Showing papers on "Interferometry published in 2002"
TL;DR: In this paper, an x-ray interferometer was developed that uses two transmission phase gratings to analyze wave front distortions in the hard X-ray range, which was used for differential phase contrast imaging of low absorbingbing test objects.
Abstract: An x-ray interferometer has been developed that uses two transmission phase gratings to analyze wave front distortions in the hard x-ray range. The interferometer is insensitive to mechanical drift and vibrations, and it is tunable over a wide range of photon energies. This setup was used for differential phase contrast imaging of low-absorbing test objects. We obtained micrographs with moire fringes of good visibility, which revealed the local phase shift gradient caused by the objects. A comparison with numerically simulated images indicates that quantitative analysis of unknown phase objects is possible.
620 citations
TL;DR: In this article, the laser diode self-mixing (or feedback) interferometric technique is reviewed as a general tool for remote sensing applications and the operating principle is outlined, and the attainable performance is compared to conventional coherent detection.
Abstract: The laser diode self-mixing (or feedback) interferometric technique is reviewed as a general tool for remote sensing applications. The operating principle is outlined, and the attainable performance is compared to conventional coherent detection. Applications to metrology and to new sensing schemes are described, experimental results are reported and the overall performance of the sensors are assessed.
554 citations
TL;DR: Two image-to-image patch offset techniques for estimating feature motion between satellite synthetic aperture radar (SAR) images are discussed and their accuracy and application range are examined in the case of the surge of Monacobreen in Northern Svalbard.
Abstract: Two image-to-image patch offset techniques for estimating feature motion between satellite synthetic aperture radar (SAR) images are discussed. Intensity tracking, based on patch intensity cross-correlation optimization, and coherence tracking, based on patch coherence optimization, are used to estimate the movement of glacier surfaces between two SAR images in both slant-range and azimuth direction. The accuracy and application range of the two methods are examined in the case of the surge of Monacobreen in Northern Svalbard between 1992 and 1996. Offset-tracking procedures of SAR images are an alternative to differential SAR interferometry for the estimation of glacier motion when differential SAR interferometry is limited by loss of coherence, i.e. in the case of rapid and incoherent flow and of large acquisition time intervals between the two SAR images. In addition, an offset-tracking procedure in the azimuth direction may be combined with differential SAR interferometry in the slant-range direction in order to retrieve a two-dimensional displacement map when SAR data of only one orbit configuration are available.
525 citations
TL;DR: The nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions is determined using coda wave interferometry.
Abstract: In coda wave interferometry, one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time. With this technique, we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions. This technique can be used in warning mode, to detect the presence of temporal changes in the medium, or in diagnostic mode, where the temporal change in the medium is quantified.
517 citations
TL;DR: A frequency‐space equation of diffraction tomography for the electric field vector is obtained within the first‐order Born approximation, using a simplified formalism resulting from using three‐dimensional spatial frequencies and replacing outgoing waves by linear combinations of homogeneous plane waves.
Abstract: We first obtain a frequency-space equation of diffraction tomography for the electric field vector, within the first-order Born approximation, using a simplified formalism resulting from using three-dimensional spatial frequencies and replacing outgoing waves by linear combinations of homogeneous plane waves. A coherent optical diffraction tomographic microscope is then described, in which a sample is successively illuminated by a series of plane waves having different directions, each scattered wave is recorded by phase-shifting interferometry, and the object is then reconstructed from these recorded waves. The measurement process in this device is analysed taking into account the illuminating wave, the wave scattered by the sample, the reference wave, and the phase relations between these waves. This analysis yields appropriate equations that take into account the characteristics of the reference wave and compensate random phase shifts. It makes it possible to obtain a high-resolution three-dimensional frequency representation in full conformity with theory. The experimentally obtained representations show index and absorptivity with a resolution limit of about a quarter of a wavelength, and have a depth of field of about 40 microm.
499 citations
07 Nov 2002
TL;DR: Optical coherence tomography (OCT) is an emerging biomedical imaging modality which can generate high-resolution, cross-sectional images of microstructure in biological systems as mentioned in this paper.
Abstract: Optical coherence tomography (OCT) is an emerging biomedical imaging modality which can generate high resolution, cross-sectional images of microstructure in biological systems. OCT is analogous to ultrasound B mode imaging, except that it uses light instead of sound. Because the velocity of light is extremely high, direct electronic detection is not possible and imaging is performed using low coherence interferometry. Echoes of light from the specimen or tissue are correlated or interfered with light that travels a known reference path length. OCT images are generated by measuring the echo time delay of optical backscattering in the tissue as a function of transverse position and the data can be displayed as a false color or grey scale image. The axial resolution is determined by the coherence length of the light source. Imaging resolutions of 1 to 15 /spl mu/m can be achieved.
417 citations
TL;DR: In this paper, a projective-measurement scheme for generating the desired correlations between the interferometric input states in order to achieve Heisenberg-limited sensitivity is described.
Abstract: Heisenberg-limited measurement protocols can be used to gain an increase in measurement precision over classical protocols. Such measurements can be implemented using, for example, optical Mach—Zehnder interferometers and Ramsey spectroscopes. We address the formal equivalence between the Mach—Zehnder interferometer, the Ramsey spectroscope and a generic quantum logic circuit. Based on this equivalence we introduce the 'quantum Rosetta stone', and we describe a projective-measurement scheme for generating the desired correlations between the interferometric input states in order to achieve Heisenberg-limited sensitivity. The Rosetta stone then tells us that the same method should work in atom spectroscopy.
417 citations
TL;DR: This work reports on the incorporation of an axicon lens into the sample arm of an interferometer to overcome the trade-off between lateral resolution and focusing depth when conventional optical elements are used.
Abstract: In optical coherence tomography, axial and lateral resolutions are determined by the source coherence length and the numerical aperture of the sampling lens, respectively. Whereas axial resolution can be improved by use of a broadband light source, there is a trade-off between lateral resolution and focusing depth when conventional optical elements are used. We report on the incorporation of an axicon lens into the sample arm of an interferometer to overcome this limitation. Using an axicon lens with a top angle of 160 degrees , we maintained 10-microm or better lateral resolution over a focusing depth of at least 6 mm. In addition to having high lateral resolution, the focusing spot has an intensity that is approximately constant over a greater depth range than when a conventional lens is used.
406 citations
TL;DR: The OCT system successfully reveals the birefringent nature of human skin tissue through the measurement of the distribution of each element of the Müller matrix of a measured object from 16 OCT images.
Abstract: We have developed a spectral interferometric optical coherence tomography (OCT) system with polarization sensitivity that is able to measure a two-dimensional tomographic image by means of one-dimensional mechanical scanning. Our system, which has an axial resolution of 32 mum , calculates the distribution of each element of the Muller matrix of a measured object from 16 OCT images. The OCT system successfully reveals the birefringent nature of human skin tissue.
289 citations
TL;DR: In this article, the authors proposed a quantum-optical coherence tomography (QOCT) for carrying out tomographic measurements with dispersion-cancelled resolution, which can also be used to extract the frequency-dependent refractive index of the medium.
Abstract: We propose a technique, called quantum-optical coherence tomography (QOCT), for carrying out tomographic measurements with dispersion-cancelled resolution. The technique can also be used to extract the frequency-dependent refractive index of the medium. QOCT makes use of a two-photon interferometer in which a swept delay permits a coincidence interferogram to be traced. The technique bears a resemblance to classical optical coherence tomography (OCT). However, it makes use of a nonclassical entangled twin-photon light source that permits measurements to be made at depths greater than those accessible via OCT, which suffers from the deleterious effects of sample dispersion. Aside from the dispersion cancellation, QOCT offers higher sensitivity than OCT as well as an enhancement of resolution by a factor of two for the same source bandwidth. QOCT and OCT are compared using an idealized sample.
237 citations
09 Jul 2002
TL;DR: In this paper, the advantages and disadvantages of white light interferometry compared to laser light interFERometry are discussed, including diffraction gratin interferometers, vertical scanning or coherence probe interferers, and white light scatterplate interferometer.
Abstract: White light interferometry is an extremely powerful tool for optical measurements. This paper discusses the advantages and disadvantages of white light interferometry compared to laser light interferometry. Three different white light interferometers are discussed: 1) diffraction gratin interferometers; 2) vertical scanning or coherence probe interferometers, and 3) white light scatterplate interferometers.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Patent•
05 Aug 2002TL;DR: In this article, an optical coherence tomography (OCT) system including an interferometer provides illuminating light along a first optical path to a sample and an optical delay line and collects light from the sample along a second optical path remitted at several scattering angles to a detector.
Abstract: An optical coherence tomography (OCT) system including an interferometer provides illuminating light along a first optical path to a sample and an optical delay line and collects light from the sample along a second optical path remitted at several scattering angles to a detector. In one embodiment, illuminating light is directed along a number of incident light paths through a focusing lens to a sample. The light paths and focusing lens are related to the sample and to both the incident light source and the detector. In another embodiment, a focusing system directs light to a location in the sample. A transmission grating or acousto-optic modulator directs light from the sample at an angle representative of the wavelength of the incident light on the transmission grating or acousto-optic modulator.
TL;DR: It is experimentally demonstrate that a power recycled Michelson with squeezed light injected into the dark port can overcome this limit and an improvement in the signal-to-noise ratio is measured and locked stably for long periods of time.
Abstract: Interferometric gravitational wave detectors are expected to be limited by shot noise at some frequencies. We experimentally demonstrate that a power recycled Michelson with squeezed light injected into the dark port can overcome this limit. An improvement in the signal-to-noise ratio of 2.3 dB is measured and locked stably for long periods of time. The configuration, control, and signal readout of our experiment are compatible with current gravitational wave detector designs. We consider the application of our system to long baseline interferometer designs such as LIGO.
TL;DR: A novel real-time phase-resolved functional optical coherence tomography system that uses optical Hilbert transformation that has high sensitivity and a larger dynamic range for measuring the Doppler frequency shift that is due to moving red blood cells.
Abstract: We have developed a novel real-time phase-resolved functional optical coherence tomography system that uses optical Hilbert transformation. When we use a resonant scanner in the reference arm of the interferometer, with an axial scanning speed of 4 kHz, the frame rate of both structural and Doppler blood-flow imaging with a size of 100 by 100 pixels is 10 Hz. The system has high sensitivity and a larger dynamic range for measuring the Doppler frequency shift that is due to moving red blood cells. Real-time images of in vivo blood flow in human skin obtained with this interferometer are presented.
TL;DR: In this paper, a low cost interrogation scheme for a refractometer based on an in-line fiber long period grating (LPG) Mach-Zehnder interferometer is demonstrated.
Abstract: A low cost interrogation scheme is demonstrated for a refractometer based on an in-line fiber long period grating (LPG) Mach–Zehnder interferometer. Using this interrogation scheme the minimum detectable change in refractive index of ?n ~ 1.8×10-6 is obtained, which is the highest resolution achieved using a fiber LPG device, and is comparable to precision techniques used in the industry including high performance liquid chromatography and ultraviolet spectroscopy.
TL;DR: In this paper, a theory is presented together with simulation results that describe three-dimensional position detection of a sphere located in a highly focused beam by back-focal plane interferometry.
Abstract: A theory is presented together with simulation results that describe three-dimensional position detection of a sphere located in a highly focused beam by back-focal plane interferometry. This technique exploits the interference of scattered and unscattered light, which is projected on a quadrant photodiode placed in the back-focal plane of a condenser lens. Due to the Gouy-phase shift inherent in focused beams, it is not only possible to determine the lateral but also the axial position of a spherical particle with nanometer accuracy. In this paper we describe the calculation of arbitrary focused electromagnetic fields, the Gouy phase shift, Mie scattering by focused beams and the resulting position signals using the angular momentum representation. The accuracy and the sensitivity of the detection system are investigated theoretically for various sphere parameters. Both accuracy and sensitivity depend on the incident light distribution as well as on the particle’s properties and position. It is further shown that the maximum capture angle of the detection lens influences the detector’s sensitivity in a nonlinear manner. Additionally, for optical trapping applications the influence of the laser power is taken into account and is considered through a noise analysis. For all investigated trapping conditions the reconstructed position deviates on average <1 nm laterally and <5 nm axially from the actual particle position.
TL;DR: In this article, a real-time phase-resolved optical coherence tomography (OCT) and optical Doppler tomography system using optical Hilbert transformation (ODT) was developed.
Abstract: We have developed a novel real-time phase-resolved optical coherence tomography (OCT) and optical Doppler tomography (ODT) system using optical Hilbert transformation. By combining circularly polarized reference and linearly polarized sample signals, in-phase and quadrature interference components are produced in separate channels and treated as the real and imaginary parts of a complex signal to obtain the phase information directly. Using a resonant scanner at an axial scanning speed of 4 kHz in the reference arm of the interferometer, both structure and blood flow velocity images with 200 axial scans can be acquired at 20 frames per second with high sensitivity and large dynamic range. Real-time videos of in vivo blood flow in the chick chorioallantoic membrane using this interferometer are presented.
TL;DR: In this article, the authors introduce the concept of spin superposition in the context of Neutron interferometers and discuss the properties of spin-symmetric and spin-superposition.
Abstract: 1. Introduction 2. Neutron interferometers and apparatus 3. Neutron interactions and the coherent scattering length 4. Coherence properties 5. Spinor symmetry and spin superposition 6. Topological and geometric phases 7. Gravitational, non-inertial, and motional effects 8. Search for speculative effects 9. Solid State physics applications 10. Perfect crystal neutron optics 11. Interpretational questions 12. References
TL;DR: In this paper, the authors used the force-susceptibility formalism of linear quantum measurements to study the dynamics of signal recycled interferometers, such as LIGO-II, and showed that, although the antisymmetric mode of motion of the four arm-cavity mirrors is originally described by a free mass, when the signal-recycling mirror is added to the interferometer, the radiation-pressure force not only disturbs the motion of that free mass randomly due to quantum fluctuations, but also makes it respond to forces as though it
Abstract: Using the force-susceptibility formalism of linear quantum measurements, we study the dynamics of signal recycled interferometers, such as LIGO-II. We show that, although the antisymmetric mode of motion of the four arm-cavity mirrors is originally described by a free mass, when the signal-recycling mirror is added to the interferometer, the radiation-pressure force not only disturbs the motion of that “free mass” randomly due to quantum fluctuations, but also, and more fundamentally, makes it respond to forces as though it were connected to a spring with a specific optical-mechanical rigidity. This oscillatory response gives rise to a much richer dynamics than previously known for SR interferometers, which enhances the possibilities for reshaping the noise curves and, if thermal noise can be pushed low enough, enables the standard quantum limit to be beaten. We also show the possibility of using servo systems to suppress the instability associated with the optical-mechanical interaction without compromising the sensitivity of the interferometer.
Patent•
21 Aug 2002TL;DR: In this paper, a method and system for de-embedding optical component characteristics from optical device measurements is described, which uses frequency domain averaging of the RBS on both sides of an optical component to determine one or more of its optical characteristics.
Abstract: Method and system are disclosed for de-embedding optical component characteristics from optical device measurements. In particular, the invention uses frequency domain averaging of the RBS on both sides of an optical component to determine one or more of its optical characteristics. Where the RBS has a slope (e.g., as in the case of a lossy fiber), a frequency domain least square fit can be used to determine the optical component characteristics. In addition, the invention uses a reference DUT to correct for variations in the frequency response of the photoreceiver. A reference interferometer is used in the invention to correct for sweep non-linearity of the TLS. The optical component characteristics are then de-embedded from optical device measurements to provide a more precise analysis of the optical device.
TL;DR: In this article, a unified theoretical framework for microwave and optical atomic clocks as well as for gravito-inertial sensors is presented, which includes a fully quantum mechanical treatment of the atomic motion in free space and in the presence of a gravitational field, and a covariant treatment including spin to evaluate general relativistic effects.
Abstract: We show that the language of atom interferometry provides a unified picture for microwave and optical atomic clocks as well as for gravito-inertial sensors. The sensitivity and accuracy of these devices is now such that a new theoretical framework common to all these interferometers is required that includes: (a) a fully quantum mechanical treatment of the atomic motion in free space and in the presence of a gravitational field (most cold-atom interferometric devices use atoms in ``free fall'' in a fountain geometry); (b) an account of simultaneous actions of gravitational and electromagnetic fields in the interaction zones; (c) a second quantization of the matter fields to take into account their fermionic or bosonic character in order to discuss the role of coherent sources and their noise properties; (d) a covariant treatment including spin to evaluate general relativistic effects. A theoretical description of atomic clocks revisited along these lines is presented, using both an exact propagator of atom waves in gravito-inertial fields and a covariant Dirac equation in the presence of weak gravitational fields. Using this framework, recoil effects, spin-related effects, beam curvature effects, the sensitivity to gravito-inertial fields and the influence of the coherence of the atom source are discussed in the context of present and future atomic clocks and gravito-inertial sensors.
TL;DR: In this paper, a new numerical a posteriori dispersion compensation technique for partial coherence interferometry and optical coherence tomography depth-scan signals is presented, based on numerical correlation of the depth scan interferometer signal with a depth-variant kernel.
TL;DR: A new phase noise model in the complex domain is introduced and validated by using both simulated and real interferograms, where a novel noise reduction algorithm, which is not based on a windowing process and without the necessity of phase unwrapping, is addressed.
Abstract: This paper addresses the problem of interferometric phase noise reduction in synthetic aperture radar interferometry. A new phase noise model in the complex domain is introduced and validated by using both simulated and real interferograms. This noise model is also derived in the complex wavelet domain, where a novel noise reduction algorithm, which is not based on a windowing process and without the necessity of phase unwrapping, is addressed. The use of the wavelet transform allows to maintain the spatial resolution in the filtered phase image and prevents to filter low coherence areas. By using both, simulated as well as real interferometric phase images, the performance of this algorithm, in terms of noise reduction, spatial resolution maintenance, and computational efficiency, is reported and compared with other conventional filtering approaches.
TL;DR: The current technology of optical coherence tomography (OCT) is reviewed and an overview of recent OCT studies in gastroenterology and cardiology is provided.
TL;DR: Molten alloys under high pressure were used to obtain fibers with long internal electrodes that are solid at room temperature and good stability and a switching voltage of 1.4kV were measured with a 1-m-long fiber device with a quadratic voltage dependence.
Abstract: Molten alloys under high pressure were used to obtain fibers with long internal electrodes that are solid at room temperature. An integrated Mach-Zehnder interferometer was constructed from a twin- ...
TL;DR: The fundamental features of an interferometer for guided matter waves, built of two combined Y-shaped beam splitters, are described, and it is found that such a device is expected to exhibit high contrast fringes even in a multimode regime, analogous to a white light interferometers.
Abstract: Atoms can be trapped and guided with electromagnetic fields, using nanofabricated structures. We describe the fundamental features of an interferometer for guided matter waves, built of two combined Y-shaped beam splitters. We find that such a device is expected to exhibit high contrast fringes even in a multimode regime, analogous to a white light interferometer.
TL;DR: An experimentally realized set of operations on a single trapped ion is sufficient to simulate a wide class of Hamiltonians of a spin-1/2 particle in an external potential and the use of nonlinear beam splitters enhances this sensitivity compared to the standard quantum limit imposed by a linear beam splitter.
Abstract: We show how an experimentally realized set of operations on a single trapped ion is sufficient to simulate a wide class of Hamiltonians of a spin-$1/2$ particle in an external potential. This system is also able to simulate other physical dynamics. As a demonstration, we simulate the action of two $n\mathrm{t}\mathrm{h}$ order nonlinear optical beam splitters comprising an interferometer sensitive to phase shift in one of the interferometer beam paths. The sensitivity in determining these phase shifts increases linearly with $n$, and the simulation demonstrates that the use of nonlinear beam splitters ($n=2,3$) enhances this sensitivity compared to the standard quantum limit imposed by a linear beam splitter ($n=1$).
01 Oct 2002-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this article, the nonlinearities in a heterodyne laser interferometer system occurring from the phase measurement system of the interferometers and from non-ideal polarization effects of the optics are modeled into one analytical expression which includes the initial polarization state of the laser source, the rotational alignment of the beam splitter along with different transmission coefficients for polarization states and rotational misalignment of the receiving polarizer.
Abstract: The non-linearities in a heterodyne laser interferometer system occurring from the phase measurement system of the interferometer and from non-ideal polarization effects of the optics are modeled into one analytical expression which includes the initial polarization state of the laser source, the rotational alignment of the beam splitter along with different transmission coefficients for polarization states and the rotational misalignment of the receiving polarizer. The model is verified using a Babinet Soleil Compensator allowing a common path for both polarization states and thereby reducing the influence of the refractive index of air. The verification shows an agreement of the model with measurements with a standard deviation of 0.2 nm. With the use of the model it is confirmed that the mean of two polarizer receivers can reduce the effect of non-linearity. However, depending on the accuracy of the polarizer angles, a second-order non-linearity remains. Also the effect of rotational misalignment of the beam splitter can not be reduced in this way.
TL;DR: The TAMA300 interferometer as discussed by the authors was developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations, and was operated for over 24 hours stably and continuously.
Abstract: TAMA300, an interferometric gravitational-wave detector with 300 m baseline length, has been developed and operated with sufficient sensitivity to detect gravitational-wave events within our galaxy and sufficient stability for observations. The interferometer was operated for over 24 h stably and continuously. With a strain-equivalent noise level of h ~ 5 × 10−21 Hz−1/2, a signal-to-noise ratio (SNR) of 30 is expected for gravitational waves generated by a coalescence of 1.4 M⊙−1.4 M⊙ binary neutron stars at 10 kpc distance. In the summer of 2000, we carried out a two-week data-taking run, called data taking 4 (DT4), collecting 160 h of data to be analysed in the search for gravitational waves. In this paper, we review the design of the TAMA300 interferometer and the results of DT4. In addition, improvements after DT4 and recent results are also reported.
TL;DR: The kinetic energy of an atom recoiling due to absorption of a photon was measured as a frequency, using an interferometric technique called "contrast interferometry."
Abstract: The kinetic energy of an atom recoiling due to absorption of a photon was measured as a frequency, using an interferometric technique called ``contrast interferometry.'' Optical standing wave pulses were used to create a symmetric three-path interferometer with a Bose-Einstein condensate. Its recoil phase, measurable with a single shot, varies quadratically with additional recoils and is insensitive to errors from vibrations and ac Stark shifts. We have measured the photon recoil frequency of sodium to 7 ppm precision, using a simple realization of this scheme. Plausible extensions should yield sufficient precision to attain a ppb-level determination of $h/m$ and the fine structure constant $\ensuremath{\alpha}$.