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1

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

2

Photoacoustic Tomography using a Michelson Interferometer with Quadrature Phase Detection  

E-print Network

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

Speirs, Rory W

2013-01-01

3

Imaging through turbulence with a quadrature-phase optical interferometer  

Microsoft Academic Search

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 2 between each measurement, allowing complex visibility measurements (modulus

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

2005-01-01

4

A Two Color Quadrature Interferometer for the TCS Experiment  

NASA Astrophysics Data System (ADS)

The TCS experiment at the Redmond Plasma Physics Labotatory (RPPL) is designed to demonstrate current sustainment and heating of a pre-formed FRC plasma using a rotating magnetic field (RMF)at 150 kHz. NE must be accurately measured between 10^19 and 10^21 m-3. We have constructed a two-color, double pass interferometer for the TCS sustainment chamber. CO2 and HeNe lasers at 10.6 and 0.63 microns are used with separate Bragg modulators to generate reference beams shifted by 40 MHz. A unique design uses a single large spherical mirror to focus all beams. We find this technique greatly facilitates alignment. The scene beams may be switched from a single table mode of operation to a through-plasma mode by insertion of a single right angle mirror. Scene beams return to the main table from a hollow corner-cube reflector insuring good signal amplitude stability even though the supporting structure is quite flexible.

Crawford, Edward; Euripides, Peter; Votroubek, George

1999-11-01

5

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

6

Quadrature Phase Interferometry: a phase-sensitive rotation shearing interferometer for diffraction-limited imaging  

NASA Astrophysics Data System (ADS)

We have developed a new technique of rotation shearing interferometry, for diffraction-limited imaging through turbulence at visible wavelengths from single ground-based telescopes. While previous rotation shearing interferometers have been used in astronomical observations, none has successfully measured visibility phase in the presence of turbulent aberrations. Our technique, called Quadrature Phase Interferometery (QPI), simultaneously obtains four interferograms, each of which observes the same interferometric baselines with differing instrumental phase contributions. These instrumental phase contributions allow full determination of the complex visibility (modulus and phase) from a single exposure, over all baselines up to the telescope diameter. Turbulent phase aberrations can be averaged out of successive exposures to obtain diffraction-limited images. The expected limiting magnitudes of this technique are comparable to those of other passive techniques such as speckle interferometry or non-redundant masking. The QPI has been tested in the laboratory and at Palomar Observatory, with encouraging results. The design principles and results will be discussed. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research.

Kern, B.; Dimotakis, P. E.; Martin, C.; Lang, D. B.; Thessin, R. N.

2004-12-01

7

Laser wavemeter with solid Fizeau wedge interferometer  

Microsoft Academic Search

A Fizeau wavemeter using a solid Fizeau wedge interferometer that is suitable for determining the wavelength of pulsed or CW laser light has been modeled and investigated experimentally. Accuracy of a few parts in 10 to the 6th over a wide wavelength range can be achieved with careful design. Experimental accuracy of 2 parts in 10 to the 6th was

Christopher Reiser; R. B. Lopert

1988-01-01

8

Laser wavemeter with solid Fizeau wedge interferometer  

SciTech Connect

A Fizeau wavemeter using a solid Fizeau wedge interferometer that is suitable for determining the wavelength of pulsed or cw laser light has been modeled and investigated experimentally. Accuracy of a few parts in 10/sup 6/ over a wide wavelength range can be achieved with careful design. Experimental accuracy of 2 parts in 10/sup 6/ was demonstrated over a range of 40 nm.

Reiser, C.; Lopert, R.B.

1988-09-01

9

Controller of the Laser Interferometer Space Antenna  

NASA Technical Reports Server (NTRS)

The Laser Interferometer Space Antenna 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. The Disturbance Reduction System comprises the pointing and positioning control of the spacecraft, electrostatic suspension control of the test masses, and point-ahead and acquisition control. This paper presents a control architecture and design for the Disturbance Reduction System to meet the stringent pointing and positioning requirements. Simulations are performed to demonstrate the feasibility of the proposed architecture.

Hyde, T. T.; Maghami, P. G.; Kim, J.

2004-01-01

10

Laser diode in a coherent resolved interferometer  

NASA Astrophysics Data System (ADS)

A short coherence length of a laser diode (LD) is required in coherent resolved interferometers. The coherence length of a LD can be reduced by modulating the source with a high frequency signal, which is superposed on the driving current for the LD. A 980nm laser diode in this paper is modulated with a frequency 40MHz and modulation depth 0.5, where its coherence length is compressed 20 times. The first side-band peak in the coherence function is reduced by 10dB, but it is hard to suppress them completely.

Sun, Dongsong; Liu, Shigang; Zhao, Yuan; Qiao, Lijie

1996-09-01

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

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

SciTech Connect

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

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

2010-04-15

16

Extraction of energy from gravitational waves by laser interferometer detectors  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the energy interaction between gravitational waves and laser interferometer gravitational wave detectors. We show that the widely held view that the laser interferometer gravitational wave detector absorbs no energy from gravitational waves is only valid under the approximation of a frequency-independent optomechanical coupling strength and a pump laser without detuning with respect to the resonance of the interferometer. For a strongly detuned interferometer, the optical-damping dynamics dissipates gravitational wave energy through the interaction between the test masses and the optical field. For a non-detuned interferometer, the frequency-dependence of the optomechanical coupling strength causes a tiny energy dissipation, which is proved to be equivalent to the Doppler friction raised by Braginsky et al.

Ma, Yiqiu; Blair, David G.; Zhao, Chunnong; Kells, William

2015-01-01

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

Interferometer combines laser light source and digital counting system  

NASA Technical Reports Server (NTRS)

Measurement of small linear displacements in digital readouts with extreme accuracy and sensitivity is achieved by an interferometer. The instrument combines a digital electro-optical fringe-counting system and a laser light source.

1965-01-01

19

Multicomponent wavefield characterization with a novel scanning laser interferometer  

E-print Network

, Staszewski et al.4 acquired two-dimensional scans of Lamb waves in metallic samples. Their costly system used OF THE SENSOR Our adaptive laser ultrasonic receiver is based on a constant-wave doubled Nd:YAG Neodymium from seismology to nondestructive testing. A new compact scanning laser ultrasonic interferometer

Boise State University

20

Submillimeter laser interferometer for high density plasma diagnostic  

NASA Astrophysics Data System (ADS)

There are presented the results of investigation of the one-channel homodyne laser interferometer ?=119 µm made on the basis of the hollow dielectric beamguide and quasioptical functional devices. The interferometer is designed for determination of the plasma electron density of the TOKAMAK-7. The density response threshold is 0.7% from the expected plasma density and the phase difference measurement total error is 5°

Kamenev, Yu. E.; Kiselyev, V. K.; Kuleshov, E. M.; Knyaz'kov, B. N.; Kononenko, V. K.; Nesterov, P. K.; Yanovsky, M. S.

1995-06-01

21

Submillimeter laser interferometer-polarimeter for plasma diagnostics  

NASA Astrophysics Data System (ADS)

There are presented the results of investigation of the homodyne laser interferometer-polarimeter (lambda) equals 195 micrometers made on the quasioptical element basis and designed for the synchronous determination of the plasma electron density ne and the poloidal magnetic field Bp in 'TOKAMAK' mountings of the thermonuclear fusion.

Kamenev, Yu. E.; Kiselyev, Vladimir K.; Kuleshov, E. M.; Knyaz'kov, B. N.; Kononenko, V. K.; Nesterov, P. K.; Yanovsky, M. S.

1994-08-01

22

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

23

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

24

High-temperature laser interferometer for thermal expansion and optical-length measurements  

Microsoft Academic Search

A simple laser interferometer has been utilized to measure the thermal expansion and optical-length variation with temperature of highly reactive fluorides at high temperatures. The interferometer is a modification of the Jamin interferometer in which a laser beam is split into two parallel beams which traverse nearly identical paths and are reflected from the sample and a reference mirror. The

T. S. AuroraS; S. M. Day; V. King; D. O. Pederson

1984-01-01

25

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

NASA Astrophysics Data System (ADS)

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

Köning, Rainer; Wimmer, Gejza; Witkovský, Viktor

2014-11-01

26

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

27

A laser interferometer dilatometer for thermal expansion measurements of composites  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

28

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

PubMed

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

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

2014-01-01

29

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

30

Lithium atom interferometer using laser diffraction : description and experiments  

E-print Network

We have built and operated an atom interferometer of the Mach-Zehnder type. The atomic wave is a supersonic beam of lithium seeded in argon and the mirrors and beam-splitters for the atomic wave are based on elastic Bragg diffraction on laser standing waves at 671 nm. We give here a detailed description of our experimental setup and of the procedures used to align its components. We then present experimental signals, exhibiting atomic interference effects with a very high visibility, up to 84.5 %. We describe a series of experiments testing the sensitivity of the fringe visibility to the main alignment defects and to the magnetic field gradient.

Alain Miffre; Marion Jacquey; Matthias Büchner; Gérard Trenec; Jacques Vigue

2005-04-08

31

Measurement of the emission linewidth of a single-frequency semiconductor laser with a ring fibre interferometer  

SciTech Connect

A simple scanning interferometer is implemented for measuring the emission linewidth of single-frequency semiconductor lasers. The free dispersion region of the interferometer is 28 MHz, the spectral resolution being 470 kHz. (laser spectroscopy)

Trikshev, A I; Kurkov, Andrei S; Tsvetkov, V B; Pyrkov, Yu N; Paramonov, V N

2011-07-31

32

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

33

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

2014-12-01

34

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

35

Ring fibre laser with interferometer based in long period grating for sensing applications  

NASA Astrophysics Data System (ADS)

This work presents two distinct configurations based on phase-wavelength conversion using a ring fibre laser with two different long period gratings interferometer topologies. The sensors are interrogated by analysing the wavelength change of the emission laser, which is directly dependent on the interferometer phase change. The first configuration integrates a Mach-Zehnder interferometer, which is based on a pair of long period gratings and is used as sensing head for bending radius and longitudinal strain measurement. The second configuration, comprehends a Michelson interferometer, which is based on a single LPG and a fibre end mirror and is used as a liquid level sensor or as an optical refractometer.

Frazão, O.; Correia, C.; Baptista, J. M.; Marques, M. B.; Santos, J. L.

2008-11-01

36

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

37

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

38

Laser impulse generation and interferometer detection of zero group velocity Lamb mode resonance  

E-print Network

Laser impulse generation and interferometer detection of zero group velocity Lamb mode resonance and antisymmetric modes for a plate of thickness d made of a material having longitudinal and transverse bulk wave

39

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

40

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

NASA Astrophysics Data System (ADS)

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

Koltchanov, Igor; Petermann, Klaus; Roths, Johannes

1997-09-01

41

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

42

Interference patterns produced by a Mach-Zehnder interferometer and a multiline HF laser  

NASA Astrophysics Data System (ADS)

The fringe pattern produced by a Mach-Zehnder interferometer illuminated with the light from a hydrogen fluoride (HF) laser operating on a large number of laser lines was investigated. Emphasis was placed on the intensity variations of the infrared fringes that are observed when one element of the interferometer is translated, thereby changing the length of one optical path. An intensity maximum similar to "white-light fringes" is observed when the two arms of the interferometer have equal optical lengths. The experimental results are compared with numerically predicted fringe patterns calculated from the spectral content of the illuminating laser beam. A method is suggested for actively controlling the phases of a number of parallel HF laser amplifiers in high-power phased-array devices.

Gross, R. W. F.; Coffer, J. G.; Turner, E. B.; Chodzko, R. A.; Warren, W. R., Jr.

1980-04-01

43

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

44

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

45

Combination of measurement and control procedures in laser Fizeau interferometers  

NASA Astrophysics Data System (ADS)

A method to combine the procedures of measurement and control of transparent wedged plates for Fizeau interferometers with object and reference channels positioned on one optical axis is proposed and experimentally tested. The results of measuring control of a glass wedged plate are presented.

Lyalikov, A. M.

2014-12-01

46

A laser interferometer for combustion, aerodynamics and heat transfer studies  

Microsoft Academic Search

A large-area interferometer is described which is based on schlieren system and designed to be used subtractively by a double exposure method. The beam is split using front and rear surface reflections from a small-angle prism. On the double exposure interferogram both the fringe spacing and shear are variable. The aim is to subtract not only aberrations and windows, but

S. S. Sandhu; F. J. Weinberg

1972-01-01

47

A laser frequency and power control system in an atomic Talbot-Lau interferometer  

NASA Astrophysics Data System (ADS)

The importance of atom interferometers that have high sensitivity and super precision is well recognized in the fields of rotation sensing, inertial and gravitational forces sensing, relativity tests, and other precision measures. So many researchers are absorbed in atom interferometers. An atom interferometer consists of many parts, among of which optical part plays a significant role because of the need of laser beams in every parts. Based on this situation and some specific quantitive requirements to laser beams, this article presents a laser frequency and power control system for atom interferometer which can realize the functions of frequency shift and scan, power stabilization and modulation, and highspeed switch. The system lies on acousto-optical modulators (AOM) and a phase-locked loop frequency synthesizer is designed in the system as a very important part which has wide capture range of frequency and well stability. The experimental results show that the designed system is available and the performances of laser through AOM are as good as expected and the phase noise of the output is restrained. In addition, the system also could be used in other instruments and devices, such as atomic clock, gravimeter, gradiometer, and gyroscope.

Yang, Ting; Hu, Zhaohui; Qi, Lu

2013-12-01

48

Errors caused by nearly parallel optical elements in a laser Fizeau interferometer utilizing strictly coherent imaging  

Microsoft Academic Search

Most commercial laser Fizeau interferometers employ a rotating diffuser on an intermediate image plane. The image formed on this plane is relayed to the detector using incoherent imaging, eliminating potential interference effects from elements after the diffuser. Systems requiring high spatial frequency resolution cannot employ the diffuser or incoherent relay system to the degradation they cause to the system transfer

Erik Novak; Chiayu Ai; James C. Wyant

1997-01-01

49

1V operation laser diode for FTTH by using active multi-mode-interferometer (MMI)  

Microsoft Academic Search

Active multi-mode-interferometer (MMI) laser diodes (LDs) achieved low operating voltage of only 1V at 10 mW light output (??1.5 ?m), due to the significant resistance reduction of 60% compared to that of regular LDs, and 1 Gbps operation.

K. Hamamoto; M. Ohya; K. Naniwae; S. Sudo; T. Sasaki; S. Shimizu; M. D. B. Razali; K. Kasahara

2005-01-01

50

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

51

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

NASA Technical Reports Server (NTRS)

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

Seidel, David J.; Dubovitsky, Serge

2000-01-01

52

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

PubMed

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

Consoli, Antonio; Esquivias, Ignacio

2012-09-24

53

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.

54

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

NASA Astrophysics Data System (ADS)

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

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

55

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

SciTech Connect

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

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

1996-06-27

56

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

E-print Network

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

Markus Herz

2005-08-23

57

Transfer function characterization of laser Fizeau interferometer for high-spatial-frequency phase measurements  

Microsoft Academic Search

Large, high power laser systems such as that being constructed by Lawrence Livermore National Laboratories for the National Ignition Facility require accurate measurements of spatial frequencies of up to 2.5 lines\\/mm over a 100mm field of view.In order to ensure accurate measurements of the parts, the test apparatus must be well characterized. The systems transfer function (STF) of the interferometer

Erik Novak; Chiayu Ai; James C. Wyant

1997-01-01

58

BRIEF COMMUNICATIONS: Computer-controlled laser radiation wavelength meter based on the Fizeau interferometer  

Microsoft Academic Search

A description is given of a computer-controlled wavelength meter designed for the 500-650 nm range. It consists of four Fizeau interferometers, multichannel photodetectors with a control system, and a microcomputer. The resolution of this instrument is 107. The minimum detectable energy is 0.1 mJ. It can deal with continuous and pulsed laser radiation. Bibtex entry for this abstract Preferred format

S. Yu Volkov; V. I. Pelipenko; Valery V. Smirnov

1982-01-01

59

Two-wavelength dye-laser operation using a reflecting Fizeau interferometer  

Microsoft Academic Search

Newly found reflection properties of the Fizeau wedge interferometer are shown to be of particular advantage in obtaining\\u000a efficient multi-wavelength operation of dye lasers. Use is made of the fact that the reflecting Fizeau wedge can ensure at\\u000a once a selective feedback for a given wavelength and quasi-total reflection in an other direction for all other wavelengths.\\u000a Fully independent tuning

M. N. Nenchev; Y. H. Meyer

1981-01-01

60

Femtosecond laser writing of a flat-top interleaver via cascaded Mach-Zehnder interferometers.  

PubMed

A flat-top interleaver consisting of cascaded Mach-Zehnder interferometers (MZIs) was fabricated in bulk glass by femtosecond laser direct writing. Spectral contrast ratios of greater than 15 dB were demonstrated over a 30 nm bandwidth for 3 nm channel spacing. The observed spectral response agreed well with a standard transfer matrix model generated from responses of individual optical components, demonstrating the possibility for multi-component optical design as well as sufficient process accuracy and fabrication consistency for femtosecond laser writing of advanced optical circuits in three dimensions. PMID:23038339

Ng, Jason C; Li, Chengbo; Herman, Peter R; Qian, Li

2012-07-30

61

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

E-print Network

Ground-based laser interferometers for gravitational-wave (GW) detection were first constructed starting 20 years ago and as of 2010 collection of several years' worth of science data at initial design sensitivities was completed. Upgrades to the initial detectors together with construction of brand new detectors are ongoing and feature advanced technologies to improve the sensitivity to GWs. This conference proceeding provides an overview of the common design features of ground-based laser interferometric GW detectors and establishes the context for the status updates of each of the four gravitational-wave detectors around the world: Advanced LIGO, Advanced Virgo, GEO600 and KAGRA.

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

2014-01-01

62

Modelling laser interferometers for the measurement of the Avogadro constant  

NASA Astrophysics Data System (ADS)

In dimensional measurements by laser interferometry, when the accuracy approaches 10-9 ?, wavefront aberra­ tions cause systematic variations of the fringe period. This paper illustrates how these effects are modeled and experimentally studied in the measurements of the lattice parameter and the topographical survey of 1 kg Si spheres, which measurements are necessary to "count" atoms and to make it possible to realize the kilogram from the Planck constant value.

Andreas, Birk; Mana, Giovanni; Massa, Enrico; Palmisano, Carlo

2013-05-01

63

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

64

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Control of the profile of a laser output beam using an inhomogeneous interferometer  

NASA Astrophysics Data System (ADS)

A method is proposed for controlling the intensity distribution over the cross section of a laser beam. In this method the laser exit mirror is an inhomogeneous interferometer whose transmission profile is continuously variable by varying its length over a range of ? / 2. The results are reported of a modification of the profile of an He-Ne laser beam from close to Gaussian to a beam having a dip on the axis, with almost no reduction in the laser output power. It is noted that an inhomogeneous interferometer can be used to control the phase distribution in a beam and to modify the mode structure of the laser radiation.

Matizen, Yu É.; Troitski?, Yu V.

1988-01-01

65

A nonintrusive laser interferometer method for measurement of skin friction  

NASA Technical Reports Server (NTRS)

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

Monson, D. J.

1982-01-01

66

Experiments with an 834 m2 ring laser interferometer  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

67

Large-Optics white light interferometer for laser wavefront test: apparatus and application  

NASA Astrophysics Data System (ADS)

There is transmitting optics of 250mm aperture with about 8 microradians in SILEX system. This is often large aperture and diffraction-limited laser beam in the laser communications. Large-Optics white light interferometer using double-shearing structure has been submitted to analysis the laser wavefront before. Six optical plates of 490 millimeters apertures are manufactured now one of which is also aperture-divided so that the precision of measured wave front is higher than the full aperture design. It is suitable for measurement of minimum diffraction-limited laser wave front and any wavelength. The interference is happened between equal optical path of the reflection and the other. The plates are the basic structures which are precisely parallel or perpendicular needed for either two plates. There are several tools equipped with the interferometer including white light test source and collimators and so on to confirm the precision of several seconds angle. The apparatus and application is explained in detail in this paper. The adjustment is important for the realization of white light test.

Luan, Zhu; Liu, Liren; Wang, Lijuan; Liu, De'an

2008-08-01

68

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

69

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

Microsoft Academic Search

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

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

2007-01-01

70

Wavelength switching of erbium-doped fiber laser by using Mach-Zehnder interferometer and cavity loss control  

NASA Astrophysics Data System (ADS)

A new wavelength-switchable erbium-doped fiber laser cavity is proposed and demonstrated. A Mach-Zehnder interferometer with controllable path-length difference was used in the laser cavity to tune the transmission peaks between two output paths of the interferometer. The erbium-doped fiber amplifier used in the laser cavity showed a tilted gain spectrum over the concerned wavelength range. A fiber bending scheme was used to switch the lasing wavelength taking advantage of the gain-tilt characteristics of the spectrum. The experimental result showed a stable four-wavelength lasing for each tuning and bending.

Lin, Chia-Ping; Wang, Likarn

2015-01-01

71

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

E-print Network

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

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

2000-06-07

72

Sightline optimization of the multichannel laser interferometer for W7-X  

SciTech Connect

A multichannel CO{sub 2} laser interferometer is planned for electron density profile measurements in the Wendelstein 7-X stellarator under construction. This article describes the mathematical methods used to find the optimum orientation of the various sightlines. The problem of reconstructing local densities from line integrated density measurements can be formulated as a matrix inversion. The quality of the reconstruction is largely determined by the condition number of the matrix describing the problem, which has to be minimized, i.e., the sightlines have to be chosen such that the information content of different channels is maximally distinct. For the W7-X interferometer four- and eight-sightline arrangements are investigated and their orientations are optimized for standard conditions of magnetic configuration and density profile. The optimized arrangements are tested by simulating the inversion of hypothetical reference density profiles in a number of different magnetic configurations. In the ideal case the error of a reconstruction using four sightlines is typically a few times larger than that with eight sightlines. The robustness of the optimization is demonstrated by a variation of the position of the whole interferometer, and the influence of noisy phase data on the reconstructed profiles is investigated. These factors significantly narrow the difference between the four- and eight-beam setups. Finally, the use of regularization methods for the analysis of experimental data is briefly discussed.

Airila, M.I.; Dumbrajs, O.; Hirsch, M.; Geiger, J.; Neuner, U.; Hartfuss, H.-J. [Helsinki University of Technology, Association Euratom-Tekes, P.O. Box 2200, FI-02015 TKK (Finland); Max-Planck-Institut fuer Plasmaphysik, Association Euratom-IPP, Wendelsteinstrasse 1, D-17491 Greifswald (Germany)

2005-02-01

73

Interferometer for the measurement of plasma density  

DOEpatents

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

Jacobson, Abram R. (Los Alamos, NM)

1980-01-01

74

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

75

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

76

Four-level atomic interferometer driven by shaped ultrafast laser pulses  

SciTech Connect

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

Clow, Stephen; Weinacht, Thomas [Department of Physics, Stony Brook University, Stony Brook, New York 11794 (United States)

2010-08-15

77

Fiber optic interferometer with tuning diode laser for gravity field measuring  

NASA Astrophysics Data System (ADS)

This paper discusses the remote sensing based on a GaAs diode laser with an external dispersive cavity (DL EDC). The scheme provides continuous generation on a single longitudinal mode of external cavity and the generation line-width less than 1 kHz or generation on a broad mode of internal laser cavity. This source of coherent radiation provided the work of fiber-optic accelerometer, which also is fiber-optic sensor of gravity field. The fiber-optic gravimeter includes fiber-optic interferometers of Mach- Zhender and has possibility to measure value and direction of gravity field's vector in three-dimensional space. Resolution of phase shift on level 10E-3 rad gives the possibility to measure the change of value of gravity field's vector on level 10E-6*g (where g - acceleration of free fall).

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

1996-10-01

78

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

79

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

80

Tunable laser with tilted-mirrors interferometer and dynamic wavelength reference  

NASA Astrophysics Data System (ADS)

The paper presents a fiber optic tunable laser built with a band pass tunable optical filtering cascade made of two tiltedmirrors (Optune) interferometers as feedback element of an optical amplifier. A dynamic wavelength reference monitors the laser wavelength. The optical cascade has 200 nm tuning range, the band pass has 0.2 dB insertion loss flatness across the entire tuning range, 0.1 nm bandwidth at 3 dB, 45 dB rejection ratio and 160 dB/nm roll-off. According to the measurements, the line width of this tunable laser is below 41 MHz. The dynamic wavelength reference generates wavelength markers with 0.1 pm relative accuracy and with 1 pm absolute accuracy across 40°C temperature interval. These markers could be used to mitigate the non-linearity of the laser tuning. It was achieved 800 nm/ms tuning speed with the tuning element working below its resonant frequency. The experiments performed in open-loop operation in 1550 nm spectral region revealed 1 pm tuning accuracy and 0.1% tuning non-linearity versus the tuning voltage across 40 nm tuning interval. Laser line roll-off is steeper than 160 dB/nm. With appropriate reflective coatings, the filtering cascade can operate also in other spectral regions (visible, UV) with tuning accuracy limited by the wavelength reference and by the laser controller. A digital signal processor monitors the operation of the tunable laser to achieve optimum performance. This tunable laser source has applications in interrogators for fiber optic sensors and in optical coherence tomography.

Miron, Nicolae

2009-02-01

81

INTRACAVITY LASER ABSORPTION SPECTROSCOPY USING QUANTUM CASCADE LASER AND FABRY-PEROT INTERFEROMETER  

E-print Network

INTRACAVITY LASER ABSORPTION SPECTROSCOPY USING QUANTUM CASCADE LASER AND FABRY pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69 Major Professor: Robert E. Peale #12;ii © 2011 Gautam Medhi #12;iii ABSTRACT Intracavity Laser

Peale, Robert E.

82

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

83

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

PubMed

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

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

2000-05-01

84

Optical beat-note frequency stabilization between two lasers using a radio frequency interferometer in the gigahertz frequency band  

NASA Astrophysics Data System (ADS)

A beat-note frequency stabilization system using a distributed-feedback laser and external cavity laser diode has become a very important technique for laser spectroscopy, where highly stabilized high-frequency beat notes are required. We have developed a simple and versatile system capable of stabilizing the high-frequency beat notes (3 to 11 GHz) of two lasers using a delayed radio frequency self-heterodyne interferometer and have confirmed its basic operation. The frequency stability of the obtained beat notes is higher than 1 MHz in the 3- to 11-GHz frequency range with an average time of 20 s.

Uehara, Tomoyuki; Tsuji, Kenichiro; Hagiwara, Kohei; Onodera, Noriaki

2014-12-01

85

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

86

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

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

88

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

PubMed

We present a space and time resolved interferometric plasma diagnostic for use on plasmas where neutral-bound electron contribution to the refractive index cannot be neglected. By recording simultaneously the plasma optical index at 532 and 1064nm, we are able to extract independently the neutral and free electron density profiles. We report a phase resolution of 30m rad , corresponding to a maximum resolution on the order of 4×10(22)m(-3) for the electron density, and of 10(24)m(-3) for the neutral density. The interferometer is demonstrated on centimeter-scale sparks triggered by laser filamentation in air with typical currents of a few tens of A. PMID:25554266

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

2014-12-01

89

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

90

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

91

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

PubMed

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. PMID:25554288

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

2014-12-01

92

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

93

C- and L-band tunable fiber ring laser using a two-taper Mach-Zehnder interferometer filter.  

PubMed

A stable C- and L-band tunable fiber ring laser, using a two-taper Mach-Zehnder interferometer (MZI) as a filter, is proposed and demonstrated experimentally. One of the two taper waists is mechanically bent to tune the laser wavelength. Being amplified by an L-band erbium-doped fiber amplifier and an erbium-doped fiber, respectively, the fiber ring laser has a full L-band (1564-1605nm) and C-band (1550-1565nm) tuning range with a side-mode suppression ratio as high as 50dB. The laser linewidth and the minimum tuning step are related to the MZI's cavity length. It was also found that thermal annealing relieved the internal stresses of the tapers and greatly improved the laser performance. PMID:20967064

Wang, Xiaozhen; Li, Yi; Bao, Xiaoyi

2010-10-15

94

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

95

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

96

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

Microsoft Academic Search

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

Peter Fritschel

2003-01-01

97

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

98

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

SciTech Connect

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

Prasad, Y. B. S. R.; Barnwal, S.; Naik, P. A.; Kamath, M. P.; Joshi, A. S.; Kumbhare, S. R.; Gupta, P. D. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Bolkhovitinov, E. A.; Rupasov, A. A. [Laboratory of Plasma Diagnostics, P.N. Lebedev Physical Institute, 53 Leninsky Prospekt, Moscow 117924 (Russian Federation)

2011-12-15

99

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

PubMed

Self-generated magnetic fields produced in laser plasmas at moderate laser intensities have been measured using a three-channel polaro-interferometer. The main elements of this device are two birefringent calcite wedges placed between two crossed polarizers. Using this device, the spatial profiles of (a) the rotation angle (polarometry), (b) the electron density (interferometry), and (c) the transmitted probe beam intensity (shadowgraphy) are recorded simultaneously using a digital camera with a large format CCD in a single laser shot. Magnetic fields of 2-4 MG had been estimated in aluminum plasma at laser intensities ~10(13) W/cm(2). It is also possible to use this device in other configurations to get time resolved information. PMID:22225217

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

2011-12-01

100

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

101

Correlated quadratures of resonance fluorescence and the generalized uncertainty relation  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

102

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

PubMed

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

Liu, Yi; Qu, Shiliang

2014-01-20

103

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

DOEpatents

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

Buchenauer, C.J.

1981-09-23

104

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

DOEpatents

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

Buchenauer, C. Jerald (Los Alamos, NM)

1984-01-01

105

Conversion of laser phase noise to amplitude noise in a Lummer-Gehrcke interferometer and in oxygen gas  

NASA Astrophysics Data System (ADS)

In order to observe laser phase noise, this noise must be converted to amplitude noise, which can be achieved using either an interferometer or an absorption resonance in an atomic/molecular vapor or gas. When phase noise is converted to amplitude noise, it is manifested as a heterodyne signal in the output of an optical square-law detector. Thus, phase noise is measured by optical heterodyne spectroscopy, or, equivalently, laser phase noise spectroscopy. In recent work on diode laser noise spectroscopy of rubidium and oxygen, the observed spectroscopic lineshapes were not in total agreement with theoretical predictions. We have repeated the previous work on the oxygen A-band transitions, and we now find qualitative agreement with theory. In addition, we have measured the diode laser noise spectrum of a Lummer-Gehrcke interferometer (LGI), comparing the heterodyne lineshape of a LGI transmission spectrum with a qualitative theory that we develop in this thesis. A theory, from other workers, predicts the intensity fluctuations from a Doppler-broadened, two-level atomic/molecular system driven with a phase-diffusing laser field. We show that a simplified version of this theory, which ignores Doppler effects of the system, is a useful approximation to the complete theory, by comparing computer-generated heterodyne lineshapes of each, for a rubidium transition. We apply this approximate theory to an oxygen A-band transition, and compare these results with our experimental measurements. For the experimental arrangement used in the present work, diode laser noise spectroscopy may also include effects of selective reflection, which is dealt with experimentally and theoretically. Diode laser phase noise has practical importance in optical communications and atomic clocks.

Wichner, Brian Donald

1999-01-01

106

The Contribution of Halo White Dwarf Binaries to the Laser Interferometer Space Antenna Signal  

NASA Astrophysics Data System (ADS)

Galactic double white dwarfs were postulated as a source of confusion limited noise for the Laser Interferometer Space Antenna (LISA), the future space-based gravitational wave observatory. Until very recently, the Galactic population consisted of a relatively well-studied disk population, a somewhat studied smaller bulge population and a mostly unknown, but potentially large halo population. It has been argued that the halo population may produce a signal that is much stronger (factor of ~5 in spectral amplitude) than the disk population. However, this surprising result was not based on an actual calculation of a halo white dwarf population, but was derived on (1) the assumption that one can extrapolate the halo population properties from those of the disk population and (2) the postulated (unrealistically) high number of white dwarfs in the halo. We perform the first calculation of a halo white dwarf population using population synthesis models. Our comparison with the signal arising from double white dwarfs in the Galactic disk+bulge clearly shows that it is impossible for the double white dwarf halo signal to exceed that of the rest of the Galaxy. Using microlensing results to give an upper limit on the content of white dwarfs in the halo (~30% baryonic mass in white dwarfs), our predicted halo signal is a factor of 10 lower than the disk+bulge signal. Even in the implausible case, where all of the baryonic halo mass is found in white dwarfs, the halo signal does not become comparable to that of the disk+bulge, and thus would still have a negligible effect on the detection of other LISA sources.

Ruiter, Ashley J.; Belczynski, Krzysztof; Benacquista, Matthew; Holley-Bockelmann, Kelly

2009-03-01

107

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

108

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

109

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

SciTech Connect

A symmetrical atom interferometer with a thermal calcium atom beam has been developed using a narrow linewidth diode laser stabilized to the resonance of a high-finesse cavity. The linewidth of the diode laser was estimated to be less than 1 Hz relative to the cavity resonance in noise measurement over the range of 100 Hz to 1 MHz, and the phase instability of the interference fringes obtained from the Allan deviation was improved to 2 mrad at an integration time of 300 s. Using this atom interferometer, the ac Stark phase shift between the {sup 1}S{sub 0} and {sup 3}P{sub 1} states of a Ca atom was measured as a function of a laser power near the resonance of the {sup 1}S{sub 0}-{sup 1} P{sub 1} transition at a wavelength of 423 nm. The decay rate of the {sup 1}P{sub 1} state was determined to be {gamma}=1.91(33)x10{sup 8} s{sup -1}.

Akatsuka, Tomoya; Mori, Yoshihiro; Sone, Nobuhiko; Ohtake, Yurie; Machiya, Mamoru; Morinaga, Atsuo [Faculty of Science and Technology, Tokyo University of Science, Noda-shi, Chiba 278-8510 (Japan)

2011-08-15

110

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

111

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

112

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

Microsoft Academic Search

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

A. Gillespie; F. Raab

1993-01-01

113

Spherical grating monochromator with interferometer control and in-vacuum reference  

NASA Astrophysics Data System (ADS)

Physical Science Laboratory's new generation of spherical grating monochromators incorporates a laser interferometer to control scan angle and an in-vacuum absolute angle reference, as well as other improvements. The design accommodates up to six gratings which can be moved axially (under motor control, with encoder position readback) at any scan angle. The gratings are cooled by means of spring-loaded clamps which conduct heat to a water-cooled plate. The instruments feature hollow roller bearings on the scan axis to minimize bearing runout, and a pseudosine-bar drive for precise control of grating angle. The interferometer angle-measuring optics are mounted inside the vacuum chamber and measure the angle between the grating scan axis and the instrument's granite base. The laser interferometer measures the grating angle with a resolution of approximately 0.02 arcsec over the entire scan range of 40°. To provide a reference for the interferometer angle measurement, we have built an in-vacuum optical reference which uses custom chrome-on-glass reticles mounted inside the vacuum chamber. Collimated light from a source outside the vacuum passes through the reticles to yield quadrature signals which precisely define an absolute reference angle for the interferometer. Repeatability of the grating angle is within a range of ±0.05 arcsec. Two of these instruments are in operation at SRRC (Taiwan) and a third instrument has been delivered to NSLS (Brookhaven).

Holly, D. J.; Mason, W. P.; Sailor, T.; Smith, R. E.; Wahl, D.

2002-03-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

115

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

116

Stabilization improvements of laser-diode closed-loop heterodyne phase-shifting interferometer for surface profile measurement.  

PubMed

To stabilize the phase-shifting Fizeau-type interferometer against environmental disturbances (namely, vibration and temperature variations), the feedback scheme that uses the current-induced frequency modulation of a laser diode (lambda = 633 nm) and the two-frequency optical heterodyne method has been investigated, with particular attention to improvement of the achievable stabilization. It is demonstrated that introduction of the proportional-integral control into the feedback system improves stabilization against the proportional control case; e.g., stabilization is improved 5 times for 100-nm(p-p) vibration at the frequency range at 30 Hz. The surface profile measurement for a sample mirror was conducted with a reproducibility of 6.8 nm in the root mean square under the subwavelength-amplitude vibration at 100 Hz. PMID:12683759

Yokota, Masayuki; Asaka, Atsuyoshi; Yoshino, Toshihiko

2003-04-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

118

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

119

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

120

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

121

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

E-print Network

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

Melanie Meinders; Roman Schnabel

2015-01-21

122

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

E-print Network

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

Meinders, Melanie

2015-01-01

123

The improved pyroelectric detectors for far-infrared laser interferometer measuring  

NASA Astrophysics Data System (ADS)

In this paper, the application of the pyroelectric detectors for Far-Infrared laser diagnostics on TOKAMAK plasma is described. We discovered experimentally that the Fabry-Perot interference could affect the performance of the pyroelectric detectors (PED). The improved pyroelectric detector (IPD) was developed for FIR laser coheront measuring. Some designing considerations about the pyroelectric detectors used in high temperature plasma conditions are mentioned.

Xiang, Gao

1990-05-01

124

Ultra low frequency noise laser by locking to an all-fibered interferometer  

Microsoft Academic Search

Very low frequency noise lasers are important tools for many applications such as high-resolution spectroscopy, optical atomic clock local oscillator, interferometric sensor (including gravitational waves detection), and coherent optical communications systems. Laser linewidth is usually reduced by locking to an ultra-stable optical cavity, using the Pound-Drever-Hall method. It led to fractional frequency instability lower than 10-15 for 1 s averaging

F. Kefelian; H. Jiang; P. Lemonde; G. Santarelli

2009-01-01

125

Digital quadrature phase detection  

DOEpatents

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

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

1992-01-01

126

Digital quadrature phase detection  

DOEpatents

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

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

1992-05-26

127

Quadrature interferometry for nonequilbrium ultracold atoms in optical lattices  

NASA Astrophysics Data System (ADS)

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

Johnson, Philip; Tiesinga, Eite

2013-03-01

128

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

129

Phase-Locked Control of Tiled-Grating Assemblies for Chirped-Pulse-Amplified Lasers Using a Mach-Zehnder Interferometer  

SciTech Connect

Multikilojoule petawatt lasers using chirped-pulse amplification are being constructed worldwide. Several systems have adopted a tiled-grating approach to meet the size requirements for the compression gratings. Grating tiles need to be precisely phased to ensure a transform-limited focal spot when focusing high-energy laser pulses in the target plane. A computer-control test system that uses a Mach-Zehnder interferometer capable of monitoring and correcting drift in the tiled-grating assemblies within the compressor is described.

Bunkenburg, J.; Kessler, T.J.; Skulski, W.; Huang, H.

2006-04-27

130

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

131

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

132

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

133

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

134

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

135

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

136

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

E-print Network

We derive a general master equation relating the gravitational-wave observables r and Omega_gw(f). Here r is the tensor-to-scalar ratio, constrained by cosmic-microwave-background (CMB) experiments; and Omega_gw(f) is the energy spectrum of primordial gravitational-waves, constrained e.g. by pulsar-timing measurements, laser-interferometer experiments, and Big Bang Nucleosynthesis (BBN). Differentiating the master equation yields a new expression for the tilt d(ln Omega_gw(f))/d(ln f). The relationship between r and Omega_gw(f) depends sensitively on the uncertain physics of the early universe, and we show that this uncertainty may be encapsulated (in a model-independent way) by two quantities: w_hat(f) and nt_hat(f), where nt_hat(f) is a certain logarithmic average over nt(k) (the primordial tensor spectral index); and w_hat(f) is a certain logarithmic average over w_tilde(a) (the effective equation-of-state in the early universe, after horizon re-entry). Here the effective equation-of-state parameter w_tilde(a) is a combination of the ordinary equation-of-state parameter w(a) and the bulk viscosity zeta(a). Thus, by comparing constraints on r and Omega_gw(f), one can obtain (remarkably tight) constraints in the [w_hat(f), nt_hat(f)] plane. In particular, this is the best way to constrain (or detect) the presence of a ``stiff'' energy component (with w > 1/3) in the early universe, prior to BBN. Finally, although most of our analysis does not assume inflation, we point out that if CMB experiments detect a non-zero value for r, then we will immediately obtain (as a free by-product) a new upper bound w_hat < 0.55 on the logarithmically averaged effective equation-of-state parameter during the ``primordial dark age'' between the end of inflation and the start of BBN.

Latham A. Boyle; Alessandra Buonanno

2007-08-17

137

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

138

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

139

Quadrature interferometry for nonequilibrium ultracold bosons in optical lattices  

E-print Network

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

Eite Tiesinga; Philip R. Johnson

2013-03-12

140

Quadrature interferometry for nonequilibrium ultracold atoms in optical lattices  

NASA Astrophysics Data System (ADS)

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

Tiesinga, E.; Johnson, P. R.

2013-01-01

141

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

142

High Resolution, Real-Time Interferometer for Coherent Beam Combination  

NASA Astrophysics Data System (ADS)

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

Simion, Sandel; Blanaru, Constantin; Ursescu, Daniel

2010-04-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

144

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

145

Dense plasma diagnostics with an amplitude division soft X-ray laser interferometer based on diffraction gratings  

Microsoft Academic Search

Summary form only given. The development of gain-saturated soft X-ray lasers has opened the possibility to extend laser interferometry to large-scale high-density plasmas that can not be probed with optical lasers. The recent advent of gain-saturated tabletop soft X-ray lasers creates the opportunity of developing portable soft X-ray tools that will allow detailed maps of the electron density evolution in

J. Filevich; K. Kanizay; M. C. Marconi; J. L. A. Chilla; O. E. Martinez; J. J. Rocca

2000-01-01

146

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

147

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

148

Synthetic quadrature phase detector/demodulator for Fourier transform spectrometers.  

PubMed

A method is developed to demodulate (velocity correct) Fourier transform spectrometer data that are taken with an analog to digital converter that digitizes equally spaced in time. This method makes it possible to use simple low-cost, high-resolution audio digitizers to record high-quality data without the need for an event timer or quadrature laser hardware and makes it possible to use a metrology laser of any wavelength. The reduced parts count and simple implementation make it an attractive alternative in space-based applications when compared to previous methods such as the Brault algorithm. PMID:19104542

Campbell, Joel

2008-12-20

149

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

PubMed

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

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

2011-12-01

150

Computer-aided mode diagnostics and parameters optimization of a picosecond laser setup based on a modified Sagnak interferometer  

NASA Astrophysics Data System (ADS)

The method of computer aided diagnostics of the picosecond laser set-up is realized and offered for testing of ultra short pulses laser. The method is based on registration of correlation function series at one pass of the optical delay line of the correlator with pulses selection by energy. Method allow to obtain laser pulses statistical distribution by duration and energy. Realization of the offered method provided with the information on parameters of lasing and with the appropriate ways of parameter optimization.

Boldovskii, Dmitry N.; Tikhonov, Eugene A.

1998-04-01

151

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

152

Numerical quadratures for singular and hypersingular integrals  

Microsoft Academic Search

We present a procedure for the design of high-order quadrature rules for the numerical evaluation of singular and hypersingular integrals; such integrals are frequently encountered in solution of integral equations of potential theory in two dimensions. Unlike integrals of both smooth and weakly singular functions, hypersingular integrals are pseudo-differential operators, being limits of certain integrals; as a result, standard quadrature

P Kolm; V Rokhlin

2001-01-01

153

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

154

Automatic quadrature control and measuring system  

NASA Technical Reports Server (NTRS)

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

Hamlet, J. F.

1973-01-01

155

Two-chord interferometry using 3.39??m He-Ne laser on a flux-coil-generated FRC.  

PubMed

A two-chord ?(IR)?3.39??m He-Ne laser interferometer system was developed for a flux-coil-generated field-reversed configuration to estimate the electron density and the total temperature of the field-reversed configuration (FRC) plasma. This two-chord heterodyne interferometer system consists of a single ?2?mW infrared He-Ne laser, a visible (?(vis)?632.8?nm) He-Ne laser for the alignment, a 40 MHz acousto-optic modulator, photodetectors, and quadrature phase detectors. Initial measurement was performed and the measured average electron densities were 2-10×10(19)?m(-3) at two different radial positions in the midplane. A time shift in density was observed as the FRC expands radially. The time evolution of the line-averaged density agrees with the density estimated from the in situ internal magnetic probes, based on a rigid-rotor profile model. PMID:21033867

Gota, H; Bolte, N; Deng, B H; Gupta, D; Kiyashko, V; Knapp, K; Mendoza, R; Morehouse, M; Roche, T; Wessel, F

2010-10-01

156

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

157

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

158

Automated setup for non-tactile high-precision measurements of roundness and cylindricity using two laser interferometers  

NASA Astrophysics Data System (ADS)

An automated setup for non-tactile high-precision measurements of roundness and cylindricity of ring gauges is presented. The aim is to minimize classical problems of tactile and radial roundness measurements such as the error influences of the used rotary table and the work piece alignment and thus to increase the accuracy and reduce the measurement time. To achieve those aims, a double interferometer concept was chosen and combined with a measurement system for the work piece alignment, a high-precision rotary table and an automated four-axis adjustment unit. The main alignment errors of the work pieces (e.g. ring gauges) such as eccentricity and tilting are either suppressed or directly detected and consequently reduced by the automated four-axis adjustment unit. Due to the non-tactile measurement concept, higher measurement velocities are achievable and surface destruction is prevented. In combination with the contactless energy supply of the four-axis adjustment unit, the radial run of the rotary table is not affected.

Kühnel, M.; Ullmann, V.; Gerhardt, U.; Manske, E.

2012-07-01

159

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

160

102?k large area atom interferometers.  

PubMed

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

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

2011-09-23

161

Simple optical system for manufacturing point diffraction interferometer plates in titanium films using a low intensity CW laser beam  

NASA Astrophysics Data System (ADS)

We propose an optical system for making pinholes in titanium films for applications in point diffraction interferometry. The optical system for fabrication is easy to implement and to align and, as a result of this, it is possible to obtain pinholes in the range of 1 to 8 ?m of diameter. The technique is based on laser ablation and, since we use a green laser, the spot produced by the focus of the optical system can be observed. Also, the damage over the titanium film can be monitored with the aid of a microscope objective lens in real time. The new technique is described and the resulting plates with the pinholes are shown. A successful application of the plates in interferometry is presented as well.

Aguilar, Juan C.; Aguilar, J. Félix; Berriel-Valdos, L. R.

2014-11-01

162

Multiple quadrature by Monte Carlo techniques  

E-print Network

MULTIPLE QUADRATURE BY MONTE CARLO TECHNIQUES A Thesis by JOHN DIETRICH VOSS Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1966 Major Subject...: Mathematics MULTIPLE QUADRATURE BY MONTE CARLO TECHNIQUES A Thesis by JOHN DIETRICH VOSS Approved as to style and content by: (Chairman of Co ittee) Ec (Head of Department) (M ember) ~ ember) May 1966 457988 ACKNOWLEDGMENTS I am deeply indebted...

Voss, John Dietrich

1966-01-01

163

JET polari-interferometer  

NASA Astrophysics Data System (ADS)

A multichannel far-infrared interferometer used on the Joint European Torus (JET) is described. The light source is a 195-?m DCN laser. The instrument is of the Mach-Zehnder type, with a heterodyne detection system. The modulation frequency (100 kHz) is produced by diffraction from a rotating grating. There are six vertical and two oblique channels. The latter rely on retroreflection from mirrors mounted on the vessel wall. Their vibration is compensated by a second wavelength interferometer at 118.8 ?m. The various subsystems are described, with emphasis on features necessitated by (a) large path lengths, (b) remote handling requirements, (c) fluctuations in atmospheric humidity, and (d) unmanned automatic operation. Typical measurements, along with real-time and off-line data analysis, are presented. The phase-shift measurement is made with an accuracy of (1)/(20) of a fringe, corresponding to a line-integrated electron density of 5×1017 m-2. Comparison with other electron density diagnostics are shown. The introduction of additional optics allows measurements of the Faraday effect and a determination of the poloidal magnetic field distribution. The signal processing and data analysis are described. Errors introduced by the calibration procedure, birefringence of the probing beams, toroidal field pickup, the flux geometry, and the density profile are considered. The Faraday angle is measured with an accuracy of 5% and a time resolution of 1-10 ms. The poloidal magnetic field is deduced with an accuracy of ±15%.

Braithwaite, G.; Gottardi, N.; Magyar, G.; O'Rourke, J.; Ryan, J.; Véron, D.

1989-09-01

164

Dual-beam skin friction interferometer  

NASA Technical Reports Server (NTRS)

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

Monson, D. J. (inventor)

1981-01-01

165

LIGO interferometer operating at design sensitivity with application to gravitational radiometry  

E-print Network

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

Ballmer, Stefan W. (Stefan Werner)

2006-01-01

166

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

PubMed Central

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

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

1989-01-01

167

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

SciTech Connect

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

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

2008-03-15

168

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

SciTech Connect

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

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

2008-03-15

169

Past and Future SOHO-Ulysses Quadratures  

NASA Technical Reports Server (NTRS)

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

Suess, Steven; Poletto, G.

2006-01-01

170

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

171

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

172

HYBRID GAUSS-TRAPEZOIDAL QUADRATURE RULES BRADLEY K. ALPERT  

E-print Network

HYBRID GAUSS-TRAPEZOIDAL QUADRATURE RULES BRADLEY K. ALPERT SIAM J. SCI. COMPUT. c 1999 Society;1552 BRADLEY K. ALPERT We derive new quadratures, based on the Euler­Maclaurin formula and its gener- alization

Alpert, Bradley K.

173

On Generalized Gaussian Quadratures for Exponentials and Their Applications  

Microsoft Academic Search

We introduce new families of Gaussian-type quadratures for weighted integrals of exponential functions and consider their applications to integration and interpolation of bandlimited functions.We use a generalization of a representation theorem due to Carathéodory to derive these quadratures. For each positive measure, the quadratures are parameterized by eigenvalues of the Toeplitz matrix constructed from the trigonometric moments of the measure.

G. Beylkin; L. Monzón

2002-01-01

174

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

E-print Network

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

Quinteros, Milton I.

2009-01-01

175

A Gauss quadrature rule for hypersingular integrals  

Microsoft Academic Search

We construct a set of polynomials ?n(x,t) which are orthogonal with respect to v(x,t)=w(x)\\/(x?t)p, t?(a,b), where w(x) is a weight function and p is an integer. As an application these polynomials can be used to extract Gaussian quadrature rules for hypersingular integrals.

S. A. Ashour; H. M. Ahmed

2007-01-01

176

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

177

Improved sensitivity in a gravitational wave interferometer and implications for LIGO  

Microsoft Academic Search

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

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

1996-01-01

178

A polarization sensitive interferometer for Faraday rotation detection.  

E-print Network

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

LaForge, Joshua Michael

2007-01-01

179

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

NASA Technical Reports Server (NTRS)

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

Hamlet, J. F. (inventor)

1974-01-01

180

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

181

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

182

Ramsey-Bordé interferometer for electrons  

NASA Astrophysics Data System (ADS)

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

Marzlin, Karl-Peter

2013-10-01

183

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

184

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

185

The AEI 10 m prototype interferometer  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

186

Surface profiling interferometer  

DOEpatents

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

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

1989-01-01

187

Photorefractive Interferometers for Ultrasonic Measurements on Paper  

SciTech Connect

Photorefractive interferometers have been employed for the detection of ultrasound in metals and composites since 1991 [1–4]. Instances of laser-generated ultrasound and laser-based detection in paper were reported in 1996 [5]. More recently, bismuth silicon oxide (BSO) photorefractive interferometers were adapted to detect ultrasound in paper [6]. In this article we discuss BSO and GaAs photorefractive detection of ultrasound on different paper grades and present the resulting waveforms. Compared to contact piezoelectric transducer methods, laser interferometry offers signifcant advantages. One of these is that it is a noncontact technique. This is especially important for on-line application to lightweight papers which could be marked or damaged by contact transducers. Broadband ultrasonic laser generation matched with the broadband sensitivity of laser interferometers is another beneft. This is important for obtaining narrow pulses in nondispersive time-of-fight determinations and for measuring the phase velocity of dispersive modes over a wide frequency band. Also, laser ultrasonic techniques provide a measure of bending stiffness through the analysis of low frequency A0 waves.

Lafond, E. F.; Brodeur, P. H.; Gerhardstein, J. P.; Habeger, C. C.; Telschow, Kenneth Louis

2002-12-01

188

Topological phase shift in a cold-atom interferometer  

NASA Astrophysics Data System (ADS)

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 dipole without spatial variation along the interferometer arms. The atom interferometer has been run with laser-cooled magnesium atoms stored in a magneto-optical trap.

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

1995-02-01

189

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

190

Squeezing of optomechanical modes in detuned Fabry-Perot interferometer  

E-print Network

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

Andrey A. Rakhubovsky; Sergey P. Vyatchanin

2012-12-12

191

Superharmonic Injection Locked Quadrature LC VCO Using Current Recycling Architecture  

E-print Network

superharmonic coupling????..?.. 7 3.1 Conventional LC VCO?????..??????????.. 8 3.2 Proposed quadrature voltage controlled oscillator??..??? 9 3.3 Current recycling mechanism?????????..???? 11 3.4 Comparison of amplitude between proposed and conventional... QVCO????????????????????..?? 13 3.5 Modeling of QVCO for mathematical analysis?????...? 16 3.6 Quadrature catch up of proposed QVCO???????..?.. 18 3.7 Impedance plot of parallel RLC??????????..?? 23 3.8 Quadrature phase error vs coupling factor...

Kalusalingam, Shriram

2011-02-22

192

A 0.5–20GHz quadrature downconverter  

Microsoft Academic Search

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

Joseph C. Bardin; Sander Weinreb

2008-01-01

193

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

194

Process control system using polarizing interferometer  

DOEpatents

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

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

1994-02-15

195

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

196

Hybrid photonic chip interferometer for embedded metrology  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

197

Fizeau plasma interferometer  

SciTech Connect

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

Frank, A.M.

1980-01-01

198

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

199

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

200

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Determination of the chromatic dispersion in single-mode fiber waveguides by a ring interferometer method  

NASA Astrophysics Data System (ADS)

A method was developed and apparatus was assembled for determination of the spectral dependence of the chromatic dispersion in a long ( ~ 1 km) section of a single-mode fiber waveguide with the aid of a ring interferometer in which the radiation phase was modulated. The radiation source was a halogen lamp coupled to a monochromator. The reproducibility in the determination of the delay time was ?? ~ 0.04 ns/km. The measured chromatic dispersion agreed well with that calculated using the refractive index profile of the blank from which the investigated fiber waveguide was drawn.

Belov, A. V.; Kurkov, Andrei S.; Semenov, V. A.; Chikolini, A. V.

1988-10-01

201

The Multidimensional Isotropic Generalization of Quadrature Filters in Geometric Algebra  

Microsoft Academic Search

In signal processing, the approach of the analytic signal is a capable and often used method. For signals of finite length, quadrature filters yield a band- pass filtered approximation of the analytic signal. In the case of multidimensional signals, the quadrature filters can only be applied with respect to a preference di- rection. Therefore, the orientation has to be sampled,

Michael Felsberg; Gerald Sommer

2000-01-01

202

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

203

Discrete ordinates quadrature schemes for multidimensional radiative transfer  

NASA Astrophysics Data System (ADS)

The fundamental problem of applying the method of discrete ordinates to radiative transfer predictions is the selection of the discrete directions and their associated weights. Both the accuracy of the solution and the computational effort depend on the angular discretization. This paper provides a sound mathematical methodology for the derivation of angular quadratures. By applying the collocation principle, the errors introduced by a quadrature are analyzed and the constituting equations of angular quadratures are identified. Special emphasis is placed on the rotational invariance of the qudrature schemes. Multidimensional radiative transfer in participating media with isotropic and anisotropic scattering is accounted for thoughout the analysis. A major goal of the present study is the construction of a new principle for multidimensional angular quadratures which is essentially a generalization of the principles employed for the well-known S(sub n) quadratures. The new construction principle has two major advantages. First, it enables a very flexible tailoring of quadratures according to the actual requirements. Second, compared to the S(sub n) quadratures, the new types of quadratures provide a higher accuracy while using the same number of nodal points.

Koch, R.; Krebs, W.; Wittig, S.; Viskanta, R.

1995-04-01

204

High-speed and high-resolution heterodyne interferometer  

NASA Astrophysics Data System (ADS)

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

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

1990-07-01

205

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

206

Ramsey-Bordé interferometer and embedded Ramsey interferometer with molecular matter waves of 39K2  

NASA Astrophysics Data System (ADS)

A matter wave interferometer based on a molecular beam of K2 has been designed for observation of both exits: with molecules in the electronically excited state and in the ground state. In addition to the excited state fluorescence the molecular ground state population is detected with a further laser. Two transitions to different electronic states were employed for this purpose and their usefulness is compared. Under the present experimental conditions both interferometer exits show a superposition of different interference patterns due to the influence of transverse and longitudinal overlaps of the interfering matter waves. The interference patterns have been analyzed to be composed of a contribution caused by a two beam splitter Ramsey interference and Ramsey-Bordé pattern with four beam splitters. This overlap of interference signals influences the suitability of the matter wave interferometer for phase measurements of the interferences.

Liu, S.; Sherstov, I.; Lisdat, C.; Knöckel, H.; Tiemann, E.

2010-06-01

207

Orbiting stellar interferometer for astrometry and imaging.  

PubMed

The orbiting stellar interferometer (OSI) is a concept for a first-generation space interferometer with astrometric and imaging goals and is responsive to the recommendations of the Astronomy and Astrophysics Survey Committee for an astrometric interferometer mission. The OSI, as developed at the Jet Propulsion Laboratory over the past several years, is a triple Michelson interferometer with articulating siderostats and optical delay lines. Two point designs for the instrument are described.

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

PMID:20820313

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

1993-04-01

208

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

SciTech Connect

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

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

2008-12-20

209

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

210

The interferometer in radio astronomy  

Microsoft Academic Search

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

N. C. Mathur

1968-01-01

211

The Fizeau Interferometer Testbed  

Microsoft Academic Search

The Fizeau Interferometer Testbed (FIT) is a collaborative effort between NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Space Corporation, and the University of Maryland. The testbed will be used to explore the principles of and the requirements for the full, as well as the pathfinder, Stellar Imager mission concept. It has a long term goal of demonstrating

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

2002-01-01

212

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

213

Non-Destructive Testing Using Two-Component Mixing Interferometer  

NASA Astrophysics Data System (ADS)

A new laser-based ultrasonic (LBU) receiver was recently introduced. The novel architecture is based on two-wave mixing in photorefractive materials and allows simultaneous measurement of in-plane and out-of-plane displacements (two- component). By taking advantage of recent developments in electronic processing and our knowledge on multi-channel interferometer, we achieved a compact optical system using only a single collecting aperture and a single laser probe beam. We will characterize the system performances and present experimental results demonstrating the capability for this compact two-component interferometer.

Wartelle, A.; Pouet, B.; Breugnot, S.

2011-06-01

214

Parametric oscillatory instability in a signal-recycled LIGO interferometer  

SciTech Connect

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

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

2007-12-31

215

An extreme ultraviolet interferometer suitable to generate dense interference pattern  

NASA Astrophysics Data System (ADS)

It has been designed a new type of interferometer working in extreme ultraviolet (XUV) region and intended for direct imprinting of densest possible (for given wavelength) interference pattern into a substrate. The interferometer belongs to the wave-front division category: each of its two aspheric mirrors reflects approximately one half of incoming laser beam and focuses it into a point image. Both focused beams have to intersect each other, and in the intersection region an interference pattern is generated. The closer the intersection region is to the abovementioned point images, the smaller the interference field is, but simultaneously the smaller the fringe-pitch is. This paper describes interferometer design (inclusive fringe-pitch calculation, and inclusive design of multilayer reflection coatings for the wavelength 46.9 nm (Ar8+ laser) - ensuring equal reflectivity at different reflection angles). The interferometer design is supplemented not only by ray-tracing verification of straight shape of interference fringes in ideal interferometer, but also by modelling of interference pattern of real interferometer with various misalignments as well as with random deformation of mirrors. These data enable to define necessary production as well as alignment tolerances.

Kolacek, K.; Schmidt, J.; Straus, J.; Frolov, O.; Prukner, V.; Melich, R.

2014-09-01

216

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

217

Achromatic self-referencing interferometer  

DOEpatents

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

Feldman, Mark (Pleasanton, CA)

1994-01-01

218

Two integrator loop quadrature oscillators: A review  

PubMed Central

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

Soliman, Ahmed M.

2012-01-01

219

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

220

Low-cost multimode fiber Mach Zehnder interferometer for differential phase demodulation  

Microsoft Academic Search

Mach-Zehnder interferometers (MZIs) are used in many optical applications, such as measurement of the coherence length of a laser, thermal dynamic flow, flatness of plane optical plates, thickness of thin films, etc. In this type of interferometer, light passing through a sample region in one direction recombines with a second leg without traversing the sample twice. In telecommunication, MZIs are

Yannick K. Lize; Robert Gomma; Raman Kashyap

2006-01-01

221

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

222

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

223

The Tidbinbilla interferometer  

NASA Technical Reports Server (NTRS)

This paper describes a technique to detect and identify weak, small-diameter radio sources with flux densities in the millijansky range. An interferometer system is proposed which will use existing 64 m and 24 m antennas of the Tidbinbilla Deep Space Network near Canberra. Design parameters of the system are described, and a schematic is presented with attention to low-noise traveling wave masers, and phase oscillation devices.

Batty, M. J.; Jauncey, D. L.; Gulkis, S.; Yerbury, M. J.

1977-01-01

224

Multipulsed dynamic moire interferometer  

DOEpatents

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

Deason, Vance A. (Idaho Falls, ID)

1991-01-01

225

Tunable and switchable multi-wavelength erbium-doped fiber ring laser based on a modified dual-pass Mach-Zehnder interferometer  

E-print Network

A tunable and switchable multi-wavelength erbium-doped fiber ring laser based on a new type tunable comb filter is proposed and demonstrated. By adjusting the polarization controllers, dual-function operation of the channel spacing tunability and the wavelength switching (interleaving) can be readily achieved. Up to 29 stable lasing lines with 0.4 nm spacing and 14 lasing wavelengths with 0.8 nm spacing in 3 dB bandwidth were obtained at room temperature. In addition, the lasing output, including the number of the lasing lines, the lasing evenness and the lasing locations, can also be flexibly adjusted through the wavelength-dependent polarization rotation mechanism.

Luo, Ai-Ping; Xu, Wen-Cheng

2010-01-01

226

The Fall 2000 and Fall 2001 SOHO-Ulysses Quadratures  

NASA Technical Reports Server (NTRS)

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

Suess, S. T.; Poletto, G.

2000-01-01

227

The Fall 2000 and Fall 2001 SOHO-Ulysses Quadratures  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

228

Hyperbolic moment equations using quadrature-based projection methods  

NASA Astrophysics Data System (ADS)

Kinetic equations like the Boltzmann equation are the basis for various applications involving rarefied gases. An important problem of many approaches since the first developments by Grad is the desired global hyperbolicity of the emerging set of partial differential equations. Due to lack of hyperbolicity of Grad's model equations, numerical computations can break down or yield nonphysical solutions. New hyperbolic PDE systems for the solution of the Boltzmann equation can be derived using quadrature-based projection methods. The method is based on a non-linear transformation of the velocity to obtain a Lagrangian velocity phase space description in order to allow for physical adaptivity, followed by a series expansion of the unknown distribution function in different basis functions and the application of quadrature-based projection methods. In this paper, we extend the proof for global hyperbolicity of the quadrature-based moment system system to arbitrary dimensions, utilizing quadrature-based projection methods for tensor product Hermite basis functions. The analytical computation of the eigenvalues shows the proposed correspondence to the Hermite quadrature points.

Koellermeier, J.; Torrilhon, M.

2014-12-01

229

TIMED Doppler Interferometer  

NASA Technical Reports Server (NTRS)

The Timed Doppler Interferometer (TIDI) will accurately and precisely determine the global vector MLTI (Mesosphere and Lower Thermosphere) wind, temperature, and density profiles. It will measure characteristics of the gravity wave and planetary wave spectra. The tidal characteristics of temperature, density, and wind in the MLTI will be determined. The neutral and ion winds will be measured to characterize the electrodynamical behavior of the MLTI. Oxygen and O2 abundances and nocticulent cloud activity will be measured. This review goes into the calibration and error sources, optical design, mechanisms design, detector design, electronics design, microprocessor and flight software design, and quality assurance and parts.

Killeen, Timothy L. (Principal Investigator)

1995-01-01

230

Quadrature interferometry for nonequilibrium ultracold bosons in optical lattices  

E-print Network

We develop an interferometric technique for making time-resolved measurements of field-quadrature operators for nonequilibrium ultracold bosons in optical lattices. The technique exploits the internal state structure of magnetic atoms to create two subsystems of atoms in different spin states and lattice sites. A Feshbach resonance turns off atom-atom interactions in one spin subsystem, making it a well-characterized reference state, while atoms in the other subsystem undergo nonequilibrium dynamics for a variable hold time. Interfering the subsystems via a second beam-splitting operation, time-resolved quadrature measurements on the interacting atoms are obtained by detecting relative spin populations. The technique can provide quadrature measurements for a variety of Hamiltonians and lattice geometries (e.g., cubic, honeycomb, superlattices), including systems with tunneling, spin-orbit couplings using artificial gauge fields, and higher-band effects. Analyzing the special case of a deep lattice with neglig...

Tiesinga, Eite

2012-01-01

231

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

232

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. (authors)

Jarrell, J. J.; Evans, T. M.; Davidson, G. G. [Oak Ridge National Laboratory, One Bethel Valley Rd., Oak Ridge, TN 37831 (United States)

2013-07-01

233

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.

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

2012-01-01

234

Absolute measurement of optical surface profile with a Fizeau interferometer  

NASA Astrophysics Data System (ADS)

An optical surface profile is measured with a laser diode Fizeau interferometer using a method of absolute measurement. Wavefront aberration in the interferometer causes an undesirable phase distribution in the interference signal. To eliminate this phase distribution, the object surface is shifted in two directions orthogonal to each other and the difference wavefront of the surface profile of the object is obtained. An absolute surface profile is estimated by representing the object surface with a polynomial function and by solving the difference equations with least-squares method.

Sasaki, Osami; Watanabe, Akihiro; Choi, Samuel; Suzuki, Takamasa

2012-11-01

235

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

236

Two-chord interferometry using 3.39 {mu}m He-Ne laser on a flux-coil-generated FRC  

SciTech Connect

A two-chord {lambda}{sub IR}{approx}3.39 {mu}m He-Ne laser interferometer system was developed for a flux-coil-generated field-reversed configuration to estimate the electron density and the total temperature of the field-reversed configuration (FRC) plasma. This two-chord heterodyne interferometer system consists of a single {approx}2 mW infrared He-Ne laser, a visible ({lambda}{sub vis}{approx}632.8 nm) He-Ne laser for the alignment, a 40 MHz acousto-optic modulator, photodetectors, and quadrature phase detectors. Initial measurement was performed and the measured average electron densities were 2-10x10{sup 19} m{sup -3} at two different radial positions in the midplane. A time shift in density was observed as the FRC expands radially. The time evolution of the line-averaged density agrees with the density estimated from the in situ internal magnetic probes, based on a rigid-rotor profile model.

Gota, H.; Deng, B. H.; Gupta, D.; Kiyashko, V.; Knapp, K.; Mendoza, R.; Morehouse, M. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Bolte, N.; Roche, T.; Wessel, F. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)

2010-10-15

237

Dynamic range enhancement imaging in laser interferometry  

NASA Astrophysics Data System (ADS)

In this paper, a novel technique to enhance the dynamic range of images acquired in a laser interferometer is presented. The irradiance of the interferometric signal received by the camera, in a Michelson interferometer, is controlled at pixel level using a spatial light modulator. It is shown that this technique increases the signal to noise ratio, hence improving the vertical resolution of interferometer systems.

Babaie, G.; Abolbashari, M.; Farahi, F.

2015-01-01

238

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

Microsoft Academic Search

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

Tan-Hsiung Ho; Shyh-Jong Chung

2010-01-01

239

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

Microsoft Academic Search

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

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

2006-01-01

240

Adaptive characteristic spatial quadratures for discrete ordinates neutral particle transport - The slab geometry case  

Microsoft Academic Search

Two new slab geometry spatial quadrature schemes for use in discrete ordinates neutral particle transport computer codes are presented. The step adaptive and linear adaptive quadratures are derived as characteristic quadratures. They differ from previous schemes in using strictly non-negative finite elements representations of the scattering source within a spatial cell. These representations adapt to match the zeroth and first

Kirk A. Mathews

1990-01-01

241

The Fizeau Interferometer Testbed  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

242

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

243

Elastic Rods, Rigid Bodies, Quaternions and the Last Quadrature  

Microsoft Academic Search

The Kirchhoff kinetic analogy relates the governing equations for the statics of elastic rods and the dynamics of rigid bodies. We discuss the analogy in light of several different Hamiltonian formulations, including a non-canonical description of rod equilibria. We focus on the last three quadratures that are required to reconstruct the rod centreline from the frame variables, which form the

S. Kehrbaum; J. H. Maddocks

1997-01-01

244

Gauss quadrature approximations to hypergeometric and confluent hypergeometric functions  

NASA Astrophysics Data System (ADS)

Integral representations of hypergeometric and confluent hypergeometric functions with real parameters and complex arguments are used to approximate these functions by Gaussian quadrature. An analysis is given of the errors involved and of estimates of the number of Gauss points required to achieve any given accuracy. Numerical examples illustrate the theory.

Gautschi, Walter

2002-02-01

245

Gauss quadrature approximations to hypergeometric and confluent hypergeometric functions  

Microsoft Academic Search

Integral representations of hypergeometric and confluent hypergeometric functions with real parameters and complex arguments are used to approximate these functions by Gaussian quadrature. An analysis is given of the errors involved and of estimates of the number of Gauss points required to achieve any given accuracy. Numerical examples illustrate the theory.

Walter Gautschi

2002-01-01

246

From Lobatto Quadrature to the Euler Constant "e"  

ERIC Educational Resources Information Center

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

Khattri, Sanjay Kumar

2010-01-01

247

Discrete ordinates quadrature schemes for multidimensional radiative transfer  

Microsoft Academic Search

The fundamental problem of applying the method of discrete ordinates to radiative transfer predictions is the selection of the discrete directions and their associated weights. Both the accuracy of the solution and the computational effort depend on the angular discretization. This paper provides a sound mathematical methodology for the derivation of angular quadratures. By applying the collocation principle, the errors

R. Koch; W. Krebs; S. Wittig; R. Viskanta

1995-01-01

248

The discrete-time quadrature subsample estimation of delay  

Microsoft Academic Search

A high-resolution discrete-time delay estimator for determining the delay between two periodic signals is described. The technique is based upon the principles of analog quadrature detection and is relatively simple to implement digitally. Simulations in the presence of system noise show that the delay estimator does not exhibit any significant bias and outperforms other estimators in medium to high SNR

Douglas L. Maskell; Graham S. Woods

2002-01-01

249

New system of miniaturization online testing of spherical interferometer  

NASA Astrophysics Data System (ADS)

With the aim to measure the radius of curvature deviation and the surface form deviation of optical elements online in the workshop, based on laser testing technique, two solutions of miniaturization without precision guider sphericity interferometer systems are described, and the principle of systems are analyzed. Compared with the traditional sphericity interferometer, the systems designed are particularly suitable for testing mirror noncontact online in workshop, advantaged in compact structure, no precision guider, high efficiency and low costs. The interferometer systems use the different radius of curvature of existing spherical test plates in the production workshop to produce reference wavefront. The systems can not only get the astigmatism and local deviation of lens, but also can reflect the radius of curvature deviation, which provides rapid and nondestructive noncontact online testing.

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

2011-11-01

250

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

251

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

252

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

253

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

254

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

255

Dual interferometer system for measuring index of refraction  

NASA Astrophysics Data System (ADS)

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

Goodwin, Eric Peter

256

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

257

PUBLISHED ONLINE: 10 FEBRUARY 2013 | DOI: 10.1038/NPHYS2542 A universal matter-wave interferometer with  

E-print Network

and show how a sequence of ionizing laser grating pulses12 can form a generic matter-wave interferometerLETTERS PUBLISHED ONLINE: 10 FEBRUARY 2013 | DOI: 10.1038/NPHYS2542 A universal matter-wave interferometer with optical ionization gratings in the time domain Philipp Haslinger, Nadine Dörre, Philipp Geyer

Loss, Daniel

258

Scanning heterodyne interferometer setup for the time-resolved thermal and free-carrier mapping in semiconductor devices  

Microsoft Academic Search

An automated scanning interferometer setup for time resolved measurement of thermal and free carrier distribution in semiconductor devices during short stress pulses is presented. The semiconductor device is probed via the thermal and free carrier induced changes in the semiconductor refractive index using a heterodyne interferometer. The setup integrates device stressing facilities, data acquisition and laser beam scanning. The time

Martin Litzenberger; Christoph Furböck; Sergey Bychikhin; Dionyz Pogany; Erich Gornik

2005-01-01

259

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

260

Hardware Verification of Time Delay Interferometry with Space-craft Motion Effects for Space-based Gravitational Wave Interferometers.  

NASA Astrophysics Data System (ADS)

The detection of gravitational waves (GWs) with the use of future space-based interferometer missions, such as the Next Gravitational Wave Observatory (NGO), will require advanced interferometry schemes in order to account for unequal arm-lengths and space-craft motion effects. These complications are resolved using measurements of one-way laser observables and post-processing combinations which cancel the laser noise and extract the differential arm-length, collectively, referred to as Time Delay Interferometry (TDI). The University of Florida (UF) has constructed a hardware-in-the-loop experiment, know as the UF Laser Interferometry Simulator (UFLIS), to replicate the pre-stabilized laser noise, multi-second light travel time delays, GW laser-phase modulation, and the formation and measurement of photodetector laser beatnotes using a microcycle phasemeter as is expected in these space-based interferometers. The measurements are then combined using the TDI combinations to verify the interferometer sensitivity after laser noise cancellation.

Mitryk, Shawn; Mueller, G.

2012-01-01

261

Laser -Aided Spherometer  

NASA Astrophysics Data System (ADS)

Laser-aided spherometer is a novel designation for a flexible and high performance instrument to the measurement of curvature radii of spherical surfaces. Combining the well established technique of Laser interferometer for linear displacement measurement with the principle of a classical spherometer frame, an accuracy of one order of a magnitude better than current type of precision interferometers is reached. This stays as the first mark on the development of an all-optical high precision spherometer.

Soares, Oliverio D. D.; Fernandez, Jose F.

1989-01-01

262

Interferometer with dynamic reference  

NASA Astrophysics Data System (ADS)

Interferometric testing of optical surfaces is problematic when strong asphericities are present. The spatial frequencies of the interference fringes exceed the detector resolution where the slope difference between test beam and reference beam is too large. CGHs are frequently used to avoid this effect but availability and flexibility is a problem. Alternatively we propose a new method to extend the dynamic range of interferometric measurements. For this purpose the reference beam in an interferometer is adapted. An active element containing a spatial light modulator (SLM) is used to vary the slope of the reference beam within a few degrees in both x- and y-directions. Hereby different areas of the interferogram become evaluable. Furthermore the active element can introduce phase shifts necessary for the phase shift interferometry algorithms. Several interferograms with different reference beam slopes are recorded and finally the phase functions are "stitched" together. By using an SLM for the reference beam tilt, no mechanical motion of any hardware which would limit the accuracy is necessary. A calibration of the tilts can be performed with interferometric accuracy.

Liesener, Jan; Tiziani, Hans J.

2004-02-01

263

Exciton-polariton Josephson interferometer in a semiconductor microcavity  

NASA Astrophysics Data System (ADS)

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

Zhang, Chuanyi; Zhang, Weifeng

2014-10-01

264

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

265

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

266

A double-pass Fizeau interferometer system for measuring the figure error of large synchrotron optics  

Microsoft Academic Search

A laser Fizeau interferometer system has been developed to characterize the figure error of large synchrotron X-ray mirrors using double-pass geometry. This opto-mechanical assembly comprises integrated rotation and translation stages to control: the output angle of the Fizeau interferometer; the surface normal of the optic under test; and the orientation of a high quality (lambda\\/100) retro-reflector. To negate the effects

Geoff D. Ludbrook; Simon G. Alcock; Stewart Scott

2010-01-01

267

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

268

Ramsey-Bordé atom interferometer having two arms with different Zeeman sublevels  

NASA Astrophysics Data System (ADS)

An atom interferometer, whose arms are in the different sublevels, was demonstrated using two ?+- and two ?--polarized, copropagating, laser beams in a magnetic field. Using the interferometer, Ramsey fringes with a width of 50 kHz were observed as a function of Zeeman shift frequency. The visibility of the interference fringes of 0.046 was obtained at an excitation power of almost ?/2 pulse area.

Yanagimachi, Shinya; Mizobuchi, Kenji; Morinaga, Atsuo

2001-10-01

269

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

270

Technical Memo #77 Error Correction in Quadrature DownConverters  

E-print Network

1 BIMA Technical Memo #77 Error Correction in Quadrature Down­Converters W. L. Urry Nov. 17 1999 0 f 1 cos(w 0 t) Asin(w 0 t+f) x(t) v 1 (t) V 1 (w) v 0 (t) V 0 (w) #12; 2 Input Spectrum Consider a real input signal x(t) with Fourier transform { } ) ( ) ( ) ( 0 0 w w w w - + + - = Á X X t x

271

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

272

Phase-Shifting Liquid Crystal Interferometers for Microgravity Fluid Physics  

NASA Astrophysics Data System (ADS)

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.

2002-11-01

273

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

274

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

275

A novel adaptive mismatch cancellation system for quadrature IF radio receivers  

Microsoft Academic Search

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

Li Yu; W. M. Snelgrove

1999-01-01

276

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

Microsoft Academic Search

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

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

2008-01-01

277

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

278

Surface profilometry by wavelength scanning Fizeau interferometer  

Microsoft Academic Search

We have applied wavelength scanning interferometry to Fizeau interferometer for surface profilometry. This interferometer is free from ambiguity of the sign in the measurement result. It is more compact in setup than the Michelson interferometer used previously. Experimental results from a step and a dip on a mirror surface are shown. In the focal depth of imaging system, we could

Akihiro Yamamoto; Ichirou Yamaguchi

2000-01-01

279

Microwave interferometer controls cutting depth of plastics  

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

280

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

281

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

282

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

283

Holographic Twyman-Green interferometer  

NASA Technical Reports Server (NTRS)

A dichromated gelatin off-axis Fresnel zone plate was designed, fabricated, and used in a new type of interferometer for optical metrology. This single hologram optical element combines the functions of a beam splitter, beam diverger, and aberrated null lens. Data presented show the successful application for an interferometric test of an f/6, 200-mm diam parabolic mirror.

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

1982-01-01

284

Building the Fizeau interferometer testbed  

Microsoft Academic Search

The Fizeau interferometer testbed (FIT) is a collaborative effort between NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Research and Engineering Corp., and the University of Maryland. The testbed is used to explore the principles of and the requirements for the full, as well as the pathfinder, stellar imager mission concept. It has a long-term goal of demonstrating

Richard G. Lyon; Kenneth G. Carpenter; Hubert Huet; Paul Cottle; Peter Petrone; Peter Dogoda; Peter Liiva; Joe Marzouk; Gregory Solyar; L. Mazzuca; X. Zhang

2004-01-01

285

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

286

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

287

Principles and improvements of quadrature-based QKD  

NASA Astrophysics Data System (ADS)

An overview of quadrature-based quantum key distribution is provided. Beginning from the comparison between single-photon schema and continuous variable schema, the article focuses on the classical and state-of-art protocols. Protocols' main procedures and security analysis are introduced, which includes the methods under individual attack and collective attack. Then recent development of unconditional security proof is introduced including the optimality of Gaussian attack and de Finetti theorem. Introduction towards discrete modulated schemas' security proof is also made. At last, the article discusses experimental realization of various protocols and the main trend in this field.

Hu, Wenhao; Shu, Di; Wang, Daqing; Liu, Yu

2010-11-01

288

Quadrature component analysis of interferograms with random phase shifts  

NASA Astrophysics Data System (ADS)

Quadrature component analysis (QCA) is an effective method for analyzing the interferograms if the phase shifts are uniformly distributed in the [0, 2?] range. However, it is hard to meet this requirement in practical applications, so a parameter named the non-orthogonal degree (NOD) is proposed to indicate the degree when the phase shifts are not well distributed. We analyze the relation between the parameter of NOD and the accuracy of the QCA algorithm by numerical simulation. By using the parameter of NOD, the relation between the distribution of the phase shift and the accuracy of the QCA algorithm is obtained. The relation is discussed and verified by numerical simulations and experiments.

Xu, Jiancheng; Chen, Zhao

2014-08-01

289

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

NASA Astrophysics Data System (ADS)

A scanning white light interferometer can characterize out of plane features and motion in M(N)EMS devices. Like any other form and displacement measuring instrument, the scanning interferometer results should be linked to the metre definition to be comparable and unambiguous. Traceability is built up by careful error characterization and calibration of the interferometer. The main challenge in this calibration is to have a reference device producing accurate and reproducible dynamic out-of-plane displacement when submitted to standard loads. We use a flat mirror attached to a piezoelectric transducer for static and (quasi)dynamic calibration of a stroboscopic scanning light interferometer. First we calibrated the piezo-scanned flexure guided transducer stage using a symmetric differential heterodyne laser interferometer developed at the Centre for Metrology and Accreditation (MIKES). The standard uncertainty of the piezo stage motion calibration was 3.0 nm. Then we used the piezo-stage as a transfer standard to calibrate our stroboscopic interferometer whose light source was pulsed at 200 Hz and 400 Hz with 0.5% duty cycle. We measured the static position and (quasi)dynamic motion of the attached mirror relative to a reference surface. This methodology permits calibrating the vertical scale of the stroboscopic scanning white light interferometer.

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

2013-04-01

290

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

291

Implementation of a reference interferometer for nanodetection.  

PubMed

A thermally and mechanically stabilized fiber interferometer suited for examining ultra-high quality factor microcavities is fashioned. After assessing its free spectral range (FSR), the module is put in parallel with a fiber taper-microcavity system and then calibrated through isolating and eliminating random shifts in the laser frequency (i.e. laser jitter noise). To realize the taper-microcavity junction and to maximize the optical power that is transferred to the resonator, a single-mode optical fiber waveguide is pulled. Solutions containing polystyrene nanobeads are then prepared and flown to the microcavity in order to demonstrate the system's ability to sense binding to the surface of the microcavity. Data is post-processed via adaptive curve fitting, which allows for high-resolution measurements of the quality factor as well as the plotting of time-dependent parameters, such as resonant wavelength and split frequency shifts. By carefully inspecting steps in the time-domain response and shifting in the frequency-domain response, this instrument can quantify discrete binding events. PMID:24798706

Vincent, Serge; Yu, Wenyan; Lu, Tao

2014-01-01

292

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

293

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

294

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

295

A quadrature closure for the reaction-source term in conditional-moment closure  

E-print Network

A quadrature closure for the reaction-source term in conditional-moment closure S.T. Smith a,*, R-0235, USA Abstract A Gaussian-quadrature closure is introduced for the conditional reaction-source term in conditional- moment closure, motivated by the desire to accurately model the dynamics of homogeneous

Raman, Venkat

296

Discrete-Time Nonlinear Filtering Algorithms Using Gauss–Hermite Quadrature  

Microsoft Academic Search

In this paper, a new version of the quadrature Kalman filter (QKF) is developed theoretically and tested experimentally. We first derive the new QKF for nonlinear systems with additive Gaussian noise by linearizing the process and measurement functions using statistical linear regression (SLR) through a set of Gauss-Hermite quadrature points that parameterize the Gaussian density. Moreover, we discuss how the

Ienkaran Arasaratnam; Simon Haykin; Robert J. Elliott

2007-01-01

297

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

298

New digital quadrature demodulator for real-time hand-held ultrasound medical imaging device  

Microsoft Academic Search

A real-time, low-power digital quadrature demodulator is proposed to process ultrasound radio frequency signals in both pulse and continuous modes. Two finite impulse response filters are combined to build a Hilbert transform and a linear approximation architecture that allows achieving the required square root operations of quadrature demodulator. The complexity and accuracy of proposed demodulator are analyzed and successfully integrated

Philippe Levesque; Mohamad Sawan

2008-01-01

299

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

300

A digital quadrature modulator with on-chip d\\/a converter  

Microsoft Academic Search

A digital quadrature modulator is presented that can replace the fir st analog IF mixer stage of a base station transmitter. It interpolates orthogonal input carriers by 16 and performs digital quadrature modulation at car- rier frequencies , and . A 12-bit D\\/A- converter is integrated on-chip using a segmented current source architecture and a proper switching technique to reduce

Johan Sommarek; Jouko Vankka; Jaakko Ketola; Ilari Teikari; Kari Halonen

2003-01-01

301

Extending quadrature methods to value multi-asset and complex path dependent options  

Microsoft Academic Search

The exposition of the quadrature (QUAD) method (Andricopoulos, Widdicks, Duck, and Newton, 2003. Universal option valuation using quadrature methods. Journal of Financial Economics 67, 447–471 (see also Corrigendum, Journal of Financial Economics 73, 603 (2004)) is significantly extended to cover notably more complex and difficult problems in option valuations involving one or more underlyings. Trials comparing several techniques in the

Ari D. Andricopoulos; Martin Widdicks; David P. Newton; Peter W. Duck

2007-01-01

302

A 0.5-20GHz Quadrature Downconverter Joseph C. Bardin and Sander Weinreb  

E-print Network

are combined with a commercial quadrature hybrid, the mixer achieves an image rejection ratio greater than 35d from 0.5-17GHz and a pair of Gilbert-cell mixers to perform downconversion. When the IF outputsmm2 . Index Terms -- Quadrature downconverter, frequen- cy doubler, frequency divider, IQ mixer

Weinreb, Sander

303

Exponential characteristic spatial quadrature for discrete ordinates radiation transport with rectangular cells  

Microsoft Academic Search

The exponential characteristic (EC) spatial quadrature for discrete ordinates neutral particle transport previously introduced in slab geometry is extended here to x-y geometry with rectangular cells. The method is derived and compared with current methods. It is similar to the linear characteristic (LC) quadrature (a linear-linear moments method) but differs by assuming an exponential distribution of the scattering source within

B. Minor; K. Mathews

1995-01-01

304

Discrete ordinates quadrature schemes based on the angular interpolation of radiation intensity  

Microsoft Academic Search

The discrete ordinates method fails in treating specular reflection at the boundary because the quadratures on the sphere do not assume any analytic representation of a function under integration and, therefore, the intensity of the specularly reflected beam is undetermined. To solve this problem a new approach to the construction of quadrature schemes is presented. The approach is based on

S. A. Rukolaine; V. S. Yuferev

2001-01-01

305

Status of the LBT interferometer  

NASA Astrophysics Data System (ADS)

The Large Binocular Telescope Interferometer, a thermal infrared imager and nulling interferometer for the LBT, is currently being integrated and tested at Steward Observatory. The system consists of a general purpose or universal beamcombiner (UBC) and three camera ports, one of which is populated currently by the Nulling and Imaging Camera (NIC). Wavefront sensing is carried out using pyramid-based "W" units developed at Arcetri Observatory. The system is designed for high spatial resolution, high dynamic range imaging in the thermal infrared. A key project for the program is to survey nearby stars for debris disks down to levels which may obscure detection of Earth-like planets. During 2007-2008 the UBC portion of the LBTI was assembled and tested at Steward Observatory. Initial integration of the system with the LBT is currently in progress as the W units and NIC are being completed in parallel.

Hinz, Philip M.; Bippert-Plymate, Teresa; Breuninger, Andy; Connors, Tom; Duffy, Brian; Esposito, Simone; Hoffmann, William; Kim, Jihun; Kraus, Joe; McMahon, Thomas; Montoya, Manny; Nash, Richard; Durney, Olivier; Solheid, Elliott; Tozzi, Andrea; Vaitheeswaran, Vidhya

2008-07-01

306

Fiber Sagnac interferometer temperature sensor  

Microsoft Academic Search

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

A. N. Starodumov; L. A. Zenteno; D. Monzon; E. De La Rosa

1997-01-01

307

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

308

Focused-laser interferometric position sensor  

SciTech Connect

We describe a simple method to measure the position shifts of an object with a range of tens of micrometers using a focused-laser (FL) interferometric position sensor. In this article we examine the effects of mechanical vibration on FL and Michelson interferometers. We tested both interferometers using vibration amplitudes ranging from 0 to 20 {mu}m. Our FL interferometer has a resolution much better than the diffraction grating periodicities of 10 and 14 {mu}m used in our experiments. A FL interferometer provides improved mechanical stability at the expense of spatial resolution. Our experimental results show that Michelson interferometers cannot be used when the vibration amplitude is more than an optical wavelength. The main purpose of this article is to demonstrate that a focused-laser interferometric position sensor can be used to measure the position shifts of an object on a less sensitive, micrometer scale when the vibration amplitude is too large to use a Michelson interferometer.

Friedman, Stephen J.; Barwick, Brett; Batelaan, Herman [Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0111 (United States)

2005-12-15

309

Terahertz single-shot quadrature phase-shifting interferometry.  

PubMed

A single-shot quadrature phase-shifting interferometry architecture is presented that is applicable to antenna coupled detector technologies. The method is based on orthogonally polarized object and reference beams and on linear and circular polarization sensitive antennas in space-division multiplexing. The technique can be adapted to two-, three-, and four-step and Gabor holography recordings. It is also demonstrated that the space-division multiplexing does not necessarily cause sparse sampling. A sub-THz detector array is presented containing multiple on-chip antennas and FET plasma wave detectors implemented in a 90 nm complementary metal-oxide semiconductor technology. As an example, two-step phase-shifting reconstruction results are given at 360 GHz. PMID:23027273

Földesy, Péter

2012-10-01

310

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

311

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

312

Gauss Legendre and Chebyshev quadratures for singular integrals  

NASA Astrophysics Data System (ADS)

Exact expressions are presented for efficient computation of the weights in Gauss-Legendre and Chebyshev quadratures for selected singular integrands. The singularities may be of Cauchy type, logarithmic type or algebraic-logarithmic end-point branching points. We provide Fortran 90 routines for computing the weights for both the Gauss-Legendre and the Chebyshev (Fejér-1) meshes whose size can be set by the user. New program summaryProgram title: SINGQUAD Catalogue identifier: AEBR_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBR_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.: 4128 No. of bytes in distributed program, including test data, etc.: 25 815 Distribution format: tar.gz Programming language: Fortran 90 Computer: Any with a Fortran 90 compiler Operating system: Linux, Windows, Mac RAM: Depending on the complexity of the problem Classification: 4.11 Nature of problem: Program provides Gauss-Legendre and Chebyshev (Fejér-1) weights for various singular integrands. Solution method: The weights are obtained from the condition that the quadrature of order N must be exact for a polynomial of degree?(N-1). The weights are expressed as moments of the singular kernels associated with Legendre or Chebyshev polynomials. These moments are obtained in analytic form amenable for computation. Additional comments: If the NAGWare f95 compiler is used, the option, "-kind = byte", must be included in the compile command lines of the Makefile. Running time: The test run supplied with the distribution takes a couple of seconds to execute.

Deloff, A.

2008-12-01

313

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

314

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

315

Broadband precision wavelength meter based on a stepping FabryProt interferometer  

E-print Network

Broadband precision wavelength meter based on a stepping Fabry­Pérot interferometer T. J. Scholl. INTRODUCTION Wavelength meters based on Michelson or Fizeau inter- ferometers have long been the standard a more general laser wavelength meter in which the FP ring pattern was employed to compare

Rehse, Steven J.

316

Spherical grating monochromator with interferometer control and in-vacuum reference  

Microsoft Academic Search

Physical Science Laboratory's new generation of spherical grating monochromators incorporates a laser interferometer to control scan angle and an in-vacuum absolute angle reference, as well as other improvements. The design accommodates up to six gratings which can be moved axially (under motor control, with encoder position readback) at any scan angle. The gratings are cooled by means of spring-loaded clamps

D. J. Holly; W. P. Mason; T. Sailor; R. E. Smith; D. Wahl

2002-01-01

317

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

318

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

SciTech Connect

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

Arakawa, Hiroyuki, E-mail: arakawa@fmt.teikyo-u.ac.jp; Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-shi, Ibaraki 311-0193 (Japan)] [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka-shi, Ibaraki 311-0193 (Japan)

2014-04-15

319

Interferometer fiber optic sensor for dc signal measurement  

NASA Astrophysics Data System (ADS)

We present a novel interferometer fiber optic sensor (IFOS) system for DC signal measurement based on the PGC (phase generated carrier) demodulation scheme. In addition to the principle of the demodulation, the compensation techniques for improving the measurement precision constrained by the laser nonlinearity in frequency modulation (FM) operation and the experimental results are described. And now, we've made a prototype water level sensor and been trying the field tests, so we show the first results compared with those of the float-typed reference sensor.

Nakajima, Yasuyuki; Sato, Ryotaku; Yoshikawa, T.; Dobashi, Koji

2001-05-01

320

Alignment of a two-beam interferometer  

NASA Technical Reports Server (NTRS)

Two beam interferometers have been proposed for space applications such as sensing the shape of a large antenna. Since alignment and adjustment of interferometers have long been considered difficult laboratory tasks, the question of making their operation sufficiently automatic for space applications is a serious one. As a first step in addressing this question certain manual procedures, which may not be well known, have been collected from widely scattered sources. These techniques are illustrated by two examples: (1) the alignment of a Mach-Zehnder interferometer and the adjustment of fringe location. (2) The adjustment of a Michelson interferometer for zero path difference (white light fringes).

Tubbs, E. F.

1980-01-01

321

An ionizing time domain matter-wave interferometer  

NASA Astrophysics Data System (ADS)

We discuss an optical matter-wave interferometer for clusters and complex molecules that uses absorptive ionization gratings in combination with Talbot-Lau interferometry in the time domain. We show recent results and present the future perspectives of the experiment. In this setup, a particle cloud passes alongside a mirror that reflects three equally timed UV lasers pulses. Electrons are detached from the particles in the antinodes of the formed standing wave gratings via single photon absorption. The created ions are extracted and only neutral particles remain in the interferometer, thus absorptive light gratings for matter waves can be realized. In contrast to material grating setups, this experiment operates in a pulsed mode, which makes the longitudinal motion of the particles negligible. This new kind of interferometer is a universal tool which will on the one hand allow us to explore the wave nature of massive particles, potentially up to a million atomic mass units and more. In combination with deflectometry and spectroscopy on the other hand, it offers the possibility to determine molecular properties, such as polarizabilities, electric and magnetic moments, absorption and ionization cross sections with high precision.

Doerre, Nadine; Haslinger, Philipp; Geyer, Philipp; Rodewald, Jonas; Nimmrichter, Stefan; Hornberger, Klaus; Arndt, Markus

2012-06-01

322

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

323

Demonstration of improved sensitivity of echo interferometers to gravitational acceleration  

E-print Network

We have developed two configurations of an echo interferometer that rely on standing wave excitation of a laser-cooled sample of rubidium atoms that measures acceleration. For a two-pulse configuration, the interferometer signal is modulated at the recoil frequency and exhibits a sinusoidal frequency chirp as a function of pulse spacing. For a three-pulse stimulated echo configuration, the signal is observed without recoil modulation and exhibits a modulation at a single frequency. The three-pulse configuration is less sensitive to effects of vibrations and magnetic field curvature leading to a longer experimental timescale. For both configurations of the atom interferometer (AI), we show that a measurement of acceleration with a statistical precision of 0.5% can be realized by analyzing the shape of the echo envelope that has a temporal duration of a few microseconds. Using the two-pulse AI, we obtain measurements of acceleration that are statistically precise to 6 parts per million (ppm) on a 25 ms timescal...

Mok, C; Carew, A; Berthiaume, R; Beattie, S; Kumarakrishnan, A

2013-01-01

324

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

325

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

326

Random-phase-shift Fizeau interferometer.  

PubMed

A new and potentially cost efficient kind of vibration-tolerant surface measurement interferometer based on the Fizeau-principle is demonstrated. The crucial novelty of this approach is the combination of two optoelectronic sensors: an image sensor with high spatial resolution and an arrangement of photodiodes with high temporal resolution. The photodiodes continuously measure the random-phase-shifts caused by environmental vibrations in three noncollinear points of the test surface. The high spatial resolution sensor takes several "frozen" images of the test surface by using short exposure times. Under the assumption of rigid body movement the continuously measured phase shifts of the three surface points enable the calculation of a virtual plane that is representative for the position and orientation of the whole test surface. For this purpose a new random-phase-shift algorithm had to be developed. The whole system was tested on an optical table without vibration isolation under the influence of random vibrations. The analysis of the root-mean-square (RMS) over ten different measurements shows a measurement repeatability of about 0.004 wave (approximately 2.5 nm for 632.8 nm laser wavelength). PMID:22193185

Broistedt, Hagen; Doloca, Nicolae Radu; Strube, Sebastian; Tutsch, Rainer

2011-12-20

327

Note: Periodic error measurement in heterodyne interferometers using a subpicometer accuracy Fabry-Perot interferometer  

NASA Astrophysics Data System (ADS)

Periodic error is the major problem that limits the accuracy of heterodyne interferometry. A traceable system for periodic error measurement is developed based on a nonlinearity free Fabry-Perot (F-P) interferometer. The displacement accuracy of the F-P interferometer is 0.49 pm at 80 ms averaging time, with the measurement results referenced to an optical frequency comb. Experimental comparison between the F-P interferometer and a commercial heterodyne interferometer is carried out and it shows that the first harmonic periodic error dominates in the commercial heterodyne interferometer with an error amplitude of 4.64 nm.

Zhu, Minhao; Wei, Haoyun; Wu, Xuejian; Li, Yan

2014-08-01

328

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

329

Apparatus and method for laser velocity interferometry  

DOEpatents

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

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

1993-09-14

330

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

331

Fizeau interferometer for global astrometry in space  

Microsoft Academic Search

We discuss the design and the performance of a Fizeau interferometer with a long focal length and a large field of view that is well suited for a global astrometry space mission. Our work focuses on the geometric optimization and minimization of aberration of such an astrometric interferometer, which is able to observe astronomical targets down to the visual magnitude

Davide Loreggia; Daniele Gardiol; Mario Gai; Mario G. Lattanzi; Deborah Busonero

2004-01-01

332

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.

333

A chevron beam-splitter interferometer  

NASA Technical Reports Server (NTRS)

Fully tilt compensated double-pass chevron beam splitter, that removes channelling effects and permits optical phase tuning, is wavelength independent and allows small errors in alignment that are not tolerated in Michelson, Machzender, or Sagnac interferometers. Device is very useful in experiments where background vibration affects conventional interferometers.

Breckinridge, J. B.

1979-01-01

334

Resonant optical nonlinearity of Nb-doped silica fiber measured with LPFG interferometer  

NASA Astrophysics Data System (ADS)

Recently, specialty fibers with various functional material doping have attracted significant attention. In this paper, we fabricated Nb-doped silica fiber and measured its resonant optical nonlinearity with long-period fiber gratings (LPFG) interferometer. The Nb-doped fiber was made with a combined MCVD and ALD technology. Then, we fabricated a pair of LPFGs and cascaded them as a Mach-Zehnder interferometer (MZI).By measuring the wavelength shifts of the interference fringe with the 532nm laser pump power, the resonant nonlinear refractive index of Nb-doped silica fiber around 1537 nm was estimated to be 8.12×10-16m2/W.

Wang, Litao; Chen, Na; Guo, Qiang; Chen, Zhenyi; Liu, Yunqi; Wang, Tingyun

2012-11-01

335

Remote photoacoustic imaging on solid material using a two-wave mixing interferometer.  

PubMed

We report on remote and contactless photoacoustic imaging (PAI) for the inspection of solid materials using a two-wave mixing interferometer. In this Letter, a semitransparent sample was excited with picosecond laser pulses. The local absorption of the electromagnetic radiation led to generation of broadband ultrasonic waves inside the sample. Ultrasonic waves arriving at the sample surface were detected utilizing a two-wave mixing interferometer. After data acquisition, the initial pressure distribution was reconstructed using a Fourier space synthetic aperture technique algorithm. We show the potential of PAI for the inspection of semitransparent solid materials. PMID:21165120

Berer, Thomas; Hochreiner, Armin; Zamiri, Saeid; Burgholzer, Peter

2010-12-15

336

Optical pumping and modulation techniques with a molecular Ramsey-Bordé interferometer  

NASA Astrophysics Data System (ADS)

Using the example of a matter-wave interferometer with K2 molecules, we present different methods to simplify the observed interference structures within a hyperfine pattern for improving phase measurements of the interference structure. We consider optical pumping for depletion of specific components to simplify the observed spectra. In connection with a lock-in amplifier, amplitude modulation as well as frequency modulation of laser beams in the interferometer are investigated for better detection of the interference pattern. As a follow-up treatment, digital filtering is demonstrated.

Lisdat, Ch.; Frank, M.; Knöckel, H.; Tiemann, E.

337

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

338

Orientational atom interferometers sensitive to gravitational waves  

SciTech Connect

We present an atom interferometer that differs from common atom interferometers as it is not based on the spatial splitting of electronic wave functions, but on orienting atoms in space. As an example we present how an orientational atom interferometer based on highly charged hydrogen-like atoms is affected by gravitational waves. We show that a monochromatic gravitational wave will cause a frequency shift that scales with the binding energy of the system rather than with its physical dimension. For a gravitational wave amplitude of h=10{sup -23} the frequency shift is of the order of 110 {mu}Hz for an atom interferometer based on a 91-fold charged uranium ion. A frequency difference of this size can be resolved by current atom interferometers in 1 s.

Lorek, Dennis; Laemmerzahl, Claus; Wicht, Andreas [Center of Applied Space Technology and Microgravity, University of Bremen, Am Fallturm, D-28359 Bremen (Germany); Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, D-12489 Berlin (Germany); Humboldt-Universitaet zu Berlin, Institut fuer Physik, Hausvogteiplatz 5-7, D-10117 Berlin (Germany)

2010-02-15

339

Impact of anomalous dispersion on the interferometer measurements of plasmas  

SciTech Connect

For many decades optical interferometers have been used to measure the electron density of plasmas. During the last ten years X-ray lasers in the wavelength range 14 to 47 nm have enabled researchers to use interferometers to probe even higher density plasmas. The data analysis assumes that the index of refraction is due only to the free electrons, which makes the index of refraction less than one and the electron density proportional to the number of fringe shifts. Recent experiments in Al plasmas observed plasmas with an index of refraction greater than one and made us question the validity of the usual formula for calculating the index of refraction. Recent calculations showed how the anomalous dispersion from the bound electrons can dominate the index of refraction in many types of plasma and make the index greater than one or enhance the index such that one would greatly overestimate the electron density of the plasma using interferometers. In this work we calculate the index of refraction of C, Al, Ti, and Pd plasmas for photon energies from 0 to 100 eV (12.4 nm) using a new average-atom code. The results show large variations from the free electron approximation under many different plasma conditions. We validate the average-atom code against the more detailed OPAL code for carbon and aluminum plasmas. During the next decade X-ray free electron lasers and other sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential.

Nilsen, J; Johnson, W R; Iglesias, C A; Scofield, J H

2004-12-16

340

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

341

Exponential characteristics spatial quadrature for discrete ordinates radiation transport in slab geometry  

Microsoft Academic Search

The exponential characteristic spatial quadrature for discrete ordinates neutral particle transport in slab geometry is derived and compared with current methods. It is similar to the linear characteristic (or, in slab geometry, the linear nodal) quadrature but differs by assuming an exponential distribution of the scattering source within each cell, S(x) = a exp(bx), whose parameters are root-solved to match

K. Mathews; G. Sjoden; B. Minor

1994-01-01

342

Adaptive characteristic spatial quadratures for discrete ordinates neutral particle transport - the rectangular cell case  

Microsoft Academic Search

Adaptive characteristic spatial quadrature schemes for use in discrete ordinates neutral particle transport computer codes in slab geometry have been introduced recently; the extension to two-dimensional Cartesian coordinates with rectangular cells is presented here. These quadratures differ from previous schemes in using strictly non-negative finite-element-like representations of the entering fluxes and scattering source, which adapt to match both the zeroth

Kirk A. Mathews; Bryan M. Minor

1993-01-01

343

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

344

Noncontact measurement of intraocular pressure using a modified Michelson interferometer  

NASA Astrophysics Data System (ADS)

This paper describes a new method to examine the intraocular pressure (IOP) without any contact with the eye. In our new approach the IOP is determined indirectly from the acoustic properties of the eye, as the resonance frequencies of the bulbus are shifting with increasing IOP. In a first step simulations were made with the Finite Element Method to explore the correlation between the IOP and the acoustic properties of the bulbus. The results showed a significant rise of the resonance-frequencies with increasing IOP. Simultaneously a in-vitro measurement system was built comprising a modified michelson interferometer to measure the vibrations, a transducer to stimulate the eye and a controlling PC. With this system measurements were made with artificial eyes and enucleated pig eyes to prove the correlation experimentally. The eyes were stimulated both contacting the eye with a transducer by a stick and contactless with sonic waves. Several series of measurements showed a proportional constant of 1,25 Hz/mmHg in average, which can be detected easily. The standard deviation measuring different pig eyes was 4,5 mmHg. Next a in-vivo system was developed to study the acoustic behavior of the human eye in the real environment. The in-vivo system consists of a miniaturized semiconductor-laser interferometer complying laser safety requirements, an automatic positioning unit and an excitation unit to stimulate vibrations of the eye. Sub-micrometer vibrations of the eye can be measured in-vivo with this system.

Drescher, Joerg; Stork, Wilhelm; Hey, Stefan; Gundlach, Arnd; Mueller-Glaser, Klaus-Dieter; Kreiner, Christine F.

1999-06-01

345

A Quadrature Free Discontinuous Galerkin Conservative Level Set Scheme  

NASA Astrophysics Data System (ADS)

In an effort to improve the scalability and accuracy of the Accurate Conservative Level Set (ACLS) scheme [Desjardins et al., J COMPUT PHYS 227 (2008)], a scheme based on the quadrature free discontinuous Galerkin (DG) methodology has been developed. ACLS relies on a hyperbolic tangent level set function that is transported and reinitialized using conservative schemes in order to alleviate mass conservation issues known to plague level set methods. DG allows for an arbitrarily high order representation of the interface by using a basis of high order polynomials while only using data from the faces of neighboring cells. The small stencil allows DG to have excellent parallel scalability. The diffusion term present in the conservative reinitialization equation is handled using local DG method [Cockburn et al., SIAM J NUMER ANAL 39, (2001)] while the normals are computed from a limited form of the level set function in order to avoid spurious oscillations. The resulting scheme is shown to be both robust, accurate, and highly scalable, making it a method of choice for large-scale simulations of multiphase flows with complex interfacial topology.

Czajkowski, Mark; Desjardins, Olivier

2010-11-01

346

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

347

Real-time digital heterodyne interferometer for high resolution plasma density measurements at ISTTOKa)  

NASA Astrophysics Data System (ADS)

With the implementation of alternating discharges (ac) at the ISTTOK tokamak, the typical duration of the discharges increased from 35to250ms. This time increase created the need for a real-time electron density measurement in order to control the plasma fueling. The diagnostic chosen for the real-time calculation was the microwave interferometer. The ISTTOK microwave interferometer is a heterodyne system with quadrature detection and a probing frequency of 100GHz (?0=3mm). In this paper, a low-cost approach for real-time diagnostic using a digital signal programable intelligent computer embedded system is presented, which allows the measurement of the phase with a 1% fringe accuracy in less than 6?s. The system increases its accuracy by digitally correcting the offsets of the input signals and making use of a judicious lookup table optimized to improve the nonlinear behavior of the transfer curve. The electron density is determined at a rate of 82kHz (limited by the analog to digital converter), and the data are transmitted for each millisecond although this last parameter could be much lower (around 12?s—each value calculated is transmitted). In the future, this same system is expected to control plasma actuators, such as the piezoelectric valve of the hydrogen injection system responsible for the plasma fueling.

Marques, T. G.; Gouveia, A.; Pereira, T.; Fortunato, J.; Carvalho, B. B.; Sousa, J.; Silva, C.; Fernandes, H.

2008-10-01

348

Real-time digital heterodyne interferometer for high resolution plasma density measurements at ISTTOK.  

PubMed

With the implementation of alternating discharges (ac) at the ISTTOK tokamak, the typical duration of the discharges increased from 35 to 250 ms. This time increase created the need for a real-time electron density measurement in order to control the plasma fueling. The diagnostic chosen for the real-time calculation was the microwave interferometer. The ISTTOK microwave interferometer is a heterodyne system with quadrature detection and a probing frequency of 100 GHz (lambda(0)=3 mm). In this paper, a low-cost approach for real-time diagnostic using a digital signal programmable intelligent computer embedded system is presented, which allows the measurement of the phase with a 1% fringe accuracy in less than 6 micros. The system increases its accuracy by digitally correcting the offsets of the input signals and making use of a judicious lookup table optimized to improve the nonlinear behavior of the transfer curve. The electron density is determined at a rate of 82 kHz (limited by the analog to digital converter), and the data are transmitted for each millisecond although this last parameter could be much lower (around 12 micros--each value calculated is transmitted). In the future, this same system is expected to control plasma actuators, such as the piezoelectric valve of the hydrogen injection system responsible for the plasma fueling. PMID:19044529

Marques, T G; Gouveia, A; Pereira, T; Fortunato, J; Carvalho, B B; Sousa, J; Silva, C; Fernandes, H

2008-10-01

349

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

350

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

351

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

352

Angle interferometer cross axis errors  

SciTech Connect

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 rotary tables when the centerline of the double comer cube mirror assembly is not square to the axes of rotation of the angle calibrator and the calibrator axis is not parallel to the rotary table axis. Commercial double comer cube assemblies typically have non-parallelism errors of ten milli-radians between their centerlines and their sides and similar values for non-squareness between their centerlines and end surfaces. The authors have developed a simple method for measuring these errors and correcting them by remachining the reference surfaces.

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

1994-01-01

353

Multiple spacecraft Michelson stellar interferometer  

NASA Technical Reports Server (NTRS)

Results of an orbital analysis and performance assessment of SAMSI (Spacecraft Array for Michelson Spatial Interferometry) are presented. The device considered includes two one-meter telescopes in orbits which are identical except for slightly different inclinations; the telescopes achieve separations as large as 10 km and relay starlight to a central station which has a one-meter optical delay line in one interferometer arm. It is shown that a 1000-km altitude, zero mean inclination orbit affords natural scanning of the 10-km baseline with departures from optical pathlength equality which are well within the corrective capacity of the optical delay line. Electric propulsion is completely adequate to provide the required spacecraft motions, principally those needed for repointing. Resolution of 0.00001 arcsec and magnitude limits of 15 to 20 are achievable.

Stachnik, R. V.; Arnold, D.; Melroy, P.; Mccormack, E. F.; Gezari, D. Y.

1984-01-01

354

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

355

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

PubMed

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

Kim, Kyowon; Murphy, Thomas E

2013-08-26

356

Implementation and applications of a Fizeau-based fiber tip interferometer  

NASA Astrophysics Data System (ADS)

It is presented the results of experimental studies through the implementation of a Fizeau-based Fiber Tip Interferometer (FTI), as the realization of the open optics Fizeau Interferometer into Fiber-optics. The FTI was constructed with off-the shelf fiber optic components and can be compacted in a way of a "sensor head" for various purposes. The FTI can be used as a single probe device or as a multiple probes device for several simultaneous measurement points. The single probe FTI is integrated by a HeNe laser, a Fiber bi-conical tapered coupler and a fiber-coupled GRIN lens. A range of applications of such homodyne interferometer device for non-contact measurements, going from ultrasound detection to temperature measurements are presented.

Baltazar-Lopez, Martin E.

2005-02-01

357

Narrowband optical filter based on a Fabry-Perot interferometer with two waveguide-grating mirrors  

SciTech Connect

The operation of a narrowband filter based on a Fabry-Perot interferometer formed by two waveguide-grating mirrors is studied upon normal incidence of light. In this case, two counterpropagating travelling waves and coupled modes are excited in a corrugated waveguide, while only one mode is excited in the case of oblique incidence of light on the filter. It is found that in the case of a small gap between the mirrors, the reflection spectrum of the interferometer depends on the phase shift {Delta}{phi} of one corrugation relative to the other. If light is incident normally on the interferometer, two or three lines appear in the transmission spectrum if {Delta}{phi} {ne} 0 or {Delta}{phi} {ne} {pi}. The appearance of the additional resonances is attributed to symmetry breaking in the system. At large distances between the mirrors, the spectra at {theta} = 0 do not exhibit any peculiarities. (laser devices and elements)

Usievich, B A; Sychugov, V A; Nurligareev, J Kh [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2007-05-31

358

The Millimeter-Wave Bolometric Interferometer  

NASA Technical Reports Server (NTRS)

The Millimeter-wave Bolometric Interferometer (MBI) is a proposed ground-based instrument designed for a wide range of cosmological and astrophysical observations including studies of the polarization of the cosmic microwave background (CMB). MBI combines the advantages of two well-developed technologies - interferometers and bolometric detectors. Interferometers have many advantages over .filled-aperture telescopes and are particularly suitable for high resolution imaging. Cooled bolometers are the highest sensitivity detectors at millimeter and sub-millimeter wavelengths. The combination of these two technologies results in an instrument with both high sensitivity and high angular resolution.

Ali, S.; Ade, P. A. R.; Bock, J. J.; Novak, G.; Piccirillo, L.; Timbie, P.; Tucker, G. S.

2004-01-01

359

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

360

Method and apparatus for measuring surface movement of an object using a 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. 38 figs.

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

1995-05-09

361

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

362

Michelson interferometer with diffractively-coupled arm resonators in second-order Littrow configuration.  

PubMed

Michelson-type laser-interferometric gravitational-wave (GW) observatories employ very high light powers as well as transmissively-coupled Fabry-Perot arm resonators in order to realize high measurement sensitivities. Due to the absorption in the transmissive optics, high powers lead to thermal lensing and hence to thermal distortions of the laser beam profile, which sets a limit on the maximal light power employable in GW observatories. Here, we propose and realize a Michelson-type laser interferometer with arm resonators whose coupling components are all-reflective second-order Littrow gratings. In principle such gratings allow high finesse values of the resonators but avoid bulk transmission of the laser light and thus the corresponding thermal beam distortion. The gratings used have three diffraction orders, which leads to the creation of a second signal port. We theoretically analyze the signal response of the proposed topology and show that it is equivalent to a conventional Michelson-type interferometer. In our proof-of-principle experiment we generated phase-modulation signals inside the arm resonators and detected them simultaneously at the two signal ports. The sum signal was shown to be equivalent to a single-output-port Michelson interferometer with transmissively-coupled arm cavities, taking into account optical loss. The proposed and demonstrated topology is a possible approach for future all-reflective GW observatory designs. PMID:23187357

Britzger, Michael; Wimmer, Maximilian H; Khalaidovski, Alexander; Friedrich, Daniel; Kroker, Stefanie; Brückner, Frank; Kley, Ernst-Bernhard; Tünnermann, Andreas; Danzmann, Karsten; Schnabel, Roman

2012-11-01

363

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

364

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.

365

Atom Interferometers with Scalable Enclosed Area  

NASA Astrophysics Data System (ADS)

Bloch oscillations (i.e., coherent acceleration of matter waves by an optical lattice) and Bragg diffraction are integrated into light-pulse atom interferometers with large momentum splitting between the interferometer arms, and hence enhanced sensitivity. Simultaneous acceleration of both arms in the same internal states suppresses systematic effects, and simultaneously running a pair of interferometers suppresses the effect of vibrations. Ramsey-Bordé interferometers using four such Bloch-Bragg-Bloch beam splitters exhibit 15% contrast at 24?k splitting, the largest so far (?k is the photon momentum); single beam splitters achieve 88?k. The prospects for reaching 100 s of ?k and applications such as gravitational wave sensors are discussed.

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

2009-06-01

366

Atom interferometers with scalable enclosed area.  

PubMed

Bloch oscillations (i.e., coherent acceleration of matter waves by an optical lattice) and Bragg diffraction are integrated into light-pulse atom interferometers with large momentum splitting between the interferometer arms, and hence enhanced sensitivity. Simultaneous acceleration of both arms in the same internal states suppresses systematic effects, and simultaneously running a pair of interferometers suppresses the effect of vibrations. Ramsey-Bordé interferometers using four such Bloch-Bragg-Bloch beam splitters exhibit 15% contrast at 24variant Planck's over 2pik splitting, the largest so far (variant Planck's over 2pik is the photon momentum); single beam splitters achieve 88variant Planck's over 2pik. The prospects for reaching 100 s of variant Planck's over 2pik and applications such as gravitational wave sensors are discussed. PMID:19658985

Müller, Holger; Chiow, Sheng-wey; Herrmann, Sven; Chu, Steven

2009-06-19

367

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

SciTech Connect

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{sup -1/2} above 20 Hz and approaches the shot-noise-limit of 20 fm Hz{sup -1/2} at 1 kHz for an optical power of 10 {mu}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. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Howard, L. P. [Precera, Inc., Damascus, Maryland 20872 (United States)

2009-03-15

368

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

369

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

370

Interferometer Designs for the Terrestrial Planet Finder  

NASA Technical Reports Server (NTRS)

The Terrestrial Planet Finder (TPF) is a space-based infrared interferometer that will combine high sensitivity and spatial resolution to detect and characterize planetary systems within 15 pc of our sun. TPF is a key element in NASA's Origins Program and is currently under study in its Pre-Project Phase. We review some of the interferometer designs that have been considered for starlight nulling, with particular attention to the architecture and subsystems of the central beam-combiner.

Lawson, P. R.; Dumont, P. J.; Colavita, M. M.

1999-01-01

371

Thermal Dephasing in the Laughlin Quasiparticle Interferometer  

Microsoft Academic Search

We report experiments on thermal dephasing of the Aharonov-Bohm oscillations in the novel Laughlin quasiparticle (LQP) interferometer, [1] where quasiparticles of the 1\\/3 FQH fluid execute a closed path around an island of the 2\\/5 fluid. In the 10.2 <=T <=141 mK temperature range, qualitatively, the experimental results follow a thermal dephasing dependence expected for an electron interferometer, and show

F. E. Camino; Wei Zhou; V. J. Goldman

2006-01-01

372

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

373

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

374

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

375

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

376

Bragg spectroscopic interferometer and quantum measurement-induced correlations in atomic Bose-Einstein condensates  

E-print Network

We theoretically analyze the Bragg spectroscopic interferometer of two spatially separated atomic Bose-Einstein condensates that was experimentally realized by Saba et al. [Science 2005 v307 p1945] by continuously monitoring the relative phase evolution. Even though the atoms in the light-stimulated Bragg scattering interact with intense coherent laser beams, we show that the phase is created by quantum measurement-induced back-action on the homodyne photo-current of the lasers, opening possibilities for quantum-enhanced interferometric schemes. We identify two regimes of phase evolution: a running phase regime which was observed in the experiment of Saba et al., that is sensitive to an energy offset and suitable for an interferometer, and a trapped phase regime, that can be insensitive to applied forces and detrimental to interferometric applications.

M. D. Lee; S. Rist; J. Ruostekoski

2012-08-02

377

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

378

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

NASA Astrophysics Data System (ADS)

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; Mase, Atsushi; Nishida, Yasushi; Cheng, C. Z.

2014-02-01

379

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

NASA Technical Reports Server (NTRS)

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

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

1971-01-01

380

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

381

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

382

Spherical grating monochromator with interferometer control and in-vacuum reference  

Microsoft Academic Search

Physical Science Laboratory’s new generation of spherical grating monochromators incorporates a laser interferometer to control scan angle and an in-vacuum absolute angle reference, as well as other improvements. The design accommodates up to six gratings which can be moved axially (under motor control, with encoder position readback) at any scan angle. The gratings are cooled by means of spring-loaded clamps

D. J. Holly; W. P. Mason; T. Sailor; R. E. Smith; D. Wahl

2002-01-01

383

Measurement of surface figure of plane optical surfaces with polarization phase-shifting Fizeau interferometer  

Microsoft Academic Search

A Fizeau interferometer based set up for measurement of surface forms of plane optical surfaces has been discussed. Phase shifting interferometry has been applied using polarization phase shifter. A linearly polarized (632.8nm) He–Ne laser has been used as the source. Light reflected from the object and the reference\\/master surfaces are made circularly polarized in opposite senses by means of two

Sanjib Chatterjee; Y. Pawan Kumar; Basanta Bhaduri

2007-01-01

384

Parallel multiplex laser feedback interferometry  

SciTech Connect

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

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

2013-12-15

385

Parallel multiplex laser feedback interferometry  

NASA Astrophysics Data System (ADS)

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

Zhang, Song; Tan, Yidong; Zhang, Shulian

2013-12-01

386

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

387

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

388

Fizeau interferometer for measurement of plasma electron current  

SciTech Connect

A high-resolution, vertically viewing far-infrared polarimeter-interferometer system is currently used on the Madison symmetric torus (MST) reversed-field pinch (RFP) to measure the plasma electron density and toroidal current density via Faraday rotation. In this article, we propose a scheme to measure the well-known Fizeau effect, whereby through modest modification of the existing apparatus, the line-integrated poloidal current density can also be directly measured. This parameter is important, since the RFP toroidal magnetic field is largely determined by currents flowing within the plasma. The Fizeau effect is a phase shift of an electromagnetic wave associated with movement of a dielectric medium. This motion can be related directly to the plasma electron current. Determining the Fizeau effect involves measurement of the phase shift between two collinear, orthogonally polarized, counterpropagating laser beams. Estimates indicate a phase shift of {approx}2 deg. is expected for typical MST parameters, well within the existing system resolution.

Brower, D.L.; Ding, W.X.; Deng, B.H.; Mahdavi, M.A.; Mirnov, V.; Prager, S.C. [Electrical Engineering Department, University of California, Los Angeles, Los Angeles, California 90095 (United States); General Atomics, San Diego, California 92121 (United States); Physics Department, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)

2004-10-01

389

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

390

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

391

Matter-wave interferometer for large molecules.  

PubMed

We demonstrate a near-field Talbot-Lau interferometer for C70 fullerene molecules. Such interferometers are particularly suitable for larger masses. Using three free-standing gold gratings of 1 microm period and a transversally incoherent but velocity-selected molecular beam, we achieve an interference fringe visibility of 40% with high count rate. Both the high visibility and its velocity dependence are in good agreement with a quantum simulation that takes into account the van der Waals interaction of the molecules with the gratings and are in striking contrast to a classical moiré model. PMID:11909334

Brezger, Björn; Hackermüller, Lucia; Uttenthaler, Stefan; Petschinka, Julia; Arndt, Markus; Zeilinger, Anton

2002-03-11

392

Continuous phase amplification with a Sagnac interferometer  

E-print Network

We describe a weak value inspired phase amplification technique in a Sagnac interferometer. We monitor the relative phase between two paths of a slightly misaligned interferometer by measuring the average position of a split-Gaussian mode in the dark port. Although we monitor only the dark port, we show that the signal varies linearly with phase and that we can obtain similar sensitivity to balanced homodyne detection. We derive the source of the amplification both with classical wave optics and as an inverse weak value.

David J. Starling; P. Ben Dixon; Nathan S. Williams; Andrew N. Jordan; John C. Howell

2009-12-16

393

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

394

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

395

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

PubMed

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

Serbes, Gorkem; Aydin, Nizamettin

2014-01-01

396

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

PubMed

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

Serbes, G; Aydin, N

2011-01-01

397

Receiver design using the dependence between quadrature components of impulsive radio noise  

Microsoft Academic Search

A new BPSK receiver based on the statistical characteristics of impulsive radio noise is proposed. First, the statistical characteristics of impulsive radio noise are investigated, and it is proved that the quadrature components of impulsive noise are dependent. Next, with the consideration of the dependence between these components, a new BPSK receiver designed for impulsive noise is proposed, and it

S. Miyamoto; M. Katayama; N. Morinaga

1995-01-01

398

Revisiting the accurate calculation of block-sample covariances using Gauss quadrature  

Microsoft Academic Search

Block-sample covariances may be calculated by discretizing a block into regularly spaced grid points, computing punctual covariance between each grid point and the sample, then averaging. Gauss quadrature is a better, more accurate method for calculating block-sample covariance as has been demonstrated in the past by other authors (the history of which is reviewed herein). This prior research is expanded

James R. Carr; Jeffrey A. Palmer

1993-01-01

399

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

400

Comparison of Consistent Integration Versus Adaptive Quadrature For Taming Aliasing Errors  

E-print Network

Mirzaee , Claes Eskilsson , Spencer J. Sherwin , Robert M. Kirby SCI Institute, University of Utah Integration Versus Adaptive Quadrature For Taming Aliasing Errors Hanieh Mirzaee1 , Claes Eskilsson2 , Spencer J. Sherwin3 and Robert M. Kirby4 August 28, 2009 Abstract Most spectral/hp element methods, whether

Utah, University of

401

Direct quadrature phase shift keying modulator using six-port technology  

E-print Network

heterodyne architecture, which requires IF mixers, in-phase and quadrature carriers and an RF upconversion. 2, which adopts a power divider and three-hybrid coupler. The circuit operates as follows: port 1, hybrid coupler branch and transmission line respectively and i represents the ith configuration of four

Frigon, Jean-François

402

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

403

An Novel Compact Quadrature Hybrid Using Broadside-Coupled Meander Lines  

Microsoft Academic Search

In this paper, we present a novel compact 3-dB quadrature directional coupler by introducing Hilbert curve to the conventional meander line structure. The proposed coupler uses a modified broadside coupled meander lines featuring Hilbert curves to achieve a smaller size. The structure of the coupler is suitable for multilayer printed circuit board (PCB) implementation. The proposed coupler with an operation

C. Y. Li; H. W. Yang; J. F. Bao; Y. P. Yan

2011-01-01

404

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

EPA Science Inventory

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

405

(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

406

Optical fiber in-line Mach-Zehnder interferometer based on dual internal mirrors formed by a hollow sphere pair.  

PubMed

We demonstrate a fiber in-line Mach-Zehnder interferometer based on dual internal mirrors formed by a hollow sphere pair and fabricated by femtosecond laser micromachining together with the fusion splicing technique. The hollow sphere surface adjacent to the fiber core can reflect part of the incident light beam to the air-cladding interface, where the light beam is reflected again before returning to the fiber core by another hollow sphere surface and recombining with the light beam remaining in the fiber core. Such an interferometer is miniature and robust, and is sensitive to environmental variations and allows simultaneous surrounding refractive index, temperature, and curvature measurement. PMID:24104641

Hu, T Y; Wang, D N

2013-08-15

407

Jamin interferometer for precise measurement of refractive index of gases  

NASA Astrophysics Data System (ADS)

Modified folded Jamin interferometer for on-line measurement of refractive index of gases was designed, constructed and tested. The accuracy of this interferometer is better than 10-6 and can be still approved about two orders by appropriate mathematical method. Interferometer is almost vibration insensitive with vibration noise equivalent to refractive index variation 2•10-9. The interferometer qualities were tested by air refractive index monitoring.

Sulc, Miroslav

2015-01-01

408

Cold atom interferometers and their applications in precision measurements  

NASA Astrophysics Data System (ADS)

Experimental realization of cold 85Rb atom interferometers and their applications in precision measurements are reported in this paper. Mach-Zehnder and Ramsey-Bordè type interferometers were demonstrated. Detailed descriptions of the interferometers are given including manipulation of cold atoms, Rabi oscillation, stimulated Raman transitions, and optical pumping. As an example of using atom interferometers in precision measurements, the quadratic Zeeman shift of hyperfine sublevels of 85Rb was determined.

Wang, Jin; Zhou, Lin; Li, Run-Bing; Liu, Min; Zhan, Ming-Sheng

2009-06-01

409

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

410

An electron Talbot-Lau interferometer and magnetic field sensing  

NASA Astrophysics Data System (ADS)

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

Bach, Roger; Gronniger, Glen; Batelaan, Herman

2013-12-01

411

Microwave Interferometer Density Diagnostic for the Levitated Dipole Experiment  

E-print Network

a multi-channel microwave interferometer. Such a device makes use the relationship between a plasma's density and its index of refraction. The beams of an interferometer acquire a phase-shift when traversing Oscillator (LO), is mixed with the RF to produce an Intermediate Frequency (IF). · Our interferometer uses

412

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

E-print Network

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

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

2012-02-29

413

Control of Formation-Flying Multi-Element Space Interferometers with Direct Interferometer-Output Feedback  

NASA Technical Reports Server (NTRS)

The long-baseline space interferometer concept involving formation flying of multiple spacecrafts holds great promise as future space missions for high-resolution imagery. A major challenge of obtaining high-quality interferometric synthesized images from long-baseline space interferometers is to accurately control these spacecraft and their optics payloads in the specified configuration. Our research focuses on the determination of the optical errors to achieve fine control of long-baseline space interferometers without resorting to additional sensing equipment. We present a suite of estimation tools that can effectively extract from the raw interferometric image relative x/y, piston translational and tip/tilt deviations at the exit pupil aperture. The use of these error estimates in achieving control of the interferometer elements is demonstrated using simulated as well as laboratory-collected interferometric stellar images.

Lu, Hui-Ling; Cheng, Victor H. L.; Lyon, Richard G.; Carpenter, Kenneth G.

2007-01-01

414

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

415

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

416

Molecular collisions in a laser field - Effect of the laser linewidth  

NASA Technical Reports Server (NTRS)

The effect of the laser linewidth on molecular collision processes taking place in a laser field is studied, using an approximation scheme that replaces the actual frequency distribution of the field by a finite number of frequencies and weights. The choice of the frequencies and weights is conveniently accomplished by the method of Gaussian quadrature. Close-coupling calculations are performed on model systems, and the results indicate that the neglect of the laser linewidth may be justified in most collision processes in a laser field.

Lee, H. W.; Devries, P. L.; George, T. F.

1978-01-01

417

Accurate radio positions with the Tidbinbilla interferometer  

NASA Technical Reports Server (NTRS)

The Tidbinbilla interferometer, designed specifically to provide accurate radio position measurements of compact radio sources in the Southern Hemisphere with high sensitivity using the 26 m and 64 m antennas of the Deep Space Network at Tidbinbilla, near Canberra, is discussed. The instrument also provides high accuracy flux density measurements for compact radio sources.

Batty, M. J.; Jauncey, D. J.; Rayner, P. T.; Gulkis, S.

1980-01-01

418

Achromatic interferometer for imaging through turbulence  

Microsoft Academic Search

It is shown that the single-aperture grating interferometer produces a deep achromatic fringe field that yields information on the source separation of a two-point source; the intensity ratio between the two points, also, can be ascertained. The primary value of this method lies in the field of application to objects of greater complexity than can be addressed by such simpler

Hsuan Chen; Lian Shentu

1992-01-01

419

A Microwave Interferometer on an Air Track.  

ERIC Educational Resources Information Center

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

Polley, J. Patrick

1993-01-01

420

Low Coherence Vibration Insensitive Fizeau Interferometer  

Microsoft Academic Search

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

Brad Kimbrough; James Millerd; James Wyant; John Hayes

2006-01-01

421

Fizeau interferometer profiles at finite acceptance angles  

Microsoft Academic Search

Instrument profiles of the wedge or Fizeau interferometer are determined under practical conditions. The appearance of subsidiary maxima on the high order side of the central maxima is confirmed, and the behaviour of these is noted as the solid angle of acceptance is varied. From these calculations it is inferred that the acceptable range of use of the instrument could

T A Hall

1969-01-01

422

The Green Bank Interferometer Control Frank Ghigo  

E-print Network

Jansky Lab control rooms 2 #12; New Control System Hardware #15; Control Computer #15; Telescope; Monitor system #15; Data logger system #15; User interfaces #15; Support libraries 15 #12; The Green Bank Interferometer Control System John Ford Frank Ghigo 1 #12; The new hardware

Groppi, Christopher

423

Theory of fractional quantum Hall interferometers  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

424

The millimeter-wave bolometric interferometer  

NASA Astrophysics Data System (ADS)

The Millimeter-wave Bolometric Interferometer (MBI) is a technology demonstrator for future searches for the B-mode polarization of the Cosmic Microwave Background (CMB). If observed, B-modes would be a direct probe of the energy scale of inflation, an energy scale that is impossible to reach with even the most sophisticated particle accelerators. In this thesis, I outline the technology differences between MBI and conventional interferometers, including the Faraday effect phase modulators (FPM) used both to control systematic effects and to allow for phase sensitive detection of signals. MBI is a four element adding interferometer with a Fizeau optical beam combiner. This allows simple scaling of the instrument to a large numbers of baselines without requiring complicated pair-wise correlations of signals. Interferometers have an advantage over imaging telescopes when measuring the CMB power spectrum as each baseline is sensitive to a single Fourier mode (angular scale) on the sky. Recovering individual baseline information with this combination scheme requires phase modulating the signal from each antenna. MBI performs this modulation with Faraday effect phase modulators. In these novel cryogenic devices a modulated magnetic field switches the phase of a millimeter-wave RF signal by +/- 90 degrees at frequencies up to a few Hertz. MBI's second season of observations occurred in the winter of 2009 at Pine Bluff Observatory a few miles west of Madsion, WI. We successfully observed interference fringes of a microwave test source located in the far field of the instrument that agree well with those expected from simulations. MBI has inspired a second generation bolometric interferometer, QUBIC, which will have hundreds of antennas and thousands of detectors. When it deploys in 2015, it will be sensitive enough to search for B-mode signals from the CMB.

Gault, Amanda Charlotte

425

Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer  

SciTech Connect

The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely when the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ?}. Experiment has proved its feasibility and practicability.

Tang, Shanzhi, E-mail: shanzhit@gmail.com [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China) [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Wang, Zhao [School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China)] [School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049 (China); Gao, Jianmin; Guo, Junjie [State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)] [State Key Laboratory for Manufacturing Systems Engineering, Xi'an Jiaotong University, Xi'an 710054 (China)

2014-04-15

426

European "synQPSK" Project: Toward Synchronous Optical Quadrature Phase Shift Keying with DFB Lasers  

E-print Network

optical distortions (polarization transformations [8, 6], polarization mode and chromatic dispersions) can://ont.upb.de/synQPSK) aims to realize all components which are not readily found on the market: LiNbO3 QPSK modulators

Noé, Reinhold

427

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

NASA Technical Reports Server (NTRS)

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

Sidi, A.; Israeli, M.

1986-01-01

428

State-labeling Wannier-Stark atomic interferometers  

NASA Astrophysics Data System (ADS)

Using cold 87Rb atoms trapped in a one-dimensional (1D)-optical lattice, atomic interferometers involving coherent superpositions between different Wannier-Stark atomic states are realized. Two different kinds of trapped interferometer schemes are presented: a Ramsey-type interferometer sensitive both to clock frequency and external forces, and a symmetric accordion-type interferometer, sensitive to external forces only. We evaluate the limits in terms of sensitivity and accuracy of those schemes and discuss their application as force sensors. As a first step, we apply these interferometers to the measurement of the Bloch frequency and the demonstration of a compact gravimeter.

Pelle, B.; Hilico, A.; Tackmann, G.; Beaufils, Q.; Pereira dos Santos, F.

2013-02-01

429

Low-cost multimode fiber Mach Zehnder interferometer for differential phase demodulation  

NASA Astrophysics Data System (ADS)

Mach-Zehnder interferometers (MZIs) are used in many optical applications, such as measurement of the coherence length of a laser, thermal dynamic flow, flatness of plane optical plates, thickness of thin films, etc. In this type of interferometer, light passing through a sample region in one direction recombines with a second leg without traversing the sample twice. In telecommunication, MZIs are used for demodulating differential phase-shift-keyed (DPSK) signals. DSPK has attracted increased attention in fiber optic transmission in recent years because of its 3-dB optical signal to noise ratio improvement over standard intensity modulated transmission, as well as for its high tolerance to nonlinear effects and coherent crosstalk. In a standard fiber MZI, two wideband fiber couplers are spliced together with one arm providing a one-bit delay to convert the phase difference into an intensity modulation. In our alternate type of MZI, the two-mode interferometer, the time delay is obtained through the difference between the propagation constants of two modes instead of through a physical path length difference. We present here a novel single multimode fiber modal interferometer for DPSK demodulation. In this design, a second mode is excited by splicing a standard fiber to a multimode fiber length such that two modes beat together before recombining in a second splice. A numerical analysis and an experimental verification of the multimode fiber parameters to maximize the extinction ratio and minimize the length of the interferometer are presented. We investigate coupling, insertion losses, temperature sensitivity and polarization effects of using modes with and without radial symmetry. The design is extremely low-cost, easily manufactured and is intrinsically less temperature sensitive than standard MZI. Although balanced detection is lost, DPSK may still be advantageous because of its high tolerance to nonlinear effects and coherent crosstalk.

Lize, Yannick K.; Gomma, Robert; Kashyap, Raman

2006-08-01

430

Investigation of Space Interferometer Control Using Imaging Sensor Output Feedback  

NASA Technical Reports Server (NTRS)

Numerous space interferometry missions are planned for the next decade to verify different enabling technologies towards very-long-baseline interferometry to achieve high-resolution imaging and high-precision measurements. These objectives will require coordinated formations of spacecraft separately carrying optical elements comprising the interferometer. High-precision sensing and control of the spacecraft and the interferometer-component payloads are necessary to deliver sub-wavelength accuracy to achieve the scientific objectives. For these missions, the primary scientific product of interferometer measurements may be the only source of data available at the precision required to maintain the spacecraft and interferometer-component formation. A concept is studied for detecting the interferometer's optical configuration errors based on information extracted from the interferometer sensor output. It enables precision control of the optical components, and, in cases of space interferometers requiring formation flight of spacecraft that comprise the elements of a distributed instrument, it enables the control of the formation-flying vehicles because independent navigation or ranging sensors cannot deliver the high-precision metrology over the entire required geometry. Since the concept can act on the quality of the interferometer output directly, it can detect errors outside the capability of traditional metrology instruments, and provide the means needed to augment the traditional instrumentation to enable enhanced performance. Specific analyses performed in this study include the application of signal-processing and image-processing techniques to solve the problems of interferometer aperture baseline control, interferometer pointing, and orientation of multiple interferometer aperture pairs.

Leitner, Jesse A.; Cheng, Victor H. L.

2003-01-01

431

Investigation of Space Interferometer Control Using Imaging Sensor Output Feedback  

NASA Technical Reports Server (NTRS)

Numerous space interferometry missions are planned for the next decade to verify different enabling technologies towards very-long-baseline interferometry to achieve high-resolution imaging and high-precision measurements. These objectives will require coordinated formations of spacecraft separately carrying optical elements comprising the interferometer. High-precision sensing and control of the spacecraft and the interferometer-component payloads are necessary to deliver sub-wavelength accuracy to achieve the scientific objectives. For these missions, the primary scientific product of interferometer measurements may be the only source of data available at the precision required to maintain the spacecraft and interferometer-component formation. A concept is studied for detecting the interferometer's optical configuration errors based on information extracted from the interferometer sensor output. It enables precision control of the optical components, and, in cases of space interferometers requiring formation flight of spacecraft that comprise the elements of a distributed instrument, it enables the control of the formation flying vehicles because independent navigation or ranging sensors cannot deliver the high-precision metrology over the entire required geometry. Since the concept can act on the quality of the interferometer output directly, it can detect errors outside the capability of traditional metrology instruments, and provide the means needed to augment the traditional instrumentation to enable enhanced performance. Specific analyses performed in this study include the application of signal-processing and image-processing techniques to solve the problems of interferometer aperture baseline control, interferometer pointing, and orientation of multiple interferometer aperture pairs.

Cheng, Victore H. L.; Leitner, Jesse A.

2003-01-01

432

Quantum metrology with parametric amplifier-based photon correlation interferometers  

PubMed Central

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

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

2014-01-01

433

Swept Frequency Laser Metrology System  

NASA Technical Reports Server (NTRS)

A swept frequency laser ranging system having sub-micron accuracy that employs multiple common-path heterodyne interferometers, one coupled to a calibrated delay-line for use as an absolute reference for the ranging system. An exemplary embodiment uses two laser heterodyne interferometers to create two laser beams at two different frequencies to measure distance and motions of target(s). Heterodyne fringes generated from reflections off a reference fiducial X(sub R) and measurement (or target) fiducial X(sub M) are reflected back and are then detected by photodiodes. The measured phase changes Delta phi(sub R) and Delta phi (sub m) resulting from the laser frequency swept gives target position. The reference delay-line is the only absolute reference needed in the metrology system and this provides an ultra-stable reference and simple/economical system.

Zhao, Feng (Inventor)

2010-01-01

434

Gaussian quadrature and lattice discretization of the Fermi-Dirac distribution for graphene.  

PubMed

We construct a lattice kinetic scheme to study electronic flow in graphene. For this purpose, we first derive a basis of orthogonal polynomials, using as the weight function the ultrarelativistic Fermi-Dirac distribution at rest. Later, we use these polynomials to expand the respective distribution in a moving frame, for both cases, undoped and doped graphene. In order to discretize the Boltzmann equation and make feasible the numerical implementation, we reduce the number of discrete points in momentum space to 18 by applying a Gaussian quadrature, finding that the family of representative wave (2+1)-vectors, which satisfies the quadrature, reconstructs a honeycomb lattice. The procedure and discrete model are validated by solving the Riemann problem, finding excellent agreement with other numerical models. In addition, we have extended the Riemann problem to the case of different dopings, finding that by increasing the chemical potential the electronic fluid behaves as if it increases its effective viscosity. PMID:23944578

Oettinger, D; Mendoza, M; Herrmann, H J

2013-07-01

435

Gaussian quadrature and lattice discretization of the Fermi-Dirac distribution for graphene  

NASA Astrophysics Data System (ADS)

We construct a lattice kinetic scheme to study electronic flow in graphene. For this purpose, we first derive a basis of orthogonal polynomials, using as the weight function the ultrarelativistic Fermi-Dirac distribution at rest. Later, we use these polynomials to expand the respective distribution in a moving frame, for both cases, undoped and doped graphene. In order to discretize the Boltzmann equation and make feasible the numerical implementation, we reduce the number of discrete points in momentum space to 18 by applying a Gaussian quadrature, finding that the family of representative wave (2+1)-vectors, which satisfies the quadrature, reconstructs a honeycomb lattice. The procedure and discrete model are validated by solving the Riemann problem, finding excellent agreement with other numerical models. In addition, we have extended the Riemann problem to the case of different dopings, finding that by increasing the chemical potential the electronic fluid behaves as if it increases its effective viscosity.

Oettinger, D.; Mendoza, M.; Herrmann, H. J.

2013-07-01

436

[Quadrature Doppler ultrasound signal denoising based on adapted local cosine transform].  

PubMed

The spectrogram of Doppler ultrasound signal has been widely used in clinical diagnosis. The additional frequency components arising from internal or external noise to the system will produce adverse effects on its subjective and quantitative analysis. A novel approach based on the adapted local cosine transform and the non-negative Garrote thresholding method was proposed to remove noise from quadrature Doppler signal. At first, the directional information was extracted from the quadrature signal. And then the denoising method based on the adapted local cosine transform is performed on the forward and backward flow signals, respectively. At last, the estimated signal was reconstructed from the denoised signals using Hilbert transform. In the simulation study, both the mean frequency and spectral width waveform were studied for the denoised signal. The simulation results had shown that this approach was superior to that based on the wavelet transform, especially under low SNR conditions. PMID:17121366

Wang, Xiaotao; Shen, Yi; Liu, Zhiyan

2006-10-01

437

An accurate quadrature technique for the contact boundary in 3D finite element computations  

NASA Astrophysics Data System (ADS)

This paper presents a new numerical integration technique for 3D contact finite element implementations, focusing on a remedy for the inaccurate integration due to discontinuities at the boundary of contact surfaces. The method is based on the adaptive refinement of the integration domain along the boundary of the contact surface, and is accordingly denoted RBQ for refined boundary quadrature. It can be used for common element types of any order, e.g. Lagrange, NURBS, or T-Spline elements. In terms of both computational speed and accuracy, RBQ exhibits great advantages over a naive increase of the number of quadrature points. Also, the RBQ method is shown to remain accurate for large deformations. Furthermore, since the sharp boundary of the contact surface is determined, it can be used for various purposes like the accurate post-processing of the contact pressure. Several examples are presented to illustrate the new technique.

Duong, Thang X.; Sauer, Roger A.

2015-01-01

438

Quadrature mirror filter banks, M-band extensions and perfect-reconstruction techniques  

Microsoft Academic Search

In this paper, quadrature mirror filters (QMF) are reviewed. After a brief introduction to multirate building blocks, the two-band QMF bank is discussed. Various distortions caused by the structure, and methods to eliminate these distortions are outlined. Perfect-reconstruction structures for the two-band case are reviewed, and the results are extended to the case of arbitrary number of channels. The relation

P. P. Vaidyanathan

1987-01-01

439

Quadrature squeezed light generation by cross-phase modulation in semiconductors  

NASA Astrophysics Data System (ADS)

We have generated pulsed quadrature squeezed light by cross-phase modulation in the single-crystal zinc-blende semiconductor ZnSe at 960 nm. Squeezing levels of at least 0.3 dB are measured (0.7 dB inferred at the crystal) with pulse widths of less than 100 fs. The technique is straightforward and should be readily applicable to other semiconductors, including waveguide structures.

Fox, A. M.; Dabbicco, M.; von Plessen, G.; Ryan, J. F.

1995-12-01

440

K- and Q-bands CMOS frequency sources with X-band quadrature VCO  

Microsoft Academic Search

Fully integrated 10-, 20-, and 40-GHz frequency sources are presented, which are implemented with a 0.18-?m CMOS process. A 10-GHz quadrature voltage-controlled oscillator (QVCO) is designed to have output with a low dc level, which can be effectively followed by a frequency multiplier. The proposed multipliers generate signals of 20 and 40 GHz using the harmonics of the QVCO. To

Sangsoo Ko; Jeong-Geun Kim; Taeksang Song; Euisik Yoon; Songcheol Hong

2005-01-01

441

Memoir on Integration of Ordinary Differential [1.2ex] Equations by Quadrature  

E-print Network

The Riccati equations reducible to first-order linear equations by an appropriate change the dependent variable are singled out. All these equations are integrable by quadrature. A wide class of linear ordinary differential equations reducible to algebraic equations is found. It depends on two arbitrary functions. The method for solving all these equations is given. The new class contains the constant coefficient equations and Euler's equations as particular cases.

Ibragimov, Nail H

2011-01-01

442

50-Gb/s silicon quadrature phase-shift keying modulator.  

PubMed

We report the first successful demonstration of quadrature phase-shift keying (QPSK) modulation using two nested silicon Mach-Zehnder modulators. 50-Gb/s QPSK signal is generated with only 2.7-dB optical signal-to-noise ratio penalties from the theoretical limit at a bit-error ratio of 10(-3). This result validates that silicon photonics could be a viable and powerful platform of photonic integrated circuits in coherent optical communications. PMID:23037242

Dong, Po; Chen, Long; Xie, Chongjin; Buhl, Lawrence L; Chen, Young-Kai

2012-09-10

443

Quadrature conductivity: A quantitative indicator of bacterial abundance in porous media  

SciTech Connect

ABSTRACT The abundance and growth stages of bacteria in subsurface porous media affect the concentrations and distributions of charged species within the solid-solution interfaces. Therefore, spectral induced polarization (SIP) measurements can be used to monitor changes in bacterial biomass and growth stage. Our goal was to gain a better understanding of the SIP response of bacteria present in a porous material. Bacterial cell surfaces possess an electric double layer and therefore become polarized in an electric field. We performed SIP measurements over the frequency range of 0.1–1 kHz on cell suspensions alone and cell suspensions mixed with sand at four pore water conductivities. We used Zymomonas mobilis at four different cell densities (in- cluding the background). The quadrature conductivity spectra exhibited two peaks, one around 0.05–0.10 Hz and the other around 1–10 Hz. Because SIP measurements on bacterial suspensions are typically made at frequencies greater than 1 Hz, these peaks have not been previously reported. In the bac-terial suspensions in growth medium, the quadrature conduc-tivity at peak I was linearly proportional to the density of the bacteria. For the case of the suspensions mixed with sands, we observed that peak II presented a smaller increase in the quadrature conductivity with the cell density. A comparison of the experiments with and without sand grains illustrated the effect of the porous medium on the overall quadrature con- ductivity response (decrease in the amplitude and shift of the peaks to the lower frequencies). Our results indicate that for a given porous medium, time-lapse SIP has potential for mon- itoring changes in bacterial abundance within porous media.

Chi Zhang; Andre Revil; Yoshiko Fujita; Junko Munakata-Marr; George Redden

2014-09-01

444

Noncritical quadrature squeezing in two-transverse-mode optical parametric oscillators  

SciTech Connect

In this article we explore the quantum properties of a degenerate optical parametric oscillator when it is tuned to the first family of transverse modes at the down-converted frequency. Recently we found [C. Navarrete-Benlloch et al., Phys. Rev. Lett. 100, 203601 (2008)] that above threshold a TEM{sub 10} mode following a random rotation in the transverse plane emerges in this system (we denote it as the bright mode), breaking thus its rotational invariance. Then, owing to the mode orientation being undetermined, we showed that the phase quadrature of the transverse mode orthogonal to this one (denoted as the dark mode) is perfectly squeezed at any pump level and without an increase in the fluctuations on its amplitude quadrature (which seems to contradict the uncertainty principle). In this article we go further in the study of this system and analyze some important features not considered previously. First we show that the apparent violation of the uncertainty principle is just that -'apparent' - as the conjugate pair of the squeezed quadrature is not another quadrature but the orientation of the bright mode (which is completely undetermined in the long term). We also study a homodyne scheme in which the local oscillator is not perfectly matched to the dark mode, as this could be impossible in real experiments due to the random rotation of the mode, showing that even in this case large levels of noise reduction can be obtained (also including the experimentally unavoidable phase fluctuations). Finally, we show that neither the adiabatic elimination of the pump variables nor the linearization of the quantum equations are responsible for the remarkable properties of the dark mode (which we prove analytically and through numerical simulations, respectively), which were simplifying assumptions used in Navarrete-Benlloch et al. [Phys. Rev. Lett. 100, 203601 (2008)]. These studies show that the production of noncritically squeezed light through spontaneous rotational symmetry breaking is a robust phenomenon.

Navarrete-Benlloch, Carlos; Roldan, Eugenio; Valcarcel, German J. de [Departament d'Optica, Universitat de Valencia, Dr. Moliner 50, 46100 Burjassot (Spain); Romanelli, Alejandro [Instituto de Fisica, Facultad de Ingenieria Universidad de la Republica, C.C. 30, C.P. 11000 Montevideo (Uruguay)

2010-04-15

445

Dynamic characteristics of shaped micro-actuators solved using the differential quadrature method  

Microsoft Academic Search

This study examined the dynamic characteristics of nonlinear electrostatic pull-in behavior for shaped actuators in micro-electro-mechanical systems (MEMS). The natural frequencies of a fixed-fixed shaped beam vibrating around its statically deflected position were calculated using the differential quadrature method (DQM). The proposed model included the nonlinear interaction between the curved electrostatic field force and the shaped micro-beam, as well as

Jao-Hwa Kuang; Chao-Jung Chen

2004-01-01

446

A 3dB Quadrature Coupler Suitable for PCB Circuit Design  

Microsoft Academic Search

A quadrature 3-dB coupler, which combines the advantages of a coplanar waveguide and microstrip line structure suitable for single-layer substrate printed circuit board (PCB) circuit design is proposed. As compared to the conventional Lange coupler, the proposed coupler with the advantages of increasing the coupled linewidths and coupling spacing without using extra bonding wires can solve the drawbacks of Lange

Jui-Chieh Chiu; Chih-Ming Lin; Yeong-Her Wang

2006-01-01

447

Quadrature mirror filter design for an arbitrary number of equal bandwidth channels  

Microsoft Academic Search

The two-channel quadrature mirror filter structure of Croisier and Esteban may be extended to an arbitrary number of equal bandwidth channels, given certain restrictions on the bandpass filters. The most serious restriction is that the stopband attenuation of eacli band-pass filter must be high for all frequencies outside twice the nominal 3 dB bandwidth of the filter. This restriction is

PETER L. CHU

1985-01-01

448

Three mode interaction noise in laser interferometer gravitational wave detectors  

NASA Astrophysics Data System (ADS)

Triply resonant three mode interactions in long optical cavities have been shown to lead to enhanced scattering of carrier light by the ultrasonic acoustic modes of the test mass mirrors. At high optical power, this can lead to parametric instability (parametric gain R>1) for a few acoustic modes with strong spectral and spatial overlap. Numerous \\sim {{10}^{3}} acoustic modes of the test masses are predicted to have R>{{10}^{-2}}. Experimental studies have shown that such modes also strongly scatter the carrier light, enabling very sensitive readout of the acoustic modes. The three-mode scattering from the thermal fluctuation of large population of ultrasonic modes would causes random changes in occupation number of the carrier light and cavity transverse optical modes. Because the thermal fluctuation time scale (set by the acoustic mode relaxation times) is typically a few seconds, the noise spectrum from thermally induced photon number fluctuations is strongly peaked at low frequency. The noise level depends on the acoustic mode structure and acoustic losses of the test masses, the transverse optical mode spectrum of the optical cavities and on the test mass temperature. We theoretically investigate the possible effect of this noise and show that in advanced detectors under construction three mode interaction noise is below the standard quantum limit, but could set limits on future low frequency detectors that aim to exceed the free mass standard quantum limit.

Ju, Li; Zhao, Chunnong; Ma, Yiqiu; Blair, David; Danilishin, Stefan L.; Gras, Slawek

2014-07-01

449

Massive Black Holes and the Laser Interferometer Space Antenna (LISA)  

NASA Technical Reports Server (NTRS)

The goals of the USA mission include both astrophysical investigations and fundamental physics tests. The main astrophysical questions concern the space density, growth, mass function, and surroundings of massive black holes. Thus the crucial issue for the USA mission is the likelihood of observing signals from such sources. Four possible sources of this kind are discussed briefly in this paper. It appears plausible, or even likely. that one or more of these types of sources can be detected and studied by LISA.

Blender, Peter L.; Hils, Dieter; Stebbins, Robin T.

1998-01-01

450

Real-Time Hand-Held Ultrasound Medical-Imaging Device Based on a New Digital Quadrature Demodulation Processor  

Microsoft Academic Search

A fully hardware-based real-time digital wideband quadrature demodulation processor based on the Hilbert transform is proposed to process ultrasound radio frequency signals. The presented architecture combines 2 finite impulse response (FIR) filters to process in-phase and quadrature signals and includes a piecewise linear approximation architecture that performs the required square root operations. The proposed implementation enables flexibility to support different

Philippe Levesque; Mohamad Sawan

2009-01-01

451

Soliton-based matter-wave interferometer  

NASA Astrophysics Data System (ADS)

We consider a matter-wave bright soliton interferometer composed of a harmonic potential trap with a Rosen-Morse barrier at its center on which an incident soliton collides and splits into two solitons. These two solitons recombine after a dipole oscillation in the trap at the position of the barrier. We focus on the characterization of the splitting process in the case in which the reflected and transmitted solitons have the same number of atoms. We obtain that the velocity of the split solitons strongly depends on the nonlinearity and on the width of the barrier and that the reflected soliton is in general slower than the transmitted one. Also, we study the phase difference acquired between the two solitons during the splitting and we fit semianalytically the main dependences with the velocity of the incident soliton, the nonlinearity, and the width of the barrier. The implementation of the full interferometer sequence is tested by means of the phase imprinting method.

Polo, J.; Ahufinger, V.

2013-11-01

452

Accurate radio positions with the Tidbinbilla interferometer  

NASA Technical Reports Server (NTRS)

The Tidbinbilla interferometer (Batty et al., 1977) is designed specifically to provide accurate radio position measurements of compact radio sources in the Southern Hemisphere with high sensitivity. The interferometer uses the 26-m and 64-m antennas of the Deep Space Network at Tidbinbilla, near Canberra. The two antennas are separated by 200 m on a north-south baseline. By utilizing the existing antennas and the low-noise traveling-wave masers at 2.29 GHz, it has been possible to produce a high-sensitivity instrument with a minimum of capital expenditure. The north-south baseline ensures that a good range of UV coverage is obtained, so that sources lying in the declination range between about -80 and +30 deg may be observed with nearly orthogonal projected baselines of no less than about 1000 lambda. The instrument also provides high-accuracy flux density measurements for compact radio sources.

Batty, M. J.; Gulkis, S.; Jauncey, D. L.; Rayner, P. T.

1979-01-01

453

Bright solitonic matter-wave interferometer.  

PubMed

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

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

2014-07-01

454

Bright Solitonic Matter-Wave Interferometer  

NASA Astrophysics Data System (ADS)

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×104 atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the Rb85 atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud.

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

2014-07-01

455

Adaptive DFT-based Interferometer Fringe Tracking  

NASA Technical Reports Server (NTRS)

An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) observatory at Mt. Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three baselines of the Michelson stellar interferometer at IOTA. Based on sliding window discrete Fourier transform (DFT) calculations that were optimized for computational efficiency and robustness to atmospheric disturbances, the algorithm has also been tested extensively on off-line data. Implemented in ANSI C on the 266 MHz PowerPC processor running the VxWorks real-time operating system, the algorithm runs in approximately 2.0 milliseconds per scan (including all three interferograms), using the science camera and piezo scanners to measure and correct the OPDs. The adaptive DFT-based tracking algorithm should be applicable to other systems where there is a need to detect or track a signal with an approximately constant-frequency carrier pulse.

Wilson, Edward; Pedretti, Ettore; Bregman, Jesse; Mah, Robert W.; Traub, Wesley A.

2004-01-01

456

Digital array scanned interferometers for astronomy  

NASA Technical Reports Server (NTRS)

Investigations are reported of digital array scanned interferometers (DASI) with silicon CCD array detectors to define the operational capabilities of a mapping (polarimetric) spectrometer for astronomical applications based on these instruments. For spectral mapping, spatially resolved spectra using a cylindrical lens to image in the interferometers's redundant coordinate are given. The signal-to-noise characteristics of the Fourier transformed data are demonstrated with regard to the effects of a rectangular sampling function, spectral multiplexing and the pixel-to-pixel variation of the CCD array. These data indicate that DASIs can offer simple, versatile (polarization) mapping spectrometers suitable for spectral mapping observations from the ultraviolet to the infrared of extended sources at variable spatial resolution, particularly where long term stable operation is essential, as for spacecraft instruments.

Smith, Wm. Hayden; Schempp, W. V.

1991-01-01

457

A stellar interferometer on the Moon  

NASA Astrophysics Data System (ADS)

The work I present in this document has been divided into two main parts, the first one related to the IOTA project and the second one related to the study on the lunar interferometer, and an introduction section. Each section can be read independently from the other, however they are presented following the logical order in which the research work has been developed. As a guide for the reader here I describe the content of each chapter, which represents the original contribution (except when it is specifically declared) to the research accomplished. This section consists in the Introduction itself, with a presentation of the motivations for this research work, and in the chapter Interferometry from the Earth and from the Moon. The first part of this chapter shows the performances which are expected to be reached by ground-based interferometers (Colavita, 1992) by using adaptive optics systems (Beckers, 1993). The evaluation is made separately for the case of high resolution imaging and for high accuracy astrometric measurements. The most optimistic results expected for ground-based instruments determine the level of the performance that has to be required from a space interferometer (both an orbiting and a lunar instrument). In the second part of the chapter I specifically deal with the case of a lunar interferometer, which allows to put together the advantages o ered by a ground-based instrument (very long baseline, a stable platform) and those offered by the space environment (absence of atmospheric turbulence, long integration times, and wavelength range of observation from the ultraviolet to the far infrared). In order to evaluate the limits of the lunar interferometer, I need to consider three subjects with which I did not explicitly dealt for the study on IOTA: the maximum length of the baseline (Tango and Twiss, 1974), the maximum integration time, and the performances obtainable at the minimum temperature of operation (Ridgway, 1990). The chapter ends with a list of the main reviews which deal with the scientific objectives of space and lunar interferometry. In Appendix A I present an introduction to the principles of optical stellar interferometry. This part is mainly derived by the study and re-elaboration of the contents of the following works: Armstrong et al. (1995), Shao and Colavita (1992), and Born and Wolf (1980). In this section I present the work I specifically developed within the IOTA project. This work allowed me to, directly or indirectly, acquire the theoretical and technical knowledge I then applied in the study on the lunar interferometer. After having identified some of the main sources of systematic error for an interferometer, I examined: the problem of the telescope alignment, the beamsplitter behaviour, the effects that thermal variations cause on the optics and their support structures. The results obtained in these analyses and the evaluations performed on the performances of other subsystems of the instrument, allowed me to proceed in the evaluation of the instrumental visibility loss for IOTA. In the first chapter (I) I present a general description of the IOTA instrument, avoiding a detailed description of each subsystem. When it is necessary, this is given in its appropriate context. The second chapter (II) is the result of the largest part of my work done on IOTA: the analisys of the alignment of each telescope of the interferometer. A non-perfect alignment of the telescope optics causes a distortion of the wavefront coming from the observed object. The distortions affecting the wavefront are responsible for the corruption of the interference fringes produced by the instrument, and eventually of the astrophysics information derived from their analysis. In order to study the effect of the optics misalignment on the performances of IOTA, I wrote a program to simulate some misalignment conditions and to evaluate the wavefront aberration they cause. For each case considered, an interferogram is produced by simulating the interference of the distorted wavefront with a plane wavefront. Th

Porro, Irene

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