Showing papers on "Interferometry published in 2000"
01 Mar 2000
TL;DR: In this paper, the authors present a review of the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering, including cartography, geodesy, land cover characterization, and natural hazards.
Abstract: Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent radar signal, interferometry has transformed radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover characterization, and natural hazards. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.
3,042 citations
TL;DR: Spectroscopic optical coherence tomography (OCT) as discussed by the authors is an extension of conventional OCT for performing cross-sectional tomographic and spectroscopic imaging, which allows the spectrum of backscattered light to be measured over the entire available optical bandwidth simultaneously in a single measurement.
Abstract: Spectroscopic optical coherence tomography (OCT), an extension of conventional OCT, is demonstrated for performing cross-sectional tomographic and spectroscopic imaging. Information on the spectral content of backscattered light is obtained by detection and processing of the interferometric OCT signal. This method allows the spectrum of backscattered light to be measured over the entire available optical bandwidth simultaneously in a single measurement. Specific spectral features can be extracted by use of digital signal processing without changing the measurement apparatus. An ultrabroadband femtosecond Ti:Al2O3 laser was used to achieve spectroscopic imaging over the wavelength range from 650 to 1000 nm in a simple model as well as in vivo in the Xenopus laevis (African frog) tadpole. Multidimensional spectroscopic data are displayed by use of a novel hue-saturation false-color mapping.
644 citations
TL;DR: In this paper, the estimation of vertical-structure parameters from combined interferometric and polarimetric radar data is described, and the authors present a method to estimate the vertical structure parameters from both interferometry and radar data.
Abstract: This paper describes the estimation of vertical-structure parameters from combined interferometric and polarimetric radar data.
512 citations
TL;DR: In this paper, the authors investigate experimental limitations in the accuracy of Fourier transform spectral interferometry, a widely used technique for determining the spectral phase difference between two light beams consisting of femtosecond light pulses.
Abstract: We investigate experimental limitations in the accuracy of Fourier-transform spectral interferometry, a widely used technique for determining the spectral phase difference between two light beams consisting of, for example, femtosecond light pulses. We demonstrate that the spectrometer's finite spectral resolution, pixel aliasing, and frequency-interpolation error can play an important role, and we provide a new and more accurate recipe for recovering the spectral phase from the experimental data. Cop. 2000 Optical Society of America
484 citations
TL;DR: The phase shift of the optical beat component between longitudinal modes of a mode-locked laser is measured and an absolute mechanical distance of 240 m was obtained to within 8-ppm accuracy by use of a series of beat frequencies with the advantage of a wide range of intermode frequency.
Abstract: A high-accuracy optical distance meter with a mode-locked femtosecond laser is proposed for distance measurements in a 310-m-long optical tunnel. We measured the phase shift of the optical beat component between longitudinal modes of a mode-locked laser. A high resolution of 50 microm at 240-m distance was obtained without cyclic error correction. The group refractive index of air is automatically extracted to an accuracy of 6 parts per million (ppm) by two-color measurement with the pulses of fundamental and second-harmonic wavelengths. Finally, an absolute mechanical distance of 240 m was obtained to within 8-ppm accuracy by use of a series of beat frequencies with the advantage of a wide range of intermode frequency, together with the results of the two-color measurement.
446 citations
TL;DR: In this article, the Sagnac effect was applied to the SAGA-effect interferometer gyroscope with a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s integration.
Abstract: We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.
409 citations
TL;DR: A new method of measurement that essentially combines Fourier-domain optical coherence tomography with spectroscopy is introduced by use of a windowed Fourier transform to obtain spectroscopic information such as the absorption properties of materials.
Abstract: A new method of measurement that essentially combines Fourier-domain optical coherence tomography with spectroscopy is introduced. By use of a windowed Fourier transform it is possible to obtain, in addition to the object structure, spectroscopic information such as the absorption properties of materials. The feasibility of this new method for performing depth-resolved spectroscopy is demonstrated with a glass filter plate. The results are compared with theoretically calculated spectra by use of the well-known spectral characteristics of the light source and the filter plate.
386 citations
TL;DR: A method for optical encryption of three-dimensional (3D) information by use of digital holography using a phase-shifting interferometer and an intensity-recording device.
Abstract: A method for optical encryption of three-dimensional (3D) information by use of digital holography is presented. A phase-shifting interferometer records the phase and amplitude information generated by a 3D object at a plane located in the Fresnel diffraction region with an intensity-recording device. Encryption is performed optically by use of the Fresnel diffraction pattern of a random phase code. Images of the 3D object with different perspectives and focused at different planes can be generated digital or optically after decryption with the proper key. Experimental results are presented.
375 citations
TL;DR: A method that combines phase-shifting and coherence-peak-sensing techniques to permit measurements with the height resolution ofphase-sh shifting interferometry without the interval-slope limitation of lambda/4 per data sample of phase- Shifting Interferometry is described.
Abstract: We describe a method that combines phase-shifting and coherence-peak-sensing techniques to permit measurements with the height resolution of phase-shifting interferometry without the interval-slope limitation of lambda/4 per data sample of phase-shifting interferometry. A five-frame algorithm is used to determine both the best-focus frame position and the fractional phase from the best-focus frame of the correlogram acquired through vertical scanning. The two surface profiles retrieved from the phase and the modulation contrast of the correlograms are compared in the phase-unwrapping process to remove fringe-order ambiguity.
289 citations
TL;DR: In this article, the first use of Michelson interferometry on the Keck I telescope for diraction-limited imaging in the near-infrared JHKL bands was reported.
Abstract: We report the —rst use of Michelson interferometry on the Keck I telescope for diUraction- limited imaging in the near-infrared JHKL bands. By using an aperture mask located close to the f/25 secondary, the 10 m Keck primary mirror was transformed into a separate-element, multiple-aperture interferometer. This has allowed diUraction-limited imaging of a large number of bright astrophysical targets, including the geometrically complex dust envelopes around a number of evolved stars. The suc- cessful restoration of these images, with dynamic ranges in excess of 200:1, highlights the signi—cant capabil- ities of sparse aperture imaging as compared with more conventional —lled-pupil speckle imaging for the class of bright targets considered here. In particular, the enhancement of the signal-to-noise ratio of the Fourier data, precipitated by the reduction in atmospheric noise, allows high-—delity imaging of complex sources with small numbers of short-exposure images relative to speckle. Multiepoch measurements con—rm the reliability of this imaging technique, and our whole data set provides a powerful demonstration of the capabilities of aperture-masking methods when utilized with the current generation of large-aperture tele- scopes. The relationship between these new results and recent advances in interferometry and adaptive optics is brie—y discussed.
TL;DR: The main theme of this review is a discussion of the mechanical and optical principles used in the various long baseline systems in operation around the world — LIGO, Virgo, TAMA300 and LCGT, and GEO600 — and in LISA, a proposed space-borne interferometer.
Abstract: Significant progress has been made in recent years on the development of gravitational wave detectors. Sources such as coalescing compact binary systems, low-mass X-ray binaries, stellar collapses and pulsars are all possible candidates for detection. The most promising design of gravitational wave detector uses test masses a long distance apart and freely suspended as pendulums on Earth or in drag-free craft in space. The main theme of this review is a discussion of the mechanical and optical principles used in the various long baseline systems being built around the world — LIGO (USA), VIRGO (Italy/France), TAMA 300 (Japan) and GEO 600 (Germany/UK) — and in LISA, a proposed space-borne interferometer.
TL;DR: A technique that combines the high speed and the high security of optical encryption with the advantages of electronic transmission, storage, and decryption is introduced and can be adapted to encrypt either the Fraunhofer or the Fresnel diffraction pattern of the input.
Abstract: A technique that combines the high speed and the high security of optical encryption with the advantages of electronic transmission, storage, and decryption is introduced. Digital phase-shifting interferometry is used for efficient recording of phase and amplitude information with an intensity recording device. The encryption is performed by use of two random phase codes, one in the object plane and another in the Fresnel domain, providing high security in the encrypted image and a key with many degrees of freedom. We describe how our technique can be adapted to encrypt either the Fraunhofer or the Fresnel diffraction pattern of the input. Electronic decryption can be performed with a one-step fast Fourier transform reconstruction procedure. Experimental results for both systems including a lensless setup are shown.
TL;DR: This work derives the optimal N-photon two-mode input state for obtaining an estimate straight phi of the phase difference between two arms of an interferometer and introduces an adaptive measurement scheme that can be thus realized, and shows that it yields a variance instraight phi very close to that from an optimal measurement.
Abstract: We derive the optimal N-photon two-mode input state for obtaining an estimate straight phi of the phase difference between two arms of an interferometer. For an optimal measurement [B. C. Sanders and G. J. Milburn, Phys. Rev. Lett. 75, 2944 (1995)], it yields a variance (Deltastraight phi)(2) approximately pi(2)/N2, compared to O(N-1) or O(N-1/2) for states considered by previous authors. Such a measurement cannot be realized by counting photons in the interferometer outputs. However, we introduce an adaptive measurement scheme that can be thus realized, and show that it yields a variance in straight phi very close to that from an optimal measurement.
TL;DR: In this paper, a new technique for optical coherence tomography imaging with spatially low-coherent light sources is presented, in which the low coherence interferometry (LCI) depth-scan is performed by the image of the light source, and therefore, simultaneously by a multitude of mutually incoherent LCI channels, to increase the probe beam power.
TL;DR: In this paper, the authors demonstrate a new heterodyne Michelson interferometer design for displacement measurements capable of fringe interpolation accuracy of one part in 36'000 using two acousto-optic modulators.
Abstract: We demonstrate a new heterodyne Michelson interferometer design for displacement measurements capable of fringe interpolation accuracy of one part in 36 000. Key to this level of accuracy are the use of two acousto-optic modulators for heterodyne frequency generation and digital signal processing demodulation electronics. We make a direct comparison of our interferometer to a commercial interferometer based on a Zeeman-stabilized laser, and show that the residual periodic errors in ours are two orders of magnitude lower than those in the commercial unit. We discuss electronically induced optical cross talk and optical feedback as sources of periodic error. Our new interferometer is simple, robust, and readily implemented.
TL;DR: In this article, the authors present a method for computing the sensitivity curve of a laser interferometer to a specific source of gravity using a set of specifications for a space-borne laser-interferometer.
Abstract: To determine whether particular sources of gravitational radiation will be detectable by a specific gravitational wave detector, it is necessary to know the sensitivity limits of the instrument. These instrumental sensitivities are often depicted ~after averaging over source position and polarization! by graphing the minimal values of the gravitational wave amplitude detectable by the instrument versus the frequency of the gravitational wave. This paper describes in detail how to compute such a sensitivity curve given a set of specifications for a spaceborne laser interferometer gravitational wave observatory. Minor errors in the prior literature are corrected, and the first ~mostly! analytic calculation of the gravitational wave transfer function is presented. Example sensitivity curve calculations are presented for the proposed LISA interferometer. PACS number~s!: 04.80.Nn, 95.55.Ym Advances in modern technology have ushered in an era of large laser interferometers designed to be used in the detection of gravitational radiation, both on the ground and in space. Such projects include the Laser Interferometric Gravitational Wave Observatory ~LIGO! and VIRGO @1,2# ground-based interferometers, and the proposed Laser Interferometer Space Antenna ~LISA! and OMEGA @3,4# spacebased interferometers. As these detectors come on-line, a new branch of astronomy will be created and a radically new view of the Universe is expected to be revealed. With the era of gravitational wave astronomy on the horizon, much effort has been devoted to the problem of categorizing sources of gravitational radiation, and extensive studies are underway to determine what sources will be visible to the various detectors. Typically, the sensitivity of detectors to sources of gravitational radiation has been illustrated using graphs which compare source strengths ~dimensionless strain! to instrument noise as functions of the gravitational wave frequency. Many different types of plots have appeared in the literature, ranging from single plots of spectral density to separate am
TL;DR: A scanning homodyne Michelson interferometer is constructed for two-dimensional imaging of high-frequency surface acoustic wave fields in SAW devices, providing information on acoustic wave distribution that cannot be obtained by merely electrical measurements.
Abstract: A scanning homodyne Michelson interferometer is constructed for two-dimensional imaging of high-frequency surface acoustic wave (SAW) fields in SAW devices. The interferometer possesses a sensitivity of ∼10-5 nm/Hz, and it is capable of directly measuring SAW’s with frequencies ranging from 0.5 MHz up to 1 GHz. The fast scheme used for locating the optimum operation point of the interferometer facilitates high measuring speeds, up to 50,000 points/h. The measured field image has a lateral resolution of better than 1 µm. The fully optical noninvasive scanning system can be applied to SAW device development and research, providing information on acoustic wave distribution that cannot be obtained by merely electrical measurements.
TL;DR: In this paper, a wavelength-tuned Fizeau interferometer is applied to the problem of flatness testing of transparent plates and the resulting front surface profile exhibits less than 2 nm of residual error attributable to spurious reflections from within the plate.
Abstract: A wavelength-tuned Fizeau interferometer is applied to the problem of flatness testing of transparent plates. When the plate is positioned at a specific distance from the reference surface and an integer-math 13-frame phase-shifting algorithm is applied, the system directly filters out unwanted interference arising from backsurface reflections. The resulting front-surface profile exhibits less than 2 nm of residual error attributable to spurious reflections from within the plate.
TL;DR: An interference fringe modulation skewing effect in white-light vertical scanning interferometry that can produce a batwings artifact in a step height measurement is described.
Abstract: An interference fringe modulation skewing effect in white-light vertical scanning interferometry that can produce a batwings artifact in a step height measurement is described. The skewing occurs at a position on or close to the edge of a step in the sample under measurement when the step height is less than the coherence length of the light source used. A diffraction model is used to explain the effect.
TL;DR: In this paper, a computer-controlled stroboscopic phase-shifting interferometer system for measuring out-of-plane motions and deformations of MEMS structures with nanometer accuracy is described.
Abstract: 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 of time-resolved surface-height maps from the captured data. The system can generate a detailed picture of microstructure dynamics in minutes. A pulsed laser diode serves as the stroboscopic light source permitting measurement of large-amplitude motion (tens of micrometers out-of-plane) at kilohertz frequencies. The high out-of-plane sensitivity of the method makes it particularly suitable for characterizing actuated micro-optical elements for which even nanometer-scale deformations can produce substantial performance degradation. We illustrate the capabilities of the system with a study of the dynamic behavior of a polysilicon surface-micromachined scanning mirror that was fabricated in the MCNC MUMPS foundry process.
TL;DR: The phase evolution of light in an optical waveguide structure has for the first time been visualized with subwavelength resolution using a novel heterodyne interferometric photon scanning tunneling microscope.
Abstract: The phase evolution of light in an optical waveguide structure has for the first time been visualized with subwavelength resolution using a novel heterodyne interferometric photon scanning tunneling microscope. Phase singularities in the optical field of the waveguide have been observed. The phase singularities of charge one appear at locations where the modal field amplitude vanishes, due to the interference of various modes in the waveguide. Excellent agreement of the data with calculations has been obtained.
TL;DR: In this article, an analysis of thermoelastic noise (thermal noise due to thermo-elastic dissipation) in finite sized test masses of laser interferometer gravitational-wave detectors is given.
Abstract: An analysis is given of thermoelastic noise (thermal noise due to thermoelastic dissipation) in finite sized test masses of laser interferometer gravitational-wave detectors. Finite-size effects increase the thermoelastic noise by a modest amount; for example, for the sapphire test masses tentatively planned for LIGO-II and plausible beam-spot radii, the increase is ≲10 percent. As a side issue, errors are pointed out in the currently used formulas for conventional, homogeneous thermal noise (noise associated with dissipation which is homogeneous and described by an imaginary part of the Young’s modulus) in finite sized test masses. Correction of these errors increases the homogeneous thermal noise by ≲5 percent for LIGO-II-type configurations.
TL;DR: The ability to achieve high acoustic sensitivity with small element sizes and to repeatably fabricate rugged sensor downleads using polymer deposition techniques suggests that this type of hydrophone can provide a practical alternative to piezoelectric hydrophone technology.
Abstract: A small aperture wideband ultrasonic optical fiber hydrophone is described. The transduction mechanism is based on the detection of acoustically induced changes in the optical thickness of a 25-/spl mu/m thick parylene polymer film acting as a low finesse Fabry Perot (FP) interferometer that is deposited directly onto the end of a single mode optical fiber. The acoustic performance compares favorably with that of PVDF needle and membrane hydrophones with a peak noise-equivalent-pressure (without signal averaging) of 10 kPa over a 25-MHz measurement bandwidth, a wideband response to 20 MHz, and a near omnidirectional performance at 10 MHz. The dynamic range was 60 dB with an upper limit of linear detection of 11 MPa and a temporal stability of <5% over a period of 20 h. The hydrophone can also measure temperature changes with a resolution of 0.065/spl deg/C, offering the prospect of making simultaneous acoustic pressure and temperature measurements. The transduction parameters of the FP sensing element were measured, yielding an ultrasonic acoustic phase sensitivity of 0.075 rad/MPa and a temperature phase sensitivity of 0.077 rad//spl deg/C. The ability to achieve high acoustic sensitivity with small element sizes and to repeatably fabricate rugged sensor downleads using polymer deposition techniques suggests that this type of hydrophone can provide a practical alternative to piezoelectric hydrophone technology.
Patent•
23 Jun 2000TL;DR: In this article, a probe consisting of an excitation source and a double-core optical fiber was used to detect an interferometer signal from the inner core of the probe.
Abstract: A probe comprises an excitation source and a double-core optical fibre. A pulsed laser signal (20) of the excitation source is supplied to the outer core (42) at one end of the optical fibre. The other end is provided with an interferometer film (18). An excitation signal (22) produced in the sample (10) modulates the thickness of the film (18). This provides an interferometer signal (26, 28) detected from the inner core (40).
TL;DR: In this paper, the phase reveals abrupt jumps in response to a minute increase in the effective thickness of a receptor layer that binds analyte particles on the sensor surface, which forms the basis for biosensing with sensitivity much higher as compared to traditional SPR sensors.
Abstract: Interferometry that detects the phase of a beam reflected under surface plasmon resonance (SPR) has been developed for bio and chemical sensing. The conditions have been found, under which the phase reveals abrupt jumps in response to a minute increase in the effective thickness of a receptor layer that binds analyte particles on the sensor surface. This forms the basis for biosensing with sensitivity much higher as compared to traditional SPR sensors. Besides, SPR interferometry (SPRI) provides spatial resolution at the micron scale. The enhanced sensitivity attributed to the phase jump and interferometric imaging of variations of the phase over the surface are demonstrated, which open up new avenues for micro-array biosensing.
TL;DR: The ALOMAR Rayleigh/Mie/Raman Lidar (RRL) as discussed by the authors is one of the state-of-the-art multiuser LIDAR systems.
Abstract: We report on the development and current capabilities of the ALOMAR Rayleigh/Mie/Raman lidar. This instrument is one of the core instruments of the international ALOMAR facility, located near And- enes in Norway at 69∞N and 16∞E. The major task of the instrument is to perform advanced studies of the Arctic middle atmosphere over altitudes between about 15 to 90 km on a climatological basis. These studies address questions about the thermal structure of the Arctic middle atmosphere, the dynamical processes acting therein, and of aerosols in the form of stratospheric background aerosol, polar stratospheric clouds, nocti- lucent clouds, and injected aerosols of volcanic or anthropogenic origin. Furthermore, the lidar is meant to work together with other remote sensing instruments, both ground- and satellite-based, and with balloon- and rocket-borne instruments performing in situ observa- tions. The instrument is basically a twin lidar, using two independent power lasers and two tiltable receiving telescopes. The power lasers are Nd:YAG lasers emit- ting at wavelengths 1064, 532, and 355 nm and produc- ing 30 pulses per second each. The power lasers are highly stabilized in both their wavelengths and the directions of their laser beams. The laser beams are emitted into the atmosphere fully coaxial with the line- of-sight of the receiving telescopes. The latter use primary mirrors of 1.8 m diameter and are tiltable within 30∞ oA zenith. Their fields-of-view have 180 lrad angular diameter. Spectral separation, filtering, and detection of the received photons are made on an optical bench which carries, among a multitude of other optical components, three double Fabry-Perot interferometers (two for 532 and one for 355 nm) and one single Fabry- Perot interferometer (for 1064 nm). A number of separate detector channels also allow registration of photons which are produced by rotational-vibrational and rotational Raman scatter on N2 and N2+O2 molecules, respectively. Currently, up to 36 detector channels simultaneously record the photons collected by the telescopes. The internal and external instrument operations are automated so that this very complex instrument can be operated by a single engineer. Currently the lidar is heavily used for measurements of temperature profiles, of cloud particle properties such as their altitude, particle densities and size distributions, and of stratospheric winds. Due to its very eAective spectral and spatial filtering, the lidar has unique capabilities to work in full sunlight. Under these conditions it can measure temperatures up to 65 km altitude and determine particle size distributions of overhead noctilucent clouds. Due to its very high mechanical and optical stability, it can also employed eAciently under marginal weather conditions when data on the middle atmosphere can be collected only through small breaks in the tropospheric cloud layers.
TL;DR: A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip that allows parallel heterodyne detection is presented and applications in surface profiling and thickness measurement are demonstrated.
Abstract: A low-coherence reflectometer based on a conventional Michelson interferometer and a novel silicon detector chip that allows parallel heterodyne detection is presented. Cross-sectional images of 64×256 pixels covering an area of 1.92 mm×1.3 mm are acquired at video rate and with a sensitivity close to the shot-noise limit. Applications in surface profiling and thickness measurement are demonstrated.
TL;DR: The experimental demonstration of a large area atom interferometer based on extended sequences of light pulses is reported, characterized through measurement of the acceleration due to gravity and demonstrated threefold enhancement in intrinsic acceleration sensitivity.
Abstract: We report the experimental demonstration of a large area atom interferometer based on extended sequences of light pulses. We characterize the interferometer through measurement of the acceleration due to gravity and demonstrate a threefold enhancement in intrinsic acceleration sensitivity. The technique is applicable to many atom interferometer configurations, including those used for measurement of rotations, gravity gradients, and $\ensuremath{\Elzxh}/m$.
TL;DR: A low-loss, long-range, single-ended distributed optical fiber sensor to measure both temperature and strain simultaneously and unambiguously and both strain and temperature measurements can be independently resolved is demonstrated.
Abstract: We demonstrate a low-loss, long-range, single-ended distributed optical fiber sensor to measure both temperature and strain simultaneously and unambiguously By using the Landau-Placzek ratio and cascaded Mach-Zehnder interferometric filters, we measure both the intensity and the frequency changes in the Brillouin backscattered signal Strain and temperature measurements can then be independently resolved A temperature resolution of 4°C, a strain resolution of 290 µepsilon, and a spatial resolution of 10m have been achieved for a sensing length of 15 km