Showing papers on "Interferometry published in 2003"
TL;DR: A signal-to-noise ratio (SNR) analysis is presented for optical coherence tomography (OCT) signals in which time-domain performance is compared with that of the spectral domain.
Abstract: A signal-to-noise ratio (SNR) analysis is presented for optical coherence tomography (OCT) signals in which time-domain performance is compared with that of the spectral domain. A significant SNR gain of several hundredfold is found for acquisition in the spectral domain. The SNR benefit is demonstrated experimentally in a hybrid time-domain-spectral-domain OCT system.
1,505 citations
TL;DR: It is derived and shown experimentally that frequency- domain ranging provides a superior signal-to-noise ratio compared with conventional time-domain ranging as used in optical coherence tomography.
Abstract: We demonstrate high-speed, high-sensitivity, high-resolution optical imaging based on optical frequency-domain interferometry using a rapidly-tuned wavelength-swept laser. We derive and show experimentally that frequency-domain ranging provides a superior signal-to-noise ratio compared with conventional time-domain ranging as used in optical coherence tomography. A high sensitivity of -110 dB was obtained with a 6 mW source at an axial resolution of 13.5 microm and an A-line rate of 15.7 kHz, representing more than an order-of-magnitude improvement compared with previous OCT and interferometric imaging methods.
1,067 citations
TL;DR: In this article, the first X-ray Talbot interferometry was demonstrated using a pair of transmission gratings made by forming gold stripes on glass plates, which were aligned on the optical axis of X-rays with a separation that caused the Talbot effect by the first grating.
Abstract: First Talbot interferometry in the hard X-ray region was demonstrated using a pair of transmission gratings made by forming gold stripes on glass plates. By aligning the gratings on the optical axis of X-rays with a separation that caused the Talbot effect by the first grating, moire fringes were produced inclining one grating slightly against the other around the optical axis. A phase object placed in front of the first grating was detected by moire-fringe bending. Using the technique of phase-shifting interferometry, the differential phase corresponding to the phase object could also be measured. This result suggests that X-ray Talbot interferometry is a novel and simple method for phase-sensitive X-ray radiography.
893 citations
TL;DR: Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned and interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample.
Abstract: Two new soft X-ray scanning transmission microscopes located at the Advanced Light Source (ALS) have been designed, built and commissioned. Interferometer control implemented in both microscopes allows the precise measurement of the transverse position of the zone plate relative to the sample. Long-term positional stability and compensation for transverse displacement during translations of the zone plate have been achieved. The interferometer also provides low-distortion orthogonal x, y imaging. Two different control systems have been developed: a digital control system using standard VXI components at beamline 7.0, and a custom feedback system based on PC AT boards at beamline 5.3.2. Both microscopes are diffraction limited with the resolution set by the quality of the zone plates. Periodic features with 30 nm half period can be resolved with a zone plate that has a 40 nm outermost zone width. One microscope is operating at an undulator beamline (7.0), while the other is operating at a novel dedicated bending-magnet beamline (5.3.2), which is designed specifically to illuminate the microscope. The undulator beamline provides count rates of the order of tens of MHz at high-energy resolution with photon energies of up to about 1000 eV. Although the brightness of a bending-magnet source is about four orders of magnitude smaller than that of an undulator source, photon statistics limited operation with intensities in excess of 3 MHz has been achieved at high energy resolution and high spatial resolution. The design and performance of these microscopes are described.
636 citations
TL;DR: This device is the first electronic analogue of the optical Mach–Zehnder interferometer, and opens the way to measuring interference of quasiparticles with fractional charges, and is highly sensitive and exhibits very high visibility.
Abstract: Double-slit electron interferometers fabricated in high mobility two-dimensional electron gases are powerful tools for studying coherent wave-like phenomena in mesoscopic systems. However, they suffer from low visibility of the interference patterns due to the many channels present in each slit, and from poor sensitivity to small currents due to their open geometry. Moreover, these interferometers do not function in high magnetic fields--such as those required to enter the quantum Hall effect regime--as the field destroys the symmetry between left and right slits. Here we report the fabrication and operation of a single-channel, two-path electron interferometer that functions in a high magnetic field. This device is the first electronic analogue of the optical Mach-Zehnder interferometer, and opens the way to measuring interference of quasiparticles with fractional charges. On the basis of measurements of single edge state and closed geometry transport in the quantum Hall effect regime, we find that the interferometer is highly sensitive and exhibits very high visibility (62%). However, the interference pattern decays precipitously with increasing electron temperature or energy. Although the origin of this dephasing is unclear, we show, via shot-noise measurements, that it is not a decoherence process that results from inelastic scattering events.
601 citations
TL;DR: In this paper, the evolution of the Ancona landslide (central Italy) was analyzed by processing 61 ERS images acquired in the time span between June 1992 and December 2000.
402 citations
TL;DR: The frequency compounding method based on incoherent summation of the magnitudes of two independent interferometric signals, which were recorded at two different center wavelengths simultaneously, results in an increased contrast and improved image quality without loss of resolution.
Abstract: We are investigating the possibility of a frequency compounding method for speckle reduction in optical coherence tomography. The method is based on incoherent summation of the magnitudes of two independent interferometric signals, which were recorded at two different center wavelengths simultaneously. We derive the corresponding statistics and compare the theoretical results with measurements obtained in a uniformly scattering sample. Finally we demonstrate our method by comparing images of human skin recorded in vivo with and without frequency compounding. The compounding method results in an increased contrast and improved image quality without loss of resolution.
349 citations
TL;DR: The Adaptive Optics NIR Instrument NAOS-CONICA has been commissioned at the VLT (UT4) between November 2001 and March 2002 as discussed by the authors, and it has been used for high spatial resolution slit-spectroscopy in the optical and thermal NIR region.
Abstract: The Adaptive Optics NIR Instrument NAOS-CONICA has been commissioned at the VLT (UT4) between November 2001 and March 2002. After summarizing the observational capabilities of this multimode instrument in combination with the powerful AO-system, we will present first on sky results of the instrumental performance for several non-direct imaging modes: High spatial resolution slit-spectroscopy in the optical and thermal NIR region has been tested. For compact sources below 2 arcsec extension, Wollaston prism polarimetry is used. For larger objects the linear polarization pattern can be analyzed by wire grids down to the diffraction limit. Coronographic masks are applied to optimize imaging and polarimetric capabilities. The cryogenic Fabry-Perot Interferometer in combination with an 8m-telescope AO-system is shown to be a powerful tool for imaging spectroscopy (3D-scans).
348 citations
TL;DR: A Michelson-type spectral interferometer that uses a common beam path for the reference and the sample arms is described, which is well suited for frequency-domain optical coherence tomography of biological samples.
Abstract: A Michelson-type spectral interferometer that uses a common beam path for the reference and the sample arms is described. This optical arrangement is more compact and stable than the more commonly used dual-arm interferometer and is well suited for frequency-domain optical coherence tomography of biological samples. With a 16-bit CCD camera, the instrument has sufficient dynamic range and resolution for imaging to depths of 2 mm in scattering biological materials. Images obtained with this spectral interferometer are presented, including cross-sectional images in a Xenopus laevis tadpole.
342 citations
TL;DR: A novel technique is presented that shows all the features of complex FDOCT with only two recorded interferograms, enabling standard phase-retrieval algorithms to double the measurement range.
Abstract: Standard Fourier-domain optical coherence tomography (FDOCT) suffers from the presence of autocorrelation terms that obscure the object information and degrade the sensitivity and signal-to-noise ratio. By exploiting the phase information of the recorded interferograms, it is possible to remove those autocorrelation terms and to double the measurement range. However, standard phase-retrieval algorithms need three to five interferograms. We present a novel technique that shows all the features of complex FDOCT with only two recorded interferograms.
301 citations
TL;DR: The current state of the field of optical stellar interferometry, concentrating on ground-based work although a brief report of space inter-ferometry missions is included as mentioned in this paper, is reviewed.
Abstract: Here I review the current state of the field of optical stellar interferometry, concentrating on ground-based work although a brief report of space interferometry missions is included. We pause both to reflect on decades of immense progress in the field as well as to prepare for a new generation of large interferometers just now being commissioned (most notably, the CHARA, Keck and VLT Interferometers). First, this review summarizes the basic principles behind stellar interferometry needed by the lay-physicist and general astronomer to understand the scientific potential as well as technical challenges of interferometry. Next, the basic design principles of practical interferometers are discussed, using the experience of past and existing facilities to illustrate important points. Here there is significant discussion of current trends in the field, including the new facilities under construction and advanced technologies being debuted. This decade has seen the influence of stellar interferometry extend beyond classical regimes of stellar diameters and binary orbits to new areas such as mapping the accretion discs around young stars, novel calibration of the cepheid period-luminosity relation, and imaging of stellar surfaces. The third section is devoted to the major scientific results from interferometry, grouped into natural categories reflecting these current developments. Lastly, I consider the future of interferometry, highlighting the kinds of new science promised by the interferometers coming on-line in the next few years. I also discuss the longer-term future of optical interferometry, including the prospects for space interferometry and the possibilities of large-scale ground-based projects. Critical technological developments are still needed to make these projects attractive and affordable.
TL;DR: X-ray interferometry for imaging applications is discussed with a review of X-rays interferometric imaging activities reported to date and the advantage ofX- Ray Interferometry in comparison with other phase-sensitive X-ray imaging methods is discussed.
Abstract: X-ray interferometry for imaging applications is discussed with a review of X-ray interferometric imaging activities reported to date. Phase measurement and phase tomography based on X-ray interferometry are also presented. Finally the advantage of X-ray interferometric imaging in comparison with other phase-sensitive X-ray imaging methods is discussed.
TL;DR: The practical limits of matter wave interferometers at finite gas pressures are explored and the required experimental vacuum conditions for interferometry with even larger objects are estimated.
Abstract: We study the loss of spatial coherence in the extended wave function of fullerenes due to collisions with background gases. From the gradual suppression of quantum interference with increasing gas pressure we are able to support quantitatively both the predictions of decoherence theory and our picture of the interaction process. We thus explore the practical limits of matter wave interferometry at finite gas pressures and estimate the required experimental vacuum conditions for interferometry with even larger objects.
15 Nov 2003
TL;DR: An interferometer topology based on 3 x 3 fiber couplers that gives instantaneous access to the magnitude and phase of die interferometric signal is presented and its performance in heterodyne and homodyne detection with a broadband light source is demonstrated.
Abstract: We present an interferometer topology based on 3 x 3 fiber couplers that gives instantaneous access to the magnitude and phase of die interferometric signal. We demonstrate its performance in heterodyne and homodyne detection with a broadband light source.
TL;DR: This technique, which employs a pair of CCD cameras to detect the in-phase and quadrature components of the heterodyne signal simultaneously, offers the advantage of phase-drift suppression in interferometric measurement.
Abstract: A two-dimensional heterodyne detection technique based on the frequency-synchronous detection method [Jpn. J. Appl. Phys. 39, 1194 (2000)] is demonstrated for full-field optical coherence tomography. This technique, which employs a pair of CCD cameras to detect the in-phase and quadrature components of the heterodyne signal simultaneously, offers the advantage of phase-drift suppression in interferometric measurement. Horizontal cross-sectional images are acquired at the rate of 100 frames/s in a single longitudinal scan, with a depth interval of 6 microm, making the rapid reconstruction of three-dimensional images possible.
TL;DR: In this paper, the authors designed and built an imaging spectrograph for the Prime Focus Instrument Package of the Southern African Large Telescope (SALT), which is a versatile instrument specializing in very high throughput, low and medium resolution (R=500-12,500) imaging spectroscopy, using volume phase holographic (VPH) gratings and a double etalon Fabry-Perot interferometer, and spectropolarimetry from 320 to 900 nm.
Abstract: The University of Wisconsin - Madison, together with Rutgers University and the South African Astronomical Observatory, is designing and building an imaging spectrograph for the Prime Focus Instrument Package of the Southern African Large Telescope (SALT). The Prime Focus Imaging Spectrograph (PFIS) will be a versatile instrument specializing in very high throughput, low and medium resolution (R=500-12,500) imaging spectroscopy, using volume phase holographic (VPH) gratings and a double etalon Fabry-Perot interferometer, and spectropolarimetry from 320 to 900 nm. The optical design includes all transmissive optics for high efficiency and compactness. To maintain throughput in the ultraviolet, only fused silica, CaF2 and NaCl are used. As NaCl is very hygroscopic, the design uses NaCl as the inner element in sealed triplets only. For the highest possible first-order spectral resolution, the collimated beam size is 150 mm - the maximum for practical Fabry-Perot etalons. The F/2.2 camera can be articulated to tune the efficiency of the VPH gratings; a complement of six gratings (5 VPH and 1 standard transmission grating) has been designed to fill the resolution-wavelength space available to the instrument. Linear, circular, and all-stokes spectropolarimetry will be performed through the use of Pancharatnam superachromatic waveplates and a Wollaston beamsplitter.
TL;DR: Results show that GB-SAR interferometry is a cost-effective solution for the monitoring of landslides and is shown to be a valid complement to space- and airborne SAR and to the traditional geodetic instruments.
Abstract: A ground-based synthetic aperture radar (GB-SAR) interferometer is used to retrieve the velocity field of a landslide. High-resolution images are obtained by means of a time domain SAR processor. An in-depth analysis of the sequence of SAR interferograms enables the recognition of a slowly deforming upper scarp in the scene, and a debris flow that feeds the accumulation zone of the landslide, where a fast change in terrain morphology is observed. The estimated deformation map is in agreement with the available measurements obtained by means of Global Positioning System receivers. Results show that GB-SAR interferometry is a cost-effective solution for the monitoring of landslides. The proposed method is shown to be a valid complement to space- and airborne SAR and to the traditional geodetic instruments.
TL;DR: The self-healing properties of interfering Bessel beams allow the simultaneous manipulation and rotation of particles in spatially separated sample cells in optical tweezers and rotators.
Abstract: We examine the properties of interfering high-order Bessel beams. We implement an experimental setup that allows us to realize these interferograms, using interfering Laguerre-Gaussian beams and an axicon. We demonstrate the use of such beams for controlled rotation of microscopic particles in optical tweezers and rotators. The self-healing properties of interfering Bessel beams allow the simultaneous manipulation and rotation of particles in spatially separated sample cells.
TL;DR: Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth.
Abstract: A diaphragm-based interferometric fiber optic sensor that uses a low-coherence light source was designed and tested for on-line detection of the acoustic waves generated by partial discharges inside high-voltage power transformers The sensor uses a fused-silica diaphragm and a single-mode optical fiber encapsulated in a fused-silica glass tube to form an extrinsic Fabry-Perot interferometer, which is interrogated by low-coherence light Test results indicate that these fiber optic acoustic sensors are capable of faithfully detecting acoustic signals propagating inside transformer oil with high sensitivity and wide bandwidth
TL;DR: The process for determining the morphology of subsurface epithelial cell nuclei using depth-resolved light scattering measurements using a second generation angle-resolving low coherence interferometry system greatly improves data acquisition and analysis times compared to the initial prototype system.
Abstract: We outline the process for determining the morphology of subsurface epithelial cell nuclei using depth-resolved light scattering measurements. The measurements are accomplished using a second generation angle-resolved low coherence interferometry system. The new system greatly improves data acquisition and analysis times compared to the initial prototype system. The calibration of the new system is demonstrated in scattering studies to determine the size distribution of polystyrene microspheres in a turbid sample. The process for determining the size of cell nuclei is discussed by analyzing measurements of basal cells in a sub-surface layer of intact, unstained epithelial tissue.
TL;DR: In this article, a data processing method for demodulating the information from the interference spectrum of a white light system is presented, and a compact white light interferometric system employing this algorithm has been developed, combined with fiber Fabry-Perot sensors.
Abstract: White light interferometry has been used in the sensing area for many years. A novel data processing method for demodulating the information from the interference spectrum of a white light system is presented. Compared with traditional algorithms, both high-resolution and large dynamic range have been achieved with a relatively low-cost system. Details of this arithmetic are discussed. A compact white light interferometric system employing this algorithm has been developed, combined with fiber Fabry-Perot sensors. A60.5-nm stability over 48 hours with a dynamic range on the order of tens of microns has been achieved with this system. The temperature dependence of this system has been analyzed, and a self-compensating data processing approach is adopted. Experimental results demonstrated a 61.5-nm shift in the temperature range of 10 to 45°C. © 2003 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1613958)
TL;DR: It is shown that SLMs may be used to generate a wide variety of optical potentials that are useful for the guiding and dipole trapping of atoms by the production of a number of different light potentials using a single SLM device.
Abstract: We discuss the application of spatial light modulators (SLMs) to the field of atom optics. We show that SLMs may be used to generate a wide variety of optical potentials that are useful for the guiding and dipole trapping of atoms. This functionality is demonstrated by the production of a number of different light potentials using a single SLM device. These include Mach-Zender interferometer patterns and the generation of a bottle-beam. We also discuss the current limitations in SLM technology with regard to the generation of both static and dynamically deformed potentials and their use in atom optics.
TL;DR: An optimization criterion is introduced that leads to frequency selection formulations that are optimized with respect to the minimum number of frequencies required for achieving the maximum target dynamic range.
Abstract: We describe a novel technique for measurement of absolute order of interference in multifrequency interferometry. An optimization criterion is introduced that leads to frequency selection formulations that are optimized with respect to the minimum number of frequencies required for achieving the maximum target dynamic range. The method is generalized to N frequencies and gives a definition of measurement reliability. We demonstrate the technique by means of coherent fringe projection for nonintrusive, full-field profilometry. Experimental data for three frequencies are presented.
TL;DR: In this article, a 40"Gbit/s all-optical XOR gate with a hybrid-integrated planar silica waveguide structure and semiconductor optical amplifiers is demonstrated.
Abstract: A 40 Gbit/s all-optical XOR gate that uses a novel topology to allow high-speed operation is demonstrated. The gate used is a Mach-Zehnder interferometer comprising a hybrid-integrated planar silica waveguide structure and semiconductor optical amplifiers.
TL;DR: A new approach to reconstructing the object wave front in phase-shifting interferometry with arbitrary unknown phase steps is proposed, capable of retrieving the original object field, including its amplitude and phase distributions simultaneously, with arbitrary and unequal phase steps in a three- or four-frame method.
Abstract: A new approach to reconstructing the object wave front in phase-shifting interferometry with arbitrary unknown phase steps is proposed. With this method the actual phase steps are first determined from measured intensities with an algorithm based on the statistic property of the object phase distribution in the recording plane. Then the original object field is calculated digitally with a derived formula. This method is simple, accurate, and capable of retrieving the original object field, including its amplitude and phase distributions simultaneously, with arbitrary and unequal phase steps in a three- or four-frame method. The effectiveness and correctness of this approach are verified by a series of computer simulations for both smooth and diffusing surfaces.
TL;DR: In this paper, an adaptive empirical model was proposed to determine growing stock volume classes using the ERS tandem coherence and the JERS backscatter data, achieving accuracies of over 80% for over a hundred ERS frames at a spatial resolution of 50 m.
TL;DR: The results show that the imaging process of s‐SNOM is wavelength‐independent, namely, that the resolution is determined by the properties of the tip only, and that the contrast is given by the complex refractive index of the sample, predictable from a simple, analytical model of tip–sample interaction.
Abstract: We describe the principles of two scattering-type near-field optical microscopes (s-SNOMs), one operating at 633 nm wavelength, the other at selectable wavelengths in the range 7.3-11.3 micro m, and compare the measurement experience. Both use interferometric detection of scattered radiation, and are therefore capable of amplitude and phase-contrast imaging. In this study both instruments use the same or even identical commercial probe tips, and measure a single, three-component, test sample. Our results show that the imaging process of s-SNOM is wavelength-independent, namely, that the resolution is determined by the properties of the tip only, and that the contrast is given by the complex refractive index of the sample, predictable from a simple, analytical model of tip-sample interaction. A novel, 'edge-darkening' artefact is described which may appear in s-SNOM and that is wavelength-independent.
TL;DR: In this article, it was shown that the use of parity measurements on just one of the output modes not only is sensitive to the phase difference but that the sensitivity approaches the Heisenberg limit for large photon number.
Abstract: Holland and Burnett [Phys. Rev. Lett. 71, 1355 (1993)] have argued that twin Fock states of equal photon number $N$ injected at both input ports of a Mach-Zehnder interferometer lead to phase measurements with accuracies approaching the Heisenberg limit $\ensuremath{\Delta}{\ensuremath{\varphi}}_{\mathrm{HL}}=1/(2N).$ However, the method of phase detection suggested by those authors, obtaining the difference of the photocurrents at the output ports of the interferometer, is not sensitive to the phase difference between the two interferometer paths; in fact, the photocurrent vanishes. In this paper we show that the use of parity measurements on just one of the output modes not only is sensitive to the phase difference but that the sensitivity approaches the Heisenberg limit for large $N.$
TL;DR: In this paper, the authors propose to measure many subapertures of the surface and stitch the results together to synthesize a full aperture map, in part because of the difficulty of measuring extensive surface areas.
Abstract: The fabrication of large high-quality optics continues to be a challenge, in part because of the difficulty of measuring extensive surface areas. One alternative is to measure many subapertures of the surface and “stitch” the results together to synthesize a full aperture map.