Academic Search

Quadrature mirror filters have an outstanding relevance in the implementation of filter banks for dividing the speech signal into frequency bands and for reconstructing it from these subbands. An analytical formula is given, which allows one to optimize the design of the basic low-pass FIR filter by means of a straight nonlinear minimization procedure.

GIANCARLO PIRANI; VALERIO ZINGARELLI

1984-01-01

345

Modeling of Nonuniform Interconnects by Using Differential Quadrature Method  

Microsoft Academic Search

This paper discusses an efficient numerical approximation technique, called the differential quadrature method (DQM), which has been adapted to model lossy nonuniform interconnects. DQM discretizes Telegrapher's equations into algebraic equations, which can be represented by compact equivalent circuit models, whose port voltages and currents are related by rational formulas in the frequency domain. Although the rationalization process in DQM is

Qinwei Xu; Pinaki Mazumder; Mayukh Bhattacharya

2001-01-01

346

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

347

A 385-500GHz Balanced Mixer with a Waveguide Quadrature Hybrid Coupler  

Microsoft Academic Search

Abstract—We developed a 385-500GHz balanced mixer with a waveguide quadrature hybrid coupler. The balanced mixer consists of an RF quadrature hybrid coupler, two double sideband (DSB) SIS mixers with noise temperature of — 60K, and an IF 180 degree hybrid coupler covering 4 - 8 GHz IF band. An RF quadrature hybrid coupler was designed and fabricated whose fabrication error

Yasutaka Serizawa; Yutaro Sekimoto; Tetsuya Ito; Wenlei Shan; Toshiaki Kamba; Naohisa Satou; Mamoru Kamikura

2006-01-01

348

Design and Measurement of a Doppler Radar With New Quadrature Hybrid Mixer for Vehicle Applications  

Microsoft Academic Search

This paper presents a novel Doppler radar sensor architecture with a quadrature hybrid mixer. Consisting of four branch-line couplers, two 45?? delay lines, and four Schottky diodes, the quadrature hybrid mixer demonstrates high transmission efficiency to pass the power from a local oscillator (LO) to an antenna without wasting received power at the oscillator port. A quadrature Doppler radar system

Tan-Hsiung Ho; Shyh-Jong Chung

2010-01-01

349

Observation of a coherence loss of an atomic wave scattered from the optical potential in a Talbot-Lau atom interferometer  

SciTech Connect

A coherence loss of an atomic wave scattered from the optical potential in an interferometer is observed. A Talbot-Lau atom interferometer is developed for that measurement using a laser-cooled lithium atomic beam. The long de Broglie wavelength of slow lithium atoms gives a short Talbot length and makes it possible to construct a small and stable atom interferometer.

Kohno, Takuya; Suzuki, Shinya; Shimizu, Kazuko [Institute for Laser Science, University of Electro-Communications, Chofu-shi, Tokyo 182-8585 (Japan)

2007-11-15

350

Lambda/2 fringe-spacing interferometer.  

PubMed

The precision of interferometry is directly linked to the fringe spacing of the recorded interferogram. Whereas all interferometric devices show a fringe spacing equal to a wavelength of the laser light we present a novel scheme of a two-beam interferometer exhibiting a fringe spacing reduced by a factor of 2; the direct detection of the beat signal is replaced with the monitoring of the fluorescence of a twofold degenerate atomic system resonant with the laser. The lambda/2 fringe spacing in the fluorescence signal is demonstrated with a hot sodium vapor excited by a broadband laser tuned to the D1 line. In the saturation regime, the dark fringes are expected to be extremely narrow, leading to the possibility of nanoscale displacement measurements or atom localization. PMID:19282922

de Chatellus, H Guillet; Pique, J-P

2009-03-15

351

In situ measurement of absorption in high-power interferometers by using beam diameter measurements.  

PubMed

We present a simple technique to make in situ measurements of the absorption in the optics of high-power laser interferometers. The measurement is particularly useful to those commissioning large-scale high power optical systems. PMID:16496883

Ottaway, David; Betzwieser, Joseph; Ballmer, Stefan; Waldman, Sam; Kells, William

2006-02-15

352

Coherent detection of frequency-hopped quadrature modulations in the presence of jamming. II - QPR Class I modulation. [Quadrature Partial Response  

NASA Technical Reports Server (NTRS)

This paper considers the performance of quadrature partial response (QPR) in the presence of jamming. Although a QPR system employs a single sample detector in its receiver, while quadrature amplitude shift keying (or quadrature phase shift keying) requires a matched-filter type of receiver, it is shown that the coherent detection performances of the two in the presence of the intentional jammer have definite similarities.

Simon, M. K.

1981-01-01

353

Advanced gravitational reference sensor for high precision space interferometers  

Microsoft Academic Search

LISA and the next generation of space-based laser interferometers require gravitational reference sensors (GRS) to provide distance measurements to picometre precision for LISA, and femtometre precision for the proposed Big Bang Observatory (BBO). We describe a stand-alone GRS structure that has the benefits of higher sensitivity and ease of fabrication. The proposed GRS structure enables high precision interferometric links in

Ke-Xun Sun; Graham Allen; Sasha Buchman; Dan DeBra; Robert Byer

2005-01-01

354

Orbiting stellar interferometer for astrometry and imaging  

NASA Astrophysics Data System (ADS)

The orbiting stellar interferometer (OSI) is a concept for a first-generation space interferometer with astrometric and imaging goals. The OSI is a triple Michelson interferometer with articulating siderostats and optical delay lines. Two point designs for the instrument are described. The 18-m design uses an 18-m maximum baseline and aperture diameters of 40 cm; the targeted astrometric performance is a wide-field accuracy of 10 microarsec for 16-mag objects in 100 s of integration time and for 20-mag objects in 1 h. The instrument would also be capable of synthesis imaging with a resolution of 5 marcsec, which corresponds to the diffraction limit of the 18-m base line. The design uses a deployed structure, which would fold to fit into an Atlas IIAS shroud, for insertion into a 900-km sun-synchronous orbit. In addition to the 18-m point design, a 7-m point design that uses a shorter base line in order to simplify deployment is also discussed. OSI's high performance is made possible by utilizing laser metrology and controlled-optics technology.

Colavita, M. M.; Shao, M.; Rayman, M. D.

1993-04-01

355

Demonstration of a squeezed-light-enhanced power- and signal-recycled Michelson interferometer.  

PubMed

We report on the experimental combination of three advanced interferometer techniques for gravitational wave detection, namely, power recycling, detuned signal recycling, and squeezed field injection. For the first time, we experimentally prove the compatibility of especially the latter two. To achieve a broadband nonclassical sensitivity improvement, we applied a filter cavity for compensation of quadrature rotation. The signal-to-noise ratio was improved by up to 2.8 dB beyond the coherent state's shot noise. The complete setup was stably locked for arbitrary times and characterized by injected single-sideband modulation fields. PMID:16384128

Vahlbruch, Henning; Chelkowski, Simon; Hage, Boris; Franzen, Alexander; Danzmann, Karsten; Schnabel, Roman

2005-11-18

356

Stabilized fiber-optic Mach-Zehnder interferometer for carrier-frequency rejection  

NASA Astrophysics Data System (ADS)

We have demonstrated stabilization of a fiber-optic Mach-Zehnder interferometer, with a centimeter-scale path difference, to the transmission minimum for the carrier wave of a frequency-modulated laser beam. A time-averaged extinction of 32 dB, limited by the bandwidth of the feedback, was maintained over several hours. The interferometer was used to remove the carrier wave from a 780 nm laser beam that had been phase modulated at 2.7 GHz.

Cooper, Nathan; Woods, Jonathan; Bateman, James; Dunning, Alexander; Freegarde, Tim

2013-08-01

357

Erbium-doped fiber laser tuning using two cascaded unbalanced Mach-Zehnder interferometers as intracavity filter: numerical analysis and experimental confirmation  

Microsoft Academic Search

We propose a new method for tuning an Er3+-doped continuous-wave fiber-ring laser. We present a novel numerical model and confirm the model with experimental results. The numerical model relies on the implementation of the analytical solution of signal propagation over small (elemental) segments of amplifier fiber rather than using the usual Runge-Kutta algorithm. The validity of the model is verified

Stéphane Calvez; X. Rejeaunier; P. Mollier; J.-P. Goedgebuer; W. T. Rhodes

2001-01-01

358

Fully balanced heat interferometer  

NASA Astrophysics Data System (ADS)

A tunable and balanced heat interferometer is proposed and analyzed. The device consists of two superconductors linked together to form a double-loop interrupted by three parallel-coupled Josephson junctions. Both superconductors are held at different temperatures, allowing the heat currents flowing through the structure to interfere. We demonstrate that thermal transport is coherently modulated through the application of a magnetic flux. Furthermore, such modulation can be tailored at will or even suppressed through the application of an extra control flux. Such a device allows for a versatile operation appearing as an attractive key to the onset of low-temperature coherent caloritronic circuits.

Martínez-Pérez, M. J.; Giazotto, F.

2013-03-01

359

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

360

Entanglement measurement of the quadrature components without homodyne detection in the bright, spatially multimode far field  

NASA Astrophysics Data System (ADS)

We present a procedure for the measurement of quadrature components of an electromagnetic field in the far field as an alternative to the traditional approach based on the homodyne detection (HD) technique. For that we suggest to use coherent sources such as phase-locked lasers or optical parametric oscillators operating above threshold. Then we show how to arrange the detection procedure in the far field that is exactly or partly equivalent to the HD. Our scheme can be applied for both the classical and nonclassical fields. The potential of the procedure is illustrated by an example which utilizes the pixellized sources of the nonclassical light. As an integral part of our investigation we develop a theory of the pixellized source of the spatiotemporally squeezed light.

Golubeva, T.; Golubev, Yu.; Samburskaya, K.; Fabre, C.; Treps, N.; Kolobov, M.

2010-01-01

361

Holographic Twyman-Green Interferometer  

NASA Technical Reports Server (NTRS)

Off-axis Fresnel zone plate used to obtain fringe visibility close to unity. Holographic Twyman-Green Interferometer (HTG) employs off-axis Fresnel zone plate (OFZP) as beam splitter and beam diverger in place of two separate elements that perform those functions in conventional TwymanGreen interferometer.

Chen, C. W.; Wyant, J. C.; Breckinridge, J. B.

1984-01-01

362

Dual-modulation fiber Fabry-Perot interferometer with double reflection for slowly-varying displacements.  

PubMed

This Letter describes a dual-amplitude modulation technique incorporated into a double reflection extrinsic-type fiber Fabry-Perot interferometer to measure periodic, nonperiodic as well as quasi-static displacements. The modulation scheme simultaneously maintains the interference signal pair in quadrature and provides a reference signal for displacements inferior to a quarter of the source wavelength. The control and phase demodulation of the interferometer carried out via software enable quasi-real-time measurement and facilitates sensor alignment. The sensor system can be exploited in the low frequency range from 10(-3) to ?500 Hz and has a resolution better than 2.2 nm, targeting applications in geophysics. PMID:22825167

Seat, H C; Chawah, P; Cattoen, M; Sourice, A; Plantier, G; Boudin, F; Chéry, J; Brunet, C; Bernard, P; Suleiman, M

2012-07-15

363

Thin-plate spline quadrature of geodetic integrals  

NASA Astrophysics Data System (ADS)

Thin-plate splines — well known for their flexibility and fidelity in representing experimental data — are especially suited for the numerical evaluation of geodetic integrals in the area where these are most sensitive to the data, i.e. in the immediate vicinity of the computation point. Quadrature rules that are exact for thin-plate splines interpolating randomly spaced data are derived for the inner zone contribution (to a planar approximation) to Stokes's formula, to the formulae of Vening Meinesz and to the L 1 gradient operator in the analytical continuation solution of Molodensky's problem. The quadrature method is demonstrated by calculating the inner zone contribution to height anomalies in a mountainous area of Lesotho and carrying out a comparison with GPS-derived heights. Height anomalies are recovered with an accuracy of 6 cm.

van Gysen, Herman

1994-09-01

364

Extraction of quadrature phase information from multiple pulse NMR signals  

NASA Technical Reports Server (NTRS)

A multiple pulse sequence (8-pulse sequence) used for high-resolution solid state NMR is analyzed with regard to the information available from each of the four wide sampling windows. It is demonstrated that full quadrature phase information can be obtained using only a single phase detector and that, for the commonly encountered situation where the spectral width is much less than the folding frequency, the signals from the various windows can be combined easily using standard complex Fourier transform software. An improvement in the signal-to-noise ratio equal to the square root of 3 is obtained over either standard single or quadrature phase detection schemes. Procedures for correcting spectral distortions are presented.

Rhim, W.-K.; Burum, D. P.; Vaughan, R. W.

1976-01-01

365

Quadrature formulae for classes of functions of low smoothness  

SciTech Connect

For Sobolev and Korobov spaces of functions of several variables a quadrature formula with explicitly defined coefficients and nodes is constructed. This formula is precise for trigonometric polynomials with harmonics from the corresponding step hyperbolic cross. The error of the quadrature formula in the classes W{sup {alpha}}{sub p}[0,1]{sup n}, E{sup {alpha}}[0,1]{sup n} is o((ln M){sup {beta}}/M{sup {alpha}}), where M is the number of nodes and {beta} is a parameter depending on the class. The problem of the approximate calculation of multiple integrals for functions in W{sup {alpha}}{sub p}[0,1]{sup n} is considered in the case when this class does not lie in the space of continuous functions, that is, for {alpha}{<=}1/p.

Nursultanov, E D [Kazakhstan Branch of Lomonosov Moscow State University, Astana (Kazakhstan); Tleukhanova, N T [Eurasian National University named after L.N.Gumilev, Astana (Kazakhstan)

2003-10-31

366

MQD--Multiplex-Quadrature Detection in Multi-Dimensional NMR  

PubMed Central

With multiplex-quadrature detection (MQD) the tasks of coherence selection and quadrature separation in N-dimensional heteronuclear NMR experiments are merged. Thus the number of acquisitions required to achieve a desired resolution in the indirect dimensions is significantly reduced. The minimum number of transients per indirect data point, which have to be combined to give pure-phase spectra, is thus decreased by a factor (3/4)N?1. This reduction is achieved without adjustable parameters. We demonstrate the advantage by MQD 3D HNCO and HCCH-TOCSY spectra affording the same resolution and the same per-scan sensitivity as standard phase-cycled ones, but obtained in only 56 % of the usual time and by resolution improvements achieved in the same amount of time.

Schlagnitweit, Judith; Hornicakova, Michaela; Zuckerstatter, Gerhard; Muller, Norbert

2012-01-01

367

On a quadrature formula of Gori and Micchelli  

NASA Astrophysics Data System (ADS)

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

Yang, Shijun

2005-04-01

368

A SIMPLE HETERODYNE TEMPORAL SPECKLE-PATTERN INTERFEROMETER  

SciTech Connect

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

Wong, W. O.; Gao, Z.; Lu, J. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong)

2010-05-28

369

Gaussian quadrature rule for arbitrary weight function and interval  

NASA Astrophysics Data System (ADS)

A program for calculating abscissas and weights of Gaussian quadrature rules for arbitrary weight functions and intervals is reported. The program is written in Mathematica. The only requirement is that the moments of the weight function can be evaluated analytically in Mathematica. The result is a FORTRAN subroutine ready to be utilized for quadrature. Program summaryTitle of program: AWGQ Catalogue identifier:ADVB Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADVB Program obtained from: CPC Program Library, Queens University, Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: Computers: Pentium IV 1.7 GHz processor Installations: 512 MB RAM Operating systems or monitors under which the program has been tested: Windows XP Programming language used: Mathematica 4.0 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of lines in distributed program, including test data, etc.:1076 No. of bytes in distributed program, including test data, etc.: 32 681 Operating systems under which program has been tested: FORTRAN Distribution format: tar.gz Nature of physical problem: Integration of functions. Method of solution: The recurrence relations defining the orthogonal polynomials for arbitrary weight function and integration interval are written in matrix form. The abscissas and weights for the corresponding Gaussian quadrature are found from the solution of the eigenvalue equation for the tridiagonal symmetric Jacobi matrix. Restrictions on the complexity of the problem: The program is applicable if the moments of the weight function can be evaluated analytically in Mathematica. For our test example the degree of the Gaussian quadrature cannot not be larger than 96. Typical running time: The running time of the test run is about 1 [s] with a Pentium IV 1.7 GHz processor.

Fukuda, H.; Katuya, M.; Alt, E. O.; Matveenko, A. V.

2005-04-01

370

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

371

A Review of Error Estimation in Adaptive Quadrature  

Microsoft Academic Search

The most critical component of any adaptive numerical quadrature routine is\\u000athe estimation of the integration error. Since the publication of the first\\u000aalgorithms in the 1960s, many error estimation schemes have been presented,\\u000aevaluated and discussed. This paper presents a review of existing error\\u000aestimation techniques and discusses their differences and their common\\u000afeatures. Some common shortcomings of these

Pedro Gonnet

2010-01-01

372

Continuous phase quadrature phase shift keyed (CPQPSK) signaling technique  

NASA Astrophysics Data System (ADS)

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

373

Nonseparable extensions of quadrature mirror filters to multiple dimensions  

Microsoft Academic Search

Generalized non-separable extensions of quadrature mirror filter (QMF) banks to two and three dimensions, in which the orientation specificity of the high-pass filters is greatly improved, are described. In particular, extensions to two dimensions with hexagonal symmetry, and 3-D spatiotemporal extensions with rhombic-dodecahedral symmetry, are discussed. Although these filters are conceived and designed on nonstandard sampling lattices, they can be

E. P. Simoncelli; E. H. Adelson

1990-01-01

374

Finite mass beam splitter in high power interferometers  

SciTech Connect

The beam splitter in high-power interferometers is subject to significant radiation-pressure fluctuations. As a consequence, the phase relations which appear in the beam splitter coupling equations oscillate and phase modulation fields are generated which add to the reflected fields. In this paper, the transfer function of the various input fields impinging on the beam splitter from all four ports onto the output field is presented including radiation-pressure effects. We apply the general solution of the coupling equations to evaluate the input-output relations of the dual-recycled laser-interferometer topology of the gravitational-wave detector GEO 600 and the power-recycling, signal-extraction topology of advanced LIGO. We show that the input-output relation exhibits a bright-port dark-port coupling. This mechanism is responsible for bright port contributions to the noise density of the output field and technical laser noise is expected to decrease the interferometer's sensitivity at low frequencies. It is shown quantitatively that the issue of technical laser noise is unimportant in this context if the interferometer contains arm cavities.

Harms, Jan; Schnabel, Roman; Danzmann, Karsten [Institut fuer Atom- und Molekuelphysik, Universitaet Hannover and Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut), Callinstr. 38, 30167 Hannover (Germany)

2004-11-15

375

An Application of the Quadrature-Free Discontinuous Galerkin Method  

NASA Technical Reports Server (NTRS)

The process of generating a block-structured mesh with the smoothness required for high-accuracy schemes is still a time-consuming process often measured in weeks or months. Unstructured grids about complex geometries are more easily generated, and for this reason, methods using unstructured grids have gained favor for aerodynamic analyses. The discontinuous Galerkin (DG) method is a compact finite-element projection method that provides a practical framework for the development of a high-order method using unstructured grids. Higher-order accuracy is obtained by representing the solution as a high-degree polynomial whose time evolution is governed by a local Galerkin projection. The traditional implementation of the discontinuous Galerkin uses quadrature for the evaluation of the integral projections and is prohibitively expensive. Atkins and Shu introduced the quadrature-free formulation in which the integrals are evaluated a-priori and exactly for a similarity element. The approach has been demonstrated to possess the accuracy required for acoustics even in cases where the grid is not smooth. Other issues such as boundary conditions and the treatment of non-linear fluxes have also been studied in earlier work This paper describes the application of the quadrature-free discontinuous Galerkin method to a two-dimensional shear layer problem. First, a brief description of the method is given. Next, the problem is described and the solution is presented. Finally, the resources required to perform the calculations are given.

Lockard, David P.; Atkins, Harold L.

2000-01-01

376

Thin-plate spline quadrature of geodetic integrals  

NASA Astrophysics Data System (ADS)

Thin-plate spline functions (known for their flexibility and fidelity in representing experimental data) are especially well-suited for the numerical integration of geodetic integrals in the area where the integration is most sensitive to the data, i.e., in the immediate vicinity of the evaluation point. Spline quadrature rules are derived for the contribution of a circular innermost zone to Stoke's formula, to the formulae of Vening Meinesz, and to the recursively evaluated operator L(n) in the analytical continuation solution of Molodensky's problem. These rules are exact for interpolating thin-plate splines. In cases where the integration data are distributed irregularly, a system of linear equations needs to be solved for the quadrature coefficients. Formulae are given for the terms appearing in these equations. In case the data are regularly distributed, the coefficients may be determined once-and-for-all. Examples are given of some fixed-point rules. With such rules successive evaluation, within a circular disk, of the terms in Molodensky's series becomes relatively easy. The spline quadrature technique presented complements other techniques such as ring integration for intermediate integration zones.

Vangysen, Herman

1989-06-01

377

Thin-plate spline quadrature of geodetic integrals  

NASA Technical Reports Server (NTRS)

Thin-plate spline functions (known for their flexibility and fidelity in representing experimental data) are especially well-suited for the numerical integration of geodetic integrals in the area where the integration is most sensitive to the data, i.e., in the immediate vicinity of the evaluation point. Spline quadrature rules are derived for the contribution of a circular innermost zone to Stoke's formula, to the formulae of Vening Meinesz, and to the recursively evaluated operator L(n) in the analytical continuation solution of Molodensky's problem. These rules are exact for interpolating thin-plate splines. In cases where the integration data are distributed irregularly, a system of linear equations needs to be solved for the quadrature coefficients. Formulae are given for the terms appearing in these equations. In case the data are regularly distributed, the coefficients may be determined once-and-for-all. Examples are given of some fixed-point rules. With such rules successive evaluation, within a circular disk, of the terms in Molodensky's series becomes relatively easy. The spline quadrature technique presented complements other techniques such as ring integration for intermediate integration zones.

Vangysen, Herman

1989-01-01

378

On the power spectral density of quadrature modulated signals  

NASA Astrophysics Data System (ADS)

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

379

All-optical wavelength conversion in SOA-based Mach Zehnder interferometer with monolithically integrated loss-coupled DFB laser diode  

NASA Astrophysics Data System (ADS)

We demonstrated monolithic integration of a continuous wave probe source consisting of a loss-coupled distributed feedback laser diode (DFB LD) and a Mach-Zehnder interferometric wavelength converter. The integrated device was fabricated using a modified buried ridge stripe (BRS) structure with an undoped InP clad layer on the top of a passive waveguide to reduce high propagation loss. A propagation loss in the passive waveguide as low as 5.29 ± 0.92 dB cm-1 was achieved. For the first time, wavelength conversion at 10 Gb s-1 was achieved with an extinction ratio of 7 dB and a power penalty of 2.8 dB at a 10-9 bit error rate. The proposed BRS structure is very useful for fabrication of photonic integrated circuits consisting of monolithic integration of active and passive waveguides.

Kim, Hyun-Soo; Kim, Jong-Hoi; Sim, Eun Deok; Baek, Yong Soon; Kim, Kang Ho; Kwon, Oh Kee; Oh, Kwang-Ryong

2004-05-01

380

Real-time determination of beam propagation factor by Mach-Zehnder point diffraction interferometer  

NASA Astrophysics Data System (ADS)

Based on a novel Mach-Zehnder point diffraction interferometer, a real-time method to determinate beam propagation factor M2 of laser beams is presented. By using the proposed point diffraction interferometer, the intensity profile and wavefront of laser beam are completely extracted from a single interferogram in one-shot measurement. Knowing the complex field of laser beam yields the beam's propagation parameters such as beam propagation factor M2 conform to the ISO standard method. The experimental method is simple, fast and operates without movable parts, which is allowed to investigate laser beams in conditions inaccessible using the existing method.

Du, Yong-zhao; Feng, Guo-ying; Li, Hong-ru; Cai, Zhen; Zhao, Hong; Zhou, Shou-huan

2013-01-01

381

The Fizeau Interferometer Testbed  

NASA Technical Reports Server (NTRS)

The Fizeau Interferometer Testbed (FIT) is a collaborative effort between NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Space Corporation, and the University of Maryland. The testbed will be used to explore the principles of and the requirements for the full, as well as the pathfinder, Stellar Imager mission concept. It has a long term goal of demonstrating closed-loop control of a sparse array of numerous articulated mirrors to keep optical beams in phase and optimize interferometric synthesis imaging. In this paper we present the optical and data acquisition system design of the testbed, and discuss the wavefront sensing and control algorithms to be used. Currently we have completed the initial design and hardware procurement for the FIT. The assembly and testing of the Testbed will be underway at Goddard's Instrument Development Lab in the coming months.

Zhang, Xiaolei; Carpenter, Kenneth G.; Lyon, Richard G,; Huet, Hubert; Marzouk, Joe; Solyar, Gregory

2003-01-01

382

The VLT Interferometer  

NASA Astrophysics Data System (ADS)

The ESO Very Large Telescope Interferometer (VLTI) is arguably the most powerful optical interferometric facility available at present. In addition to the wide choice of baselines and the light collecting power of its 8.2 m and 1.8 m telescopes, the VLTI also offers a smooth and user-friendly operation which makes interferometry accessible to any astronomer and covers a wide range of scientific applications. Behind the routine scientific operations, however, the VLTI is in constant evolution. I will present some of the technological and instrumental improvements which are planned for the near and mid-term future, and discuss their implications for astrometry in particular. Among them, the PRIMA facility and the proposed GRAVITY instrument are designed to reach the level of 10 microarcseconds in the near-infrared.

Richichi, A.

2008-07-01

383

Radio Seeing Monitor Interferometer  

NASA Astrophysics Data System (ADS)

A two-element interferometer for monitoring atmospheric phase fluctuations (radio seeing) is presented; this uses the unmodulated beacon signal at 11.715 GHz from a geostationary satellite. The system measures phase differences on the signal received by two small antennas separated by 50 m. The system incorporates the best features from previous designs: a heterodyne phase-lock receiver and an IQ demodulator system. Phase fluctuations measured at this frequency may be extrapolated to millimetric and submillimetric wavelengths since the atmosphere is not dispersive at these frequencies. The instrument has been tested at the Observatory San Pedro Martir (Mexico) at 2800 m above sea level. The final destination of the instrument is Cerro la Negra (Mexico), where the Large Millimeter Telescope is under construction, at an altitude of 4600 m.

Hiriart, David; Valdez, Jorge; Zaca, Placido; Medina, José L.

2002-10-01

384

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

385

MIT's interferometer CST testbed  

NASA Technical Reports Server (NTRS)

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

1990-01-01

386

THE KECK INTERFEROMETER NULLER  

SciTech Connect

The Keck Interferometer Nuller (KIN), the first operational separated-aperture infrared nulling interferometer, was designed to null the mid-infrared emission from nearby stars so as to ease the measurement of faint circumstellar emission. This paper describes the basis of the KIN's four-beam, two-stage measurement approach and compares it to the simpler case of a two-beam nuller. In the four-beam KIN system, the starlight is first nulled in a pair of nullers operating on parallel 85 m Keck-Keck baselines, after which 'cross-combination' on 4 m baselines across the Keck apertures is used to modulate and detect residual coherent off-axis emission. Comparison to the constructive stellar fringe provides calibration. The response to an extended source is similar in the two cases, except that the four-beam response includes a term due to the visibility of the source on the cross-combiner baseline-a small effect for relatively compact sources. The characteristics of the dominant null depth errors are also compared for the two cases. In the two-beam nuller, instrumental imperfections and asymmetries lead to a series of quadratic, positive-definite null leakage terms. For the four-beam nuller, the leakage is instead a series of correlation cross-terms combining corresponding errors in each of the two nullers, which contribute offsets only to the extent that these errors are correlated on the timescale of the measurement. This four-beam architecture has allowed a significant ({approx}order of magnitude) improvement in mid-infrared long-baseline fringe-visibility accuracies.

Serabyn, E.; Mennesson, B.; Colavita, M. M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koresko, C. [Argon ST, Inc., 1386 Connellsville Road, Lemont Furnace, PA 15456 (United States); Kuchner, M. J., E-mail: Gene.Serabyn@jpl.nasa.gov [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-03-20

387

Dual interferometer system for measuring index of refraction  

NASA Astrophysics Data System (ADS)

The optical power of a lens is determined by the surface curvature and the refractive index, n. Knowledge of the index is required for accurate lens design models and for examining material variations from sample to sample. The refractive index of glass can be accurately measured using a prism spectrometer, but measuring the index of soft contact lens materials presents many challenges. These materials are non-rigid, thin, and must remain hydrated in a saline solution during testing. Clearly an alternative to a prism spectrometer must be used to accurately measure index. A Dual Interferometer System has been designed, built and characterized as a novel method for measuring the refractive index of transparent optical materials, including soft contact lens materials. The first interferometer is a Low Coherence Interferometer in a Twyman-Green configuration with a scanning reference mirror. The contact lens material sample is placed in a measurement cuvette, where it remains hydrated. By measuring the locations of the multiple optical interfaces, the physical thickness t of the material is measured. A new algorithm has been developed for processing the low coherence signals obtained from the reflection at each optical interface. The second interferometer is a Mach-Zehnder interferometer with a tunable HeNe laser light source. This interferometer measures the optical path length (OPL) of the test sample in the cuvette in transmission as a function of five wavelengths in the visible spectrum. This is done using phase-shifting interferometry. Multiple thickness regions are used to solve 2pi phase ambiguities in the OPL. The outputs of the two interferometers are combined to determine the refractive index as a function of wavelength: n(lambda) = OPL(lambda)/t. Since both t and OPL are measured using a detector array, n is measured at hundreds of thousands of data points. A measurement accuracy of 0.0001 in refractive index is achieved with this new instrument, which is verified using custom glass calibration samples.

Goodwin, Eric Peter

388

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

389

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)

1997-01-01

390

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. 41 figs.

Erskine, D.J.

1997-06-24

391

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

392

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. 41 figs.

Erskine, D.J.

1999-06-08

393

Polarizing optical interferometer having a dual use optical element  

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.

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

1995-04-04

394

Polarizing optical interferometer having a dual use optical element  

DOEpatents

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

Kotidis, Petros A. (Waban, MA); Woodroffe, Jaime A. (North Reading, MA); Rostler, Peter S. (Newton, MA)

1995-01-01

395

Quadrature rules with multiple nodes for evaluating integrals with strong singularities  

NASA Astrophysics Data System (ADS)

We present a method based on the Chakalov-Popoviciu quadrature formula of Lobatto type, a rather general case of quadrature with multiple nodes, for approximating integrals defined by Cauchy principal values or by Hadamard finite parts. As a starting point we use the results obtained by L. Gori and E. Santi (cf. On the evaluation of Hilbert transforms by means of a particular class of Turan quadrature rules, Numer. Algorithms 10 (1995), 27-39; Quadrature rules based on s-orthogonal polynomials for evaluating integrals with strong singularities, Oberwolfach Proceedings: Applications and Computation of Orthogonal Polynomials, ISNM 131, Birkhauser, Basel, 1999, pp. 109-119). We generalize their results by using some of our numerical procedures for stable calculation of the quadrature formula with multiple nodes of Gaussian type and proposed methods for estimating the remainder term in such type of quadrature formulae. Numerical examples, illustrations and comparisons are also shown.

Milovanovic, Gradimir V.; Spalevic, Miodrag M.

2006-05-01

396

Balloon exoplanet nulling interferometer (BENI)  

NASA Astrophysics Data System (ADS)

We evaluate the feasibility of a balloon-borne nulling interferometer to detect and characterize an exosolar planet and the surrounding debris disk. The existing instrument consists of a three-telescope Fizeau imaging interferometer with thre fast steering mirrors and three delay lines operating at 800 Hz for closed-loop control of wavefront errors and fine pointing. A compact visible nulling interferometer would be coupled to the imaging interferometer and in principle, allows deep starlight suppression. Atmospheric simulations of the environment above 100,000 feet show that balloonborne payloads are a possible path towards the direct detection and characterization of a limited set of exoplanets and debris disks. Furthermore, rapid development of lower cost balloon payloads provide a path towards advancement of NASA technology readiness levels for future space-based exoplanet missions. Discussed are the BENI mission and instrument, the balloon environment and the feasibility of such a balloon-borne mission.

Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Ford, Holland; Petro, Larry; Herman, Jay; Rinehart, Stephen; Carpenter, Kenneth; Marzouk, Joe

2009-08-01

397

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

398

Angle interferometer cross axis errors.  

National Technical Information Service (NTIS)

The authors have found what appears to be a previously unreported error in the measurement of surface plate flatness and the measurement of angular displacement errors in rotary tables using angle interferometers.

J. B. Bryan D. L. Carter S. L. Thompson

1993-01-01

399

Mechanical vibrations - laser interferometry measurements  

Microsoft Academic Search

The paper describes a laser interferometer designed to measure the onset of natural vibrations of turbine blades. The range of measurement extends from a fraction of a micron to a distance of a few millimeters with a resolution of 0.15 microns for frequencies of several kilohertz. The role of Speckle phenomena is considered. The capabilities of the laser interferometer are

M. Philbert

1978-01-01

400

Dual-recycled cavity-enhanced Michelson interferometer for gravitational-wave detection.  

PubMed

The baseline design for an Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO) is a dual-recycled Michelson interferometer with cavities in each of the Michelson interferometer arms. We describe one possible length-sensing and control scheme for such a dual-recycled, cavity-enhanced Michelson interferometer. We discuss the principles of this scheme and derive the first-order sensing signals. We also present a successful experimental verification of our length-sensing system using a prototype tabletop interferometer. Our results demonstrate the robustness of the scheme against deviations from the idealized design. We also identify potential weaknesses and discuss possible improvements. These results as well as other benchtop experiments that we present form the basis for a sensing and control scheme for Advanced LIGO. PMID:12638883

Müller, Guido; Delker, Tom; Tanner, David B; Reitze, David

2003-03-01

401

Quantum Enhancement of the Zero-Area Sagnac Interferometer Topology for Gravitational Wave Detection  

NASA Astrophysics Data System (ADS)

Only a few years ago, it was realized that the zero-area Sagnac interferometer topology is able to perform quantum nondemolition measurements of position changes of a mechanical oscillator. Here, we experimentally show that such an interferometer can also be efficiently enhanced by squeezed light. We achieved a nonclassical sensitivity improvement of up to 8.2 dB, limited by optical loss inside our interferometer. Measurements performed directly on our squeezed-light laser output revealed squeezing of 12.7 dB. We show that the sensitivity of a squeezed-light enhanced Sagnac interferometer can surpass the standard quantum limit for a broad spectrum of signal frequencies without the need for filter cavities as required for Michelson interferometers. The Sagnac topology is therefore a powerful option for future gravitational-wave detectors, such as the Einstein Telescope, whose design is currently being studied.

Eberle, Tobias; Steinlechner, Sebastian; Bauchrowitz, Jöran; Händchen, Vitus; Vahlbruch, Henning; Mehmet, Moritz; Müller-Ebhardt, Helge; Schnabel, Roman

2010-06-01

402

102({h_bar}/2{pi})k Large Area Atom Interferometers  

SciTech Connect

We demonstrate atom interferometers utilizing a novel beam splitter based on sequential multiphoton Bragg diffractions. With this sequential Bragg large momentum transfer (SB-LMT) beam splitter, we achieve high contrast atom interferometers with momentum splittings of up to 102 photon recoil momenta (102({h_bar}/2{pi})k). To our knowledge, this is the highest momentum splitting achieved in any atom interferometer, advancing the state-of-the-art by an order of magnitude. We also demonstrate strong noise correlation between two simultaneous SB-LMT interferometers, which alleviates the need for ultralow noise lasers and ultrastable inertial environments in some future applications. Our method is intrinsically scalable and can be used to dramatically increase the sensitivity of atom interferometers in a wide range of applications, including inertial sensing, measuring the fine structure constant, and detecting gravitational waves.

Chiow, Sheng-wey; Kovachy, Tim; Chien, Hui-Chun; Kasevich, Mark A. [Department of Physics, Stanford University, Stanford, California 94305 (United States)

2011-09-23

403

Proposed studies of a 30 meter imaging interferometer concept. [spaceborne astronomy  

NASA Technical Reports Server (NTRS)

An imaging interferometer in space based on the use of 15 m sections of graphite-epoxy truss structure to form the basic mechanical support system is suggested. One simple design is a Y-shaped array of 3 coplanar arms, each 15 m long and 1.5 m in diameter, together with a perpendicualr mast of similar length. Roughly 15 observing telescopes of 0.5 m diameter would be used, with laser interferometers controlling the optical pathlengths. The total mass of the imaging interferometer is 3000 kg. With this design, the entire interferometer can be carried to orbit with a single STS launch and then deployed. The interferometer could be operated either in a fully illuminated Sun-synchronous orbit at 1400 km altitude or loosely attached to the Space Station.

Stebbins, R. T.; Bender, P. L.; Faller, J. E.

1987-01-01

404

Optical field's quadrature excitation studied by new Hermite-polynomial operator identity  

NASA Astrophysics Data System (ADS)

We study the optical field's quadrature excitation state Xm|0>, where X = (a + a†)/?2 is the quadrature operator. We find it is ascribed to the Hermite-polynomial excitation state. For the first time, we determine this state's normalization constant which turns out to be a Laguerre polynomial. This is due to the integration method within the ordered product of operators (IWOP). The normalization for the two-mode quadrature excitation state is also completed by virtue of the entangled state representation.

Fan, Hong-Yi; He, Rui; Da, Cheng; Liang, Zu-Feng

2013-08-01

405

A 400–500 GHz Balanced SIS Mixer with a Waveguide Quadrature Hybrid Coupler  

Microsoft Academic Search

We have developed a 400–500 GHz low-noise balanced SIS (Superconductor Insulator Superconductor) mixer, which is based on\\u000a a waveguide RF quadrature hybrid coupler. The RF quadrature hybrid was designed and fabricated as a broadband hybrid with\\u000a good performance at 4 K. The fabricated RF quadrature hybrid was measured at room temperature with a submillimeter vector\\u000a network analyzer to check amplitude

Yasutaka Serizawa; Yutaro Sekimoto; Mamoru Kamikura; Wenlei Shan; Tetsuya Ito

2008-01-01

406

Electro-optic heterodyne interferometer.  

PubMed

We propose a new configuration for using a triangle-wave signal to drive the electro-optic modulator in an electro-optic heterodyne interferometer system. The new configuration is adapted to measure the phase retardation of a wave plate and the optical rotation angle of a chiral medium. By adding optic elements, the second-harmonic component amplitude of the interferometer photodetector output signal became proportional to the phase retardation or optical rotation angle of the samples being tested. PMID:17514267

Kuo, Wen-Kai; Kuo, Jen-Yu; Huang, Cheng-Yung

2007-06-01

407

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

408

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

409

A quantum scattering interferometer.  

PubMed

The collision of two ultracold atoms results in a quantum mechanical superposition of the two possible outcomes: each atom continues without scattering, and each atom scatters as an outgoing spherical wave with an s-wave phase shift. The magnitude of the s-wave phase shift depends very sensitively on the interaction between the atoms. Quantum scattering and the underlying phase shifts are vitally important in many areas of contemporary atomic physics, including Bose-Einstein condensates, degenerate Fermi gases, frequency shifts in atomic clocks and magnetically tuned Feshbach resonances. Precise experimental measurements of quantum scattering phase shifts have not been possible because the number of scattered atoms depends on the s-wave phase shifts as well as the atomic density, which cannot be measured precisely. Here we demonstrate a scattering experiment in which the quantum scattering phase shifts of individual atoms are detected using a novel atom interferometer. By performing an atomic clock measurement using only the scattered part of each atom's wavefunction, we precisely measure the difference of the s-wave phase shifts for the two clock states in a density-independent manner. Our method will enable direct and precise measurements of ultracold atom-atom interactions, and may be used to place stringent limits on the time variations of fundamental constants. PMID:17443182

Hart, Russell A; Xu, Xinye; Legere, Ronald; Gibble, Kurt

2007-04-19

410

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

411

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

412

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

413

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

414

Analyzing the total structural intensity in beams using a homodyne laser Doppler vibrometer  

NASA Astrophysics Data System (ADS)

The total structural intensity in beams can be considered as composed of three kinds of waves: bending, longitudinal, and torsional. In passive and active control applications, it is useful to separate each of these components in order to evaluate its contribution to the total structural intensity flowing through the beam. In this paper, a z-shaped beam is used in order to allow the three kinds of waves to propagate. The contributions of the structural intensity due to the three kinds of waves are computed from measurements made over the surface of the beam with a simple homodyne interferometric laser vibrometer. The optical sensor incorporates some additional polarizing optics to a Michelson type interferometer to generate two optical signals in quadrature, which are processed to display velocities and/or displacements. This optical processing scheme is used to remove the directional ambiguity from the velocity measurement and allows to detect nearly all backscattered light collected from the object. This paper investigates the performance of the laser vibrometer in the estimation of the different wave components. The results are validated by comparing the total structural intensity computed from the laser measurements with the measured input power. Results computed from measurements using PVDF sensors are also shown, and compared with the non-intrusive laser measurements.

Freschi, Agnaldo A.; Pereira, Allan K.; Ahmida, Khaled M.; Frejlich, Jaime; Arruda, Jose R. d. F.

1998-06-01

415

Analysis of light noise sources in a recycled Michelson interferometer with Fabry-Perot arms.  

PubMed

We present a method by which the effect of laser field variations on the signal output of an interferometric gravitational wave detector is rigorously determined. Using the Laser Interferometer Gravitational Wave Observatory (LIGO) optical configuration of a power recycled Michelson interferometer with Fabry-Perot arm cavities as an example, we calculate the excess noise after the input filter cavity (mode cleaner) and the dependence of the detector strain sensitivity on laser frequency and amplitude noise, radio frequency oscillator noise, and scattered-light phase noise. We find that noise on the radio frequency sidebands generally limits the detector's sensitivity. PMID:10641846

Camp, J B; Yamamoto, H; Whitcomb, S E; McClelland, D E

2000-01-01

416

Global feed-forward vibration isolation in a km scale interferometer  

NASA Astrophysics Data System (ADS)

Using a network of seismometers and sets of optimal filters, we implemented a feed-forward control technique to minimize the seismic contribution to multiple interferometric degrees of freedom of the Laser Interferometer Gravitational-wave Observatory interferometers. The filters are constructed by using the Levinson-Durbin recursion relation to approximate the optimal Wiener filter. By reducing the RMS of the interferometer feedback signals below ˜10 Hz, we have improved the stability and duty cycle of the joint network of gravitational wave detectors. By suppressing the large control forces and mirror motions, we have dramatically reduced the rate of non-Gaussian transients in the gravitational wave signal stream.

DeRosa, Ryan; Driggers, Jennifer C.; Atkinson, Dani; Miao, Haixing; Frolov, Valery; Landry, Michael; Giaime, Joseph A.; Adhikari, Rana X.

2012-11-01

417

Sub-50 nm patterning by immersion interference lithography using a Littrow prism as a Lloyd's interferometer.  

PubMed

We present a simple setup that combines immersion lithography with a Lloyd's mirror interferometer. Aiming for smaller structure sizes, we have replaced the usual Lloyd's interferometer by a triangular Littrow prism with one metal-coated side, which acts as a mirror. Because of the higher refractive index of the prism, the wavelength and, thus, the attainable structure sizes, are decreased significantly. Using a laser with a wavelength of 244nm, we could produce line patterns with a period of less than 100nm and a width of 45nm. The introduced setup retains all the advantages of a Lloyd's mirror interferometer, in particular the flexibility in periodicity. PMID:20967096

de Boor, Johannes; Kim, Dong Sik; Schmidt, Volker

2010-10-15

418

A prototype imaging second harmonic interferometer  

SciTech Connect

We have built a prototype imaging second harmonic interferometer, which is intended to test critical elements of a design for a tangential array interferometer on C-Mod{sup 6}. The prototype uses a pulsed, 35 mJ, 10 Hz multimode, Nd:YAG laser, LiB{sub 3}O{sub 5} doublers, a fan beam created by a cylindrical lens, four retroreflector elements, and a CCD camera as a detector. The prototype also uses a polarization scheme in which the interference information is eventually carried by two second harmonic beams with crossed polarization. These are vector summed and differenced, and separated, by a Wollaston prism, to give two spots on the CCD. There is a pair of these spots for each retroreflector used. The phase information is directly available as the ratio of the difference to sum the intensities of the two spots. We have tested a single channel configuration of this prototype, varying the phase by changing the pressure in an air cell, and we have obtained a 5:1 light to dark ratio, and a clear sinusoidal variation of the ratio as a function of pressure change. {copyright} {ital 1997 American Institute of Physics.}

Jobes, F.C.; Bretz, N.L. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

1997-01-01

419

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

2012-05-01

420

Rotation sensing with a dual atom-interferometer Sagnac gyroscope  

NASA Astrophysics Data System (ADS)

We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10-10 rad s-1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.

Gustavson, T. L.; Landragin, A.; Kasevich, M. A.

2000-06-01

421

High-contrast Mach–Zehnder lithium-atom interferometer in the Bragg regime  

Microsoft Academic Search

.   We have constructed an atom interferometer of the Mach–Zehnder type, operating with a supersonic beam of lithium. Atom diffraction\\u000a uses Bragg diffraction on laser standing waves. With first-order diffraction, our apparatus has given a large signal and a\\u000a very good fringe contrast (74%), which we believe to be the highest ever observed with thermal atom interferometers. This\\u000a apparatus will

R. Delhuille; C. Champenois; M. Büchner; L. Jozefowski; C. Rizzo; G. Trénec; J. Vigué

2002-01-01

422

Measurement of the Sensitivity Function in a Time-Domain Atomic Interferometer  

Microsoft Academic Search

We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave packets. The sensitivity function is calculated in the case of a three-pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at the Laboratoire National de Metrologie et d'Essais-Systeme

Patrick Cheinet; Benjamin Canuel; Franck Pereira Dos Santos; Alexandre Gauguet; Florence Yver-Leduc; Arnaud Landragin

2008-01-01

423

Measurement of the sensitivity function in time-domain atomic interferometer  

Microsoft Academic Search

We present here an analysis of the sensitivity of a time-domain atomic interferometer to the phase noise of the lasers used to manipulate the atomic wave-packets. The sensitivity function is calculated in the case of a three pulse Mach-Zehnder interferometer, which is the configuration of the two inertial sensors we are building at BNM-SYRTE. We successfully compare this calculation to

P. Cheinet; B. Canuel; F. Pereira Dos Santos; A. Gauguet; F. Leduc; A. Landragin

2005-01-01

424

Demonstration of a Sagnac-Type Cold Atom Interferometer with Stimulated Raman Transitions  

Microsoft Academic Search

Cold-matter-wave Sagnac interferometers possess many advantages over their thermal atomic beam counterparts when they are used as precise inertial sensors. We report a realization of a Sagnac-type interferometer with cold atoms. Cold rubidium atoms are prepared in a magneto-optical trap and are pushed by resonant laser pulse to form slow atomic beam. In the interference region, atomic wave packets are

Ping Wang; Run-Bing Li; Hui Yan; Jin Wang; Ming-Sheng Zhan

2007-01-01

425

Sub-Kilohertz Optical Spectroscopy with a Time Domain Atom Interferometer  

Microsoft Academic Search

We report on the sub-kilohertz optical spectroscopy on the 1S0- 3P1 intercombination transition in magnesium at 457 nm. The spectroscopic signal is probed by a time domain atom interferometer. The realization of this time domain atom interferometer with laser cooled and trapped atoms allows extremely long interaction times and leads to resolutions down to 491 Hz (FWHM). This corresponds to

F. Ruschewitz; J. L. Peng; H. Hinderthür; N. Schaffrath; K. Sengstock; W. Ertmer

1998-01-01

426

The application of a shear interferometer of diffraction type to shock-tube studies  

Microsoft Academic Search

The feasibility of applying a shear interferometer of diffraction type to shock-tube studies is assessed; the device is based on the standard IAB-451 shadow-photography instrument, operates at a ruby-laser wavelength of 694.3 nm, and assures a wave-surface shear of 100 mm for a focal distance of 1918 mm. Some results on the application of the interferometer to studies in a

L. L. Kolyshkina; V. D. Shevtsov; V. V. Arkhipov

1980-01-01

427

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

2012-05-01

428

An extreme ultraviolet interferometer using high order harmonic generation  

NASA Astrophysics Data System (ADS)

We present a new interferometer technique based on the interference of high-order harmonic generation radiation from translatable successive gas jets. The phase shifts in the apparatus are shown to originate from the Gouy phase shift of the driving laser. The technique can be used to deliver time delays between light pulses and we demonstrate the unprecedented capability of delivering pulses of extreme ultraviolet light delayed in time by as small as 100 zeptoseconds.

Laban, D. E.; Palmer, A. J.; Wallace, W. C.; Gaffney, N. S.; Notermans, R. P. M. J. W.; Clevis, T. T. J.; Pullen, M. G.; Jiang, D.; Quiney, H. M.; Litvinyuk, I. V.; Kielpinski, D.; Sang, R. T.

2014-04-01

429

Ultrasensitive biosensor based on SU8 planar interferometer  

Microsoft Academic Search

SU-8 resist was used as a core\\/cladding waveguide material to fabricate a Mach-Zehnder interferometer (MZI) for biochemical sensing. The refractive index and the UV lithography processes of the SU-8 resist were optimized to give a SU-8 MZI chip with single-mode and high-efficiency transmission. Optical measurements reveal that the SU-8 MZI chip can transmit the NIR laser (?=1310 nm) with a

B. Y. Shew; Y. H. Tsai; C. H. Kuo

2005-01-01

430

Wide-band measurement of mechanical thermal noise using a laser interferometer 1 Please note that this article is now reprinted in its entirity and in its correct version. The Publisher apologises to the author and readers for any inconvenience and confusion caused as a result of serious production errors in the original publication. 1 2 PII of original article: S0375-9601(99)00636-2 2  

Microsoft Academic Search

We have measured the displacement thermal noise of a mechanical cantilever, made of phosphor bronze, using a laser interferometer. The measured noise spectrum agrees well with an estimation based on the fluctuation–dissipation theorem with a mechanical-admittance measurement. The frequency range where we could measure the thermal noise was from 50 to 500Hz; this range is important for the noise characterization

Mariko Kajima; Nobuhiro Kusumi; Shigenori Moriwaki; Norikatsu Mio

1999-01-01

431

Wideband quadrature error correction (using SVD) for stepped-frequency radar receivers  

Microsoft Academic Search

We present a new technique which corrects the wideband quadrature errors associated with homodyne stepped frequency radar receivers. The correction algorithm is derived using singular value decomposition (SVD) which diagonalizes and scales the covariance matrix of a test signal while preserving the coherent phasor alignment across all frequency steps of the homodyne receiver. Using our technique, the wideband quadrature errors

D. A. Noon; I. D. Longstaff; G. F. Stickley

1999-01-01

432

Mean-Square Error Optimization of Quadrature Receivers for CPM with Modulation Index 1\\/2  

Microsoft Academic Search

Detection of continuous phase modulation (CPM) signals can be accomplished using quadrature coherent detectors which include a pair of linear and time-invariant postdetection filters. Performance of the quadrature detectors is highly sensitive to the postdetection filters response. This paper presents a rigorous derivation of an optimum postdetection filter response. The derivation is based on minimizing the mean-square interference subject, to

MOHAMMED S. EL-TANANY; SAMY A. MAHMOUD

1987-01-01

433

An adaptive Stochastic Finite Elements approach based on Newton–Cotes quadrature in simplex elements  

Microsoft Academic Search

In this paper an adaptive Stochastic Finite Elements approach with Newton–Cotes quadrature and simplex elements is developed for resolving the effect of random parameters in flow problems. The stochastic response is represented by a piecewise polynomial approximation by subdividing probability space into simplex elements. The quadrature approximation in the elements leads to solving uncoupled deterministic problems for varying parameter values.

Jeroen A. S. Witteveen; Alex Loeven; Hester Bijl

2009-01-01

434

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

435

Results from a Prototype Second Harmonic Tangential Array Interferometer  

NASA Astrophysics Data System (ADS)

A tabletop tangential array interferometer operating at 1.06 and 0.53 mm has been built to test its sensitivity for use on C-Mod. This type of interferometer is insensitive to mechanical vibrations. The prototype uses a pulsed, 35 mJ, 10 Hz multimode, Nd:YAG laser, LiB3O5 non-critically phase matched doublers, a fan beam created by a cylindrical lens, several retro-reflector elements to define the array, and a CCD camera detector. This interferometer has beam diameters of a few millimeters and spatial resolution of a few centimeters as needed for C-Mod. Commercial lasers and CCD arrays are available which can scale this design to ~20kHz. Tokamak applications typically require a limiting sensitivity of 10-3 fringes and maximum changes of ~1 fringe. The limiting sensitivity of the prototype system has been investigated along with technical limitations on elements of the optical system relevant to its use on tokamaks. In particular methods of normalizing shot-to-shot and spatial mode variations in the laser intensity are examined. The use of visible and near visible components allows a compact optical design and efficient use of port space. Supported by US DoE Contract Nos. DE-AC02-76-CH0-3073 and DE-AC02-78ET51013.

Bretz, N.; Jobes, F.; Humensk, B.; Irby, J.

1996-11-01

436

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

437

Interferometer mirror tilt correcting system  

NASA Technical Reports Server (NTRS)

An interferometer is described, having several means for automatically adjusting the angular tilt of a reflecting surface in one of two paths to maintain the exit beams from the two paths parallel to each other. Three detectors at the output of the interferometer were disposed on mutually perpendicular axes which define a plane normal to the nominal exit beam axis. One detector at the origin of the axes was used as a reference for separate phase difference comparison with the outputs of the other two detectors on the X and Y axes to develop servo error signals.

Schindler, R. A. (inventor)

1977-01-01

438

Atom Interferometers with Scalable Enclosed Area  

Microsoft Academic Search

Bloch oscillations (i.e., coherent acceleration of matter waves by an optical lattice) and Bragg diffraction are integrated into light-pulse atom interferometers with large momentum splitting between the interferometer arms, and hence enhanced sensitivity. Simultaneous acceleration of both arms in the same internal states suppresses systematic effects, and simultaneously running a pair of interferometers suppresses the effect of vibrations. Ramsey-Bordé interferometers

Holger Müller; Sheng-Wey Chiow; Sven Herrmann; Steven Chu

2009-01-01

439

Digital Fringe Counting for Intrinsic Fabry-Perot Interferometers  

NASA Technical Reports Server (NTRS)

A digital dual-wavelength method of demodulating long (17cm) Intrinsic Fabry-Perot Interferometers (IFPI) is presented. The method builds upon previous techniques using small shifts in the lasing wavelength of a laser diode induced by changes in the driving current. The intensity of the light reflected from the IFPI is sampled at two carefully selected values of laser diode drive current. Digital logic is then used to count fringes based upon these two sampled values. Experimental verification of the method is described.

Froggatt, Mark; Melvin, Leland

1996-01-01

440

Adaptive compensation for the nonlinearity error in a heterodyne interferometer  

NASA Astrophysics Data System (ADS)

Laser interferometry has been widely used in the field of nano-metrology due to its superior properties, such as its almost unlimited resolution and its flexible set up. In practical measurements with a heterodyne laser interferometer, however, some obstacles, such as environmental and nonlinearity errors, limit its measurement accuracy. In this paper, we compensate for nonlinearity errors by applying the recursive weighted least-squares method and the robust observer based Kalman filter algorithm, consecutively. To demonstrate the performance of the two proposed algorithms, we performed simulations and experiments. The experimental results show the improved accuracy obtained by using the proposed algorithms.

Kim, Pyungjun; Kim, Kiho; You, Kwanho

2012-12-01

441

Magdalena Ridge Observatory Interferometer: Status Update.  

National Technical Information Service (NTIS)

The Magdalena Ridge Observatory Interferometer (MROI) is a ten element optical and near-infrared imaging interferometer being built in the Magdalena mountains west of Socorro, NM at an altitude of 3230 m. The interferometer is being designed and built by ...

C. A. Haniff D. F. Buscher E. J. Bakker M. J. Creech-Eakman T. A. Coleman

2006-01-01

442

Microwave interferometer controls cutting depth of plastics  

NASA Technical Reports Server (NTRS)

Microwave interferometer system controls the cutting of plastic materials to a prescribed depth. The interferometer is mounted on a carriage with a spindle and cutting tool. A cross slide, mounted on the carriage, allows the interferometer and cutter to move toward or away from the plastic workpiece.

Heisman, R. M.; Iceland, W. F.

1969-01-01

443

Atomic interferometer based on adiabatic population transfer  

Microsoft Academic Search

We demonstrate an atomic interferometer based on the transfer of population between two ground states via adiabatic following using a nonabsorbing ``dark'' superposition state. This type of interferometer promises to be useful for precise measurement of the photon recoil energy and also for large area atomic interferometers since it allows transfer of a large number of photon recoil momenta to

Martin Weitz; Brenton C. Young; Steven Chu

1994-01-01

444

Orientational atom interferometers sensitive to gravitational waves  

Microsoft Academic Search

We present an atom interferometer that differs from common atom interferometers as it is not based on the spatial splitting of electronic wave functions, but on orienting atoms in space. As an example we present how an orientational atom interferometer based on highly charged hydrogen-like atoms is affected by gravitational waves. We show that a monochromatic gravitational wave will cause

Dennis Lorek; Claus Lämmerzahl; Andreas Wicht

2010-01-01

445

Harmonic Golay coded excitation based on harmonic quadrature demodulation method.  

PubMed

Harmonic coded excitation techniques have been used to increase SNR of harmonic imaging with limited peak voltage. Harmonic Golay coded excitation, in particular, generates each scan line using four transmit-receive cycles, unlike conventional Golay coded excitation method, thus resulting in low frame rates. In this paper we propose a method of increasing the frame rate of said method without impacting the image quality. The proposed method performs two transmit-receive cycles using QPSK code to ensure that the harmonic components of incoming signals are Golay coded and uses harmonic quadrature demodulation to extract compressed second harmonic component only. The proposed method has been validated through mathematical analysis and MATLAB simulation, and has been verified to yield a limited error of -52.08dB compared to the ideal case. Therefore, the proposed method doubles the frame rate compared to the existing harmonic Golay coded excitation method without significantly deteriorating the image quality. PMID:19164018

Kim, Sang-Min; Song, Jae-Hee; Song, Tai-Kyong

2008-01-01

446

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

447

Exact quantum correlations of conjugate variables from joint quadrature measurements  

NASA Astrophysics Data System (ADS)

We demonstrate that for two canonically conjugate operators qˆ, pˆ, the global correlation -2, and the local correlations (p)- and (q)- can be measured exactly by Von Neumann-Arthurs-Kelly joint quadrature measurements. Here (q) and (p) denote the conditional expectation values of momentum at a given position, and position at a given momentum respectively. These correlations provide a sensitive experimental test of quantum phase space probabilities quite distinct from the probability densities of q, p. E.g. for EPR states, and entangled generalized coherent states, phase space probabilities which reproduce the correct position and momentum probability densities have to be modified to reproduce these correlations as well.

Roy, S. M.

2013-11-01

448

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

449

Spectral measurement of the caesium D(2) line with a tunable heterodyne interferometer.  

PubMed

The optical properties of a caesium atomic beam driven on a resonant hyperfine transition in the D(2) line were studied as a function of the probe laser frequency. Using a third off-resonant laser system, a heterodyne interferometer allowed simultaneous absorption and phase shift measurements of either the probe or the coupling laser. The signal features of the probe and coupling laser