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1

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

2

Quadrature laser interferometer for in-line thickness measurement of glass panels using a current modulation technique.  

PubMed

A thickness measurement system is proposed for in-line inspection of thickness variation of flat glass panels. Multi-reflection on the surfaces of glass panel generates an interference signal whose phase is proportional to the thickness of the glass panel. For accurate and stable calculation of the phase value, we obtain quadrature interference signals using a current modulation technique. The proposed system can measure a thickness profile with high speed and nanometric resolution, and obtain higher accuracy through real-time nonlinear error compensation. The thickness profile, measured by a transmissive-type experimental setup, coincided with a comparative result obtained using a contact-type thickness measurement system within the range of ±40??nm. The standard deviations of the measured thickness profiles and their waviness components were less than 3 nm with a scanning speed of 300??mm/s. PMID:25090083

Kim, Jong-Ahn; Kang, Chu-Shik; Eom, Tae Bong; Jin, Jonghan; Suh, Ho Suhng; Kim, Jae Wan

2014-07-10

3

Compensation for the variable cyclic error in homodyne laser interferometers.  

PubMed

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

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

2015-01-01

4

DESIGN NOTE: Single chip optical fibre interferometer thermal phase-quadrature controller  

NASA Astrophysics Data System (ADS)

A simple method of quadrature control for an interferometer is described in which a thermal fibre modulator is provided by a fibre coated with a metal jacket which can be vacuum evaporated or simply painted on, either to the bare fibre or to the jacket. The electronic feedback control is provided by a single power amplifier chip.

Rogers, S. J.; Brown, J. B.; Jones, J. D. C.; Chan, R. K. Y.; Wong, H. H.

1996-02-01

5

Imaging through turbulence with a quadrature-phase optical interferometer.  

PubMed

We present an improved technique for imaging through turbulence at visible wavelengths using a rotation shearing pupil-plane interferometer, intended for astronomical and terrestrial imaging applications. While previous astronomical rotation shearing interferometers have made only visibility modulus measurements, this interferometer makes four simultaneous measurements on each interferometric baseline, with phase differences of pi/2 between each measurement, allowing complex visibility measurements (modulus and phase) across the entire input pupil in a single exposure. This technique offers excellent wavefront resolution, allowing operation at visible wavelengths on large apertures, is potentially immune to amplitude fluctuations (scintillation), and may offer superior calibration capabilities to other imaging techniques. The interferometer has been tested in the laboratory under weakly aberrating conditions and at Palomar Observatory under ordinary astronomical observing conditions. This research is based partly on observations obtained at the Hale Telescope. PMID:16353815

Kern, Brian; Dimotakis, Paul E; Martin, Chris; Lang, Daniel B; Thessin, Rachel N

2005-12-01

6

Noisy quadrature of squeezed light and laser cooling  

E-print Network

The laser cooling of atoms is a result of the combined effect of doppler shift, light shift and polarization gradient. These are basically undesirable phenomena. However, they combine gainfully in realizing laser cooling and trapping of the atoms. In this paper we discuss the laser cooling of atoms in the presence of the squeezed light with the decay of atomic dipole moment into noisy quadrature. We show that the higher decay rate of the atomic dipole moment into the noisy quadrature, which is also an undesirable effect, may contribute in realizing larger cooling force vis-a-vis normal laser light.

G. M. Saxena; A. Agarwal

2008-07-01

7

Wavelength-Tunable Laser-Diode Interferometer  

Microsoft Academic Search

Laser diodes (LDs) have been applied to a phase-measuring interferometer through the wavelength tunability of LDs by controlling their currents. Laser-diode interferometers based on a heterodyne technique are reviewed. A two-wavelength laser-diode interferometer is demonstrated with current control of dual LDs in opposite directions. A synthetic wavelength makes it possible to extend the range of interferometric measurements. The wavelength is

Yukihiro Ishii

1999-01-01

8

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

9

A Heterodyne Interferometer For Testing Laser Diodes  

NASA Astrophysics Data System (ADS)

A heterodyne, Mach-Zehnder interferometer system has been developed for testing the wavefront quality of laser diode collimator pens. The testing system is described and the problems associated with testing laser diodes are discussed.

1983-11-01

10

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

11

Laser-Ranging Long Baseline Differential Atom Interferometers for Space  

E-print Network

High sensitivity differential atom interferometers are promising for precision measurements in science frontiers in space, including gravity field mapping for Earth science studies and gravitational wave detection. We propose a new configuration of twin atom interferometers connected by a laser ranging interferometer (LRI-AI) to provide precise information of the displacements between the two AI reference mirrors and a means to phase-lock the two independent interferometer lasers over long distances, thereby further enhancing the feasibility of long baseline differential atom interferometers. We show that a properly implemented LRI-AI can achieve equivalent functionality to the conventional differential atom interferometer measurement system. LRI-AI isolates the laser requirements for atom interferometers and for optical phase readout between distant locations, thus enabling optimized allocation of available laser power within a limited physical size and resource budget. A unique aspect of LRI-AI also enables...

Chiow, Sheng-wey; Yu, Nan

2015-01-01

12

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

13

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

14

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

15

Laser diode interferometer for vibration and sound pressure measurements  

SciTech Connect

The authors describe a laser diode interferometer for vibration measurement constructed using two acousto-optic tunable filters with slightly different frequencies. A sound pressure measurement of a condenser microphone using a combination of a polarization maintaining fiber and the laser diode interferometer is demonstrated.

Takahashi, H.; Masuda, C.; Gotoh, Y.; Koyama, J. (Dept. of Electronics, Shibaura Institute of Technology, Tokyo 108 (JP))

1989-04-01

16

The Laser Interferometer Space Antenna: An Overview  

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) is a joint ESA-NASA mission that will explore the Universe for gravitational wave sources between 0.1 mHz and 1 Hz. Anticipated sources of gravitational waves include: the inspiral of supermassive black holes resulting from galactic mergers; the inspiral of intermediate mass black holes; the inspiral of compact objects into supermassive black holes; thousands of close, compact binaries in our own Galaxy; and, possibly, density fluctuations in the early universe if their (much more uncertain) amplitude permits. LISA consists of three spacecraft orbiting the Sun in a triangular formation. Gravitational waves are detected by interferometrically monitoring the 5 million kilometer separations between free-falling reference masses within the spacecraft. LISA employs technology from Â"drag-freeÂ" control systems, spaceborne accelerometers, microthrusters, interferometric distance-ranging and precision measurements to measure strains of 10-23 over very long baselines.

Stebbins, Robin

2004-05-01

17

Fiber-optic interferometer using frequency-modulated laser diodes  

NASA Technical Reports Server (NTRS)

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

Beheim, G.

1986-01-01

18

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

E-print Network

We show that a recent claim that matter wave interferometers have a much higher sensitivity than laser interferometers for a comparable physical setup is unfounded. We point out where the mistake in the earlier analysis is made. We also disprove the claim that only a description based on the geodesic deviation equation can produce the correct physical result. The equations for the quantum dynamics of non-relativistic massive particles in a linearly perturbed spacetime derived here are useful for treating a wider class of related physical problems. A general discussion on the use of atom interferometers for the detection of gravitational waves is also provided.

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

2004-12-17

19

Long-term laser frequency stabilization using fiber interferometers  

E-print Network

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

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

2014-01-01

20

Primary acceleration calibration by heterodyne laser interferometer and PXI instrument  

NASA Astrophysics Data System (ADS)

A heterodyne laser interferometer and a PXI bus instrument make a primary acceleration calibration system. The modified heterodyne laser interferometer has a frequency stabilized laser and a high frequency accuracy Bragg cell. The system is capable of vibration (both sinusoidal and random) and shock calibration. This paper introduces the principle of the system. An accelerometer is calibrated by this system using different exciting signals include sinusoidal, random and half-sin. It shows the system is flexible in primary vibration and shock calibration and high accuracy will be attainable.

Zhang, Li; Peng, Jun

2004-06-01

21

LIGO - The Laser Interferometer Gravitational-Wave Observatory  

Microsoft Academic Search

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,

Alex Abramovici; William E. Althouse; Ronald W. P. Drever; Yekta Gursel; Seiji Kawamura; Frederick J. Raab; David Shoemaker; Lisa Sievers; Robert E. Spero; Kip S. Thorne; R. E. Vogt; R. Weiss; S. E. Whitcomb; M. E. Zucker

1992-01-01

22

Laser interferometer space antenna dynamics and controls model  

Microsoft Academic Search

A 19 degree-of-freedom (DOF) dynamics and controls model of a laser interferometer space antenna (LISA) spacecraft has been developed. This model is used to evaluate the feasibility of the dynamic pointing and positioning requirements of a typical LISA spacecraft. These requirements must be met for LISA to be able to successfully detect gravitational waves in the frequency band of interest

Peiman G. Maghami; T. Tupper Hyde

2003-01-01

23

Laser diode feedback interferometer for measurement of displacements without ambiguity  

Microsoft Academic Search

We report what, to our knowledge, is the first example of laser feedback interferometer capable of measuring displacements of arbitrary form using a single interferometric channel. With a GaAlAs laser diode we can measure 1.2-m displacements, with interferometric resolution, simply by means of the backreflection from the surface (reflective or diffusive) under test. The operation is performed at moderate (i.e.,

S. Donati; G. Giuliani; S. Merlo

1995-01-01

24

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

25

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

26

Dual-frequency laser displacement and angle interferometer  

NASA Astrophysics Data System (ADS)

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

Zhao, Shijie; Wei, Haoyun; Li, Yan

2014-11-01

27

Data Processing for LISA's Laser Interferometer Tracking System (LITS)  

E-print Network

The purpose of this paper is twofold. First, we will present recent results on the data processing for LISA, including algorithms for elimination of clock jitter noise and discussion of the generation of the data averages that will eventually need to be telemetered to the ground. Second, we will argue, based partly on these results, that a laser interferometer tracking system (LITS) that employs independent lasers in each spacecraft is preferable for reasons of simplicity to that in which the lasers in two of the spacecraft are locked to the incoming beam from the third.

Ronald W. Hellings

2000-12-08

28

Research on beam splitting prism in laser heterodyne interferometer  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

29

Angular vibration measurement using grating and laser interferometer  

NASA Astrophysics Data System (ADS)

Primary angular acceleration calibration standard is developed by CIMM to generate standard rotational angle, angular velocity and angular acceleration, which are traceable to the International System of Units (SI). It can be used to calibrate angular transducers, i.e. angular accelerometer, angular velocity transducer, and rotational angle transducer to obtain amplitude sensitivity and phase shift by sinusoidal vibration. The measurement systems based on grating and laser interferometers are introduced in this paper. The measurement system based on PXI bus instrument is used to control the angular exciter, measure the output signal of the laser interferometers and the transducer to be calibrated synchronously. The methods for calculating the amplitude and phase of sinusoidal angular movement are investigated and high performance has been achieved. It shows the standard can be used in angular movement calibration in the frequency range from 0.1Hz to 200Hz.

Zhang, Li; Peng, Jun

2006-06-01

30

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

31

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

32

A digital heterodyne laser interferometer for studying cochlear mechanics.  

PubMed

Laser interferometry is the technique of choice for studying the smallest displacements of the hearing organ. For low intensity sound stimulation, these displacements may be below 1 nm. This cannot be reliably measured with other presently available techniques in an intact organ of Corti. In a heterodyne interferometer, light is projected against an object of study and motion of the target along the optical axis causes phase and frequency modulations of the back-reflected light. To recover object motion, the reflected light is made to interfere with a reference beam of artificially altered frequency, producing a beating signal. In conventional interferometers, this carrier signal is demodulated with analog electronics. In this paper, we describe a digital implementation of the technique, using direct carrier sampling. In order to obtain the necessary reference signal for demodulation we introduce an additional third light path. Together, this results in lower noise and reduces the cost of the system. Within the hearing organ, different structures may move in different directions. It is therefore necessary to precisely measure the angle of incidence of the laser light, and to precisely localize the anatomical structure where the measurement is performed. Therefore, the interferometer is integrated with a laser scanning confocal microscope that permits us to map crucial morphometric parameters in each experiment. We provide key construction parameters and a detailed performance characterization. We also show that the system accurately measures the diminutive vibrations present in the apical turn of the cochlea during low-level sound stimulation. PMID:19428537

Jacob, Stefan; Johansson, Cecilia; Ulfendahl, Mats; Fridberger, Anders

2009-05-15

33

A simple pendulum laser interferometer for determining the gravitational constant.  

PubMed

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

Parks, Harold V; Faller, James E

2014-10-13

34

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

NASA Technical Reports Server (NTRS)

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

Siegman, A. E.

1975-01-01

35

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

PubMed Central

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

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

2014-01-01

36

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

37

Detection of volcanic infrasound with a ring laser interferometer  

NASA Astrophysics Data System (ADS)

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

Dunn, Robert W.; Hosman, Ashley R.

2014-11-01

38

Laser Doppler interferometer for vibration of rotating curved surfaces  

NASA Astrophysics Data System (ADS)

With the rapid advancement of today's ultra-high performance mechanical or mechatronic system such as magnetic or optical disk drives, improving metrology capabilities to examine the performance characteristics of these system are growing ever more important. The primary tested studied in this paper is an ultra-high precision ball-bearing spindle that possesses non-repeatable runout of less than 100nm. The metrology tool adopted is laser Doppler interferometer system that has Megahertz bandwidth and nanometer resolutions. Experimental data obtained clearly indicates that measuring vertical runout of a spindle motor is a straightforward process. However, a fundamental effect was identified, where the radial runout data was found to drift upward or downward with time, when using the laser Doppler system to measure the radial runout of ultra-high precision rotational systems whose surface profile is not flat. All of the underlying reasons that cause this undesirable effect were proposed and verified. Approaches that can be adopted to circumvent this apparent limitation on adopting the laser Doppler interferometer systems to measure rotational curved surface were implemented to further extend its application horizon. The experimental data realized and the application experience obtained were shown to further advance our measurement capabilities.

Wu, Giin-Yuan; Lee, Chih-Kung; Lin, San; Wakabayashi, Takenori; Ono, K.

1999-10-01

39

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

40

Design and Use of a Laser Interferometer for Ultrasonic Bonding Studies  

Microsoft Academic Search

An in-line laser interferometer was developed to study motions during ultrasonic bonding. The interferometer consists of a 2 milliwatt He-Ne laser with output mirrors at both ends, a lens with adjustment apparatus, and a photodiode detector. The detector output is displayed on an oscilloscope. The lens permits the beam to be focussed to a spot diameter less than 25 micrometers.

Byron D. Martin

1976-01-01

41

The laser interferometer system for the large optics diamond turning machine  

SciTech Connect

The purpose of this report is to describe the Laser Interferometer System designed for the Large Optics Diamond Turning Machine (LODTM). To better understand the laser interferometer system, it is useful to begin with an overview of the LODTM metrology system.

Baird, E D; Donaldson, R R; Patterson, S R

1999-06-29

42

Path-length measurement performance evaluation of polarizing laser interferometer prototype  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

43

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

SciTech Connect

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

Terentyev, V S; Simonov, V A [Institute of Automation and Electrometry, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation)

2013-08-31

44

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

45

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

46

Multicomponent wavefield characterization with a novel scanning laser interferometer.  

PubMed

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

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

2010-07-01

47

Multicomponent wavefield characterization with a novel scanning laser interferometer  

SciTech Connect

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

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

2010-07-15

48

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

49

Differential interferometer for measurement of displacement of laser resonator mirrors  

NASA Astrophysics Data System (ADS)

This paper covers a description and a technique of a possible optical method of mode locking within a laser resonator. The measurement system is a part of instrumentation of laser-based experiment OSQAR at CERN. The OSQAR experiment aims at search of axions, axion-like particles and measuring of ultra-fine vacuum magnetic birefringence. It uses a laser resonator to enhance the coupling constant of hypothetical photon-to-axion conversion. The developed locking-in technique is based on differential interferometry. Signal obtained from the measurement provide crucial information for adaptive control of the locking-in of the resonator in real time. In this paper we propose several optical setups used for measurement and analysis of mutual position of the resonator mirrors. We have set up a differential interferometer under our laboratory conditions. We have done measurements with hemi-spherical cavity resonator detuned with piezo crystals. The measurement was set up in a single plane. Laser light was directed through half-wave retarder to a polarizing beam splitter and then converted to circular polarization by lambda/4 plates. After reflection at the mirrors, the beam is recombined in a beam splitter, sent to analyser and non-polarizing beam splitter and then inspected by two detectors with mutually perpendicular polarizers. The 90 degrees phase shift between the two arms allows precise analysis of a mutual distance change of the mirrors. Because our setup was sufficiently stable, we were able to measure the piezo constant and piezo hysteresis. The final goal is to adapt the first prototype to 23 m resonator and measure the displacement in two planes.

Macúchová, Karolina; N?mcová, Šárka; Hošek, Jan

2015-01-01

50

A microchip laser feedback interferometer with nanometer resolution and increased measurement speed based on phase meter  

NASA Astrophysics Data System (ADS)

We introduce a new signal processing method based on phase meter into heterodyne microchip Nd:YAG laser feedback interferometer. The nanometer resolution and a higher measurement speed are realized. The factors determining the accuracy are analyzed. The displacements of the Physik Instrumente nanopositioning system and two piezoelectric transducers were measured. Experimental results indicate laser feedback interferometer's ability of measuring nanoscale displacement and present promising application prospects in noncooperative targets measurement.

Zhang, Song; Tan, Yidong; Ren, Zhou; Zhang, Yongqin; Zhang, Shulian

2014-09-01

51

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

52

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

E-print Network

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

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

2004-03-18

53

Two-modality laser diode interferometer for high-accuracy measurement of long-range absolute distance  

Microsoft Academic Search

This paper presents a two-modality laser diode (LD) interferometer which combine as two-wavelength sinusoidal phase modulating (SPM) interferometer with a wavelength scanning interferometer (WSI) for measurement of distance over long range with high accuracy. Moreover, the intensity modulation due to power changes of LD is suppressed by appropriately choosing the modulation amplitude of injection current (IC) of LD. Triangle wave

Bofan Wang; Zhongliang Li; Xiangzhao Wang; Peng Bu

2010-01-01

54

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

55

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

NASA Technical Reports Server (NTRS)

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

Tinto, M.

1998-01-01

56

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

NASA Technical Reports Server (NTRS)

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

Tinto, M.; Armstrong, J. W.

1998-01-01

57

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

58

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

59

Sensing and Control in Dual-Recycling Laser Interferometer Gravitational-Wave Detectors  

Microsoft Academic Search

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

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

2003-01-01

60

Very small portable holographic interferometers and compact speckle interferometer with semiconductor laser sources well suited for industrial inspections  

NASA Astrophysics Data System (ADS)

Current manufacturing processes require rapid, reliable methods and compact, user-friendly, elegant devices capable to work even in unpromising environment. Innovative user- friendly methods and techniques as well as small holographic and speckle interferometers are presented in this paper. The devices are very compact, easy to operate, incorporate semiconductor laser sources and do not require personnel skilled in optics. Miniature semiconductor laser sources were successfully used in holography and laser speckle metrology for the tasks of 3-dimensional data acquisition, storage and display. Semiconductor lasers enable compact recording and display devices which are easy in operation and well fitted to practical industrial environments. Novel inspection methods and compact devices incorporating miniature semiconductor laser sources can be applied for automated inspections and optical precision measurements in optomechatronic systems. They fit well for real time monitoring of local deformations. Presented devices and techniques meet modern industrial requirements and permit to work in unpromising environment, perform in situ checks of products and components. Vast experimental data are given and the possibilities of innovative devices and techniques are properly illustrated in multiple practical examples. Photographs from holograms and holographic interferograms recorded with semiconductor lasers and successive sets of snapshots during real time monitoring of thermal fields are presented.

Petrov, Valery

2001-10-01

61

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

Microsoft Academic Search

A new two color far infrared (FIR) laser interferometer under development for future fusion devices will be presented. The laser wavelength is optimized from the consideration of the beam refraction effect due to plasma density gradient and signal-to-noise ratio for an expected phase shift due to plasmas. Laser lines of 57.2 and 47.6 mum are found to be suitable for

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

2004-01-01

62

In-plane ESPI using an achromatic interferometer with low-coherence laser source  

NASA Astrophysics Data System (ADS)

The use of an achromatic interferometer is explored as a means of doing in-plane ESPI measurements using a laser diode as the light source. This interferometer type, which uses a diffraction grating in place of the conventional beamsplitter, has two features that make it suitable for making ESPI measurements over extended areas, even when using a low-coherence laser diode source. First, the parallelogram optical geometry of the interferometer causes all rays passing through to have the same optical path lengths. Second, the interferometer is achromatic, whereby the piezo-actuated mirror that steps the illumination light does so by the same phase angle, independent of wavelength. This latter feature accommodates the spectral impurity of a laser diode source. A periodic variation of fringe visibility is observed in experiments, where narrow ranges of high visibility occur at regular spatial intervals. This behavior derives from the clustered discrete spectral character of laser diode light output. A method to 'tune' the interferometer by slightly rotating the diffraction grating is described so as to achieve consistent high fringe visibility throughout the measured images.

Schajer, Gary S.; Zhang, Yijian; Melamed, Samuel

2015-04-01

63

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

NASA Technical Reports Server (NTRS)

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

Tinto, Massimo

1999-01-01

64

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

65

Effect of laser phase noise in Sagnac interferometers  

Microsoft Academic Search

A theoretical analysis of the responsivity and the noise caused by backscattering in a Sagnac interferometer used as a sensor for reciprocal measurands, such as acoustic waves, is presented. Both Rayleigh backscattering and reflections from splices are taken into account. The noise power is found to increase proportionally to the source coherence time, and a noise equivalent phase shift in

K. Krakenes; K. Blotekjaer

1993-01-01

66

Prototype tests of a combined CO{sub 2} laser interferometer/polarimeter for ITER (abstract)  

SciTech Connect

Line density measurements on ITER are expected to be provided by a conventional vibration-compensated CO{sub 2} laser interferometer. This type of interferometer relies on maintaining an accurate measurement of hundreds of vibration fringes during the entire time history of the plasma. Because of the very long pulse lengths (1000 s) and the possibility of fringe counting errors, a second method that measures the Faraday rotation of a laser beam with a tangential laser beam path through the plasma will be used to provide a history-independent measurement of the line density with somewhat reduced accuracy. These two measurements can be accomplished in a combined interferometer/polarimeter system that uses a single CO{sub 2} laser and detector. We have constructed a prototype of this type of system, which uses two acousto-optic modulators to generate two beams, shifted from the laser frequency by 40 and 45 MHz. These probe beams are converted to left- and right-hand circular polarization and combined into a single probe beam. Vibrations are simulated by moving a mirror in the reference beam path, and the Faraday rotation is simulated by rotating the linear polarized probe beam. Frequency analysis of the interference signal from a single detector is used to separate the phase of the interferometer and the phase of the polarization rotation. Limits on the phase resolution of the two methods and possible sources of error will be presented. {copyright}{ital 1999 American Institute of Physics.}

Carlstrom, T.N.; Snider, R.T. [General Atomics, 13-410, P. O. Box 85608, San Diego, California 92186-5608 (United States)] [General Atomics, 13-410, P. O. Box 85608, San Diego, California 92186-5608 (United States)

1999-01-01

67

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

PubMed Central

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

Šmíd, Radek; ?ížek, Martin; Mikel, B?etislav; ?íp, Ond?ej

2015-01-01

68

Three-coordinate laser heterodyne interferometer for metrological assurance of scanning probe microscopes  

NASA Astrophysics Data System (ADS)

In this article we present the developed three-coordinate laser heterodyne interferometer that can be integrated in the commercially available industrial scanning probe and electron microscopes. It allows one to ensure traceability of measurements in nanometer range to the primary standard of meter. As outcome, the regular calibration of scanners becomes unnecessary, while the reproducibility and accuracy of the measurements dramatically increases.

Kazieva, Tatiana V.; Kuznetsov, Andrey P.; Gubskiy, Konstantin L.; Reshetov, Vladimir N.

2015-01-01

69

A Fiber Based Interferometer with Discrete Tunable Laser for Fourier Domain Optical Coherence Tomography  

Microsoft Academic Search

We demonstrate a fiber interferometer with a discrete tunable laser source, which has the feasibility to be utilized in Fourier domain optical coherence tomography (FD-OCT). The structure of the experimental system, its operation principle and theoretical analysis are presented, showing that sampled grating distributed Bragg reflector (SG-DBR) lasers have the potentiality to be adopted as light source in FD-OCT.

Luo Wei; Ma Xiaohong; Zhao Huafeng

2006-01-01

70

Density profile measurement using a multichannel difluoromethane laser interferometer system on ATF  

NASA Astrophysics Data System (ADS)

Recent results of the electron density profile measurement on the Advanced Toroidal Facility (ATF) are presented. A multichannel difluoromethane laser interferometer system has been routinely employed to study density evolution in ECH as well as neutral-beam-heated plasma discharges with gas fueling and pellet injection. A chordal inversion code has been developed, and has been used successfully to reconstruct the asymmetric density profiles. Cross-correlation of density profile measurements among FIR interferometer, Thomson scattering, the heavy-ion beam probe, and the fast reciprocating Langmuir probe has been achieved. Radial density profiles measured by the four diagnostics are generally in good agreement and are hollow profiles under most experimental conditions.

Ma, C. H.; Baylor, L. R.; Hutchinson, D. P.; Murakami, M.; Wilgen, J. B.

71

Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna  

E-print Network

The random superposition of many weak sources will produce a stochastic background of gravitational waves that may dominate the response of the LISA (Laser Interferometer Space Antenna) gravitational wave observatory. Unless something can be done to distinguish between a stochastic background and detector noise, the two will combine to form an effective noise floor for the detector. Two methods have been proposed to solve this problem. The first is to cross-correlate the output of two independent interferometers. The second is an ingenious scheme for monitoring the instrument noise by operating LISA as a Sagnac interferometer. Here we derive the optimal orbital alignment for cross-correlating a pair of LISA detectors, and provide the first analytic derivation of the Sagnac sensitivity curve.

Neil J. Cornish

2001-08-27

72

Dispersion interferometer based on a CO{sub 2} laser for TEXTOR and burning plasma experiments  

SciTech Connect

A dispersion interferometer based on a continuous-wave CO{sub 2} laser source ({lambda}=9.57 {mu}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 {sub min}=2x10{sup 17} m{sup -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. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk, 630090 (Russian Federation); Forschungszentrum Juelich GmbH, Association EURATOM-FZ Juelich, Institut fuer Plasmaphysik, Trilateral Euregio Cluster, 52425 Juelich (Germany)

2006-05-15

73

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.

74

Laser-interferometer gravitational-wave optical-spring detectors  

E-print Network

Using a quantum mechanical approach, we show that in a gravitational-wave interferometer composed of arm cavities and a signal recycling cavity, e.g., the LIGO-II configuration, the radiation-pressure force acting on the mirrors not only disturbs the motion of the free masses randomly due to quantum fluctuations, but also and more fundamentally, makes them respond to forces as though they were connected to an (optical) spring with a specific rigidity. This oscillatory response gives rise to a much richer dynamics than previously known, which enhances the possibilities for reshaping the LIGO-II's noise curves. However, the optical-mechanical system is dynamically unstable and an appropriate control system must be introduced to quench the instability.

Alessandra Buonanno; Yanbei Chen

2002-04-10

75

Laser-interferometer position-feedback for precision machine tools  

SciTech Connect

Diamond turning of off-axis parabolic mirrors is used to provide high-quality turning and focusing optics for the Los Alamos Scientific Laboratory's laser-fusion research. These mirrors are fabricated at the Oak Ridge Y-12 Plant on a large machine tool that incorporates lasers, air bearings, and linear-motor slide-drives to meet the part specifications of 0.63 ..mu..m (25 ..mu..in) on contour and 63 nm (2.5 ..mu..in) on surface finish. This report discusses the application of lasers to this machine and other precision machine tools.

Barkman, W.E.

1980-04-15

76

Performance comparison of piezoelectric accelerometer and laser interferometer in vibration monitoring and measurements  

NASA Astrophysics Data System (ADS)

In this paper, vibration monitoring and measurement carried out in the newly developed nanometer metrology laboratory in Birmingham University, is described with respect to measurement methods and instrument performance. Two types of instrument -- piezoelectric accelerometer (B&K type 8318 with a type 2140 bus-controlled frequency analyzer) and laser interferometer (Renishaw ML10 laser interferometer with the Keithley multi-channel FFT analyzer) were used in vibration measurement on capability verification of a vibration isolation system. Vibration results from a concrete block are presented. From the point of view of the measured vibration results, it is demonstrated that the performance of the above two instruments is not completely the same in the different frequency ranges. The related comparison and discussions are presented in this paper.

Wei, Hong; Stout, Kenneth J.

1995-12-01

77

Heterodyne Stabilization for the Laser Interferometer Space Antenna (LISA)  

NASA Astrophysics Data System (ADS)

LISA is a joint NASA/ESA space mission to detect gravitational waves from 0.1 mHz to 1 Hz generated e.g. by super-massive black hole mergers. Three spacecraft move in a triangular constellation on a heliocentric orbit. Their distances are monitored interferometrically with laser links. LISA detects fluctuations of the 5 million km arm lengths on a picometer scale. The requirement for the frequency stability of the lasers is 141 Hz/?Hz. I will present a new stabilization scheme based on heterodyne interferometry. It requires less components than the currently envisioned Pound Drever Hall technique and can easily be integrated into LISA's interferometry measurement system. The two lasers of each spacecraft are injected into the same optical cavity. Near resonance, the phase of the reflected light is sensitive to frequency fluctuations. The second, off-resonant beam can be used to lock the primary laser to the cavity resonance. I will discuss this technique and present experimental results. This work is supported by NASA Contract #00078244 and NASA Grant NNX08AG75G.

Eichholz, Johannes; Hochman, Steven; Preston, Alix; Mueller, Guido

2010-10-01

78

Multicomponent wavefield characterization with a novel scanning laser interferometer  

E-print Network

includes three laser beam heads and involves extensive alignment with a location/ range-finding geometry module; the alignment can be a lim- iting factor for spatial resolution, and therefore restricts the out-of-plane and the horizontal in-plane displacement components, on the fly. As an example, we

Boise State University

79

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

80

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

81

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

SciTech Connect

In this paper, we systematically study preheating in laser-direct-drive shocks by using a velocity interferometer system for any reflector (VISAR). Using the VISAR, we measured free surface velocity histories of Al samples over time, 10–70??m thick, driven directly by a laser at different frequencies (2?, 3?). Analyzing our experimental results, we concluded that the dominant preheating source was X-ray radiation. We also discussed how preheating affected the material initial density and the measurement of Hugoniot data for high-Z materials (such as Au) using impedance matching. To reduce preheating, we proposed and tested three kinds of targets.

Shu, Hua; Fu, Sizu; Huang, Xiuguang; Wu, Jiang; Xie, Zhiyong; Zhang, Fan; Ye, Junjian; Jia, Guo; Zhou, Huazhen [Shanghai Institute of Laser Plasma, P.O. BOX 800-229, Shanghai 201800 (China)

2014-08-15

82

LISA, the Laser Interferometer Space Antenna, Requires the Ultimate in Lasers, Clocks, and Drag-Free Control  

Microsoft Academic Search

\\u000a The existence of gravitational waves is the most prominent of Einstein’s predictions that has not yet been directly verified.\\u000a The space project LISA shares its goal and principle of operation with the ground-based interferometers currently being operated,\\u000a the detection and measurement of gravitational waves by laser interferometry. Ground and space detection differ in their frequency\\u000a ranges, and thus in the

Albrecht Rüdiger; Gerhard Heinzel; Michael Tröbs

2008-01-01

83

Laser line wavelength sensor based in a dual-wavelength fiber laser with a Hi-Bi loop Sagnac interferometer  

NASA Astrophysics Data System (ADS)

We present an experimental method for straight forward dual wavelength Erbium doped fiber linear cavity laser characterization based in laser line spectrum behavior due to the Hi-Bi FOLM transmission spectrum wavelength displacement by temperature variations in the fiber loop. The laser operation is for a single and dual mode, obtained through the adjustment of the cavity losses by the Sagnac interferometer spectrum wavelength displacement due to the temperature variation of the fiber loop. The method allow determine the laser operation from a single emission line and a two emission lines simultaneously through the Sagnac transmittance spectrum optical power variations measurement due to wavelength spectrum shifting for each laser wavelength generated separately and overlapping these obtained spectrums.

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

2014-06-01

84

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

85

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

86

Density profile measurement using a multichannel difluoromethane laser interferometer system on ATF  

NASA Astrophysics Data System (ADS)

Recent results of the electron density profile measurement on the Advanced Toroidal Facility are presented. A multichannel difluoromethane laser interferometer system has been routinely employed to study density evolution in electron cyclotron heated as well as neutral-beam-heated plasma discharges with gas fueling and pellet injection. A chordal inversion code has been developed, and has been used successfully to reconstruct the asymmetric density profiles. Cross-correlation of density profiles measurements among far-infrared interferometer, Thomson scattering, the heavy-ion beam probe, and the fast reciprocating Langmuir probe has been achieved. Radial density profiles measured by the four diagnostics are generally in good agreement and are hollow profiles under most experimental conditions.

Ma, C. H.; Baylor, L. R.; Hutchinson, D. P.; Murakami, M.; Wilgen, J. B.

1992-10-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

88

Quadrature Amplitude Modulated Microwave Signal Generation Using a Single Electro-Optic Nd:YVO Solid-State Laser  

Microsoft Academic Search

In this communication a new optical scheme is described that is able to generate quadrature amplitude modulation RF signals, with exceptional flexibility and tunability. The device readily implements a channel-adaptive transmitter for wireless communications with multiple modulation formats and radio bands. Due to the optical generation, the transmitter is particularly ideal for radio over fiber applications.

Gabor Kovacs; Tibor Berceli; Peter Herczfeld

2009-01-01

89

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

90

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

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

1992-01-01

91

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

NASA Astrophysics Data System (ADS)

Wall shear stress measurements beneath crossing-shock-wave / turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symmetric 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.

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

1994-06-01

92

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

93

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

94

Monitoring and multiplexing fiber Fabry-Perot interferometer sensors using a linearly tunable Er:fiber laser  

NASA Astrophysics Data System (ADS)

A new method for the monitoring of interferometer fiber optic sensors which utilizes a frequency-scanned fiber laser is investigated. The interrogation technique is based on the principle that if the laser frequency varies linearly with time, the optical signal reflected or transmitted is intensity-modulated at a frequency proportional to the optical path difference (OPD) in the interferometer. Fourier components in the detected optical output signal then correspond to the OPDs of any interferometers which have contributed to this modulation. The position of a peak in the power spectrum of this signal is proportional to the OPD of the interferometer responsible for that peak. Fine tuning of the OPD value is determined from the phase of the corresponding Fourier component. Experimentally, an Er:fiber laser scanned over a 46 nm range centered at 1545 nm was used to monitor intrinsic fiber Fabry-Perot interferometers (FFPIs). Variations in the laser scan rate were compensated using the optical signal modulated by a reference FFPI held at constant temperature. For three multiplexed sensors arranged in series, temperature was measured from 20°C to 610°C with a 0.02°C resolution.

Wan, Xiaoke; Taylor, Henry F.

2003-07-01

95

Interferometer systems in machine industry  

NASA Astrophysics Data System (ADS)

In the report the arrangements of laser interferometers for machine history are presented; the laser interferometer LSP30 for investigation of geometry of machine tools, the setup for inspection of ball screw and laser liner for CNC machine. Outstanding feature of the interferometers is the stabilization system of laser frequency using surface stabilized ferroelectric liquid cells (SSFLC).

Rzepka, Janusz; Pienkowski, Janusz; Sambor, Slawomir; Budzyn, Grzegorz

2003-10-01

96

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

SciTech Connect

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

Baburin, N V; Borozdov, Yu V; Danileiko, Yu K; Denker, B I; Ivanov, A D; Osiko, Vyacheslav V; Sverchkov, S E; Sidorin, A V; Chikov, V A [Laser Materials and Technology Research Center, A. M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Ifflander, R; Hack, R [Haas-Laser GmbH, Schramberg (Germany); Kertesz, I; Kroo, N [Research Institute for Solid State Physics, Budapest XII (Hungary)

1998-07-31

97

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

98

Direct Measurement of Complex Index of Aerosol by Multi-wavelength Laser Interferometer  

NASA Astrophysics Data System (ADS)

Complex index of Aerosol is an important parameter in environment protection and climate change. Aerosol scattering and absorption both strictly depend on complex index of aerosol, Aerosol complex index not only decide the atmospheric temperature headed or been cool, but also have an effect of budget of earth and atmospheric radiation. A new method, which uses multi-wavelength laser interferometer, is proposed. This method is quietly different the others which obtained complex index by scattering measurement. Laser cross through aerosol can produce extinction and phase delay, using interferometer phase delay and extinction can be measured. Complex index of aerosol is obtained from extinction and phase delay by inversion with generic algorithm. Simulation and analysis give a primary glue of feasibility. Further research would be developed.

Li, B.; Li, Z.; yes

2011-12-01

99

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

100

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

101

Two-modality laser diode interferometer for high-accuracy measurement of long-range absolute distance  

NASA Astrophysics Data System (ADS)

This paper presents a two-modality laser diode (LD) interferometer which combine as two-wavelength sinusoidal phase modulating (SPM) interferometer with a wavelength scanning interferometer (WSI) for measurement of distance over long range with high accuracy. Moreover, the intensity modulation due to power changes of LD is suppressed by appropriately choosing the modulation amplitude of injection current (IC) of LD. Triangle wave is used to modulate the IC of one LD with that of the other LD being constant at first. Thus the interferometer works as a wavelength scanning interferometer. An initial estimate of the distance can be obtained from the phase change of the interference signal. Then sinusoidal wave is used for modulating IC of both LDs to realize a two-wavelength SPM interferometer. However, the modulation of the IC of two LDs results in not only the wavelength modulation but also the intensity modulation. This intensity modulation will cause a measured phase error. To eliminate this error, SPM depths are appropriately chosen, therefore the distance to be measured can be accurately obtained with synthetic-wavelength algorithm. Experimental results indicate that an absolute distance measurement accuracy of 1?m can be achieved over the range of 40mm to 100mm.

Wang, Bofan; Li, Zhongliang; Wang, Xiangzhao; Bu, Peng

2010-08-01

102

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

SciTech Connect

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

Shu, D.

1985-02-01

103

An antiresonant ring interferometer for coupled laser cavities, laser output coupling, mode locking, and cavity dumping  

Microsoft Academic Search

An antiresonant ring-mirror configuration, the optical analog of a microwave reentrant hybrid tee, is suggested for several potential laser applications including coupled laser cavities, variable laser output coupling, intracavity harmonic output coupling, mode locking, cavity dumping, and pulse code modulation.

A. Siegman

1973-01-01

104

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

105

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

SciTech Connect

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

Smith, Tristan L. [California Institute of Technology, Mail Code 130-33, Pasadena, California 91125 (United States); Peiris, Hiranya V. [Kavli Institute for Cosmological Physics and Enrico Fermi Institute, University of Chicago, Chicago Illinois 60637 (United States); Cooray, Asantha [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)

2006-06-15

106

Monostatic coaxial 1.5 ?m laser Doppler velocimeter using a scanning Fabry-Perot interferometer.  

PubMed

We present a laser Doppler velocimeter (LDV) in monostatic coaxial arrangement consisting of off-the-shelf telecom-grade components: a single frequency laser (wavelength ? = 1.5 ?m) and a high-finesse scanning Fabry-Perot interferometer (sFPI). In contrast to previous 1.5 ?m LDV systems based on heterodyne detection, our sFPI-LDV has the advantages of having large remote sensing range not limited by laser coherence, high velocity dynamic range not limited by detector bandwidth and inherent sign discrimination of Doppler shift. The more optically efficient coaxial arrangement where transmitter and receiver optics share a common axis reduces the number of components and greatly simplifies the optical alignment. However, the sensitivity to unwanted backreflections is increased. To circumvent this problem, we employ a custom optical circulator design which compared to commercial fiber-optic circulator achieves ~40 dB reduction in strength of unwanted reflections (i.e. leakage) while maintaining high optical efficiency. Experiments with a solid target demonstrate the performance of the sFPI-LDV system with high sensitivity down to pW level at present update rates up to 10 Hz. PMID:24103985

Rodrigo, Peter John; Pedersen, Christian

2013-09-01

107

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

NASA Astrophysics Data System (ADS)

This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Modulation of the drive current causes thermal tuning of the laser light frequency. Reflection of this frequency-modulated light from a fiber Fabry-Perot interferometer (FFPI) sensor produces fringe patterns which can be used to measure the optical path difference of the sensor. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The response characteristics of FFPI sensors were determined experimentally for square, triangular, saw-tooth waveforms at frequencies from 10kHz to 100kHz. The dependence of VCSEL frequency on the dc bias current was determined from spectral measurements to be ˜165GHz/mA. An independent measurement of this quantity based on counting fringes from the FFPI sensor as the laser modulated was in good agreement with this value. The effect of optical feedback into the laser was also studied. By observing the fringe shift as the FFPI sensor was heated, a fractional change in optical length with temperature of 6.95 X 10-6/°C was determined in good agreement with previous measurements on a 1300nm single mode fiber. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers. The results of these experiments show that the 850nm VCSEL/FFPI combination gives regular fringe patterns at much lower bias current and modulating current amplitudes than their 1300nm DFB/FFPI counterparts.

Lee, Kyung-Woo

108

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

109

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

110

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

111

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

112

Inner air-cavity based fiber in-line Mach -Zehnder interferometer fabricated by femtosecond laser and fusion splicing  

NASA Astrophysics Data System (ADS)

We demonstrate a miniaturized fiber in-line Mach-Zehnder interferometer high-temperature sensor based on inner aircavity adjacent to the fiber core, fabricated by femto-second laser micromachining and fusion splicing technique. Such a device is robust and insensitive to ambient refractive index change, with high temperature sensitivity of ~43.2 pm/°C, up to 1000°C,while exhibiting low cross-sensitivity to strain.

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

2013-09-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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

Malyutin, A. A.

1988-08-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

116

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

NASA Astrophysics Data System (ADS)

Wall shear stress measurements beneath crossing-shock-wave/turbulent boundary-layer interactions have been made for three interactions of different strengths. The interactions are generated by two sharp fins at symetric angles of attack mounted on a flat plate. The shear stress measurements were made for fin angles of 7 and 11 deg at Mach 3 and 15 deg at Mach 3.85. The measurements were made using a laser interferometer skin-friction meter, a device that determines the wall shear by optically measuring the time rate of thinning of an oil film placed on the test model surface. Results of the measurements reveal high skin-friction coefficients in the vicinity of the fin/plate junction and the presence of quasi-two-dimensional flow separation on the interaction center line. Additionally, two Navier-Stokes computations, one using a Baldwin-Lomax turbulence model and one using a k-epsilon model, are compared with the experimental results for the Mach 3.85, 15-deg interaction case. Although the k-epsilon model did a reasonable job of predicting the overall trend in portions of the skin-friction distribution, neither computation fully captured the physics of the near-surface flow in this complex interaction.

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

1994-06-01

117

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

118

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

119

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

SciTech Connect

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

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

1991-02-01

120

LISA, the Laser Interferometer Space Antenna, Requires the Ultimate in Lasers, Clocks, and Drag-Free Control  

NASA Astrophysics Data System (ADS)

The existence of gravitational waves is the most prominent of Einstein’s predictions that has not yet been directly verified. The space project LISA shares its goal and principle of operation with the ground-based interferometers currently being operated, the detection and measurement of gravitational waves by laser interferometry. Ground and space detection differ in their frequency ranges, and thus in the detectable sources. Toward low frequencies, ground-based detection is limited by seismic noise, and yet more fundamentally by “gravity-gradient noise,” thus covering the range from a few Hz on upward to a few kHz. It is only in space that detection of signals below, say, 1 Hz is possible, opening a wide window to a different class of interesting sources of gravitational waves. The project LISA consists of three spacecraft in heliocentric orbits, forming a triangle of 5 million km sides. A technology demonstrator, the LISA Pathfinder, designed to test vital LISA technologies, is to be launched by ESA in 2009.

Rüdiger, Albrecht; Heinzel, Gerhard; Tröbs, Michael

121

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

122

Atom Interferometers  

E-print Network

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

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

2007-12-21

123

A variable coefficient microwave photonic filter based on multi-wavelength fiber laser and Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

A microwave photonic filter (MPF) with variable coefficient is proposed and demonstrated, which is constructed by a multi-wavelength fiber laser and Mach-Zehnder interferometer (MZI). Through changing the slope characteristics of Mach-Zehnder interference spectrum adjusted by optical variable delay line (OVDL), the conversion from phase modulation (PM) to intensity modulation (IM) is realized. The multi-wavelength fiber laser with Lyot-Sagnac optical filter has variable wavelength spacing. So the designed filter has a variable number of taps and tap weights. As a result, the tunable range of passband center frequency is 2.6 GHz. The reconfigurability of MPF can be also realized by adjusting the output of fiber laser.

Cao, Ye; Liu, Ce; Tong, Zheng-rong

2014-11-01

124

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

125

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

SciTech Connect

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

Hilbert, V.; Rödel, C.; Zastrau, U., E-mail: ulf.zastrau@uni-jena.de [Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743 Jena (Germany); Brenner, G.; Düsterer, S.; Dziarzhytski, S.; Harmand, M.; Przystawik, A.; Redlin, H.; Toleikis, S. [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg (Germany); Döppner, T.; Ma, T. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Fletcher, L. [Department of Physics, University of California, Berkeley, California 94720 (United States); Förster, E. [Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, Max-Wien-Platz 1, 07743 Jena (Germany); Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena (Germany); Glenzer, S. H.; Lee, H. J. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Hartley, N. J. [Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Kazak, L.; Komar, D.; Skruszewicz, S. [Institut für Physik, Universität Rostock, 18051 Rostock (Germany); and others

2014-09-08

126

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

127

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

128

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

NASA Astrophysics Data System (ADS)

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

Kiriyama, Hiromitsu; Nakano, Fumihiko; Yamakawa, Koichi

2002-08-01

129

Dual Wavelength Single Longitudinal Mode Ytterbium-Doped Fiber Laser Using a Dual-Tapered Mach-Zehnder Interferometer  

NASA Astrophysics Data System (ADS)

This paper describes a dual wavelength single longitudinal mode (SLM) demonstration for a proposed ytterbium-doped fiber laser. A dualtapered Mach-Zehnder interferometer (MZI) was inserted into the laser ring cavity setup to ensure a stable dual wavelength and SLM operation. The consequent dual wavelength lasing operation had a wavelength spacing of 0.94 nm and a side mode suppression ratio (SMSR) of 50 dB, with the linewidth of this setup measured as 294.15 kHz. A stability test allowed for a measurement of max power fluctuation as less than 0.8 dB for each wavelength and which was indicative of a stable dual wavelength operation.

Ahmad, H.; Salim, M. A. M.; Azzuhri, S. R.; Zulkifli, M. Z.; Harun, S. W.

2015-03-01

130

Signal recycled laser-interferometer gravitational-wave detectors as optical springs  

E-print Network

Using the force-susceptibility formalism of linear quantum measurements, we study the dynamics of signal recycled interferometers, such as LIGO-II. We show that, although the antisymmetric mode of motion of the four arm-cavity mirrors is originally described by a free mass, when the signal-recycling mirror is added to the interferometer, the radiation-pressure force not only disturbs the motion of that ``free mass'' randomly due to quantum fluctuations, but also and more fundamentally, makes it respond to forces as though it were connected to a spring with a specific optical-mechanical rigidity. This oscillatory response gives rise to a much richer dynamics than previously known for SR interferometers, which enhances the possibilities for reshaping the noise curves and, if thermal noise can be pushed low enough, enables the standard quantum limit to be beaten. We also show the possibility of using servo systems to suppress the instability associated with the optical-mechanical interaction without compromising the sensitivity of the interferometer.

Alessandra Buonanno; Yanbei Chen

2001-07-05

131

Uncertainty propagation: Quadrature  

NSDL National Science Digital Library

The quadrature formula relates the fluctuations of a function to fluctuations in the variables on which the function depends. In this derivation, we approximate a multivariable function using a Taylor expansion, and we assume that fluctuations in the underlying variables are statistically independent, which allows us to apply an identity previously derived in the unit on statistics. Namely, "variances of sums are sums of variances" for variables that fluctuate independently.

2013-06-21

132

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

SciTech Connect

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

Thrane, Eric; Mandic, Vuk [School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Ballmer, Stefan [LIGO Laboratory, California Institute of Technology, MS 18-34, Pasadena, California 91125 (United States); Romano, Joseph D. [University of Texas at Brownsville, Brownsville, Texas 78520 (United States); Mitra, Sanjit [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); LIGO Laboratory, California Institute of Technology, MS 18-34, Pasadena, California 91125 (United States); Observatoire de la Cote d'Azur, BP 4229, 06304 Nice Cedex 4 (France); Talukder, Dipongkar; Bose, Sukanta [Department of Physics, Washington State University, Pullman, Washington 99164-2814 (United States)

2009-12-15

133

A laser probe based on a Sagnac interferometer with fast mechanical scan for RF surface and bulk acoustic wave devices.  

PubMed

This paper describes the development of a phasesensitive laser probe with fast mechanical scan for RF surface and bulk acoustic wave (SAW/BAW) devices. The Sagnac interferometer composed of micro-optic elements was introduced for the selective detection of RF vertical motion associated with RF SAW/BAW propagation and vibration. A high-pass characteristic of the interferometer makes the measurement very insensitive to low-frequency vibration. This feature allows us to apply the fast mechanical scan to the interferometric measurement without badly sacrificing its SNR and spatial resolution. The system was applied to the visualization of a field pattern on the vibrating surface of an RF BAW resonator operating in the 2 GHz range. The field pattern was obtained in 17 min as a 2-D image (500 × 750 pixel with 0.4 ?m resolution and SNR of 40 dB). The system was also applied to the characterization of an RF SAW resonator operating in the 1 GHz range, and the applicability of the system was demonstrated. PMID:21244986

Hashimoto, Ken-ya; Kashiwa, Keiskue; Wu, Nan; Omori, Tatsuya; Yamaguchi, Masatsune; Takano, Osamu; Meguro, Sakae; Akahane, Koichi

2011-01-01

134

Femtosecond laser fabrication of directional couplers and Mach-Zehnder interferometers  

E-print Network

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

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

2007-01-01

135

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

E-print Network

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

Lee, Kyung-Woo

2006-10-30

136

Discrete observability and numerical quadrature  

NASA Technical Reports Server (NTRS)

The authors consider the problem of approximate observability of a one-dimensional diffusion equation on a finite spatial domain with spatial point measurements. The problem of the optimal selection of the measurement points is considered under three conditions: (1) no preassigned measurement nodes; (2) one preassigned node and; (3) two preassigned nodes. The main observation is that the optimal choice is related to three classical procedures in numerical analysis: (1) Gaussian quadrature; (2) Radau quadrature and; (3) Lobatto quadrature. It is shown that the existence of the Radau and Lobatto quadrature is closely related to classical root locus theory.

Martin, Clyde F.; Wang, Xiaochang; Stamp, Mark

1991-01-01

137

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

PubMed Central

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

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

2011-01-01

138

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

139

Dual surface interferometer  

DOEpatents

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

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

1980-09-12

140

Dual surface interferometer  

DOEpatents

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

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

1982-01-01

141

Interference without an interferometer: a different approach to measuring, compressing, and shaping ultrashort laser pulses  

Microsoft Academic Search

The inherent brevity of ultrashort laser pulses prevents a direct measurement of their electric field as a func- tion of time; therefore different approaches based on autocorrelation have been used to characterize them. We present a discussion, guided by experimental studies, regarding accurate measurement, compression, and shaping of ultrashort laser pulses without autocorrelation or interferometry. Our approach based on phase

Yves Coello; Vadim V. Lozovoy; Tissa C. Gunaratne; Bingwei Xu; Ian Borukhovich; Chien-hung Tseng; Thomas Weinacht; Marcos Dantus

2008-01-01

142

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

143

Picometer-accuracy, laser-metrology gauge for Keck interferometer differential-phase subsystem  

NASA Astrophysics Data System (ADS)

Keck Interferometer differential-phase planet-detection system requires a picometer accuracy, large (2 ?m to 4 ?m) amplitude optical path-length modulator that can operate at fairly high frequencies (250 Hz, 750 Hz, and 1250 Hz, a partial, triangular wave motion). We have developed a gauge which monitors the amplitude of the motion of the path-length modulator and which is capable of reaching a sensitivity of at least 3 pm per sqrt(Hz) within a band width of 1 Hz at 250 Hz, 750 Hz, and 1250 Hz. Two of these gauges are built. The gauges are compared to each other while monitoring a common optical path-length modulator to determine their accuracy. In this paper, the gauge construction details, the results of the gauge accuracy tests as well as the final path-length modulator performance details are presented.

Gursel, Yekta

2003-02-01

144

Optimized quadrature surface coil designs  

PubMed Central

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

Kumar, Ananda; Bottomley, Paul A.

2008-01-01

145

Fiber Fizeau interferometer for remote passive sensing  

NASA Astrophysics Data System (ADS)

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

Bush, Jeff; Suh, Kwang

2012-06-01

146

Phase-locked scanning interferometer for frequency stabilization of multiple lasers.  

PubMed

We report a simple scheme for stabilizing and tuning the length of a conventional piezo-driven optical cavity against the resonant transmission of a master laser. In contrast with other schemes, we drive the piezo at its mechanical resonance of 5 kHz over an amplitude equivalent to one free spectral range and use a feedback circuit that incorporates phase-sensitive detection of the master-laser transmission. The bandwidth of our cavity-lock circuit is limited only by the resonance frequency of the cavity piezo and is 1.4 kHz. The stabilized mean cavity length reaches in 30 s a minimum Allan deviation of approximately 10 kHz (a length stability of 20 parts per trillion) equaling that of the polarization-stabilized He-Ne we use as our master laser. Here, we investigate the mechanical characteristics of the cavity, describe the lock circuit and its measured performance, and provide simple analytical relations between the phase-sensitive signal and cavity displacement. Our setup economizes the cost and amount of equipment necessary for stabilizing multiple continuous-wave lasers operating at different wavelengths. PMID:18163716

Tonyushkin, Alexei A; Light, Adam D; Di Rosa, Michael D

2007-12-01

147

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

NASA Astrophysics Data System (ADS)

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

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

1993-07-01

148

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

SciTech Connect

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

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

2013-11-18

149

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

150

Rotatable shear plate interferometer  

DOEpatents

A rotatable shear plate interferometer comprises a transparent shear plate mounted obliquely in a tubular supporting member at 45.degree. with respect to its horizontal center axis. This tubular supporting member is supported rotatably around its center axis and a collimated laser beam is made incident on the shear plate along this center axis such that defocus in different directions can be easily measured.

Duffus, Richard C. (Livermore, CA)

1988-01-01

151

Generation dynamics of a self-starting self-pumped phase-conjugate Nd:YAG laser with a three-mirror interferometer inside the loop cavity  

NASA Astrophysics Data System (ADS)

The generation dynamics of a pulse-periodical Nd:YAG laser with a three-mirror interferometer inside a loop cavity is investigated numerically. A parametrical back coupling is made by dynamics gratings in an active element inside the interferometer. An index mirror of the interferometer lets the intensity of colliding reference waves change and influence on the formation of holographic gain gratings, born in the process of four-wave mixing. The mathematical model is based on kinetic equations in the single mode and single frequency approximation in description of radiation propagation in the free space and in an active medium. Also the mathematical model includes the coupled waves equation in the description of four-wave mixing. The mathematical modeling has shown, that the investigated scheme allows to receive larger power output parameters of radiation in a regime of phase-conjugation in LiF:F2-, in comparison with an ordinary loop scheme. The comparative analysis of generation dynamics in an offered scheme and in the loop scheme wihtout any three-mirror interferometer showed the differentiation of mechanisms of dynamic gratings formation in Nd:YAG active mediums and defined conditions for optimal work of each schemes. The conditions for optimal work of each schemes were defined.

Kyalbieva, Svetlana A.; Gavrilov, Andrey V.; Teterin, P. E.

2004-03-01

152

Actively Q-switched dual-wavelength laser with double-cladding Er/Yb-doped fiber using a Hi-Bi Sagnac interferometer  

NASA Astrophysics Data System (ADS)

An actively Q-switched double-wavelength Er/Yb fiber laser is experimentally demonstrated. The linear cavity is formed by a pair of fiber Bragg gratings on one side and a Sagnac interferometer (SI) with high birefringence fiber in the loop on the opposite side. A 3?m of double-cladding Er/Yb-doped fiber used as a gain medium is pumped by a 978?nm laser diode. The SI is used to adjust the internal cavity losses for simultaneous dual-wavelength laser generation. The adjustment is performed by temperature variations of the high birefringence fiber in the SI loop. The maximum average output power for the Q-switched laser operation in dual-wavelength mode was around 68?mW with a repetition rate of 40?kHz for 2?W of pump power. The minimum pulse duration was around 280?ns. The maximum pulse energy was 1.75?µJ.

Durán-Sánchez, M.; Álvarez Tamayo, R. I.; Pottiez, O.; Ibarra-Escamilla, B.; Hernández-García, J. C.; Beltran-Perez, G.; Kuzin, E. A.

2015-02-01

153

Laser Interferometer Measurements of the Viscoelastic Properties of Tectorial Membrane Mutants  

NASA Astrophysics Data System (ADS)

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

Jones, Gareth; Russell, Ian; Lukashkin, Andrei

2011-11-01

154

Laser Interferometer GW Detectors - a Dwarf and a Giant (geo 600 and Lisa)  

NASA Astrophysics Data System (ADS)

In 2003, five ground-based laser-interferometric gravitational wave detectors are being commissioned for scientific use. With armlengths of km scales, they cover the audio frequency range: 10 Hz up to a few kHz. Although one of the smallest in size, the British-German detector GEO 600 incorporates some advanced features that will later find their way also into upgraded versions of the larger detectors. The space project LISA is composed of three spacecraft in a triangular formation, of 5 million km sides. LISA will thus search in a much lower frequency band, below 1 Hz and down to 10-4 Hz. A technology demonstrator (LTP on SMART-2) will be launched in 2006,and launch of LISA proper is planned for 2011/12.

Rüdiger, Albrecht

155

Heterodyne Interferometer Angle Metrology  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

156

Optimization of single-layer sol-gel antireflection coatings on potassium dihydrogen phosphate crystals in quadrature geometry for second-harmonic conversion of high-power Nd:glass lasers  

NASA Astrophysics Data System (ADS)

Quadrature geometry of two potassium dihydrogen phosphate crystals is a standard configuration to achieve efficient second-harmonic conversion of Nd:glass high-power lasers. Antireflection coatings on the entrance face of the first crystal and on the exit face of the second one are easily designed using quarterwave optical thicknesses adjusted separately for minimum reflectivity at the fundamental wavelength and at its second harmonic. It is however not possible to simultaneously obtain the lowest reflectivity for both the wavelengths on the inner faces. We describe a theoretical optimization of a single-layer sol-gel silica coating that allows maximum transmission of energy in the fundamental and second harmonic, taken together, across the inner faces of the two crystals. The optimum thickness is a function of the conversion efficiency to the second harmonic, and hence of the incident intensity of the fundamental wave. We have deposited sol-gel silica single-layer coatings of this optimum thickness, and the total reflectivity at fundamental and second-harmonic wavelengths taken together was measured and compared with the theoretically calculated values.

Pareek, Rakesh; Kumbhare, Mohan; Joshi, Anandvardhan; Banerjee, Arup; Gupta, Parshottam

2010-09-01

157

Quadrature for Meshless Methods Ivo Babuska  

E-print Network

Quadrature for Meshless Methods Ivo Babuska Uday Banerjee John E. Osborn and Qiaoluan Li § Abstract In this paper we discuss quadrature schemes for meshless methods. We consider the Neumann Problem concerning Meshless Methods (MM) is the problem of numerical quadrature. In spite of its importance, only

Banerjee, Uday

158

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

159

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

160

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. Observation means including film and video cameras may be used to view and record the resultant fringe patterns.

Deason, Vance A. (Shelley, ID); Ward, Michael B. (Idaho Falls, ID)

1989-01-01

161

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

162

Hierarchical Quadrature for Singular Integrals  

Microsoft Academic Search

Abstract We introduce a method,for the computation of singular integrals arising in the discretization of integral equations. The basic method is based on the concept of admissible subdomains, known, e.g., from panel clustering techniques and H-matrices: We split the domain of integration into a hierarchy of subdomains and perform standard quadrature on those subdomains that are amenable to it. By

Steffen Börm; Wolfgang Hackbusch

2005-01-01

163

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

PubMed

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

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

2003-11-15

164

Temperature-tuned erbium-doped fiber ring laser with Mach-Zehnder interferometer based on two quasi-abrupt tapered fiber sections  

NASA Astrophysics Data System (ADS)

We present a wavelength tuning of an Erbium-Doped Fiber Ring Laser (EDFRL) based in a Mach-Zehnder fiber interferometer (MZFI) that consists on two tapers fabricated on commercial SMF28 from Corning as an intracavity filter. The MZFI spectral interference pattern is modified by external refractive index changes that alter the light transmission characteristics. In this work, the fiber device is immersed into a glycerol solution with higher dispersion in its refractive index in relation with temperature. Since the temperature sensitiveness of the glycerol is much higher than that of the fiber in a temperature range from 25-110 °C, therefore, the spectral changes are mainly due to the dispersion of glycerol refractive index when heat increases. Also, when this device is inserted into the EDFRL cavity, the gain spectrum of the EDF is modified accordingly and the changes, which can be controlled in an electrical heater, allow the tuning of the laser wavelength determined by the interference fringes. A wavelength shift as high as 180 pm/°C and a tunable range of 12 nm are obtained. The side mode suppression ratio (SMSR) of the fiber laser is around 25-30 dB depending on the notch filtering position. The insertion losses of the filter are below 0.3 dB and the measured wavelength shift has a quasilinear dependence as a function of temperature in the 80-110 °C. This method is very simple, portable and inexpensive over traditional methods to tune a fiber laser.

Selvas-Aguilar, R.; Martínez-Rios, A.; Anzueto-Sánchez, G.; Castillo-Guzmán, A.; Hernández-Luna, M. C.; Robledo-Fava, R.

2014-10-01

165

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

166

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

167

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

168

Temperature compensated two-mode fiber interferometer  

E-print Network

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

Doma, Jagdish Ramchandra

1993-01-01

169

Error Analysis of Quadrature Rules. Classroom Notes  

ERIC Educational Resources Information Center

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

Glaister, P.

2004-01-01

170

Quadrature Generation Techniques in CMOS Relaxation Oscillators  

E-print Network

) A differential VCO running at twice the desired operating frequency followed by a divide-by-2 circuit: Design. These are inspired by similar techniques used to couple LC-VCO's in quadrature. The QRXO's are designed in a UMC 0.4GHz quadrature oscillators are designed and simulated in a UMC 0.18µm CMOS process. The shunt

Krishnapura, Nagendra

171

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

172

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

173

Modulator-free quadrature amplitude modulation signal synthesis  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

174

Michelson Interferometer  

NASA Technical Reports Server (NTRS)

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

Rogers, Ryan

2007-01-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

176

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

177

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

178

Comparison of fiber Fabry-Perot interferometer sensor using 850nm VCSEL vs 1300nm DFB laser as light source  

NASA Astrophysics Data System (ADS)

This research represents the first effort to apply vertical cavity surface emitting lasers (VCSELs) to the monitoring of interferometric fiber optic sensors. Spectral characteristics were measured for 850nm VCSELs to determine the combination of dc bias current, modulation current amplitude and modulation frequency for which single mode VCSEL operation and regular fringe patterns are achieved. The performance of 850nm VCSEL/FFPI systems was compared with their counterparts using 1300nm distributed feedback (DFB) lasers.

Lee, Kyungwoo; Taylor, Henry F.

2006-09-01

179

Modulator-free quadrature amplitude modulation signal synthesis.  

PubMed

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

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

2014-01-01

180

Gaussian quadrature for multiple orthogonal polynomials  

NASA Astrophysics Data System (ADS)

We study multiple orthogonal polynomials of type I and type II, which have orthogonality conditions with respect to r measures. These polynomials are connected by their recurrence relation of order r+1. First we show a relation with the eigenvalue problem of a banded lower Hessenberg matrix Ln, containing the recurrence coefficients. As a consequence, we easily find that the multiple orthogonal polynomials of type I and type II satisfy a generalized Christoffel-Darboux identity. Furthermore, we explain the notion of multiple Gaussian quadrature (for proper multi-indices), which is an extension of the theory of Gaussian quadrature for orthogonal polynomials and was introduced by Borges. In particular, we show that the quadrature points and quadrature weights can be expressed in terms of the eigenvalue problem of Ln.

Coussement, Jonathan; van Assche, Walter

2005-06-01

181

ANTIGAUSSIAN QUADRATURE FORMULAS DIRK P. LAURIE  

E-print Network

ANTI­GAUSSIAN QUADRATURE FORMULAS DIRK P. LAURIE Abstract. An anti­Gaussian quadrature formula is an (n + 1)­point formula of de­ gree 2n \\Gamma 1 which integrates polynomials of degree up to 2n + 1 with an error equal in magnitude but of opposite sign to that of the n­point Gaussian formula. Its inten­ ded

Laurie, Dirk

182

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

183

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

184

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

185

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

E-print Network

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

John G. Baker; James Ira Thorpe

2012-01-26

186

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

187

Error Bounds for Quadrature Methods Involving Lower Order Derivatives  

ERIC Educational Resources Information Center

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

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

2003-01-01

188

A Numerical quadrature for the Schwarz-Chimera Method  

E-print Network

A Numerical quadrature for the Schwarz-Chimera Method J. -B. Apoung Kamga1 and Olivier Pironneau2 1 Curie Olivier.Pironneau@upmc.fr Summary. Chimera [9] happens to be a version of Schwarz' method quadrature for the Schwarz-Chimera Method 3 3 Numerical Quadrature As such, the scheme is too costly

189

Accurate recovery of recursion coefficients from Gaussian quadrature formulas  

E-print Network

Accurate recovery of recursion coefficients from Gaussian quadrature formulas@na-net.ornl.gov _____________________________________________________________________________ 1 Introduction Gaussian quadrature formulas are efficient and elegant. They are deservedly of view of the numerical analyst, the calculation of Gaussian quadrature formulas is a particularly

Laurie, Dirk

190

Gauss Legendre quadrature over a triangle  

Microsoft Academic Search

This paper presents a Gauss Legendre quadrature method for numerical int egration over the standard triangular surface: {(x, y) | 0, 1 ,1 } x y xy ?? +? in the Cartesian two-dimensional (x, y) sp ace. Mathematical transforma- tion from (x, y) space to ( ?, ?) space map the standard triangle in ( x, y) space to a

H. T. RATHOD; K. V. NAGARAJA; B. VENKATESUDU; N. L. RAMESH

2004-01-01

191

FAST AND OBLIVIOUS CONVOLUTION QUADRATURE ACHIM SCH  

E-print Network

FAST AND OBLIVIOUS CONVOLUTION QUADRATURE ACHIM SCH Ë? ADLE # , MAR â?? IA L â?? OPEZ­FERN â?? ANDEZ approximation to a continuous temporal convolution using only O(N log N) multiplications and O(log N) active scales, and in the common situation where the Laplace transform F (s) (the transfer function

Tübingen, Universität

192

Multivariate Quadrature on Adaptive Sparse Grids  

Microsoft Academic Search

In this paper, we study the potential of adaptive sparse grids for multivariate numerical quadrature in the moderate or high dimensional case, i. e. for a number of dimensions beyond three and up to several hundreds. There, conventional methods typically suffer from the curse of dimension or are unsatisfactory with respect to accuracy. Our sparse grid approach, based upon a

Hans-joachim Bungartz; Stefan Dirnstorfer

2003-01-01

193

Programmable Active Inductor Based Quadrature VCO Design  

Microsoft Academic Search

This work proposes an inductor-less programmable quadrature VCO which adopts a modified grounded active inductor with a PMOS resistor in the feedback path. The model of the active inductor using PMOS resistor feedback is also presented in this work, which is more accurate than the previous models by considering the effect of the parasitic capacitance in the feedback path. The

Guochi Huang; Byung-Sung Kim

2007-01-01

194

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

195

Modulator-free quadrature amplitude modulation signal synthesis  

PubMed Central

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

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

2014-01-01

196

Achromatic deep nulling with a three-dimensional Sagnac interferometer.  

PubMed

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

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

2009-07-01

197

An IR spatial interferometer at 10 mum wavelength and measurement of stellar dust shells  

Microsoft Academic Search

The University of California Infrared Spatial Interferometer (ISI) for the 10 mum wavelength region is briefly described and results obtained on 13 prominent stars and on atmospheric phenomena are discussed. The interferometer has two movable telescopes of 1.65 m aperture and operates in principle like a modern radio interferometer, using heterodyne detection, CO2 laser local oscillators, RF delay lines, and

C. H. Townes; M. Bester; W. C. Danchi; C. G. Degiacomi; L. J. Greenhill

1994-01-01

198

Phase shifting interferometer  

DOEpatents

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

Sommargren, Gary E. (Santa Cruz, CA)

1999-01-01

199

Phase shifting interferometer  

DOEpatents

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

Sommargren, G.E.

1999-08-03

200

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

201

An automatic michelson interferometer with frince dropout correction  

Microsoft Academic Search

An automatic Michelson-type fringe counting interferometer (Lambda-meter) allowing for interpolation to 1\\/50 of a wavelength is described. The movable part of the interferometer consists of a carriage which slides on two polished steel bars and transports two corner cube retroreflectors. A missing-fringe digital control logic identifies and instantaneously corrects for laser interference fringe dropouts, caused by short-time laser light instabilities.

J. Kowalski; R. Neumann; S. Noehte; R. Schwarzwald; H. Suhr; G. Zu Putlitz

1985-01-01

202

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

E-print Network

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

Betzwieser, Joseph (Joseph Charles)

2008-01-01

203

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

SciTech Connect

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

Hori, Yasuaki; Hirai, Akiko; Minoshima, Kaoru

2011-03-10

204

Dispersion interferometer using modulation amplitudes on LHD (invited)  

SciTech Connect

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

Akiyama, T., E-mail: takiyama@lhd.nifs.ac.jp; Yasuhara, R.; Kawahata, K. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-shi, Gifu 509-5292 (Japan); Okajima, S.; Nakayama, K. [Chubu University, Matsumoto-cho, Kasugai-shi, Aichi 487-8501 (Japan)

2014-11-15

205

Optical displacement measurement with GaAs\\/AlGaAs-based monolithically integrated Michelson interferometers  

Microsoft Academic Search

Two monolithically integrated optical displacement sensors fabricated in the GaAs\\/AlGaAs material system are reported. These single-chip microsystems are configured as Michelson interferometers and comprise a distributed Bragg reflector (DBR) laser, photodetectors, phase shifters, and waveguide couplers. While the use of a single Michelson interferometer allows measurement of displacement magnitude only, a double Michelson interferometer with two interferometer signals in phase

Daniel Hofstetter; Hans P. Zappe; R. Dandliker

1997-01-01

206

Infrared Spatial Interferometer  

Microsoft Academic Search

THe IR Spatial Interferometer (ISI) is an interferometer installed on Mt. Wilson and operating in the 10 micrometers wavelength region, using heterodyne detection and two movable 1.65 m telescopes. Its general technology and characteristics, recent changes, and observational results are broadly discussed. Some compensation for atmospheric path length fluctuations is demonstrated. Stellar observations show, among other characteristics, that many stars

Charles H. Townes; Manfred Bester; William C. Danchi; D. D. Hale; John D. Monnier; Everett A. Lipman; Peter G. Tuthill; Mark A. Johnson; Donald L. Walters

1998-01-01

207

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

208

Monitoring the resonant properties of the magmatic structures of Elbrus volcano based on observation of lithospheric deformations by the Baksan laser interferometer - strainmeter  

NASA Astrophysics Data System (ADS)

The Elbrus volcanic center is located on the northern slope of the main ridge of the Greater Caucasus. It includes Mount Elbrus, a double-top stratovolcano, and a number of small volcanic centers concentrated on its western flank. According to present understandings, the Elbrus volcano falls into the category of the so-called dormant volcanoes that become reactivated. It is a typical volcano of a continental type. During a number of years to study magmatic structures of the Elbrus volcano, their resonant properties and dynamics the new resonant method has been used. The idea of method is simple enough. Magmatic structures, being a resonator, upon incidence of a broadband powerful seismic signal generate the secondary seismic waves, having a set of resonant modes and containing information about physical and mechanical properties of structure inhomogeneities. These resonant modes are determined by geometrical parameters and elastic properties of the magma chamber as well as by magma properties. Estimation of the resonant parameters is based on the analysis of lithosphere deformations recorded by the wide-band Baksan laser interferometer-strainmeter with a 75-m armlength which is installed in the underground tunnel of the Baksan Neutrino Observatory, 20 km apart from Mt. Elbrus. Here we report the analysis of the teleseismic signals excited by seven mean-power earthquakes (the magnitude, as a rule, didn't exceed 6), that occurred within 2005-2010 in so-called "a near zone» of the volcano Elbrus (<1500 km). The relative proximity of the earthquake focuses to the volcanic edifice creates the possibility to excite the eigen oscillations of the Elbrus resonant structures (magma chambers), at the same time, the energies of these moderate-power earthquakes are not enough to excite the free oscillations of the Earth. Spectral analysis revealed quite confidently 10 groups of resonance modes in the range of periods of 30 -150 s. In this group of the resonant modes, three modes are stand out with the periods of 62.1 s, 64.3 s, and 67.9 s, which are excited in 100% of seismic events. The intensities of these modes in the spectra are maximal, or close to the maximum. Estimates of Q-factor of the selected regional resonant modes lie in the range 250-300, that assumes that the revealed modes are generated by the structures containing magmatic fluids with a large gas component. The resonant parameters (frequencies and Q-factors of the resonant modes) we have found were interpreted in the framework of contemporary models of magma resonators. We estimated the depth and dimensions of the shallow magma chamber, as well as the properties of the magma fluid which are corroborated by available geological and geophysical evidence. Our interpretation of observational materials suggests that the intrachamber pressure seems to be rising owing to the advent of new portions of hot lava from a deep magma source. The stated approach provides a window to volcano dynamics and lays a foundation of the new "resonant" method for monitoring the state of volcano. This work is supported by the Russian Foundation for Basic Research.

Milyukov, V.; Myasnikov, A.

2012-04-01

209

An extrinsic fiber Fabry-Perot interferometer for dynamic displacement measurement  

NASA Astrophysics Data System (ADS)

A versatile fiber interferometer was proposed for high precision measurement. The sensor exploited a double-cavity within the unique sensing arm of an extrinsic-type fiber Fabry-Perot interferometer to produce the quadrature phase-shifted interference fringes. Interference signal processing was carried out using a modified zero-crossing (fringe) counting technique to demodulate two sets of fringes. The fiber interferometer has been successfully employed for dynamic displacement measurement under different displacement profiles over a range of 0.7 ?m to 140 ?m. A dedicated computer incorporating the demodulation algorithm was next used to interpret these detected data as well as plot the displacement information with a resolution of ?/64. A commercial displacement sensor was employed for comparison purposes with the experimental data obtained from the fiber interferometer as well as to gauge its performance, resulting in the maximum error of 2.8% over the entire displacement range studied.

Pullteap, S.; Seat, H. C.

2015-03-01

210

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

211

Aspheric Surfaces Centration (Rotary Scan Interferometer)  

NASA Astrophysics Data System (ADS)

Tilt and offset of aspheric surfaces are detected by a narrow aperture interferometer which performs a zonal rotary scan by means of a precise air-bearing spindle. Positioning of unknown aspheric surfaces with respect to machining or measuring apparatus requires centration of the samples (i.e. tilt and offset) and also longitudinal setting. The accuracy of the scanning interferometer is based on the precise axis of rotation of an Intop-Watt-type air-bearing spindle which steers the contactlessly probing laser interferometer beam on a conical path. Thus, a center and an axis of symmetry are defined. The system allows alignment of the aspheric surface and it also permits to detect coincidence between the scan-cone apex and the center of the sphere best fit to the zone being scanned.

Langenbeck, Peter

1981-05-01

212

Multi-probe system comprising three laser interferometers and one autocollimator for measuring flat bar mirror profile with nanometer accuracy on a high-precision micro-coordinate measuring machine  

NASA Astrophysics Data System (ADS)

We described a multi-probe system comprising three laser interferometers and one autocollimator to measure a flat bar mirror profile with nanometer accuracy. The simulation and pre-experiment of multi-probe system have been conducted on an X-Y linear stage which is composed of a ball bearing slider and a stepping motor. The two standard deviation of the flat bar mirror profile is mainly fitting the range of simulation results (+/-20 nm). Comparison of our measured data with the results measured by ZYGO white light interferometer system showed agreement to within approximately +/-30 nm, excluding some points at the edge of the mirror. From the pre-experiment results, we conclude that the systematic error caused by accuracy of the moving stage can't be ignored. To eliminate this systematic error, the multi-probe system has been implemented on a high-precision micro-coordinate measuring machine (M-CMM) that has been built at the Advanced Industrial Science and Technology (AIST).

Yang, Ping; Takamura, Tomohiko; Takahashi, Satoru; Takamasu, Kiyoshi; Sato, Osamu; Osawa, Sonko; Takatsuji, Toshiyuki

2011-08-01

213

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

214

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

215

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

216

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

217

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

218

Phase shifting diffraction interferometer  

DOEpatents

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

Sommargren, Gary E. (Santa Cruz, CA)

1996-01-01

219

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

220

Phase-visibility modulating interferometry by binary non-quadrature amplitude modulation with neutral density filters  

NASA Astrophysics Data System (ADS)

An alternative method for phase retrieval based on spatial and binary non-quadrature amplitude modulation (NQAM) is presented. This proposal is based on the superposition of a probe beam with a reference beam modulated in phase and amplitude (PAM) by NQAM, which is implemented by two neutral density filters (NDF) in a three-beam Mach-Zehnder interferometer (MZI). The principal advantage of this proposal lies in an analytical relationship between the variations of phase and visibility in an interferogram with the variations in the amplitudes of the reference beams used to implement NQAM; thus, the interferograms can be normalized and their introduced phase variations can be known from the measured intensities. Consequently it is possible to successfully retrieve the object phase. It is worthy to note that this method is capable of accepting that the phase and visibility variations in the interferograms could be spatial functions.

Rivera-Ortega, Uriel; Meneses-Fabian, Cruz; Rodriguez-Zurita, Gustavo; Robledo-Sanchez, Carlos

2014-04-01

221

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

PubMed

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

Wan, Xiaoke; Wang, Ji; Ge, Jian

2010-10-10

222

Application of Adaptive Quadrature to Axisymmetric Vortex Sheet Motion  

E-print Network

Application of Adaptive Quadrature to Axi­symmetric Vortex Sheet Motion Qing Nie Institute to treat. In this paper, we present an accurate adaptive quadrature to compute the motion of a vortex sheet in vortex sheet motion [7] or during the Rayleigh­Taylor instability [8]. The situation is very different

223

State reconstruction formulae for the S-distributions and quadratures  

NASA Astrophysics Data System (ADS)

We consider the method of infinite matrix inversion in the context of quantum state reconstruction. Using this method we give rigorous proofs for reconstruction formulae for the Cahill-Glauber s-parametrized distributions and the rotated quadrature distributions. We also demonstrate how to construct the s-distributions from the quadrature data.

Kiukas, Jukka; Pellonpää, Juha-Pekka; Schultz, Jussi

2010-08-01

224

Wideband digital Quadrature Transformation based on perfect reconstruction filter banks  

Microsoft Academic Search

Quadrature Transformation based on Hilbert transform method to wideband signal is not suited to engineering application because the group delay can make severe aliasing. Wideband digital quadrature transformation based on perfect reconstruction filter banks is put forward in this paper. The wideband signal is divided into sub-band signals by analysis filter bank, then let the negative parts of the output

Xiaohong Huang; Zhenmiao Deng

2011-01-01

225

Higher Order variance and Gauss Jacobi Quadrature : II Rene BLACHER  

E-print Network

of the first Gaussian component . . . . . . . . . . . . . . . . . . . 28 4.3.5 Estimation of the Other GaussianHigher Order variance and Gauss Jacobi Quadrature : II Ren´e BLACHER Laboratory LJK Universit the study of higher order variances and quadrature Gauss Jacobi. Recall that the variance of order j

Paris-Sud XI, Université de

226

A multivariate quadrature based moment method for supersonic combustion modeling  

E-print Network

A multivariate quadrature based moment method for supersonic combustion modeling Pratik Donde) of thermochemical variables can be used for accurately computing the combustion source term. Quadrature based- ture method of moments (DQMOM) is well suited for multivariate problems like combustion. Numerical

Raman, Venkat

227

ANTI-GAUSSIAN QUADRATURE FORMULAS DIRK P. LAURIE  

E-print Network

ANTI-GAUSSIAN QUADRATURE FORMULAS DIRK P. LAURIE Abstract. An anti-Gaussian quadrature formula is an (n + 1)-point formul* *a of de between the results obtained from the two formulas. We show t* *hat an anti- Gaussian formula has

Laurie, Dirk

228

State reconstruction formulas for the s-distributions and quadratures  

E-print Network

We consider the method of infinite matrix inversion in the context of quantum state reconstruction. Using this method we give rigorous proofs for reconstruction formulas for the Cahill-Glauber s-parametrized distributions and the rotated quadrature distributions. We also demonstrate how to construct the s-distributions from the quadrature data.

Jukka Kiukas; Juha-Pekka Pellonpää; Jussi Schultz

2009-09-18

229

An evaluation procedure for scanning interferometer based wavemeters  

NASA Astrophysics Data System (ADS)

A common approach to wavelength measurement is the travelling interferometer (wavemeter). We present an evaluation procedure that allows to achieve high precision with a compact device. The zero crossings of the interference signal corresponding to the reference laser is used to sample the signal of the probe laser. Electronic noise and fluctuations of the laser frequency cancel due to the large number of sample points. The evaluation procedure has been applied to a wavemeter based on a continuously moving Mach-Zehnder interferometer. A travelling path of 10 cm was sufficient to yield 3?-accuracy of ? ?/ ?=3.2×10 -9, demonstrated by comparison with cesium saturation spectroscopy.

Knaak, Kai-Martin; Götte, S.; Kluge, H.-J.; Ewald, G.; Wendt, K. D. A.

2004-02-01

230

On open electromagnetic resonators: relation between interferometers and resonators  

SciTech Connect

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

Manenkov, Aleksandr A; Bykov, Vladimir P; Kuleshov, N V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2010-05-26

231

Developmental testing of a prototype all-reflection Michelson interferometer  

Microsoft Academic Search

A prototype all-reflective Michelson interferometer is tested using visible laser, sodium, and mercury light sources. The design uses an off-axis parabolic mirror for collimation, a plane diffraction grating, and two plane mirrors to divide and recombine incident light. Interference fringes were seen using the laser light source, but instrument performance with other sources was unreliable as a result of difficulties

Allan D. Risley Jr.

1993-01-01

232

The May 1997 SOHO-Ulysses Quadrature  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

233

Noise cancellation properties of displacement noise free interferometer  

NASA Astrophysics Data System (ADS)

We have demonstrated the practical feasibility of a displacement- and frequency-noise-free laser interferometer (DFI) by partially implementing a recently proposed optical configuration using bi-directional Mach-Zehnder interferometers (MZIs). The noise cancellation efficiency was evaluated by comparing the displacement noise spectrum of the MZIs and the DFI, demonstrating up to 50 dB of noise cancellation. In addition, the possible extension of DFI as QND device is explored.

Sato, Shuichi; Kawamura, Seiji; Nishizawa, Atsushi; Chen, Yanbei

2010-05-01

234

Status and progress on the upgraded infrared spatial interferometer  

Microsoft Academic Search

The U.C. Berkeley Infrared Spatial Interferometer is a two telescope stellar interferometer operating in the 9-12 micron atmospheric window, utilizing heterodyne detection with CO2 laser local oscillators. Science with the ISI has been focused on the measurements of the spatial distribution of dust and molecules around mass-losing late type stars, and more recently precision measurements of stellar diameters in the

William C. Danchi; Charles H. Townes; Walter Fitelson; David D. S. Hale; John D. Monnier; Samuel Tevosjan; Jonathon Weiner

2003-01-01

235

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

236

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

237

Ultrasonic Interferometers Revisited  

ERIC Educational Resources Information Center

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

Greenslade, Thomas B., Jr.

2007-01-01

238

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

239

Noncritical quadrature squeezing through spontaneous polarization symmetry breaking.  

PubMed

We discuss the possibility of generating noncritical quadrature squeezing by spontaneous polarization symmetry breaking. We first consider Type II frequency-degenerate optical parametric oscillators but discard them for a number of reasons. Then we propose a four-wave-mixing cavity, in which the polarization of the output mode is always linear but has an arbitrary orientation. We show that in such a cavity, complete noise suppression in a quadrature of the output field occurs, irrespective of the parameter values. PMID:20596191

Garcia-Ferrer, Ferran V; Navarrete-Benlloch, Carlos; de Valcárcel, Germán J; Roldán, Eugenio

2010-07-01

240

Noncritical quadrature squeezing through spontaneous polarization symmetry breaking  

E-print Network

We discuss the possibility of generating noncritical quadrature squeezing by spontaneous polarization symmetry breaking. We consider first type-II frequency-degenerate optical parametric oscillators, but discard them for a number of reasons. Then we propose a four-wave mixing cavity in which the polarization of the output mode is always linear but has an arbitrary orientation. We show that in such a cavity complete noise suppression in a quadrature of the output field occurs, irrespective of the parameter values.

Garcia-Ferrer, Ferran V; de Valcárcel, Germán J; Roldán, Eugenio

2010-01-01

241

Noncritical quadrature squeezing through spontaneous polarization symmetry breaking  

E-print Network

We discuss the possibility of generating noncritical quadrature squeezing by spontaneous polarization symmetry breaking. We consider first type-II frequency-degenerate optical parametric oscillators, but discard them for a number of reasons. Then we propose a four-wave mixing cavity in which the polarization of the output mode is always linear but has an arbitrary orientation. We show that in such a cavity complete noise suppression in a quadrature of the output field occurs, irrespective of the parameter values.

Ferran V. Garcia-Ferrer; Carlos Navarrete-Benlloch; Germán J. de Valcárcel; Eugenio Roldán

2010-03-12

242

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

243

Nd:YAG holographic interferometer for aerodynamic research  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

244

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

245

Design and fabrication of a high-damage threshold infrared Smattt interferometer  

SciTech Connect

It has been shown that a Smartt interferometer may be used as a very precise alignment tool for infrared lasers. This interferometer may also be used effectively to investigate the phase front of a laser pulse. To use this tool for applications to high-power, fast-pulse laser systems such as Helios and Antares; however, it has been necessary to fabricate a structure with the unique optical characteristics of the Smartt interferometer combined with a very high optical-damage threshold. We have been successful in this effort by utilizing the high technology, process control, and unique properties of semiconductor-grade, single-crystal Si.

Hammond, R.B.; Gibbs, A.J.

1981-01-01

246

Searching for gravitational waves with a geostationary interferometer  

NASA Astrophysics Data System (ADS)

We analyze the sensitivities of a geostationary gravitational wave interferometer mission operating in the sub-Hertz band. Because of its smaller armlength, in the lower part of its accessible frequency band (10-4-2×10-2 Hz) our proposed Earth-orbiting detector will be less sensitive, by a factor of about seventy, than the Laser Interferometer Space Antenna (LISA) mission. In the higher part of its band instead (2×10-2-10 Hz), our proposed interferometer will have the capability of observing super-massive black holes (SMBHs) with masses smaller than ˜106 M?. With good event rates for these systems, a geostationary interferometer will be able to accurately probe the astrophysical scenarios that account for their formation.

Tinto, Massimo; de Araujo, Jose C. N.; Aguiar, Odylio D.; Alves, Márcio E. S.

2013-08-01

247

Sensitivity curves for spaceborne gravitational wave interferometers  

E-print Network

To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted (after averaging over source position and polarization) by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first (mostly) analytic calculation of the gravitational wave transfer function is presented. Example sensitivity curve calculations are presented for the proposed LISA interferometer. We find that previous treatments of LISA have underestimated its sensitivity by a factor of $\\sqrt{3}$.

Shane L. Larson; William A. Hiscock; Ronald W. Hellings

2000-01-10

248

A continuous cold atomic beam interferometer  

NASA Astrophysics Data System (ADS)

We demonstrate an atom interferometer that uses a laser-cooled continuous beam of 87Rb atoms having velocities of 10-20 m/s. With spatially separated Raman beams to coherently manipulate the atomic wave packets, Mach-Zehnder interference fringes are observed at an interference distance of 2L = 19 mm. The apparatus operates within a small enclosed area of 0.07 mm2 at a bandwidth of 190 Hz with a deduced sensitivity of 7.8 × 10 - 5 rad / s / ?{ Hz } for rotations. Using a low-velocity continuous atomic source in an atom interferometer enables high sampling rates and bandwidths without sacrificing sensitivity and compactness, which are important for applications in real dynamic environments.

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

2015-03-01

249

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

250

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

251

One-element interferometer  

NASA Astrophysics Data System (ADS)

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

Balasubramanyam, Ramesh

2014-11-01

252

Optical and Infrared Interferometers  

NASA Astrophysics Data System (ADS)

Stellar interferometers achieve limiting angular resolution inaccessible to evennext-generation single-aperture telescopes. Arrays of small or modest apertureshave achieved baselines exceeding 300 m producing submilliarcsecond resolutionsat visible and near-infrared wavelengths. The technical cost and challenge inbuilding interferometric arrays is substantial due to the very high toleranceimposed by optical physics on the precision of beam combination and optical pathlength matching for two or more telescopes. This chapter presents the basic theoryand overall design considerations for an interferometer with an emphasis on thepractical aspects of constructing a working instrument that overcomes obstaclesimposed by the atmosphere, submicron path length matching requirements,limitations on number of telescopes and their layout, light losses throughmultiple reflections and transmissions necessary to superimpose telescopebeams in the beam-combining laboratory, and other realities of the art ofinterferometry. The basic design considerations for an interferometer arelaid out starting with site selection and telescope placement and thenfollowed through to beam combination and measurement of interferometricvisibility and closure phase after the encountering of numerous subsystems byincoming wavefronts. These subsystems include active wavefront sensing fortip/tilt correction or even full-up adaptive optics, telescope design fordirecting collimated beams over large distances, diffraction losses, polarizationmatching, optical path length insertion and active compensation, correctionfor atmospheric refraction and differential dispersion in glass and air,separation of light into visible and near-infrared channels, alignment over longoptical paths, high-precision definition of the three-dimensional layout of aninterferometric array, and, finally, a variety of beam-combining schemes fromsimple two-way combiners to multitelescope imaging combiners in thepupil and image planes. Much has been learned from a modest but robustcollection of successful interferometers over the last 25 years or so, andinterferometry is poised to become a mainstream technique for astrophysicalresearch.

ten Brummelaar, Theo A.; McAlister, Harold A.

253

Interferometer density measurements of a high-velocity plasmoid  

SciTech Connect

The plasmoid produced by a half-scale contoured gap coaxial plasma accelerator using ablative polyethylene capillary plasma injectors is measured using a quadrature heterodyne HeNe interferometer. The plasmoid is found to have a sharp rise in density at the leading edge, with a gradual falloff after the peak density. For this early test series, an average bulk density of 5x10{sup 14} cm{sup -3} is observed, with densities up to 8x10{sup 14} cm{sup -3} seen on some shots. Although plasmoid mass is only about 58 mug due to the low current and injected mass used in these tests, good shot-to-shot repeatability is attained making analysis relatively straightforward, thus providing a solid foundation for interpreting future experimental results.

Case, A.; Messer, S.; Bomgardner, R.; Witherspoon, F. D. [HyperV Technologies Corp., Chantilly, Virginia 20151 (United States)

2010-05-15

254

High-speed three-wave polarimeter-interferometer diagnostic for Madison symmetric torus  

E-print Network

developed on the Madison symmetric torus reversed field pinch to provide simultaneous measurement infrared FIR laser interferometry and polarimetry have been successfully used to diagnose reversed field, simultaneous interferometer and polar- imeter measurements are necessary to accurately assess plasma

Wisconsin at Madison, University of

255

Gauss Quadratures - the Keystone of Lattice Boltzmann Models  

NASA Astrophysics Data System (ADS)

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

Piaud, Benjamin; Blanco, Stéphane; Fournier, Richard; Ambru?, Victor Eugen; Sofonea, Victor

2014-01-01

256

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

257

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

258

Discrete Ordinate Quadrature Selection for Reactor-based Eigenvalue Problems  

SciTech Connect

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

Jarrell, Joshua J [ORNL; Evans, Thomas M [ORNL; Davidson, Gregory G [ORNL

2013-01-01

259

Vibration analysis of structural elements using differential quadrature method  

PubMed Central

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

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

2012-01-01

260

On spectral quadrature for linear-scaling Density Functional Theory  

NASA Astrophysics Data System (ADS)

We provide a unified description of the Fermi operator expansion and recursion methods within the technique of spectral quadrature. Through rigorous error estimates, we prove that this approach is linear-scaling, stable and exponentially convergent. We use this analysis to determine the influence of smearing, band-gap, position of Fermi energy, and spectral width of the Hamiltonian on the convergence rates obtained in practical calculations. Additionally, we establish that super-geometric convergence can be achieved when the erfc function is used for smearing. We validate the spectral quadrature method and the accuracy of our analysis by means of selected examples.

Suryanarayana, Phanish

2013-10-01

261

Rational choices for the wavelengths of a two color interferometer  

SciTech Connect

If in a two color interferometer for plasma density measurements, the two wavelengths are chosen to have a ratio that is a rational number, and if the signals from each of the wavelengths are multiplied in frequency by the appropriate integer of the rational number and then heterodyned together, the resultant signal will have all effects of component motion nulled out. A phase measurement of this signal will have only plasma density information in it. With CO{sub 2} lasers, it is possible to find suitable wavelength pairs which are close enough to rational numbers to produce an improvement of about 100 in density resolution, compared to standard two color interferometers.

Jobes, F.C.

1995-07-01

262

Multidimensional velocity estimation with ultrasound using spatial quadrature  

Microsoft Academic Search

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

M. E. Aderson

1998-01-01

263

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

264

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

265

Heterodyne imaging speckle interferometer  

NASA Astrophysics Data System (ADS)

A heterodyne imaging speckle interferometer coupled with lithium niobate is developed for whole field dynamic deformation imaging. In this device, the carrier frequency is introduced by the dual-transverse linear electro-optic effect. It is electrically controlled within a large range, which is twice the angular velocity of the driving alternating electric fields. By setting the angular velocity, the carrier frequency can fit most of area-array detectors, making it feasible to achieve whole field real time imaging. By using temporal evolution of the light intensity in heterodyne interferometry, the temporal intensity analysis method is employed to extract the deformation at each pixel dynamically. The principle and system configuration are described. The preliminary experiment is conducted with a cantilever beam and the results are compared with theoretical simulations to validate the proposed approach.

Wang, Shengjia; Gao, Zhan; Feng, Ziang; Zhang, Xiaoqiong; Yang, Dong; Yuan, Hao

2015-03-01

266

Solar viewing interferometer prototype  

NASA Astrophysics Data System (ADS)

The Earth Atmospheric Solar-Occultation Imager (EASI) is a proposed interferometer with 5 telescopes on an 8-meter boom in a 1D Fizeau configuration. Placed at the Earth-Sun L2 Lagrange point, EASI would perform absorption spectroscopy of the Earth"s atmosphere occulting the Sun. Fizeau interferometers give spatial resolution comparable to a filled aperture but lower collecting area. Even with the small collecting area the high solar flux requires most of the energy to be reflected back to space. EASI will require closed loop control of the optics to compensate for spacecraft and instrument motions, thermal and structural transients and pointing jitter. The Solar Viewing Interferometry Prototype (SVIP) is a prototype ground instrument to study the needed wavefront control methods. SVIP consists of three 10 cm aperture telescopes, in a linear configuration, on a 1.2-meter boom that will estimate atmospheric abundances of O2, H2O, CO2, and CH4 versus altitude and azimuth in the 1.25 - 1.73 micron band. SVIP measures the Greenhouse Gas absorption while looking at the sun, and uses solar granulation to deduce piston, tip and tilt misalignments from atmospheric turbulence and the instrument structure. Tip/tilt sensors determine relative/absolute telescope pointing and operate from 0.43 - 0.48 microns to maximize contrast. Two piston sensors, using a robust variation of dispersed fringes, determine piston shifts between the baselines and operate from 0.5 - 0.73 microns. All sensors are sampled at 800 Hz and processed with a DSP computer and fed back at 200 Hz (3 dB) to the active optics. A 4 Hz error signal is also fed back to the tracking platform. Optical performance will be maintained to better than ?/8 rms in closed-loop.

Lyon, Richard G.; Herman, Jay R.; Abuhassan, Nader; Marx, Catherine T.; Kizhner, Semion; Crooke, Julie; Toland, Ronald W.; Mariano, Albert; Salerno, Cheryl; Brown, Gary; Cazeau, Tony; Petrone, Peter P., III; Mamakos, Billy; Tournois, Severine C.

2004-10-01

267

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

268

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

269

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

270

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

271

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

272

Design of a dual species atom interferometer for space  

E-print Network

Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth's gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species $^{85}$Rb/$^{87}$Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry...

Schuldt, Thilo; Krutzik, Markus; Bote, Lluis Gesa; Gaaloul, Naceur; Hartwig, Jonas; Ahlers, Holger; Herr, Waldemar; Posso-Trujillo, Katerine; Rudolph, Jan; Seidel, Stephan; Wendrich, Thijs; Ertmer, Wolfgang; Herrmann, Sven; Kubelka-Lange, André; Milke, Alexander; Rievers, Benny; Rocco, Emanuele; Hinton, Andrew; Bongs, Kai; Oswald, Markus; Franz, Matthias; Hauth, Matthias; Peters, Achim; Bawamia, Ahmad; Wicht, Andreas; Battelier, Baptiste; Bertoldi, Andrea; Bouyer, Philippe; Landragin, Arnaud; Massonnet, Didier; Lévèque, Thomas; Wenzlawski, Andre; Hellmig, Ortwin; Windpassinger, Patrick; Sengstock, Klaus; von Klitzing, Wolf; Chaloner, Chris; Summers, David; Ireland, Philip; Mateos, Ignacio; Sopuerta, Carlos F; Sorrentino, Fiodor; Tino, Guglielmo M; Williams, Michael; Trenkel, Christian; Gerardi, Domenico; Chwalla, Michael; Burkhardt, Johannes; Johann, Ulrich; Heske, Astrid; Wille, Eric; Gehler, Martin; Cacciapuoti, Luigi; Gürlebeck, Norman; Braxmaier, Claus; Rasel, Ernst

2014-01-01

273

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

274

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

275

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

276

A robust sinusoidal signal processing method for interferometers  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

277

Direct sampling of a smoothed Wigner function from quadrature distributions  

NASA Astrophysics Data System (ADS)

We propose the reconstruction of a smoothed Wigner function from quadrature distributions instead of the Wigner function itself to avoid the problems with the inverse Radon transformation. Starting from the well known relation between s-parametrized quasiprobability distributions W(x,p,s) and quadrature component distributions w(xicons/Journals/Common/Theta" ALT="Theta" ALIGN="MIDDLE"/>,icons/Journals/Common/Theta" ALT="Theta" ALIGN="TOP"/>), we show that the sampling function needed to determine a smoothed Wigner function W(x,p,-|s|) is basically a shifted and scaled version of the well known pattern function necessary to reconstruct the probability of finding no photon in the signal field. An analogous result has been recently found in the literature. Here we obtain this result in a very concise and alternative way.

Richter, Th

1999-12-01

278

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

279

On Gauss-Kronrod quadrature formulae of Chebyshev type  

NASA Astrophysics Data System (ADS)

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

Notaris, Sotirios E.

1992-04-01

280

Michelson Interferometer (MINT)  

NASA Technical Reports Server (NTRS)

MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.

Lacis, Andrew; Carlson, Barbara

1993-01-01

281

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

282

Wide-Band Low-Noise Quadrature VCO Design  

Microsoft Academic Search

A 2.9 GHz quadrature VCO designed in a 0.18 um CMOS process achieves a very wide tuning range of 77% when the supply voltage equals 1.8 V. The phase noise is -120 dB\\/Hz at 1MHz offset for the oscillation frequency of 2 GHz, and -104 dB\\/Hz at 1MHz offset for the oscillation frequency of 4 GHz. The coupled oscillator architecture

Yong-hong Yan; Yan Xie; Wei Peng; Yun Zeng

2008-01-01

283

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

284

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

285

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

286

Development of an Interferometer Diagnostic for the Spheromak Turbulent Physics Experiment (STPX)  

NASA Astrophysics Data System (ADS)

Laser interferometry is a proven method for measuring electron density in fusion plasmas. Typically, far-infrared interferometers are used because of the large phase shift due to the change in the index of refraction of the plasma and their relative insensitivity to vibrations. A two-color (CO2: ?=10.6 ?m, HeNe: ?=633 nm) interferometer has been designed for installation on STPX. The interferometer is a Mach-Zehnder configuration with a single-chord, double pass probe beam. The laser beams copropagate along a 10-meter path for vibration subtraction along with frequency modulation for heterodyne detection. Detection is carried out using a HgCdTe photoconductor for the CO2 and a Si APD for the HeNe. The capabilities and challenges with the installation of the interferometer on STPX will be discussed.

Clark, Jerry; Titus, J.; Alexander, A. B.; Mezonlin, E. D.

2012-10-01

287

Advanced quadratures and periodic boundary conditions in parallel 3D S{sub n} transport  

SciTech Connect

Significant updates in numerical quadratures have warranted investigation with 3D Sn discrete ordinates transport. We show new applications of quadrature departing from level symmetric (S{sub 2}o). investigating 3 recently developed quadratures: Even-Odd (EO), Linear-Discontinuous Finite Element - Surface Area (LDFE-SA), and the non-symmetric Icosahedral Quadrature (IC). We discuss implementation changes to 3D Sn codes (applied to Hybrid MOC-Sn TITAN and 3D parallel PENTRAN) that can be performed to accommodate Icosahedral Quadrature, as this quadrature is not 90-degree rotation invariant. In particular, as demonstrated using PENTRAN, the properties of Icosahedral Quadrature are suitable for trivial application using periodic BCs versus that of reflective BCs. In addition to implementing periodic BCs for 3D Sn PENTRAN, we implemented a technique termed 'angular re-sweep' which properly conditions periodic BCs for outer eigenvalue iterative loop convergence. As demonstrated by two simple transport problems (3-group fixed source and 3-group reflected/periodic eigenvalue pin cell), we remark that all of the quadratures we investigated are generally superior to level symmetric quadrature, with Icosahedral Quadrature performing the most efficiently for problems tested. (authors)

Manalo, K.; Yi, C.; Huang, M.; Sjoden, G. [Nuclear and Radiological Engineering Program, G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 770 State Street, Atlanta, GA 30332-0745 (United States)

2013-07-01

288

Achieving resonance in the Advanced LIGO gravitational-wave interferometer  

NASA Astrophysics Data System (ADS)

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

Staley, A.; Martynov, D.; Abbott, R.; Adhikari, R. X.; Arai, K.; Ballmer, S.; Barsotti, L.; Brooks, A. F.; DeRosa, R. T.; Dwyer, S.; Effler, A.; Evans, M.; Fritschel, P.; Frolov, V. V.; Gray, C.; Guido, C. J.; Gustafson, R.; Heintze, M.; Hoak, D.; Izumi, K.; Kawabe, K.; King, E. J.; Kissel, J. S.; Kokeyama, K.; Landry, M.; McClelland, D. E.; Miller, J.; Mullavey, A.; O'Reilly, B.; Rollins, J. G.; Sanders, J. R.; Schofield, R. M. S.; Sigg, D.; Slagmolen, B. J. J.; Smith-Lefebvre, N. D.; Vajente, G.; Ward, R. L.; Wipf, C.

2014-12-01

289

Lateral shearing interferometer for measuring photoinduced refractive index change in As(2)S(3).  

PubMed

We have built and demonstrated a lateral shearing interferometer as a process engineering and control tool for the fabrication and characterization of direct-laser-written waveguide structures in chalcogenide glasses. Photoinduced change in refractive index of 0.154+/-0.002 was measured for as-deposited amorphous As(2)S(3) thin films at 633 nm with an estimated measurement uncertainty of 1.3% for this air-gap interferometer configuration. The simple design of this interferometer can easily be adapted to other wavelengths including mid- and long-wave infrared regions to measure changes in refractive index or material inhomogeneities in transmissive materials. PMID:19044448

Krishnaswami, Kannan; Bernacki, Bruce E; Hô, Nicolas; Allen, Paul J; Anheier, Norman C

2008-09-01

290

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

291

Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics  

NASA Technical Reports Server (NTRS)

The initial focus of this project was to eliminate both of these problems in the Liquid Crystal Point-Diffraction Interferometer (LCPDI). Progress toward that goal will be described, along with the demonstration of a phase shifting Liquid Crystal Shearing Interferometer (LCSI) that was developed as part of this work. The latest LCPDI, other than a lens to focus the light from a test section onto a diffracting microsphere within the interferometer and a collimated laser for illumination, the pink region contained within the glass plates on the rod-mounted platform is the complete interferometer. The total width is approximately 1.5 inches with 0.25 inches on each side for bonding the electrical leads. It is 1 inch high and there are only four diffracting microspheres within the interferometer. As a result, it is very easy to align, achieving the first goal. The liquid crystal electro-optical response time is a function of layer thickness, with thinner devices switching faster due to a reduction in long-range viscoelastic forces between the LC molecules. The LCPDI has a liquid crystal layer thickness of 10 microns, which is controlled by plastic or glass microspheres embedded in epoxy 'pads' at the corners of the device. The diffracting spheres are composed of polystyrene/divinyl benzene polymer with an initial diameter of 15 microns. The spheres deform slightly when the interferometer is assembled to conform to the spacing produced by the microsphere-filled epoxy spacer pads. While the speed of this interferometer has not yet been tested, previous LCPDIs fabricated at the Laboratory for Laser Energetics switched at a rate of approximately 3.3 Hz, a factor of 10 slower than desired. We anticipate better performance when the speed of these interferometers is tested since they are approximately three times thinner. Phase shifting in these devices is a function of the AC voltage level applied to the liquid crystal. As the voltage increases, the dye in the liquid crystal tends to become more transparent, thus introducing a rather large amount of error into the phase-shifting measurement. While that error can be greatly reduced by normalization, we prefer eliminating the source of the error. To that end, we have pursued development of a 'blend' of custom dyes that will not exhibit these properties. That goal has not yet been fully achieved. Guardalben, et al, presented a similar set of interferograms in a paper partially funded by this grant. Shearing interferometers are a second class of common path interferometers. Typically they consist of a thick glass plate optimized for equal reflection from the front and back surface. While not part of the original thrust of the project, through the course of laboratory work, we demonstrated a prototype of a shearing interferometer capable of phase shifting using a commercial liquid crystal retardation plate. A schematic of this liquid crystal shearing interferometer (LCSI) and a sample set of interferograms are in the reference. This work was also supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. Additional information is included in the original extended abstract.

Griffin, DeVon W.; Marshall, Keneth L.

2002-01-01

292

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

SciTech Connect

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

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

2012-06-15

293

Fiber optic two-color vibration compensated interferometer for plasma density measurements  

Microsoft Academic Search

A fiber optic, heterodyne, two-color interferometer utilizing wavelength division multiplexing technology has been developed for measuring electron density in plasmas. Vibration compensation is accomplished via common path 1.31 and 1.55 mum distributed feedback laser interferometers. All beam combining, splitting, frequency modulation, and collimation are accomplished by shared single-mode fiber optic components. Measurements of an argon radio-frequency generated plasma with electron

M. A. van Zeeland; R. L. Boivin; T. N. Carlstrom; T. Deterly; D. K. Finkenthal

2006-01-01

294

Fiber optic two-color vibration compensated interferometer for plasma density measurements  

Microsoft Academic Search

A fiber optic, heterodyne, two-color interferometer utilizing wavelength division multiplexing technology has been developed for measuring electron density in plasmas. Vibration compensation is accomplished via common path 1.31 and 1.55 ?m distributed feedback laser interferometers. All beam combining, splitting, frequency modulation, and collimation are accomplished by shared single-mode fiber optic components. Measurements of an argon radio-frequency generated plasma with electron

M. A. Van Zeeland; R. L. Boivin; T. N. Carlstrom; T. Deterly; D. K. Finkenthal

2006-01-01

295

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

296

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

E-print Network

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

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

2005-10-27

297

Topological phase shift in a cold-atom interferometer  

Microsoft Academic Search

Matter-wave interferences in a four-pulse version of a Ramsey-Bordé atom interferometer have been utilized to study phase shifts. A topological phase shift analogous to the scalar Aharonov-Bohm effect proposed for charged-particle interferences in the presence of a pulsed electrostatic potential has been investigated. The time-dependent potential has been generated by the interaction of a laser field with an induced atomic

J. H. Müller; D. Bettermann; V. Rieger; K. Sengstock; U. Sterr; W. Ertmer

1995-01-01

298

Mach-Zehnder interferometer for movement monitoring  

NASA Astrophysics Data System (ADS)

Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons around the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 kHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and the gained spectra at repeated drops of balls were compared. Those stroked upon the same place and from the same elevation and dispersion of the obtained frequency spectra was evaluated. These experiments were performed on the series of 20 repeated drops from highs of 0,5 and 1m. The evaluation of experiments displayed that the dispersion of measured values is lower than 4%. Frequency response has been verified with the loudspeaker connected to signal generator and amplifier. Various slabs have been measured and frequency ranges were compared for particular slab designs.

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

2012-06-01

299

Improving the performances of current optical interferometers & future designs  

NASA Astrophysics Data System (ADS)

The number of astrophysical studies making use of interferometers has steadily increased during the past 15 years. Nevertheless, the performances of interferometers are still limited: their sensitivity does not exceed magnitude V=12, and their imaging capability could yet be improved by increasing the number of telescopes/sub-apertures. In the context of the ELTs, it is not certain how future interferometry projects will be financed. However, interferometry remains the only way to observe compact astrophysical objects at very high angular resolution (< milli-arcsecond), like gravitational micro-lensing events, central engines of AGNs, proto-planetary disks, exoplanets, etc. The aim of this workshop was to review and discuss the development of technologies that could improve the performances of current and future interferometers: new optical designs; techniques to improve the accuracy of measurements (visibility, closure-phase, etc.); progress on delay-line performances; solutions without delay-lines; technologies for larger apertures at lower cost (ex: lightweight replica mirrors); optimized beam combiners (integrated optic, pupil densifier, etc.); fringe tracking systems; laser telemetry applied to interferometry; heterodyne interferometry; progress in heterodyne detection using new technologies (laser comb, time propagation technologies, etc.); progress in image reconstruction techniques; progress in nulling interferometry; and important science cases that could benefit from progress in interferometry (report of observations at the limit of current interferometers). Nearly 50 oral presentations have been delivered, followed by very lively discussions which eventually emerged with the proposition to organize the "Planet Formation Interferometer/Imager" (PFI) project. The present proceedings reflect most of the highlights of this international colloquium.

Arnold, L.; Le Coroller, H.; Surdej, J.

2014-04-01

300

LISA Interferometer Test Bench at UF  

NASA Astrophysics Data System (ADS)

LISA, a joint NASA/ESA space mission to detect gravitational waves in the 10-4 to 10-1 Hz frequency band, is scheduled to launch in 2015. LISA will consist of three spacecraft in a heliocentric orbit forming a triangle with a 5 Gm baseline. In order to detect gravitational waves, LISA will use laser interferometry to measure changes in spacecraft separations with pm accuracy. The interferometer signals will be dominated by laser frequency noise. The dominant laser frequency noise will be subtracted from the data stream by post-processing the data using time delay interferometry (TDI). This algorithm relies on a strong correlation between all LISA signals taken at different times and different spacecraft as well as on very low noise and large dynamic range phase meters and on accurate timing information. At the University of Florida, we are developing an experimental LISA simulator to test implementations of various aspects of LISA interferometry and TDI. Realistic light travel times between the spacecraft are simulated using an electronic phase delay technique. In this paper we will present preliminary results of an experimental implementation of TDI to test LISA-like signals in the laboratory. This work is supported by NASA grant BEFS04-0019-0019.

Reddy Guntaka, Sridhar; Cruz, Rachel J.; Ira Thorpe, J.; Hartman, Michael; Tanner, David B.; Mueller, Guido

2006-04-01

301

Novel spectral imaging method for Fizeau interferometer  

NASA Astrophysics Data System (ADS)

There are two different types of beam combination: Fizeau interferometer and Michelson interferometer. Pupil plane beam combination is referred as Fizeau interferometer. On the other hand, image plane beam combination is referred as Michelson interferometer. In general, working principles of Michelson interferometers are based on double Fourier interferometry. It is possible to acquire two-dimensional spatial and one-dimensional spectral information of the sky by applying a Fourier transform spectrometer algorithm and the Van Cittert-Zernike theorem. This imaging scheme is referred to as the double Fourier interferometry. On the other hand, it is so far thought to be difficult to perform the imaging with a Fizeau interferometer, because Fizeau interferometers basically don't have a delay line that is equipped with Michelson interferometers. Here, Matsuo et al.1 presented a new spectral imaging method for Fizeau interferometers, based on double Fourier interferometry. They noticed that a delay axis in Michelson interferometers is equal to the axis of a fringe pattern on an image plane in Fizeau interferometers. Therefore, this new approach can acquire three-dimensional information of the sky using a linear array detector placed on the image plane. In this paper, we compare the new spectral imaging method for Fizeau interferometer with the conventional one used for Michelson interferometer and discuss spectral resolutions and field of views of these imaging methods.

Matsuo, Taro; Shibai, H.; Kawada, M.; Hattori, M.; Ohta, S. I.; Matsuo, H.

2008-07-01

302

Optomechanical cooling with generalized interferometers.  

PubMed

The fields in multiple-pass interferometers, such as the Fabry-Pérot cavity, exhibit great sensitivity not only to the presence but also to the motion of any scattering object within the optical path. We consider the general case of an interferometer comprising an arbitrary configuration of generic beam splitters and calculate the velocity-dependent radiation field and the light force exerted on a moving scatterer. We find that a simple configuration, in which the scatterer interacts with an optical resonator from which it is spatially separated, can enhance the optomechanical friction by several orders of magnitude. PMID:20867443

Xuereb, André; Freegarde, Tim; Horak, Peter; Domokos, Peter

2010-07-01

303

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

304

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

305

Enhanced 16 Spiral quadrature amplitude modulation scheme for coherent optical orthogonal frequency division multiplexing systems  

NASA Astrophysics Data System (ADS)

We propose an enhanced 16 Spiral quadrature amplitude modulation (QAM) (16 E-Spiral QAM) scheme to overcome the laser phase noise in a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Considering both additive white Gaussian noise and large phase noise, 16 E-Spiral QAM schemes have a better transmission performance compared to conventional 16 QAM CO-OFDM systems. The simulated results show that the required optical signal-to-noise ratio (OSNR) of the proposed 16 QAM is, respectively, 0.8 and 2.3 dB less than 16 Spiral and conventional 16 QAM at a bit error rate (BER) of 10-3 in a back-to-back case. After 800-km transmission over a single-mode fiber, the tolerance for the laser linewidth of the 16 E-Spiral QAM can improve about 30 kHz with an OSNR of 18 dB compared to that of a conventional 16 QAM.

He, Jing; Li, Chong; Chen, Lin; Chen, Ming

2014-09-01

306

Optical arbitrary waveform characterization via dual-quadrature spectral interferometry.  

PubMed

We introduce the use of dual-quadrature spectral interferometry for amplitude and phase characterization of 100% duty factor optical arbitrary waveforms generated via spectral line-by-line pulse shaping. We demonstrate this technique for measurement of optical arbitrary waveforms composed of approximately 30 spectral lines from a 10 GHz frequency comb with 1.4 micros data acquisition time at an average power level of 10 microwatts. We then demonstrate coherent spectral phase measurements of pulses strongly dispersed by propagation over 50 km of optical fiber. PMID:19129869

Supradeepa, V R; Leaird, Daniel E; Weiner, Andrew M

2009-01-01

307

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

308

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

309

A compact high-sensitivity heterodyne interferometer for industrial metrology  

NASA Astrophysics Data System (ADS)

For translation and tilt metrology, we developed a compact fiber-coupled polarizing heterodyne interferometer which is based on a highly symmetric design where both, measurement and reference beam have similar optical pathlengths and the same frequency and polarization. The method of differential wavefront sensing is implemented for tilt measurement. With this setup we reached noise levels below 5 pm/square root of Hz; Hz in translation and below 10 nrad/square root of Hz; in tilt measurement, both for frequencies above 10-2 Hz. While this setup is developed with respect to the requirements of the LISA (Laser Interferometer Space Antenna) space mission, we here present the current status of its adoption to industrial applications. We currently design a very compact and quasi-monolithic setup of the interferometer sensor head based on ultra-low expansion glass material. The resulting compact and robust sensor head can be used for nano-positioning control. We also plan to implement a scan of the measurement beam over the surface under investigation enabling high resolution 3D profilometry and surface property measurements (i. e. roughness, evenness and roundness). The dedicated low-noise (<=1nm/square root of Hz) piezo-electric actuator in the measurement beam of the interferometer will be realized using integrated micro-system technology and can either be implemented in one or two dimensions.

Schuldt, Thilo; Gohlke, Martin; Weise, Dennis; Peters, Achim; Johann, Ulrich; Braxmaier, Claus

2008-04-01

310

A heterodyne interferometer for high-performance industrial metrology  

NASA Astrophysics Data System (ADS)

We developed a compact, fiber-coupled heterodyne interferometer for translation and tilt metrology. Noise levels below 5 pm/?Hz in translation and below 10 nrad/?Hz in tilt measurement, both for frequencies above 10-2 Hz, were demonstrated in lab experiments. While this setup was developed with respect to the LISA (Laser Interferometer Space Antenna) space mission current activities focus on its adaptation for dimensional characterization of ultra-stable materials and industrial metrology. The interferometer is used in high-accuracy dilatometry measuring the coefficient of thermal expansion (CTE) of dimensionally highly stable materials such as carbon-fiber reinforced plastic (CFRP) and Zerodur. The facility offers the possibility to measure the CTE with an accuracy better 10-8/K. We also develop a very compact and quasi-monolithic sensor head utilizing ultra-low expansion glass material which is the basis for a future space-qualifiable interferometer setup and serves as a prototype for a sensor head used in industrial environment. For high resolution 3D profilometry and surface property measurements (i. e. roughness, evenness and roundness), a low-noise (<=1nm/? Hz) actuator will be implemented which enables a scan of the measurement beam over the surface under investigation.

Schuldt, Thilo; Gohlke, Martin; Weise, Dennis; Johann, Ulrich; Peters, Achim; Braxmaier, Claus

2008-11-01

311

Analyzing algorithms for nonlinear and spatially nonuniform phase shifts in the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports  

SciTech Connect

Phase-shifting interferometry has many advantages, and the phase shifting nature of the Liquid Crystal Point Diffraction Interferometer (LCPDI) promises to provide significant improvement over other current OMEGA wavefront sensors. However, while phase-shifting capabilities improve its accuracy as an interferometer, phase-shifting itself introduces errors. Phase-shifting algorithms are designed to eliminate certain types of phase-shift errors, and it is important to chose an algorithm that is best suited for use with the LCPDI. Using polarization microscopy, the authors have observed a correlation between LC alignment around the microsphere and fringe behavior. After designing a procedure to compare phase-shifting algorithms, they were able to predict the accuracy of two particular algorithms through computer modeling of device-specific phase shift-errors.

Jain, N. [Pittsford Sutherland High School, NY (United States)

1999-03-01

312

Keck Interferometer Science: Present and Future  

Microsoft Academic Search

The Keck Interferometer is a NASA funded project developed by the Jet Propulsion Laboratory, the William M. Keck Observatory and the Michelson Science Center at the California Institute of Technology. A technical description of the interferometer is given elsewhere in this volume1. This paper will discuss the science topics and goals ofthe Keck Interferometer project, including a brief description of

Rachel Akeson

313

The magnesium ramsey interferometer: Applications and prospects  

Microsoft Academic Search

In this paper it will be shown that an atom interferometer, based on the coherent splitting of the atomic wavefunction by four travelling waves (Ramsey interferometer), may be explained by a purely mechanical interpretation. As our first application of this Ramsey interferometer we have measured the phase shifts respectively optical length changes in a magnesium atomic beam caused by the

U. Sterr; K. Sengstock; J. H. Müller; D. Bettermann; W. Ertmer

1992-01-01

314

Design of a dual species atom interferometer for space  

NASA Astrophysics Data System (ADS)

Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth's gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species 85Rb/87Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry, the detection unit, the vacuum system for 10-11 mbar ultra-high vacuum generation, and the high-suppression factor magnetic shielding as well as the thermal control system. The laser system is based on a hybrid approach using fiber-based telecom components and high-power laser diode technology and includes all laser sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and switching of the laser beams is carried out on an optical bench using Zerodur bonding technology. The instrument consists of 9 units with an overall mass of 221 kg, an average power consumption of 608 W (814 W peak), and a volume of 470 liters which would well fit on a satellite to be launched with a Soyuz rocket, as system studies have shown.

Schuldt, Thilo; Schubert, Christian; Krutzik, Markus; Bote, Lluis Gesa; Gaaloul, Naceur; Hartwig, Jonas; Ahlers, Holger; Herr, Waldemar; Posso-Trujillo, Katerine; Rudolph, Jan; Seidel, Stephan; Wendrich, Thijs; Ertmer, Wolfgang; Herrmann, Sven; Kubelka-Lange, André; Milke, Alexander; Rievers, Benny; Rocco, Emanuele; Hinton, Andrew; Bongs, Kai; Oswald, Markus; Franz, Matthias; Hauth, Matthias; Peters, Achim; Bawamia, Ahmad; Wicht, Andreas; Battelier, Baptiste; Bertoldi, Andrea; Bouyer, Philippe; Landragin, Arnaud; Massonnet, Didier; Lévèque, Thomas; Wenzlawski, Andre; Hellmig, Ortwin; Windpassinger, Patrick; Sengstock, Klaus; von Klitzing, Wolf; Chaloner, Chris; Summers, David; Ireland, Philip; Mateos, Ignacio; Sopuerta, Carlos F.; Sorrentino, Fiodor; Tino, Guglielmo M.; Williams, Michael; Trenkel, Christian; Gerardi, Domenico; Chwalla, Michael; Burkhardt, Johannes; Johann, Ulrich; Heske, Astrid; Wille, Eric; Gehler, Martin; Cacciapuoti, Luigi; Gürlebeck, Norman; Braxmaier, Claus; Rasel, Ernst

2015-03-01

315

Design of a dual species atom interferometer for space  

E-print Network

Atom interferometers have a multitude of proposed applications in space including precise measurements of the Earth's gravitational field, in navigation & ranging, and in fundamental physics such as tests of the weak equivalence principle (WEP) and gravitational wave detection. While atom interferometers are realized routinely in ground-based laboratories, current efforts aim at the development of a space compatible design optimized with respect to dimensions, weight, power consumption, mechanical robustness and radiation hardness. In this paper, we present a design of a high-sensitivity differential dual species $^{85}$Rb/$^{87}$Rb atom interferometer for space, including physics package, laser system, electronics and software. The physics package comprises the atom source consisting of dispensers and a 2D magneto-optical trap (MOT), the science chamber with a 3D-MOT, a magnetic trap based on an atom chip and an optical dipole trap (ODT) used for Bose-Einstein condensate (BEC) creation and interferometry, the detection unit, the vacuum system for $10^{-11}$ mbar ultra-high vacuum generation, and the high-suppression factor magnetic shielding as well as the thermal control system. The laser system is based on a hybrid approach using fiber-based telecom components and high-power laser diode technology and includes all laser sources for 2D-MOT, 3D-MOT, ODT, interferometry and detection. Manipulation and switching of the laser beams is carried out on an optical bench using Zerodur bonding technology. The instrument consists of 9 units with an overall mass of 221 kg, an average power consumption of 608 W (819 W peak), and a volume of 470 liters which would well fit on a satellite to be launched with a Soyuz rocket, as system studies have shown.

Thilo Schuldt; Christian Schubert; Markus Krutzik; Lluis Gesa Bote; Naceur Gaaloul; Jonas Hartwig; Holger Ahlers; Waldemar Herr; Katerine Posso-Trujillo; Jan Rudolph; Stephan Seidel; Thijs Wendrich; Wolfgang Ertmer; Sven Herrmann; André Kubelka-Lange; Alexander Milke; Benny Rievers; Emanuele Rocco; Andrew Hinton; Kai Bongs; Markus Oswald; Matthias Franz; Matthias Hauth; Achim Peters; Ahmad Bawamia; Andreas Wicht; Baptiste Battelier; Andrea Bertoldi; Philippe Bouyer; Arnaud Landragin; Didier Massonnet; Thomas Lévèque; Andre Wenzlawski; Ortwin Hellmig; Patrick Windpassinger; Klaus Sengstock; Wolf von Klitzing; Chris Chaloner; David Summers; Philip Ireland; Ignacio Mateos; Carlos F. Sopuerta; Fiodor Sorrentino; Guglielmo M. Tino; Michael Williams; Christian Trenkel; Domenico Gerardi; Michael Chwalla; Johannes Burkhardt; Ulrich Johann; Astrid Heske; Eric Wille; Martin Gehler; Luigi Cacciapuoti; Norman Gürlebeck; Claus Braxmaier; Ernst Rasel

2014-12-08

316

Angle interferometer cross axis errors  

Microsoft Academic Search

Angle interferometers are commonly used to measure surface plate flatness. An error can exist when the centerline of the double comer cube mirror assembly is not square to the surface plate and the guide bar for the mirror sled is curved. Typical errors can be one to two microns per meter. A similar error can exist in the calibration of

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

1994-01-01

317

Quadrature imposition of compatibility conditions in Chebyshev methods  

NASA Technical Reports Server (NTRS)

Often, in solving an elliptic equation with Neumann boundary conditions, a compatibility condition has to be imposed for well-posedness. This condition involves integrals of the forcing function. When pseudospectral Chebyshev methods are used to discretize the partial differential equation, these integrals have to be approximated by an appropriate quadrature formula. The Gauss-Chebyshev (or any variant of it, like the Gauss-Lobatto) formula can not be used here since the integrals under consideration do not include the weight function. A natural candidate to be used in approximating the integrals is the Clenshaw-Curtis formula, however it is shown that this is the wrong choice and it may lead to divergence if time dependent methods are used to march the solution to steady state. The correct quadrature formula is developed for these problems. This formula takes into account the degree of the polynomials involved. It is shown that this formula leads to a well conditioned Chebyshev approximation to the differential equations and that the compatibility condition is automatically satisfied.

Gottlieb, D.; Streett, C. L.

1990-01-01

318

Fast convolution quadrature for the wave equation in three dimensions  

NASA Astrophysics Data System (ADS)

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

Banjai, L.; Kachanovska, M.

2014-12-01

319

Achromatic three-wave lateral shearing interferometer for wavefront analysis and correction  

NASA Astrophysics Data System (ADS)

After six years of existence, Achromatic Three-Wave Lateral Shearing Interferometer (ATWLSI) is currently in use in wave-front analysis of high-intensity ultra-short laser pulses. The purpose of this paper is to compare ATWLSI to the well-known Hartmann-Shack wave-front sensor (HSWFS) for different generic applications: optical testing, atmospheric turbulence and ultra-short laser pulses analysis and correction. This qualitative comparison is made on the basis of a description of HSWFS, seen as a lateral shearing interferometer.

Primot, Jerome; Guerineau, Nicolas

1999-08-01

320

Single mode double Michelson-type laser cavity resonator  

SciTech Connect

A cavity resonator arrangement for a single mode laser is disclosed. A double Michelson interferometer is substituted for one of the mirrors of a conventional Fabry-Perot interferometer. The positions of the three mirrors of this double Michelson interferometer are positioned with respect to the mirror limiting the cavity resonator through dc controlled piezoelectric shims.

Aminoff, C.; Laloe, F.; Pinard, M.; Trenec, G.

1981-09-22

321

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

E-print Network

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

Adhikari, Rana, 1974-

2004-01-01

322

Application of Adaptive Quadrature to Axi-symmetric Vortex Sheet Motion  

E-print Network

Application of Adaptive Quadrature to Axi-symmetric Vortex Sheet Motion Qing Nie Institute to treat. In this paper, we present an accurate adaptive quadrature to compute the motion of a vortex sheet in vortex sheet motion [7] or during the Rayleigh-Taylor instability [8]. The situation is very dierent

323

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

324

Arctangent Demodulation With DC Offset Compensation in Quadrature Doppler Radar Receiver Systems  

Microsoft Academic Search

Direct-conversion microwave Doppler radar can be used to detect cardiopulmonary activity at a distance. One challenge for such detection in single channel receivers is demodulation sensitivity to target position, which can be overcome by using a quadrature receiver. This paper presents a mathematical analysis and experimental results demonstrating the effectiveness of arctangent demodulation in quadrature receivers. A particular challenge in

Byung-Kwon Park; Olga Boric-Lubecke; Victor M. Lubecke

2007-01-01

325

A Numerical quadrature for the Schwarz-Chimera J. -B. Apoung Kamga1  

E-print Network

A Numerical quadrature for the Schwarz-Chimera Method J. -B. Apoung Kamga1 and Olivier Pironneau2 1 Curie Olivier.Pironneau@upmc.fr Abstract Chimera [10] happens to be a version of Schwarz' method fvih, (8) #12;A Numerical quadrature for the Schwarz-Chimera Method 3 Theorem 2. (see Hecht et al. [4

Pironneau, Olivier

326

Fringe Measurement and Control for the Keck Interferometer  

NASA Astrophysics Data System (ADS)

The paper describes the measurement and control algorithms of the near-infrared fringe trackers of the Keck Interferometer (KI). The fringe trackers provide fringe amplitude measurements for visibility science, and feedback and feedforward signals for fringe tracking and cophasing, respectively. Fringe measurement uses temporal path length modulation with synchronous array readout, and implements bias corrections of both the quadratures and the fringe power to provide high accuracy. The KI implementation uses sliding-window estimation to reduce control latency, and implements signal-to-noise (S/N) estimators that minimize biases from intensity scintillation. An inner-loop/outer-loop controller is used for ordinary fringe tracking, and a discrete-unwrapping controller is used for cophasing. A robust algorithm is used to estimate the slowly-varying dispersion to provide a target for the discrete-unwrapping controller and to estimate water-vapor seeing. The cophasing system is optimized for low control latency, and includes active control of narrowband disturbances. Measurements of the feedback and feedforward transfer functions as implemented are consistent with the predictions of a controls model; on-sky performance data are also presented.

Colavita, M. M.; Booth, A. J.; Garcia-Gathright, J. I.; Vasisht, G.; Johnson, R. L.; Summers, K. R.

2010-07-01

327

Self-induced diffraction patterns in nonlinear Fabry-Perot interferometer on lithium niobate  

NASA Astrophysics Data System (ADS)

The effects of self-action of light fields within Fabry-Perot interferometers based on photorefractive lithium niobate plates both, of X- and Z- cuts are experimentally investigated. Formation of one-dimensional practically regular diffractive elements within the interferometers with slightly non-parallel input and output surfaces has been demonstrated at laser light wavelength of 532 nm. It has been found that these diffractive elements are formed due to the photorefractive response of the crystal to the steady-state optical interference patterns appeared within the interferometer at multiple reflections of light beam. From the Raman-Nath far field diffraction patterns the ordinary refractive index change within the interferometer on Z-cut crystal has been estimated.

Shandarov, V.; Perin, A.; Ryabchenok, V.

2015-03-01

328

Multi-channel far-infrared HL-2A interferometer-polarimeter.  

PubMed

An HL-2A interferometer is upgraded to a multi-channel interferometer?polarimeter, which includes four chords for the interferometer and four chords for the polarimeter. The far-infrared lasers (at ? = 432.5 ?m and 30 mW power) are used to probe plasmas horizontally in the midplane of HL-2A. A conventional heterodyne technique is used for the interferometer. Two counter-rotating circularly polarized waves are used to measure the Faraday rotation effect. A fast-phase comparator with temporal resolution of 1 ?s and phase resolution 0.1° is developed. Further, the distortion of the polarization caused by the beam-splitters and the other optical components is also investigated. PMID:23126994

Zhou, Y; Deng, Z C; Li, Y G; Yi, J

2012-10-01

329

Development of a multichannel dispersion interferometer at TEXTOR  

SciTech Connect

The design and main characteristics of 14-channel dispersion interferometer for plasma profile measurement and control in TEXTOR tokamak are presented. The diagnostic is engineered on the basis of modular concept, the 10.6 {mu}m CO{sub 2} laser source and all optical and mechanical elements of each module are arranged in a compact housing. A set of mirrors and retroreflectors inside the TEXTOR vacuum vessel provides full coverage of the torus cross section with 12 vertical and two diagonal lines of sight, no rigid frame for vibration isolation is required. Results of testing of the single-channel prototype diagnostic and the pilot module of the multichannel dispersion interferometer are presented.

Lizunov, A.; Bagryansky, P.; Khilchenko, A.; Kovalenko, Yu. V.; Solomakhin, A. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation); Biel, W.; Lambertz, H. T.; Krasikov, Yu.; Mitri, M.; Schweer, B. [Forschungszentrum Juelich GmbH, Association EURATOM-FZ Juelich, Institut fuer Plasmaphysik, Trilateral Euregio Cluster, 52425 Juelich (Germany); Dreier, H. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany)

2008-10-15

330

A Fiber Interferometer for the Magnetized Shock Experiment  

SciTech Connect

The Magnetized Shock Experiment (MSX) at Los Alamos National Laboratory requires remote diagnostics of plasma density. Laser interferometry can be used to determine the line-integrated density of the plasma. A multi-chord heterodyne fiber optic Mach-Zehnder interferometer is being assembled and integrated into the experiment. The advantage of the fiber coupling is that many different view chords can be easily obtained by simply moving transmit and receive fiber couplers. Several such fiber sets will be implemented to provide a time history of line-averaged density for several chords at once. The multiple chord data can then be Abel inverted to provide radially resolved spatial profiles of density. We describe the design and execution of this multiple fiber interferometer.

Yoo, Christian [Los Alamos National Laboratory

2012-08-30

331

Tunable semiconductor lasers  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

332

Astrophysical Adaptation of Points, the Precision Optical Interferometer in Space  

NASA Technical Reports Server (NTRS)

POINTS (Precision Optical INTerferometer in Space) would perform microarcsecond optical astrometric measurements from space, yielding submicroarcsecond astrometric results from the mission. It comprises a pair of independent Michelson stellar interferometers and a laser metrology system that measures both the critical starlight paths and the angle between the baselines. The instrument has two baselines of 2 m, each with two subapertures of 35 cm; by articulating the angle between the baselines, it observes targets separated by 87 to 93 deg. POINTS does global astrometry, i.e., it measures widely separated targets, which yields closure calibration, numerous bright reference stars, and absolute parallax. Simplicity, stability, and the mitigation of systematic error are the central design themes. The instrument has only three moving-part mechanisms, and only one of these must move with sub-milliradian precision; the other two can tolerate a precision of several tenths of a degree. Optical surfaces preceding the beamsplitter or its fold flat are interferometrically critical; on each side of the interferometer, there are only three such. Thus, light loss and wavefront distortion are minimized. POINTS represents a minimalistic design developed ab initio for space. Since it is intended for astrometry, and therefore does not require the u-v-plane coverage of an imaging, instrument, each interferometer need have only two subapertures. The design relies on articulation of the angle between the interferometers and body pointing to select targets; the observations are restricted to the 'instrument plane.' That plane, which is fixed in the pointed instrument, is defined by the sensitive direction for the two interferometers. Thus, there is no need for siderostats and moving delay lines, which would have added many precision mechanisms with rolling and sliding parts that would be required to function throughout the mission. Further, there is no need for a third interferometer, as is required when out-of-plane observations are made. An instrument for astrometry, unlike those for imaging, can be compact and yet scientifically productive. The POINTS instrument is compact and therefore requires no deployment of precision structures, has no low-frequency (i.e., under 100 Hz) vibration modes, and is relatively easy to control thermally. Because of its small size and mass, it is easily and quickly repointed between observations. Further, because of the low mass, it can be economically launched into high Earth orbit which, in conjunction with a solar shield, yields nearly unrestricted sky coverage and a stable thermal environment.

Reasenberg, Robert D.; Babcock, Robert W.; Murison, Marc A.; Noecker, M. Charles; Phillips, James D.; Schumaker, Bonny L.; Ulvestad, James S.; McKinley, William; Zielinski, Robert J.; Lillie, Charles F.

1996-01-01

333

Stellar Interferometer Technology Experiment (SITE)  

NASA Technical Reports Server (NTRS)

The MIT Space Engineering Research Center and the Jet Propulsion Laboratory stand ready to advance science sensor technology for discrete-aperture astronomical instruments such as space-based optical interferometers. The objective of the Stellar Interferometer Technology Experiment (SITE) is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled-Structures Technologies (CST). SITE mounts to the Mission Peculiar Experiment Support System inside the Shuttle payload bay. Starlight, entering through two apertures, is steered to a combining plate where it is interferred. Interference requires 27 nanometer pathlength (phasing) and 0.29 archsecond wavefront-tilt (pointing) control. The resulting 15 milli-archsecond angular resolution exceeds that of current earth-orbiting telescopes while maintaining low cost by exploiting active optics and structural control technologies. With these technologies, unforeseen and time-varying disturbances can be rejected while relaxing reliance on ground alignment and calibration. SITE will reduce the risk and cost of advanced optical space systems by validating critical technologies in their operational environment. Moreover, these technologies are directly applicable to commercially driven applications such as precision matching, optical scanning, and vibration and noise control systems for the aerospace, medical, and automotive sectors. The SITE team consists of experienced university, government, and industry researchers, scientists, and engineers with extensive expertise in optical interferometry, nano-precision opto-mechanical control and spaceflight experimentation. The experience exists and the technology is mature. SITE will validate these technologies on a functioning interferometer science sensor in order to confirm definitely their readiness to be baselined for future science missions.

Crawley, Edward F.; Miller, David; Laskin, Robert; Shao, Michael

1995-01-01

334

Portable Doppler interferometer system for shock diagnostics and high speed motion  

SciTech Connect

VISAR (Velocity Interferometer System for Any Reflector) is a system that uses the Doppler effect and is widely used for measuring the velocity of projectiles, detonations, flying plates, shock pressures (particle velocity) and other high speed/high acceleration motion. Other methods of measurement such as accelerometers and pressure gauges have disadvantages in that they are sensitive to radiation, electromagnetic pulses, and their mass can drastically alter the velocity of the projectile. VISAR uses single frequency-single mode laser fight focused onto a target of interest. Reflected fight from the target is collected and sent through a modified, unequal leg Michelson interferometer. In the interferometer the light is split into two components which travel through the legs of the interferometer cavity and are then recombined. When the light recombines, an interference pattern is created which can range from dark (destructive interference) to bright (constructive interference). When the target moves, the reflected laser light experiences a frequency shift (increase) with respect to the frequency from the target in a static condition. Since the Doppler shifted light is split and routed through an unequal leg interferometer cavity, there is a time lag of the light containing the Doppler information at the recombination point in the interferometer. The effect of the time lag is to create a sinusoidally changing interference pattern (commonly called fringes). Since the interferometer time delay, laser wavelength, and the speed of light are known, an accurate measurement of target velocity/acceleration may be measured by analyzing both the number of tinges and the speed of tinge generation (system accuracy is 3--4%).

Fleming, K.J.; Crump, O.B. Jr.

1994-05-01

335

Polarized-interferometer feasibility study  

NASA Technical Reports Server (NTRS)

The feasibility of using a polarized-interferometer system as a rendezvous and docking sensor for two cooperating spacecraft was studied. The polarized interferometer is a radio frequency system for long range, real time determination of relative position and attitude. Range is determined by round trip signal timing. Direction is determined by radio interferometry. Relative roll is determined from signal polarization. Each spacecraft is equipped with a transponder and an antenna array. The antenna arrays consist of four crossed dipoles that can transmit or receive either circularly or linearly polarized signals. The active spacecraft is equipped with a sophisticated transponder and makes all measurements. The transponder on the passive spacecraft is a relatively simple repeater. An initialization algorithm is developed to estimate position and attitude without any a priori information. A tracking algorithm based upon minimum variance linear estimators is also developed. Techniques to simplify the transponder on the passive spacecraft are investigated and a suitable configuration is determined. A multiple carrier CW signal format is selected. The dependence of range accuracy and ambiguity resolution error probability are derived and used to design a candidate system. The validity of the design and the feasibility of the polarized interferometer concept are verified by simulation.

Raab, F. H.

1983-01-01

336

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

337

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

NASA Technical Reports Server (NTRS)

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

Smith, J. G.

1974-01-01

338

Analysis and applications of quadrature hybrids as RF circulators  

SciTech Connect

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

Hanna, S.M.; Keane, J.

1993-12-31

339

Quadrature formula for evaluating left bounded Hadamard type hypersingular integrals  

NASA Astrophysics Data System (ADS)

Left semi-bounded Hadamard type Hypersingular integral (HSI) of the form H(h,x) = 1/? ?{1+x/1-x }?-1 **1?{1-t/1+t }h(t)/(t-x)2 dt,x?(-1.1), Where h(t) is a smooth function is considered. The automatic quadrature scheme (AQS) is constructed by approximating the density function h(t) by the truncated Chebyshev polynomials of the fourth kind. Numerical results revealed that the proposed AQS is highly accurate when h(t) is choosing to be the polynomial and rational functions. The results are in line with the theoretical findings.

Bichi, Sirajo Lawan; Eshkuvatov, Z. K.; Nik Long, N. M. A.; Okhunov, Abdurahim

2014-12-01

340

Residual Distribution Schemes for Conservation Laws Via Adaptive Quadrature  

NASA Technical Reports Server (NTRS)

This paper considers a family of nonconservative numerical discretizations for conservation laws which retains the correct weak solution behavior in the limit of mesh refinement whenever sufficient order numerical quadrature is used. Our analysis of 2-D discretizations in nonconservative form follows the 1-D analysis of Hou and Le Floch. For a specific family of nonconservative discretizations, it is shown under mild assumptions that the error arising from non-conservation is strictly smaller than the discretization error in the scheme. In the limit of mesh refinement under the same assumptions, solutions are shown to satisfy an entropy inequality. Using results from this analysis, a variant of the "N" (Narrow) residual distribution scheme of van der Weide and Deconinck is developed for first-order systems of conservation laws. The modified form of the N-scheme supplants the usual exact single-state mean-value linearization of flux divergence, typically used for the Euler equations of gasdynamics, by an equivalent integral form on simplex interiors. This integral form is then numerically approximated using an adaptive quadrature procedure. This renders the scheme nonconservative in the sense described earlier so that correct weak solutions are still obtained in the limit of mesh refinement. Consequently, we then show that the modified form of the N-scheme can be easily applied to general (non-simplicial) element shapes and general systems of first-order conservation laws equipped with an entropy inequality where exact mean-value linearization of the flux divergence is not readily obtained, e.g. magnetohydrodynamics, the Euler equations with certain forms of chemistry, etc. Numerical examples of subsonic, transonic and supersonic flows containing discontinuities together with multi-level mesh refinement are provided to verify the analysis.

Barth, Timothy; Abgrall, Remi; Biegel, Bryan (Technical Monitor)

2000-01-01

341

Configurations of a new atomic interferometer for gravitational wave detection  

E-print Network

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

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

2013-12-30

342

A nonlocal polarization interferometer for entanglement detection  

E-print Network

We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the anti-diagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization entangled source. Correlations between these interferometers exhibit non-local interference, while single photon interference is suppressed. This interferometer also allows for a unique version of the CHSH-Bell test where the local reality is the photon polarization. We present the relevant theory and experimental results.

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

2014-10-22

343

Nonlocal polarization interferometer for entanglement detection  

NASA Astrophysics Data System (ADS)

We report a nonlocal interferometer capable of detecting entanglement and identifying Bell states statistically. This is possible due to the interferometer's unique correlation dependence on the antidiagonal elements of the density matrix, which have distinct bounds for separable states and unique values for the four Bell states. The interferometer consists of two spatially separated balanced Mach-Zehnder or Sagnac interferometers that share a polarization-entangled source. Correlations between these interferometers exhibit nonlocal interference, while single-photon interference is suppressed. This interferometer also allows for a unique version of the Clauser-Horne-Shimony-Holt-Bell test where the local reality is the photon polarization. We present the relevant theory and experimental results.

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

2014-10-01

344

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

Microsoft Academic Search

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

Alvarado Tarun; Julius Jecong; Caesar Saloma

2005-01-01

345

Fizeau interferometer for measurement of plasma electron current D. L. Brower,a)  

E-print Network

-interferometer system is currently used on the Madison symmetric torus (MST) reversed-field pinch (RFP) to measure measurement of the phase shift between two collinear, orthogonally polarized, counterpropagating laser beams On the Madison symmetric torus (MST) reversed-field pinch (RFP), a multichannel, vertically viewing, far

Wisconsin at Madison, University of

346

Diffraction phases in atom interferometers M. Buchner, R. Delhuille, A. Miffre, C. Robilliard, and J. Vigue*  

E-print Network

Diffraction phases in atom interferometers M. Bu¨chner, R. Delhuille, A. Miffre, C. Robilliard November 2002; published 16 July 2003 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

Paris-Sud XI, Université de

347

Development of a FIR interferometer for ATF: Part II—System design  

Microsoft Academic Search

Because of the highly elliptical cross section of the Advanced Toroidal Facility (ATF) plasma, a large number of interferometer channels are required to determine the radial density profile by Abel inversion. A 15-channel system is being developed using a single fan-shaped beam through the plasma and observing the phase shift across the profile with a 15-element detector array. The laser

W. H. Casson; D. P. Hutchinson

1986-01-01

348

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

ERIC Educational Resources Information Center

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

Rudmin, J. W.; And Others

1980-01-01

349

Programs for computing abscissas and weights for classical and nonclassical Gaussian quadrature formulas  

NASA Technical Reports Server (NTRS)

Computer programs for computing Gaussian quadrature abscissas and weights are described. For the classical case the programs use Laguerre iteration to compute abscissas as zeros of orthogonal polynomials. The polynomials are evaluated from known recursion coefficients. The nonclassical case is handled similarly except that the recursion coefficients are computed by numerical integration. A sample problem, with input and output, is presented to illustrate the use of the programs. It computes the quadrature abscissas and weights associated with the weight function over the interval (0,1) for quadrature orders from 16 to 96 in increments of 8.

Desmarais, R. N.

1975-01-01

350

Multidimensional Hermite-Gaussian quadrature formulae and their application to nonlinear estimation  

NASA Technical Reports Server (NTRS)

A simplified technique is proposed for calculating multidimensional Hermite-Gaussian quadratures that involves taking the square root of a matrix by the Cholesky algorithm rather than computation of the eigenvectors of the matrix. Ways of reducing the dimension, number, and order of the quadratures are set forth. If the function f(x) under the integral sign is not well approximated by a low-order algebraic expression, the order of the quadrature may be reduced by factoring f(x) into an expression that is nearly algebraic and one that is Gaussian.

Mcreynolds, S. R.

1975-01-01

351

Hand held phase-shifting diffraction Moire interferometer  

DOEpatents

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

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

1994-09-20

352

Hand held phase-shifting diffraction moire interferometer  

DOEpatents

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

Deason, Vance A. (Idaho Falls, ID); Ward, Michael B. (Idaho Falls, ID)

1994-01-01

353

LVDT calibration using a phase modulation optical interferometer calibrated by an x-ray interferometer  

NASA Astrophysics Data System (ADS)

We have calibrated an LVDT using an optical and x-ray interferometer. We have calibrated optical interferometer using x-ray interferometer. The LVDT has calibrated by the optical interferometer. We made the monolithic x-ray interferometer with a double parallel spring structure for the translation of an analyzer lamella. One period of the x-ray interference fringe corresponds to the lattice parameter, 0.192 nm. The nonlinearity of optical interferometer has been calibrated by an x-ray interferometer. We have used a phase modulation optical interferometer. This calibration using the x-ray interferometer is directly traceable to primary standards. We have achieved the resolution of an x-ray interferometer and optical interferometer better than 0.01 nm. The optical phase stability of the interferometer is less than +/- 150 pm. For the control of environmental temperature, we have used PID method. PID controller controlled the temperature inside chamber. Temperature drift was less than +/- 3 mK (k = 2).

Park, Jin Won; Jo, Jae Gun; Byun, Sang Ho; Kim, Jeong Eun; Eom, Cheon Il

2004-08-01

354

Ordinary SQUID interferometers and superfluid helium matter wave interferometers: The role of quantum fluctuations  

SciTech Connect

When comparing the operation of a superfluid helium matter wave quantum interferometer (He SQUID) with that of an ordinary direct-current quantum interferometer (dc SQUID), we estimate their resolution limitation that correspond to quantum fluctuations. An alternative mode of operation of the interferometer as a unified macroquantum system is considered.

Golovashkin, A. I.; Zherikhina, L. N., E-mail: zherikh@sci.lebedev.ru; Tskhovrebov, A. M. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Izmailov, G. N.; Ozolin, V. V. [Moscow Aviation Institute (State Technical University) (Russian Federation)

2010-08-15

355

Integrated Optical Interferometers with Micromachined Diaphragms for Pressure Sensing  

NASA Technical Reports Server (NTRS)

Optical pressure sensors have been fabricated which use an integrated optical channel waveguide that is part of an interferometer to measure the pressure-induced strain in a micromachined silicon diaphragm. A silicon substrate is etched from the back of the wafer leaving a rectangular diaphragm. On the opposite side of the wafer, ring resonator and Mach-Zehnder interferometers are formed with optical channel waveguides made from a low pressure chemical vapor deposited film of silicon oxynitride. The interferometer's phase is altered by pressure-induced stress in a channel segment positioned over the long edge of the diaphragm. The phase change in the ring resonator is monitored using a link-insensitive swept frequency laser diode, while in the Mach-Zehnder it is determined using a broad band super luminescent diode with subsequent wavelength separation. The ring resonator was found to be highly temperature sensitive, while the Mach-Zehnder, which had a smaller optical path length difference, was proportionally less so. The quasi-TM mode was more sensitive to pressure, in accord with calculations. Waveguide and sensor theory, sensitivity calculations, a fabrication sequence, and experimental results are presented.

DeBrabander, Gregory N.; Boyd, Joseph T.

1996-01-01

356

Cherenkov parametric optical oscillations in a ''double'' Fabry--Perot interferometer  

SciTech Connect

Attention is drawn to the possibility of generating Cherenkov optical parametric oscillations with a tunable frequency in a ''double'' Fabry--Perot interferometer placed inside a laser resonator. A theory of such oscillations is given. Expressions are obtained for steady-state radiation intensities and for the efficiency of conversion of laser radiation into a coupled parametric oscillation mode. The high (of the order of unity) efficiency and the low threshold of parametric oscillations (corresponding to a laser output power of the order of 10/sup -4/ W) should make it possible to use low-power cw lasers as pump sources.

Lugovoi, V.N.

1982-08-01

357

Solar CIV Vacuum-Ultraviolet Fabry-Perot Interferometers  

NASA Technical Reports Server (NTRS)

Aims: A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (PPI) is designed for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155 nm). Methods: The integral part of the CIV narrow passband filter package (with a 2-10 pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157 nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The static interferometer of the filter is envisioned as being hudt using a set of fixed MgF2 plates. The four-mirror prefilter is designed to have dielectric multilayer n-stacks employing the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2 pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Results. Spectro-polarimetry observations of the transition region CIV emission can be performed to increase the understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where most of the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Designs of multiple VUV FPIs can be developed for integration into future orbiting solar observatories to obtain rapid cadence, spectral imaging of the transition region.

Gary, G. Allen; West, Edward A.; Rees, David; McKay, Jack A.; Zukic, Maumer; Herman, Peter

2006-01-01

358

Variable path cryogenic acoustic interferometer  

NASA Astrophysics Data System (ADS)

We describe a variable path acoustic interferometer for use at cryogenic temperatures. Movement is enabled without mechanical coupling via two piezoelectric bimorphs wired and mounted in a manner that preserves the parallelism of two ultrasonic transducers that define the acoustic path. A certain degree of in situ alignment can also be accomplished. Path length sweeps from 0 to 180 ?m have been made at cryogenic temperatures and preliminary sound velocity measurements in liquid 4He and gaseous 3He near 4 K are presented which agree well with past measurements.

Kucera, D. M.; Ketterson, J. B.

1998-12-01

359

A high sensitivity heterodyne interferometer as optical readout for the LISA inertial sensor  

NASA Astrophysics Data System (ADS)

The ESA/NASA joint space mission LISA (Laser Interferometer Space Antenna), which is planned to be launched around 2015, aims at detecting gravitational waves in the frequency band 3*10-5 Hz to 1 Hz. It consists of three satellites which form an equilateral triangle in space, representing a Michelson-interferometer with an armlength of ~ 5 million kilometer. The end mirrors of the interferometer are realized by free flying proof masses. In the current baseline design--the so-called "strap-down" architecture--the laser light coming from the distant spacecraft is not reflected by the proof mass, but the beat signal with the local oscillator is measured on the optical bench. In addition, the distance between optical bench and its associated proof mass has to be measured with the same sensitivity as in the distant spacecraft interferometer, i. e. below 10 pm/sqrt(Hz) for the translation measurement (for frequencies above 2.8*10-3 Hz with an f-2 relaxation down to 3*10-5 Hz) and below 20 nrad/sqrt(Hz) for the tilt measurement (for frequencies above 10-4 Hz with an f-1 relaxation down to 3*10-5 Hz). Here, we present a compact setup of a heterodyne interferometer which serves as a demonstrator for an optical readout for the LISA proof mass position. We measured initial noise levels below 1 nm/sqrt(Hz) and 1 urad/sqrt(Hz), respectively, for frequencies > 10-3 Hz.

Schuldt, Thilo; Kraus, Hans-Jürgen; Weise, Dennis; Braxmaier, Claus; Peters, Achim; Johann, Ulrich

2006-08-01

360

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

E-print Network

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

Atsushi Nishizawa; Seiji Kawamura; Masa-aki Sakagami

2007-06-03

361

Subnanosecond velocity interferometer measurements of detonating PBX-9502  

SciTech Connect

A velocity interferometer system was recently assembled which includes a high speed electronic streak camera to measure the particle velocity-time history of a diffusely reflecting surface. It has been named ORVIS for Optically Recorded Velocity Interferometer System. Measurements were made on detonating PBX-9502 (95/5 mixture of TATB and Kel-F) to determine the structure of the detonation front to see how the results compare with the measurements of Hayes, et al., using electromagnetic gauges embedded in superfine TATB. Measurements were made by reflecting laser light off a copper foil surface and then routing it through a velocity interferometer with a glass etalon in one leg to delay the light by 250 or 500 picoseconds, depending on the setup. The interferometer was tuned such that a pattern of straight fringes was obtained rather than the normal bull's-eye pattern. a cylindrical lens was used to focus each fringe to a dot to concentrate the light. This made the fringe pattern a line of dots which was focused on the slit of an Imacon 790 streak camera capable of streak rates up to 1 mm/ns. With this setup a time resolution of 300 to 500 picoseconds could be attained at the maximum streak rate. These experiments demonstrate that shock-front rise time measurements are now possible to a time resolution of several hundred picoseconds and we feel this approach can be used to attain about 50 picosecond time resolution. It is a powerful method to probe the structure of both shock and detonation waves.

Sheffield, S.A.; Bloomquist, D.D.

1981-01-01

362

Reissner-Mindlin Legendre Spectral Finite Elements with Mixed Reduced Quadrature  

SciTech Connect

Legendre spectral finite elements (LSFEs) are examined through numerical experiments for static and dynamic Reissner-Mindlin plate bending and a mixed-quadrature scheme is proposed. LSFEs are high-order Lagrangian-interpolant finite elements with nodes located at the Gauss-Lobatto-Legendre quadrature points. Solutions on unstructured meshes are examined in terms of accuracy as a function of the number of model nodes and total operations. While nodal-quadrature LSFEs have been shown elsewhere to be free of shear locking on structured grids, locking is demonstrated here on unstructured grids. LSFEs with mixed quadrature are, however, locking free and are significantly more accurate than low-order finite-elements for a given model size or total computation time.

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

2012-10-01

363

A quadrature-based technique for robust design with computer simulations  

E-print Network

This thesis presents a method for estimating transmitted variance to enable robust parameter design in computer simulations. This method is based on the Hermite-Gaussian quadrature for a single input. It is extended to ...

Lin, Yiben

2007-01-01

364

On numerical integration with high-order quadratures: with application to the Rayleigh-Sommerfeld integral  

NASA Astrophysics Data System (ADS)

The paper focusses on the advantages of using high-order Gauss-Legendre quadratures for the precise evaluation of integrals with both smooth and rapidly changing integrands. Aspects of their precision are analysed in the light of Gauss' error formula. Some "test examples" are considered and evaluated in multiple precision to ? 200 significant decimal digits with David Bailey's multiprecision package to eliminate truncation/rounding errors. The increase of precision on doubling the number of subintervals is analysed, the relevant quadrature attribute being the precision increment. In order to exemplify the advantages that high-order quadrature afford, the technique is then used to evaluate several plots of the Rayleigh-Sommerfeld diffraction integral for axi-symmetric source fields defined on a planar aperture. A comparison of the high-order quadrature method against various FFT-based methods is finally given.

Evans, W. A. B.; Torre, A.

2012-11-01

365

Interferometer for Space Station Windows  

NASA Technical Reports Server (NTRS)

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

Hall, Gregory

2003-01-01

366

The DELTA Synchrotron Light Interferometer  

SciTech Connect

Synchrotron radiation sources like DELTA, the Dortmund Electron Accelerator, a third generation synchrotron light source, need an optical monitoring system to measure the beam size at different points of the ring with high resolution and accuracy. These measurements also allow an investigation of the emittance of the storage ring, an important working parameter for the efficiency of working beamlines with experiments using the synchrotron radiation. The resolution limits of the different types of optical synchrotron light monitors at DELTA are investigated. The minimum measurable beamsize with the normal synchrotron light monitor using visible light at DELTA is about 80 {mu}m. Due to this a synchrotron light interferometer was built up and tested at DELTA. The interferometer uses the same beamline in the visible range. The minimum measurable beamsize is with about 8 {mu}m one order of magnitude smaller. This resolution is sufficient for the expected small vertical beamsizes at DELTA. The electron beamsize and emittance were measured with both systems at different electron beam energies of the storage ring. The theoretical values of the present optics are smaller than the measured emittance. So possible reasons for beam movements are investigated.

Berges, U. [DELTA, University of Dortmund, Maria-Goeppert-Mayer Str. 2, 4421 Dortmund (Germany); Fachbereich Physik, University of Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund (Germany)

2004-05-12

367

All-Digital Quadrature Detection With TAD for Radio-Controlled Clocks\\/Watches  

Microsoft Academic Search

Time analog-to-digital converters (TADs) based on the power-supply voltage dependence of CMOS gate propagation delay time can be constructed solely of CMOS digital circuits and are characterized by output of the time integral of input voltage, with no dead time. This paper describes digital quadrature detection (DQD) by TAD (TAD-DQD). With TAD-DQD, the in-phase and quadrature components of the input

Sumio Masuda; Takamoto Watanabe; Shigenori Yamauchi; Tomohito Terasawa

2009-01-01

368

A dual band SiGe quadrature VCO design for GSM\\/DCS-PCS applications  

Microsoft Academic Search

A dual hand SiGe fully integrated quadrature Voltage Controlled Oscillator (VCO) for GSM\\/DCS-PCS applications is presented. This circuit is implemented in a 0.35pm BiCMOS SiGe process and is made of two cross-coupled differential VCOs, with integrated resonator, to ensure the quadrature outputs. At 2.7 V power supply voltage and a total power dissipation of 41.6 mW, the proposed VCO features

David CORDEAU; Jean-Marie PAILLOT; Giuseppe De ASTIS; Lucian DASCALESCU

2004-01-01

369

Improvement of Return Loss Bandwidth of Balanced Amplifier Using Metamaterial-Based Quadrature Power Splitters  

Microsoft Academic Search

A new balanced amplifier (BA) using metamaterial-based quadrature power splitters (QPSs) is presented in this letter. Instead of using conventional 90 couplers, the developed BA is implemented by two parallel amplifiers with broadband metamaterial-based QPSs at input and output ends. Since the QPSs can provide a broadband quadrature phase difference between two outputs, the input\\/output reflections from two amplifiers can

Chao-Hsiung Tseng; Chih-Lin Chang

2008-01-01

370

A Continuously Operating, Flux Locked, Superfluid Interferometer  

NASA Astrophysics Data System (ADS)

We report the characteristics of a flux locked, superfluid 4He interferometer that can continuously measure time-varying rotation rates. We describe the principles underlying the interferometer, including the dynamics of a superfluid chemical potential battery used to obtain continuous operation. We also discuss noise and drift issues and their possible amelioration.

Joshi, Aditya; Packard, Richard

2013-07-01

371

CIST....CORRTEX interferometer simulation test  

SciTech Connect

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

Heinle, R.A.

1994-12-01

372

In-line Sagnac interferometer current sensor  

Microsoft Academic Search

The authors demonstrate for the first time a near shot noise limited in-line Sagnac interferometer current sensor. It is shown to have a number of advantages over the optical current sensors based on polarimetric Faraday and Faraday\\/Sagnac loop interferometer topologies, including lower sensitivity to environmental disturbances, less demanding optical components, and easy installation.

J. Blake; P. Tantaswadi; R. T. de Carvalho

1996-01-01

373

Dual-prism interferometer for collimation testing  

SciTech Connect

An air-wedge lateral-shear interferometer using two prisms is presented. With a variable shear, the interferometer is suitable for testing collimation of a wide range of beam sizes down to a few millimeters in diameter. No antireflection coatings are necessary. Collimation for a light source with short coherent length is also demonstrated.

Hii, King Ung; Kwek, Kuan Hiang

2009-01-10

374

AN ATOM INTERFEROMETER GYROSCOPE JAMES GREENBERG  

E-print Network

AN ATOM INTERFEROMETER GYROSCOPE By JAMES GREENBERG A Thesis Submitted to the Honors College gyroscope that is sensitive to the abso- lute rotation rate of the lab with respect to an inertial frame. We accelerations of ±0.005g and absolute rotation rates of ±0.5E. Sensitive atom interferometer gyroscopes

Cronin, Alex D.

375

Efficient Implementations of the Quadrature-Free Discontinuous Galerkin Method  

NASA Technical Reports Server (NTRS)

The efficiency of the quadrature-free form of the dis- continuous Galerkin method in two dimensions, and briefly in three dimensions, is examined. Most of the work for constant-coefficient, linear problems involves the volume and edge integrations, and the transformation of information from the volume to the edges. These operations can be viewed as matrix-vector multiplications. Many of the matrices are sparse as a result of symmetry, and blocking and specialized multiplication routines are used to account for the sparsity. By optimizing these operations, a 35% reduction in total CPU time is achieved. For nonlinear problems, the calculation of the flux becomes dominant because of the cost associated with polynomial products and inversion. This component of the work can be reduced by up to 75% when the products are approximated by truncating terms. Because the cost is high for nonlinear problems on general elements, it is suggested that simplified physics and the most efficient element types be used over most of the domain.

Lockard, David P.; Atkins, Harold L.

1999-01-01

376

Optimally smooth symmetric quadrature mirror filters for image coding  

NASA Astrophysics Data System (ADS)

Symmetric quadrature mirror filters (QMFs) offer several advantages for wavelet-based image coding. Symmetry and odd-length contribute to efficient boundary handling and preservation of edge detail. Symmetric QMFs can be obtained by mildly relaxing the filter bank orthogonality conditions. We describe a computational algorithm for these filter banks which is also symmetric in the sense that the analysis and synthesis operations have identical implementations, up to a delay. The essence of a wavelet transform is its multiresolution decomposition, obtained by iterating the lowpass filter. This allows one to introduce a new design criterion, smoothness (good behavior) of the lowpass filter under iteration. This design constraint can be expressed solely in terms of the lowpass filter tap values (via the eigenvalue decomposition of a certain finite-dimensional matrix). Our innovation is to design near- orthogonal QMFs with linear-phase symmetry which are optimized for smoothness under iteration, not for stopband rejection. The new class of optimally smooth QMF filter banks yields high performance in a practical image compression system.

Heller, Peter N.; Shapiro, Jerome M.; Wells, Raymond O., Jr.

1995-04-01

377

Radiation transport modeling using extended quadrature method of moments  

SciTech Connect

The radiative transfer equation describes the propagation of radiation through a material medium. While it provides a highly accurate description of the radiation field, the large phase space on which the equation is defined makes it numerically challenging. As a consequence, significant effort has gone into the development of accurate approximation methods. Recently, an extended quadrature method of moments (EQMOM) has been developed to solve univariate population balance equations, which also have a large phase space and thus face similar computational challenges. The distinct advantage of the EQMOM approach over other moment methods is that it generates moment equations that are consistent with a positive phase space density and has a moment inversion algorithm that is fast and efficient. The goal of the current paper is to present the EQMOM method in the context of radiation transport, to discuss advantages and disadvantages, and to demonstrate its performance on a set of standard one-dimensional benchmark problems that encompass optically thin, thick, and transition regimes. Special attention is given in the implementation to the issue of realizability—that is, consistency with a positive phase space density. Numerical results in one dimension are promising and lay the foundation for extending the same framework to multiple dimensions.

Vikas, V., E-mail: vvikas@iastate.edu [Department of Aerospace Engineering, 2271 Howe Hall, Iowa State University, Ames, IA 50011 (United States); Hauck, C.D., E-mail: hauckc@ornl.gov [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Wang, Z.J., E-mail: zjw@ku.edu [Department of Aerospace Engineering, 2120 Learned Hall, University of Kansas, Lawrence, KS 66045 (United States); Fox, R.O., E-mail: rofox@iastate.edu [Department of Chemical and Biological Engineering, 2114 Sweeney Hall, Iowa State University, Ames, IA 50011 (United States)

2013-08-01

378

Directional dual-tree complex wavelet packet transforms for processing quadrature signals.  

PubMed

Quadrature signals containing in-phase and quadrature-phase components are used in many signal processing applications in every field of science and engineering. Specifically, Doppler ultrasound systems used to evaluate cardiovascular disorders noninvasively also result in quadrature format signals. In order to obtain directional blood flow information, the quadrature outputs have to be preprocessed using methods such as asymmetrical and symmetrical phasing filter techniques. These resultant directional signals can be employed in order to detect asymptomatic embolic signals caused by small emboli, which are indicators of a possible future stroke, in the cerebral circulation. Various transform-based methods such as Fourier and wavelet were frequently used in processing embolic signals. However, most of the times, the Fourier and discrete wavelet transforms are not appropriate for the analysis of embolic signals due to their non-stationary time-frequency behavior. Alternatively, discrete wavelet packet transform can perform an adaptive decomposition of the time-frequency axis. In this study, directional discrete wavelet packet transforms, which have the ability to map directional information while processing quadrature signals and have less computational complexity than the existing wavelet packet-based methods, are introduced. The performances of proposed methods are examined in detail by using single-frequency, synthetic narrow-band, and embolic quadrature signals. PMID:25388779

Serbes, Gorkem; Gulcur, Halil Ozcan; Aydin, Nizamettin

2014-11-12

379

Raman pulse duration effect in gravity gradiometers composed of two atom interferometers  

E-print Network

We investigated the Raman pulse duration effect in a gravity gradiometer with two atom interferometers. Since the two atom clouds in the gradiometer experience different gravitational fields, it is hard to compensate the Doppler shifts of the two clouds simultaneously by chirping the frequency of a common Raman laser, which leads to an appreciable phase shift. When applied to an experiment measuring the Newtonian gravitational constant G, the effect contributes to a systematic offset as large as -49ppm in Nature 510, 518 (2014). Thus an underestimated value of G measured by atom interferometers can be partly explained due to this effect.

Shao, Cheng-Gang; Zhou, Min-Kang; Tan, Yu-Jie; Chen, Le-Le; Luo, Jun; Kun-Hu, Zhong

2015-01-01

380

Interferometer real time control development for SIM  

NASA Astrophysics Data System (ADS)

Real Time Control (RTC) for the Space Interferometry Mission will build on the real time core interferometer control technology under development at JPL since the mid 1990s, with heritage from the ground based MKII and Palomar Testbed Interferometer projects developed in the late '80s and early '90s. The core software and electronics technology for SIM interferometer real time control is successfully operating on several SIM technology demonstration testbeds, including the Real-time Interferometer Control System Testbed, System Testbed-3, and the Microarcsecond Metrology testbed. This paper provides an overview of the architecture, design, integration, and test of the SIM flight interferometer real time control to meet challenging flight system requirements for the high processor throughput, low-latency interconnect, and precise synchronization to support microarcsecond-level astrometric measurements for greater than five years at 1 AU in Earth-trailing orbit. The electronics and software architecture of the interferometer real time control core and its adaptation to a flight design concept are described. Control loops for pointing and pathlength control within each of four flight interferometers and for coordination of control and data across interferometers are illustrated. The nature of onboard data processing to fit average downlink rates while retaining post-processed astrometric measurement precision and accuracy is also addressed. Interferometer flight software will be developed using a software simulation environment incorporating models of the metrology and starlight sensors and actuators to close the real time control loops. RTC flight software and instrument flight electronics will in turn be integrated utilizing the same simulation architecture for metrology and starlight component models to close real time control loops and verify RTC functionality and performance prior to delivery to flight interferometer system integration at Lockheed Martin's Sunnyvale facility. A description is provided of the test environment architecture supporting the RTC path to flight.

Bell, Charles E.

2003-02-01

381

Miniature interferometer for refractive index measurement in microfluidic chip  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

382

Status and Progress on the Upgraded Infrared Spatial Interferometer  

NASA Technical Reports Server (NTRS)

The U.C. Berkeley Infrared Spatial Interferometer is a two telescope stellar interferometer operating in the 9-12 micron atmospheric window, utilizing heterodyne detection with CO2 laser local oscillators. Science with the ISI has been focused on the measurements of the spatial distribution of dust and molecules around mass-losing late type stars, and more recently precision measurements of stellar diameters in the mid-infrared avoiding molecular lines. Also during the past few years, a NSF sponsored program of expansion from two to three telescopes has been underway. This expansion will allow the ISI to make visibility observations on three simultaneous baselines and a measure a closure phase. The third telescope was completed last year and shipped to Mt. Wilson, and more recently a Central Control Facility and Master Laser Oscillator Facility were also completed and recently shipped to Mt. Wilson. In this talk we report progress on this program and highlight some of the most recent astrophysical results.

Danchi, W. C.; Townes, C. H.; Fitelson, W.; Hale, D.; Monnier, J.; Tevosian, S.; Weiner, J.; Oegerle, William (Technical Monitor)

2002-01-01

383

Laser barometer  

DOEpatents

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

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

2001-02-06

384

Mach-Zehnder interferometer fringe projector for variable-resolution video moire  

NASA Astrophysics Data System (ADS)

A Mach-Zehnder based variable resolution fringe projection system has been built for 3D video moire machine vision. This system uses the three main advantages of the Mach- Zehnder - 1) There is no optical feedback to the laser source; 2) The interferometer can accept two different laser wavelengths simultaneously; and 3) The interferometer produces two orthogonal output beams. The lack of optical feedback makes the Mach-Zehnder especially attractive for use with high power laser diode sources which are sensitive to optical feedback. When the two input ports are used with two different wavelength laser, the target can be illuminated by simultaneous projection of two different sets of colored fringes with two different spatial frequencies. This can allow more reliable reconstruction of the 3D surface over discontinuous jumps. Finally, the lack of feedback to the source coupled with the dual outputs means that he Mach-Zehnder fringe projector is very efficient in that 100 percent of the laser light is projected onto the prime and reference targets. Setup and alignment of this interferometer will be discussed for both parallel and diverging light. Plots of fringe visibility will be given for both outputs and both inputs.Application to a video moire based real time 3D error map machine vision system will be discussed.

Kalmanson, Phillip C.; Schutte, August; Hart, Chris L.; Blatt, Joel H.

1998-12-01

385

X-ray shearing interferometer  

DOEpatents

An x-ray interferometer for analyzing high density plasmas and optically opaque materials includes a point-like x-ray source for providing a broadband x-ray source. The x-rays are directed through a target material and then are reflected by a high-quality ellipsoidally-bent imaging crystal to a diffraction grating disposed at 1.times. magnification. A spherically-bent imaging crystal is employed when the x-rays that are incident on the crystal surface are normal to that surface. The diffraction grating produces multiple beams which interfere with one another to produce an interference pattern which contains information about the target. A detector is disposed at the position of the image of the target produced by the interfering beams.

Koch, Jeffrey A. (Livermore, CA)

2003-07-08

386

Beam shuttering interferometer and method  

DOEpatents

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

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

1993-07-27

387

Beam shuttering interferometer and method  

DOEpatents

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

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

1993-01-01

388

Interferometry technique to eliminate noise in interference data based on a Mach-Zehnder interferometer.  

PubMed

Some experiments based on interferometry, such as studying refractive index changes, need a long time to be completed, and any movement or oscillation in the order of wavelength during that time may wash out the interference fringes or at least reduce the quality of the interferogram. In this work, a new technique is presented to enhance the interferometric data during such experiments. The main idea behind this technique is the use of a reference beam to monitor all surrounding changes during the experiment. Laser light was divided into two parallel beams and then entered into a Mach-Zehnder interferometer. One of the beams was used as a reference signal to measure interferometer drift and the other one was passed through the sample to measure the refractive index changes simultaneously in a single interferometer. Noise was extracted from the data with a written computer code to achieve a noise-free output. PMID:24663448

Azari, Amin; Mohajerani, Ezedin; Abedi, Zahra; Shams, Afshin

2014-03-20

389

Solid optical ring interferometer for high-throughput feedback-free spectral analysis and filtering.  

PubMed

We describe a simple and inexpensive optical ring interferometer for use in high-resolution spectral analysis and filtering. It consists of a solid cuboid, reflection-coated on two opposite sides, in which constructive interference occurs for waves in a rhombic trajectory. Due to its monolithic design, the interferometer's resonance frequencies are insensitive to environmental disturbances over time. Additional advantages are its simplicity of alignment, high-throughput, and feedback-free operation. If desired, it can be stabilized with a secondary laser without disturbance of the primary signal. We illustrate the use of the interferometer for the measurement of the spectral Mollow triplet from a quantum dot and characterize its long-term stability for filtering applications. PMID:25725820

Petrak, B; Peiris, M; Muller, A

2015-02-01

390

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

SciTech Connect

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

Tarun, Alvarado; Jecong, Julius; Saloma, Caesar

2005-12-01

391

Portable, solid state, fiber optic coupled Doppler interferometer system for detonation and shock diagnostics  

NASA Technical Reports Server (NTRS)

VISAR (Velocity Interferometer System for Any Reflector) is a specialized Doppler interferometer system that is gaining world-wide acceptance as the standard for shock phenomena analysis. The VISAR's large power and cooling requirements, and the sensitive and complex nature of the interferometer cavity have restricted the traditional system to the laboratory. This paper describes the new portable VISAR, its peripheral sensors, and the role it played in optically measuring ground shock of and underground nuclear detonation. The Solid State VISAR uses a prototype diode pumped Nd:YAG laser and solid state detectors that provide a suitcase-size system with low power requirements. A special window and sensors were developed for fiber optic coupling (1 kilometer long) to the VISAR. The system has proven itself as a reliable, easy to use instrument that is capable of field test use and rapid data reduction using only a notebook personal computer (PC).

Fleming, K. J.; Crump, O. B.

1994-01-01

392

Solid optical ring interferometer for high-throughput feedback-free spectral analysis and filtering  

NASA Astrophysics Data System (ADS)

We describe a simple and inexpensive optical ring interferometer for use in high-resolution spectral analysis and filtering. It consists of a solid cuboid, reflection-coated on two opposite sides, in which constructive interference occurs for waves in a rhombic trajectory. Due to its monolithic design, the interferometer's resonance frequencies are insensitive to environmental disturbances over time. Additional advantages are its simplicity of alignment, high-throughput, and feedback-free operation. If desired, it can be stabilized with a secondary laser without disturbance of the primary signal. We illustrate the use of the interferometer for the measurement of the spectral Mollow triplet from a quantum dot and characterize its long-term stability for filtering applications.

Petrak, B.; Peiris, M.; Muller, A.

2015-02-01

393

Laser Frequency Stabilization  

NASA Technical Reports Server (NTRS)

Laser ranging and interferometry are essential technologies allowing for many astounding new spacebased missions such as the Laser Interferometer Space Antenna (LISA) to measure gravitational radiation emitted from distant super massive black hole mergers or distributed aperture telescopes with unprecedented angular resolution in the NIR or visible regime. The requirements on laser frequency noise depend on the residual motion and the distances between the spacecraft forming the interferometer. The intrinsic frequency stability of commercial lasers is several orders of magnitude above these requirements. Therefore, it is necessary for lasers to be stabilized to an ultrastable frequency reference so that they can be used to sense and control distances between spacecraft. Various optical frequency references and frequency stabilization schemes are considered and investigated for the applicability and usefulness for space-based interferometry missions.

Donelan, Darsa; Mueller, Guido; Thorpe, James; Livas, Jeffrey

2011-01-01

394

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

395

X-ray Interferometer Using Prism Optics  

SciTech Connect

Two-beam X-ray interferometer using refractive optics has been developed. A prism made of acrylic resin is used as the beam deflector for hard X-ray wavefront dividing interferometer. This configuration is the same as that of the Fresnel's bi-prism interferometer or the Leith-Upatnieks type two-beam holography in visible light region. Therefore, quantitative analysis of the degree of transversal coherence can be performed by measuring the visibility of interference fringes. It is also possible to realize two-beam holographic imaging in hard X-ray regions.

Suzuki, Yoshio [JASRI/SPring-8 Mikazuki, Hyogo 6791-5198 (Japan)

2004-05-12

396

Highly-sensitive gas pressure sensor using twin-core fiber based in-line Mach-Zehnder interferometer.  

PubMed

A Mach-Zehnder interferometer based on a twin-core fiber was proposed and experimentally demonstrated for gas pressure measurements. The in-line Mach-Zehnder interferometer was fabricated by splicing a short section of twin-core fiber between two single mode fibers. A micro-channel was created to form an interferometer arm by use of a femtosecond laser to drill through one core of the twin-core fiber. The other core of the fiber was remained as the reference arm. Such a Mach-Zehnder interferometer exhibited a high gas pressure sensitivity of -9.6 nm/MPa and a low temperature cross-sensitivity of 4.4 KPa/°C. Moreover, ultra-compact device size and all-fiber configuration make it very suitable for highly-sensitive gas pressure sensing in harsh environments. PMID:25836884

Li, Zhengyong; Liao, Changrui; Wang, Yiping; Xu, Lei; Wang, Dongning; Dong, Xiaopeng; Liu, Shen; Wang, Qiao; Yang, Kaiming; Zhou, Jiangtao

2015-03-01

397

Corner cube reflector lateral displacement evaluation simultaneously with interferometer length measurement  

NASA Astrophysics Data System (ADS)

The novel corner cube reflector (CCR) system for a distance measuring interferometer is presented. The proposed system allows reflector lateral displacement evaluation (relative to the beam axis) simultaneously with the interferometer length measurement. Laser beam in measuring arm of the interferometer is divided into two parallel beams that are used for the interferometer distance measurement and lateral shifts of the assembly in relation to the beam axis.The CCR assembly is based on applying a position sensitive detector placed behind the CCR that has truncated vertex. Due to the proposed configuration of the cube corner and photodetector, the rotations of the CCR assembly does not cause error in the lateral displacement measurement in relation to the beam axis.The theoretical analysis and experimental verification of the system metrological feasibilities are presented. The general limitations and design problems are shown. The proposed system can be used basically for measurement and compensation of global or local cosine errors especially in short range of the interferometer displacement measurement, where known techniques are ineffective. Possible applications of the system for Coordinate Measuring Machines accuracy testing are indicated.

Zamiela, Grzegorz; Dobosz, Marek

2013-09-01

398

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

NASA Technical Reports Server (NTRS)

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

Pearson, Earl F.

1996-01-01

399

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

E-print Network

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

Nishizawa, Atsushi; Sakagami, Masa-aki

2007-01-01

400

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

NASA Astrophysics Data System (ADS)

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

Primeau, Brian C.; Greivenkamp, John E.

2012-03-01

401

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

E-print Network

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

Byer, Robert L.

402

Design and Application of Quadrature Compensation Patterns in Bulk Silicon Micro-Gyroscopes  

PubMed Central

This paper focuses on the detailed design issues of a peculiar quadrature reduction method named system stiffness matrix diagonalization, whose key technology is the design and application of quadrature compensation patterns. For bulk silicon micro-gyroscopes, a complete design and application case was presented. The compensation principle was described first. In the mechanical design, four types of basic structure units were presented to obtain the basic compensation function. A novel layout design was proposed to eliminate the additional disturbing static forces and torques. Parameter optimization was carried out to maximize the available compensation capability in a limited layout area. Two types of voltage loading methods were presented. Their influences on the sense mode dynamics were analyzed. The proposed design was applied on a dual-mass silicon micro-gyroscope developed in our laboratory. The theoretical compensation capability of a quadrature equivalent angular rate no more than 412 °/s was designed. In experiments, an actual quadrature equivalent angular rate of 357 °/s was compensated successfully. The actual compensation voltages were a little larger than the theoretical ones. The correctness of the design and the theoretical analyses was verified. They can be commonly used in planar linear vibratory silicon micro-gyroscopes for quadrature compensation purpose. PMID:25356646

Ni, Yunfang; Li, Hongsheng; Huang, Libin

2014-01-01

403

Design and application of quadrature compensation patterns in bulk silicon micro-gyroscopes.  

PubMed

This paper focuses on the detailed design issues of a peculiar quadrature reduction method named system stiffness matrix diagonalization, whose key technology is the design and application of quadrature compensation patterns. For bulk silicon micro-gyroscopes, a complete design and application case was presented. The compensation principle was described first. In the mechanical design, four types of basic structure units were presented to obtain the basic compensation function. A novel layout design was proposed to eliminate the additional disturbing static forces and torques. Parameter optimization was carried out to maximize the available compensation capability in a limited layout area. Two types of voltage loading methods were presented. Their influences on the sense mode dynamics were analyzed. The proposed design was applied on a dual-mass silicon micro-gyroscope developed in our laboratory. The theoretical compensation capability of a quadrature equivalent angular rate no more than 412 °/s was designed. In experiments, an actual quadrature equivalent angular rate of 357 °/s was compensated successfully. The actual compensation voltages were a little larger than the theoretical ones. The correctness of the design and the theoretical analyses was verified. They can be commonly used in planar linear vibratory silicon micro-gyroscopes for quadrature compensation purpose. PMID:25356646

Ni, Yunfang; Li, Hongsheng; Huang, Libin

2014-01-01

404

Polarization mismatch errors in radio phase interferometers.  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

405

The effect of rotations on Michelson interferometers  

NASA Astrophysics Data System (ADS)

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

Maraner, Paolo

2014-11-01

406

Active noise cancellation in a suspended interferometer  

E-print Network

We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results ...

Driggers, Jennifer C.

407

The VLA Atmospheric Phase Interferometer  

NASA Astrophysics Data System (ADS)

The Atmospheric Phase Interferometer (API) is a two-element atmospheric seeing monitor located at the Very Large Array (VLA) site. The instrument measures turbulent refractive index variation through the atmosphere by examining phase differences in a satellite beacon signal detected at two (or more) antennas. With this measurement, the VLA scheduling software is able to consider atmospheric stability when determining which frequency observation to schedule next. We are in the process of extending this two-element interferometer to four elements, which will allow us to measure the turbulence in two dimensions and at multiple length scales. This thesis will look at some statistical properties of turbulence, the effects of atmospheric stability on radio interferometric observations, and discuss details of the instrument and the data that it collects. The thesis will also cover some techniques and principles of signal processing, and an analysis of some data from the instrument. The results demonstrate that other surface atmospheric variables (e.g. windspeed, water vapor pressure) show the same structure function exponent as the atmospheric phase fluctuations. In particular, the structure functions of water vapor partial pressure and wind speed show the same exponent as the phase. Though the agreement between meteorological variables and atmospheric phase is scientifically satisfying, these surface measurements are not nearly as sensitive as the API saturation phase measurement, and therefore cannot be used to schedule telescope time in its stead. What is informative about these results is that the similar structure functions for API and meteorological data are detecting reinforce the claim that both measurements represent turbulent transport, and not instrumental noise. Data from the instrument reveals that measurements are consistent with both Kolmogorov turbulence theory, and with prior observations. The API predominately measures three-dimensional isotropic turbulence, but is capable of seeing the transition to two-dimensional "thin screen" turbulence. There is evidence that water vapor scale height can be estimated from the API data. We can expect to be able measure and document variations in the water vapor scale height by looking at variation of structure function exponents. Once the reliability of the method is established, a series of altitude profiles could allow further validation of this method of scale height determination. We look at a method for statistical excision of instrumental noise from the data. The ability to discriminate noise from signal based on structure function exponent leads to a path to possible noise elimination techniques. With the redundant measurement baselines of the new API, experimental processing techniques such as this could be deployed on some baselines, but not others, leaving the production functions for VLA scheduling in a known state while allowing instrument improvement studies to proceed.

Morris, Keith

2014-05-01

408

Stroboscopic interferometer system for dynamic MEMS characterization  

Microsoft Academic Search

We describe a computer-controlled stroboscopic phase-shifting interferometer system for measuring out-of-plane motions and deformations of MEMS structures with nanometer accuracy. To aid rapid device characterization, our system incorporates (1) an imaging interferometer that records motion at many points simultaneously without point-by-point scanning, (2) an integrated computer-control and data-acquisition unit to automate measurement, and (3) an analysis package that generates sequences

Matthew R. Hart; Robert A. Conant; Kam Y. Lau; Richard S. Muller

2000-01-01

409

Temporal impulse response of the Talbot interferometer  

NASA Astrophysics Data System (ADS)

The Talbot interferometer has been shown earlier to act as an optical tapped delay-line in the time domain. The interferometer is based on the self-imaging effect. It consists of two gratings separated by a multiple of the self-imaging distance. Here, we determine its temporal behaviour experimentally. First, the impulse response is measured directly in the time domain by means of femtosecond pulse technology and second, by spectroscopy we measure its power spectrum. Results confirm earlier theoretical considerations.

Knuppertz, Hans; Jahns, Jürgen; Grunwald, Rüdiger

2007-09-01

410

Advanced gravitational reference sensor for high precision space interferometers  

NASA Astrophysics Data System (ADS)

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 three-dimensional directions. The GRS housing provides the optical reference surface onto which the transmitted laser beam, and the independent received laser beam are referenced. The stand-alone GRS allows balanced optical probing of the distance of the proof mass relative to the housing at a power and wavelength that differ from the transmitted and received wavelengths and with picometre sensitivity without radiation pressure imbalance. The single parameter that reduces proof mass disturbance forces is the gap spacing. Optical readout allows the use of a large gap between the GRS housing and proof mass. We propose using rf-modulated optical interferometry to measure both relative displacement and absolute distance. Further we propose to use a reflective grating beamsplitter within the GRS and on the external optical bench. The reflective grating design eliminates the in-path transmissive optical components and the dn/dT related optical path effects, and simplifies the optical bench structure. Inside the GRS, a near-Littrow mounted grating enables picometre precision measurement at microwatts of optical power. Preliminary experimental results using a grating beamsplitter interferometer are presented, which demonstrate an optical sensing sensitivity of 30 pm Hz-1/2.

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

2005-05-01

411

Microchip laser with active output mirror  

Microsoft Academic Search

Presented is an operator model of a microchip laser with an active output mirror based on Fabry-Perot interferometer. Considered are apodizing properties of a mirror-interferometer composed of two spherical, semi-transparent reflectors with variable gap between those. Proposed is an operator model describing the mirror under diffraction approximation. Results of numerical simulation of the micro-chip laser with variable thermal lens and

V. V. Kiyko; V. I. Kislov; E. N. Ofitserov

2010-01-01

412

A fiber-optic interferometer with subpicometer resolution for dc and low-frequency displacement measurement  

NASA Astrophysics Data System (ADS)

We have developed a fiber-optic interferometer optimized for best performance in the frequency range from dc to 1 kHz, with displacement linearity of 1% over a range of ± 25 nm, and noise-limited resolution of 2 pm. The interferometer uses a tunable infrared laser source (nominal 1550 nm wavelength) with high amplitude and wavelength stability, low spontaneous self-emission noise, high sideband suppression, and a coherence control feature that broadens the laser linewidth and dramatically lowers the low-frequency noise in the system. The amplitude stability of the source, combined with the use of specially manufactured "bend-insensitive" fiber and all-spliced fiber construction, results in a robust homodyne interferometer system, which achieves resolution of 40 fm Hz-1/2 above 20 Hz and approaches the shot-noise-limit of 20 fm Hz-1/2 at 1 kHz for an optical power of 10 ?W, without the need for differential detection. Here we describe the design and construction of the interferometer, as well as modes of operation, and demonstrate its performance.

Smith, D. T.; Pratt, J. R.; Howard, L. P.

2009-03-01

413

Integrated optic chip for laser threat identification  

Microsoft Academic Search

In this conference last year, we proposed free-space gratings, Fizeau interferometers and wavefront estimation for detecting the different lasers deployed in the battlefield for range finding, target designation, communications, dazzle, location of targets, munitions guidance, and destruction. Since last year, advanced laser weapons of the electron cyclotron type, are in development, such as the free-electron laser, that are tunable and

Alastair D. McAulay

2010-01-01

414

On the Potential of Large Ring Lasers  

E-print Network

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

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

2007-07-10

415

Keck Interferometer Nuller science highlights  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

416

On the Spectrum of Field Quadratures for a Finite Number of Photons  

E-print Network

The spectrum and eigenstates of any field quadrature operator restricted to a finite number $N$ of photons are studied, in terms of the Hermite polynomials. By (naturally) defining \\textit{approximate} eigenstates, which represent highly localized wavefunctions with up to $N$ photons, one can arrive at an appropriate notion of limit for the spectrum of the quadrature as $N$ goes to infinity, in the sense that the limit coincides with the spectrum of the infinite-dimensional quadrature operator. In particular, this notion allows the spectra of truncated phase operators to tend to the complete unit circle, as one would expect. A regular structure for the zeros of the Christoffel-Darboux kernel is also shown.

Emilio Pisanty; Eduardo Nahmad-Achar

2012-09-04

417

On the Computation of High Order Rys Quadrature Weights and Nodes  

NASA Technical Reports Server (NTRS)

Since its introduction in 1976, the Rys Quadrature method has proven a very attractive method for evaluating electron repulsion integrals for calculations using Gaussian type orbitals. Since then, there have been considerable refinements of the method, but at it's core, Gaussian weights and nodes are used to exactly evaluate using a numerical approach to the transform integral. One of the powers of the Rys Quadrature method is the relative ease in evaluating integrals involving functions of high angular momentum. In this work we report on the complete resolution of these numerical difficulties, and we have easily computed accurate quadrature weights and nodes up to order 101. All calculations were carried out using 128-bit precision.

Schwenke, David W.

2014-01-01

418

An amplitude modulated laser system for distance and displacement measurement  

NASA Technical Reports Server (NTRS)

A laser distance and displacement measurement system is being developed to monitor small displacements in large space structures for strain analysis and structural control. The reflected laser beam is focused on a detector and the detected signal is mixed with the reference. Small displacements are indicated by a change in modulation frequency which is adjusted to maintain quadrature between the received signal and the reference signal from the voltage-controlled oscillator in a phase-locked loop. Measurement of absolute distance is accomplished by sweeping the modulation frequency from a quadrature lock point to an adjacent lock point.

Rogowski, Robert S.; Heyman, Joseph S.; Holben, Milford S., Jr.

1986-01-01

419

Discrete variable representation in electronic structure theory: Quadrature grids for least-squares tensor hypercontraction  

NASA Astrophysics Data System (ADS)

We investigate the application of molecular quadratures obtained from either standard Becke-type grids or discrete variable representation (DVR) techniques to the recently developed least-squares tensor hypercontraction (LS-THC) representation of the electron repulsion integral (ERI) tensor. LS-THC uses least-squares fitting to renormalize a two-sided pseudospectral decomposition of the ERI, over a physical-space quadrature grid. While this procedure is technically applicable with any choice of grid, the best efficiency is obtained when the quadrature is tuned to accurately reproduce the overlap metric for quadratic products of the primary orbital basis. Properly selected Becke DFT grids can roughly attain this property. Additionally, we provide algorithms for adopting the DVR techniques of the dynamics community to produce two different classes of grids which approximately attain this property. The simplest algorithm is radial discrete variable representation (R-DVR), which diagonalizes the finite auxiliary-basis representation of the radial coordinate for each atom, and then combines Lebedev-Laikov spherical quadratures and Becke atomic partitioning to produce the full molecular quadrature grid. The other algorithm is full discrete variable representation (F-DVR), which uses approximate simultaneous diagonalization of the finite auxiliary-basis representation of the full position operator to produce non-direct-product quadrature grids. The qualitative features of all three grid classes are discussed, and then the relative efficiencies of these grids are compared in the context of LS-THC-DF-MP2. Coarse Becke grids are found to give essentially the same accuracy and efficiency as R-DVR grids; however, the latter are built from explicit knowledge of the basis set and may guide future development of atom-centered grids. F-DVR is found to provide reasonable accuracy with markedly fewer points than either Becke or R-DVR schemes.

Parrish, Robert M.; Hohenstein, Edward G.; Martínez, Todd J.; Sherrill, C. David

2013-05-01

420

Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment  

SciTech Connect

This study presents a simple and powerful technique for multichannel measurements of the density profile in laboratory plasmas by microwave interferometry. This technique uses electromechanical microwave switches to temporally switch the connection between multiple receiver antennas and one phase-detection circuit. Using this method, the phase information detected at different positions is rearranged into a time series that can be acquired from a minimum number of data acquisition channels (e.g., two channels in the case of quadrature detection). Our successfully developed multichannel microwave interferometer that uses the antenna switching method was applied to measure the radial electron density profiles in a magnetized plasma experiment. The advantage of the proposed method is its compactness and scalability to multidimensional measurement systems at low cost.

Kawamori, Eiichirou; Lin, Yu-Hsiang [Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan (China)] [Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan (China); Mase, Atsushi [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga 816-8580 (Japan)] [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga 816-8580 (Japan); Nishida, Yasushi; Cheng, C. Z. [Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan (China) [Institute of Space and Plasma Sciences, National Cheng Kung University, Tainan 70101, Taiwan (China); Plasma and Space Science Center, National Cheng Kung University, Tainan 70101, Taiwan (China)

2014-02-15

421

Dual-quadrature coherent receiver for 100G Ethernet applications based on polymer planar lightwave circuit.  

PubMed

A dual-quadrature coherent receiver based on a polymer planar lightwave circuit (PLC) is presented. This receiver comprises two separate optical 90°-hybrid chips made of polymer waveguides and hybridly integrated with InGaAs/InP photodiode (PD) arrays. The packaged receiver was successfully operated in 112 Gbit/s dual-polarization quadrature phase-shift keying (QPSK) transmission experiments. In back-to-back configuration the OSNR requirement for a BER value of 10(-3) was 15.1 dB which has to be compared to a theoretical limit of 13.8 dB. PMID:22274014

Wang, Jin; Kroh, Marcel; Theurer, Abongwa; Zawadzki, Crispin; Schmidt, Detlef; Ludwig, Reinhold; Lauermann, Matthias; Zhang, Ziyang; Beling, Andreas; Matiss, Andreas; Schubert, Colja; Steffan, Andreas; Keil, Norbert; Grote, Norbert

2011-12-12

422

Performance of staggered quadrature modulations over nonlinear satellite channels with uplink noise and intersymbol interference  

NASA Technical Reports Server (NTRS)

In this paper, the performance of staggered quadrature modulations over nonlinear satellite channels is analyzed. The effects of uplink noise and intersymbol interference caused by transmitter filtering are included. The approach taken employs computational techniques based on moments of the interference. The expressions for the system bit error rate are derived for a general transponder model characterized by AM-AM and AM-PM conversion characteristics. Specific numerical results are presented for a hard-limited satellite repeater using staggered quadrature overlapped raised cosine (SQORC) and minimum-shift-keying (MSK) modulations.

Simon, M. K.; Divsalar, D.; Omura, J. K.

1982-01-01

423

Laser angle sensor  

NASA Technical Reports Server (NTRS)

A laser angle measurement system was designed and fabricated for NASA Langley Research Center. The instrument is a fringe counting interferometer that monitors the pitch attitude of a model in a wind tunnel. A laser source and detector are mounted above the model. Interference fringes are generated by a small passive element on the model. The fringe count is accumulated and displayed by a processor in the wind tunnel control room. This report includes optical and electrical schematics, system maintenance and operation procedures.

Pond, C. R.; Texeira, P. D.

1985-01-01

424

Laser angle sensor development  

NASA Technical Reports Server (NTRS)

Electrical and optical parameters were developed for a two axis (pitch/roll) laser angle sensor. The laser source and detector were mounted in the plenum above the model. Two axis optical distortion measurements of flow characteristics in a 0.3 transonic cryogenic tunnel were made with a shearing interferometer. The measurement results provide a basis for estimating the optical parameters of the laser angle sensor. Experimental and analytical information was generated on model windows to cover the reflector. A two axis breadboard was assembled to evaluate different measurement concepts. The measurement results were used to develop a preliminary design of a laser angle sensor. Schematics and expected performance specifications are included.

Pond, C. R.; Texeira, P. D.

1980-01-01

425

Mach-Zehnder fiber interferometer for people monitoring  

NASA Astrophysics Data System (ADS)

Fiber optical interferometers belong to highly sensitive equipments that are able to measure slight changes like distortion of shape, temperature and electric field variation and etc. Their great advantage is that they are insensitive on ageing component, from which they are composed of. It is in virtue of herewith, that there are evaluated no changes in optical signal intensity but number interference fringes. To monitor the movement of persons, eventually to analyze the changes in state of motion we developed method based on analysis the dynamic changes in interferometric pattern. We have used Mach- Zehnder interferometer with conventional SM fibers excited with the DFB laser at wavelength of 1550 nm. It was terminated with optical receiver containing InGaAs PIN photodiode. Its output was brought into measuring card module that performs on FFT of the received interferometer signal. The signal rises with the composition of two waves passing through single interferometer arm. The optical fiber SMF 28e in one arm is referential; the second one is positioned on measuring slab at dimensions of 1x2m. A movement of persons over the slab was monitored, signal processed with FFT and frequency spectra were evaluated. They rose owing to dynamic changes of interferometric pattern. The results reflect that the individual subjects passing through slab embody characteristic frequency spectra, which are individual for particular persons. The scope of measuring frequencies proceeded from zero to 10 KHz. It was also displayed in experiments that the experimental subjects, who walked around the slab and at the same time they have had changed their state of motion (knee joint fixation), embodied characteristic changes in their frequency spectra. At experiments the stability of interferometric patterns was evaluated as from time aspects, so from the view of repeated identical experiments. Two kinds of balls (tennis and ping-pong) were used to plot the repeatability measurements and the gained spectra at repeated drops of balls were compared. Those stroked upon the same place and from the same elevation and dispersion of the obtained frequency spectra was evaluated. These experiments were performed on the series of 20 repeated drops from highs of 0,5 and 1m. The evaluation of experiments displayed that the dispersion of measured values is lower than 4%.

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

2010-10-01

426

Laser interferometry for next generation satellite gravimetry  

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

427

Optical image hiding with a modified Mach-Zehnder interferometer  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

428

Quantum correlations in a noisy neutron interferometer  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

429

High resolution Fourier interferometer-spectrophotopolarimeter  

NASA Technical Reports Server (NTRS)

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

Fymat, A. L. (inventor)

1976-01-01

430

Quantum correlations in a noisy neutron interferometer  

E-print Network

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

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

2014-05-30

431

Orbit analysis of a geostationary gravitational wave interferometer detector array  

E-print Network

We analyze the trajectories of three geostationary satellites forming the GEOstationary GRAvitational Wave Interferometer (GEOGRAWI)~\\cite{tinto}, a space-based laser interferometer mission aiming to detect and study gravitational radiation in the ($10^{-4} - 10$) Hz band. The combined effects of the gravity fields of the Earth, the Sun and the Moon make the three satellites deviate from their nominally stationary, equatorial and equilateral configuration. Since changes in the satellites relative distances and orientations could negatively affect the precision of the laser heterodyne measurements, we have derived the time-dependence of the inter-satellite distances and velocities, the variations of the polar angles made by the constellation's three arms with respect to a chosen reference frame, and the time changes of the triangle's enclosed angles. We find that, during the time between two consecutive station-keeping maneuvers (about two weeks), the relative variations of the inter-satellite distances do not exceed a value of $0.05$ percent, while the relative velocities between pairs of satellites remain smaller than about $0.7 \\ {\\rm m/s}$. In addition, we find the angles made by the arms of the triangle with the equatorial plane to be periodic functions of time whose amplitudes grow linearly with time; the maximum variations experienced by these angles as well as by those within the triangle remain smaller than $3$ arc-minutes, while the East-West angular variations of the three arms remain smaller than about $15$ arc-minutes during the two-weeks period. The relatively small variations of these orbit parameters result into a set of system functional and performance requirements that are less stringent than those characterizing an interplanetary mission.

Massimo Tinto; Jose C. N. de Araujo; Helio K. Kuga; Marcio E. S. Alves; Odylio D. Aguiar

2014-10-11

432

Dynamic stability analysis of FGM plates by the moving least squares differential quadrature method  

Microsoft Academic Search

The present paper investigates the dynamic stability of thick functionally graded material plates subjected to aero-thermo-mechanical loads, using a novel numerical solution technique, the moving least squares differential quadrature method. Temperature field is assumed to be a uniform distribution over the plate plane, and varied in the thickness direction only. Material properties are assumed to be temperature dependent and graded

Wu Lanhe; Wang Hongjun; Wang Daobin

2007-01-01

433

Quadrature in meshless methods for general elliptic problems with natural boundary  

E-print Network

Quadrature in meshless methods for general elliptic problems with natural boundary conditions on the meshless method used to approximate the solution of an elliptic partial dif- ferential equation with non-constant coefficients with Neumann boundary conditions. We considered meshless methods with shape functions

Banerjee, Uday

434

A parallel method for time discretization of parabolic equations based on Laplace transformation and quadrature  

Microsoft Academic Search

We consider the discretization in time of an inhomogeneous parabolic equation in a Banach space setting, using a representation of the solution as an integral along a smooth curve in the complex left half plane, which, after transformation to a nite interval is then evaluated to high accuracy by a quadrature rule. This reduces the problem to a nite set

DONGWOO SHEEN; IAN H. SLOAN; VIDAR THOMEE

2003-01-01

435

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

E-print Network

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

Trefethen, Nick

436

Front-end-of-line quadrature-clocked voltage-dependent capacitance measurement  

Microsoft Academic Search

We report on Front-End-Of-Line Quadrature-clocked Voltage-dependent Capacitance Measurement (QVCM), a charge based capacitance measurement technique applicable to modern logic CMOS technologies with leaky gate oxides. QVCM test structures are designed using only first level of metal and support parallel test of multiple devices. Results for 45 nm SOI FETs illustrate the power of the developed technique.

Stas Polonsky; Paul Solomon; Jiun-hsin Liao; Lou Medina; Mark Ketchen

2011-01-01

437

A filter family designed for use in quadrature mirror filter banks  

Microsoft Academic Search

This paper discusses a family of filters that have been designed for Quadrature Mirror Filter (QMF) Banks. These filters provide a significant improvement over conventional optimal equiripple and window designs when used in QMF banks. The performance criterion for these filters differ from those usually used for filter design in a way which makes the usual filter design techniques difficult

J. D. Johnston

1980-01-01

438

Comparison of discrete singular convolution and generalized differential quadrature for the vibration analysis of rectangular plates  

Microsoft Academic Search

This paper presents a comprehensive comparison study between the discrete singular convolution (DSC) and the well-known global method of generalized differential quadrature (GDQ) for vibration analysis so as to enhance the understanding of the DSC algorithm. The DSC method is implemented through Lagrange's delta sequence kernel (DSC-LK), which utilizes local Lagrange polynomials to calculate weighting coefficients, whereas, the GDQ requires

C. H. W. Ng; Yibao Zhao; G. W. Wei

2004-01-01

439

Supersonic combustion studies using a multivariate quadrature based method for combustion modeling  

E-print Network

Supersonic combustion studies using a multivariate quadrature based method for combustion modeling function (PDF) of thermochemical variables can be used for accurately computing the combustion source term of predictive models for supersonic combustion is a critical step in design and development of scramjet engines

Raman, Venkat

440

Numerical Quadratures for Singular and Hypersingular Integrals in Boundary Element Methods  

Microsoft Academic Search

A method is developed for the computation of the weights and nodes of a numer- ical quadrature which integrates functions containing singularities up to order 1\\/x2, without the requirement to know the coefficients of the singularities exactly. The work is motivated by the need to evaluate such integrals on boundary elements in potential problems and is a simplification of a

Michael Carley

2007-01-01

441

Accurate cell counts in live mouse embryos using optical quadrature and differential interference contrast microscopy  

NASA Astrophysics Data System (ADS)

Present imaging techniques used in in vitro fertilization (IVF) clinics are unable to produce accurate cell counts in developing embryos past the eight-cell stage. We have developed a method that has produced accurate cell counts in live mouse embryos ranging from 13-25 cells by combining Differential Interference Contrast (DIC) and Optical Quadrature Microscopy. Optical Quadrature Microscopy is an interferometric imaging modality that measures the amplitude and phase of the signal beam that travels through the embryo. The phase is transformed into an image of optical path length difference, which is used to determine the maximum optical path length deviation of a single cell. DIC microscopy gives distinct cell boundaries for cells within the focal plane when other cells do not lie in the path to the objective. Fitting an ellipse to the boundary of a single cell in the DIC image and combining it with the maximum optical path length deviation of a single cell creates an ellipsoidal model cell of optical path length deviation. Subtracting the model cell from the Optical Quadrature image will either show the optical path length deviation of the culture medium or reveal another cell underneath. Once all the boundaries are used in the DIC image, the subtracted Optical Quadrature image is analyzed to determine the cell boundaries of the remaining cells. The final cell count is produced when no more cells can be subtracted. We have produced exact cell counts on 5 samples, which have been validated by Epi-Fluorescence images of Hoechst stained nuclei.

Warger, William C., II; Newmark, Judith A.; Zhao, Bing; Warner, Carol M.; DiMarzio, Charles A.

2006-02-01

442

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

E-print Network

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

Tang, William C

443

Computing extinction maps of star nulling interferometers.  

PubMed

Herein is discussed the performance of spaceborne nulling interferometers searching for extra-solar planets, in terms of their extinction maps projected on-sky. In particular, it is shown that the designs of Spatial Filtering (SF) and Achromatic Phase Shifter (APS) subsystems, both required to achieve planet detection and characterization, can sensibly affect the nulling maps produced by a simple Bracewell interferometer. Analytical relationships involving cross correlation products are provided and numerical simulations are performed, demonstrating marked differences in the aspect of extinction maps and the values of attained fringes contrasts. It is concluded that depending on their basic principles and designs, FS and APS will result in variable capacities for serendipitous discoveries of planets orbiting around their parent star. The mathematical relationships presented in this paper are assumed to be general, i.e. they should apply to other types of multi-apertures nulling interferometers. PMID:18542551

Hénault, Francois

2008-03-31

444

BioCD: Self-referencing interferometer for biosensing  

NASA Astrophysics Data System (ADS)

The holy-grail of modern medical science is to provide personalized health-care. An individual's state of health can be correlated to the pattern of concentration of several 'marker' molecules, for e.g. the presence of Prostate Specific Antigen (PSA) beyond a certain threshold in the body is a strong indication of prostate cancer. To realize the dream of personalized healthcare, a large number of markers have to be identified and correlated to the state of health across diverse populations. The identified markers have to be quantified subsequently to define an individual's state of health. The technology used to achieve the above should be sensitive, accurate, reliable, high-throughput and should be cheap and simple enough to be able to be available in a clinician's office. Interferometry has been used as a sensitive metrology tool in fields ranging from semiconductor inspection to astronomy. This thesis demonstrates a self-referencing interferometric biosensor (BioCD) with a surface normal design potentially capable of scaling up to thousands of tests per sensor substrates. The sensor concept is similar to an optical CD in that gold microstructures fabricated on the BioCD surface act as wavefront splitting interferometers. In contrast to the optical CD, the BioCD operates in a condition called quadrature, which provides maximum linear response to small phase changes caused by protein binding events. The gold microstructures generate a carrier wave when the BioCD is spun, and protein binding is detected as a modulation of an envelope of the carrier wave pattern created by the immobilized capture proteins. By immobilizing reference and target proteins, differential measurements that automatically subtract out non-specific binding can be obtained. We have demonstrated a detection limit of about 1 ng/ml with this technology, which is a clinically relevant figure for many human and veterinary applications. The specific and non-specific binding signals are separated by 4 orders of magnitude implying that potentially as many simultaneous tests can be performed with a single substrate.

Varma, Manoj

445

Exact Integrations of Polynomials and Symmetric Quadrature Formulas over Arbitrary Polyhedral Grids  

NASA Technical Reports Server (NTRS)

This paper is concerned with two important elements in the high-order accurate spatial discretization of finite volume equations over arbitrary grids. One element is the integration of basis functions over arbitrary domains, which is used in expressing various spatial integrals in terms of discrete unknowns. The other consists of quadrature approximations to those integrals. Only polynomial basis functions applied to polyhedral and polygonal grids are treated here. Non-triangular polygonal faces are subdivided into a union of planar triangular facets, and the resulting triangulated polyhedron is subdivided into a union of tetrahedra. The straight line segment, triangle, and tetrahedron are thus the fundamental shapes that are the building blocks for all integrations and quadrature approximations. Integrals of products up to the fifth order are derived in a unified manner for the three fundamental shapes in terms of the position vectors of vertices. Results are given both in terms of tensor products and products of Cartesian coordinates. The exact polynomial integrals are used to obtain symmetric quadrature approximations of any degree of precision up to five for arbitrary integrals over the three fundamental domains. Using a coordinate-free formulation, simple and rational procedures are developed to derive virtually all quadrature formulas, including some previously unpublished. Four symmetry groups of quadrature points are introduced to derive Gauss formulas, while their limiting forms are used to derive Lobatto formulas. Representative Gauss and Lobatto formulas are tabulated. The relative efficiency of their application to polyhedral and polygonal grids is detailed. The extension to higher degrees of precision is discussed.

Liu, Yen; Vinokur, Marcel

1997-01-01

446

Computer control of a far infrared interferometer  

NASA Technical Reports Server (NTRS)

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

Breecher, J.

1977-01-01

447

Heterodyne interferometers - Practical limitations and improvements  

NASA Astrophysics Data System (ADS)

Heterodyne interferometers are very sensitive tools for probing surface displacements. The wide bandwidth (about 1 GHz) and the high resolution allow many applications in the field of bulk (BAW) and surface acoustic waves (SAW). However all these interferometers exhibit low-frequency phase fluctuations depending on the optical mounting. Recent versions of these instruments reduce the noise down to the theoretical value. This paper shows the spectral density of phase fluctuations for three different configurations. The results are analyzed and the noise sources are identified.

Cretin, B.; Xie, W.-X.; Hauden, D.

1988-02-01

448

Fiberoptic Fabry-Perot engine pressure sensor system using a continuous wave laser source  

E-print Network

A fiber optic Fabry-Perot engine pressure sensor using a continuous wave laser source is implemented and tested. The operating point of the Fabrv-Perot sensor is locked to the quadrature point by electronic feedback control of laser temperature...

Choi, Han-Sun

1994-01-01

449

(presentation) Precision Mechanisms for Space Interferometers: A Tutorial  

NASA Technical Reports Server (NTRS)

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

Agronin, Michael L.

1993-01-01

450

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

PubMed

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

Pang, Yong; Yu, Baiying; Vigneron, Daniel B; Zhang, Xiaoliang

2014-02-01

451

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

PubMed Central

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

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

2014-01-01

452

CIV Vacuum Ultraviolet Fabry-Perot Interferometers for Transition-Region Magnetography  

NASA Technical Reports Server (NTRS)

The vacuum ultraviolet region allows remote sensing of the upper levels of the solar atmosphere where the magnetic field dominates the physics. Obtaining an imaging interferometer that observes the transition region is the goal of this program. This paper gives a summary of our instrument development program (1998-2005) for a high-spectral-resolution, piezoelectric tunable Vacuum Ultraviolet Fabry-Perot Interferometer (VUV FPI) for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CN (155nm). A VUV interferometer will allow us to observe the magnetic field, flows, and heating events in the mid-transition region. The MSFC VUV FPI has measured values of FWHM approx. 9pm, FSR approx. 62pm, finesse approx. 5.3 and transmittance approx. 50% at 157nm. For the measurements, the University of Toronto's F2 eximer laser was used as an appropriate proxy for CIV 155nm. This has provided the first tunable interferometer with a FWHM compatible to VUV filter magnetograph.

Gary, G. Allen; West, Edward A.; Rees, David; Zukic, Maumer; Herman, Peter; Li, Jianzhao

2006-01-01

453

Liquid crystal point diffraction interferometer. Ph.D. Thesis - Arizona Univ., 1995  

NASA Technical Reports Server (NTRS)

A new instrument, the liquid crystal point diffraction-interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffraction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with very high data density and with automated data reduction. This dissertation describes the theory of both the PDI and liquid crystal phase control. The design considerations for the LCPDI are presented, including manufacturing considerations. The operation and performance of the LCPDI are discussed, including sections regarding alignment, calibration, and amplitude modulation effects. The LCPDI is then demonstrated using two phase objects: defocus difference wavefront, and a temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to theoretical or independently measured results and show excellent agreement. A computer simulation of the LCPDI was performed to verify the source of observed periodic phase measurement error. The error stems from intensity variations caused by dye molecules rotating within the liquid crystal layer. Methods are discussed for reducing this error. Algorithms are presented which reduce this error; they are also useful for any phase-stepping interferometer that has unwanted intensity fluc