The Experts below are selected from a list of 24342 Experts worldwide ranked by ideXlab platform

Daniel A. Shaddock - One of the best experts on this subject based on the ideXlab platform.

  • crosstalk reduction for multi channel optical phase metrology
    Optics Express, 2020
    Co-Authors: Paul G Sibley, Samuel P. Francis, R L Ward, Lyle E Roberts, Daniel A. Shaddock
    Abstract:

    Digitally enhanced heterodyne interferometry (DEHI) combines the sub-wavelength Displacement measurements of conventional laser interferometry with the multiplexing capabilities of spread-spectrum modulation techniques to discriminate between multiple electric fields at a single photodetector. Technologies that benefit from DEHI include optical phased arrays, which require the simultaneous phase measurement of a large number of electric fields. A consequence of measuring the phase of multiple electric fields is the introduction of crosstalk, which can degrade measurement precision. This work analytically and experimentally investigates the crosstalk when using DEHI to measure the phase of an arbitrarily large number of electric fields at a single photodetector. Also considered is the practical limit the dynamic range of the photodetector and shot noise imposes on the number of electric fields that can be discriminated. We describe how to minimize crosstalk by design. Experimental results demonstrate up to 55 dB suppression of crosstalk between two electric fields with a phase measurement bandwidth of 20 kHz and 1-10 pm/Hz Displacement Sensitivity for audio frequencies. Additionally, we demonstrate scaling of crosstalk proportional to the square-root of the number of electric fields when using an M-sequence modulation. Based on this analysis, we estimate that digitally enhanced heterodyne interferometry should be capable of measuring the phase of several hundreds of electric fields at a single photodetector while maintaining the same measurement bandwidth.

  • Multi-link laser interferometry architecture for interspacecraft Displacement metrology
    Journal of Geodesy, 2018
    Co-Authors: Samuel P. Francis, Timothy T.-y. Lam, David E. Mcclelland, Daniel A. Shaddock
    Abstract:

    Targeting a future Gravity Recovery and Climate Experiment (GRACE) mission, we present a new laser interferometry architecture that can be used to recover the Displacement between two spacecraft from multiple interspacecraft measurements. We show it is possible to recover the Displacement between the spacecraft centers of mass in post-processing by forming linear combinations of multiple, spatially offset, interspacecraft measurements. By canceling measurement error due to angular misalignment of the spacecraft, we remove the need for precise placement or alignment of the interferometer, potentially simplifying spacecraft integration. To realize this multi-link architecture, we propose an all-fiber interferometer, removing the need for any ultrastable optical components such as the GRACE Follow-On mission’s triple mirror assembly. Using digitally enhanced heterodyne interferometry, the number of links is readily scalable, adding redundancy to our measurement. We present the concept, an example multi-link implementation and the signal processing required to recover the center of mass Displacement from multiple link measurements. Finally, in a simulation, we analyze the limiting noise sources in a 9 link interferometer and ultimately show we can recover the $$80\;\text {nm}/\sqrt{\text {Hz}}$$ 80 nm / Hz Displacement Sensitivity required by the GRACE Follow-On laser ranging interferometer.

  • subpicometer length measurement using heterodyne laser interferometry and all digital rf phase meters
    Optics Letters, 2010
    Co-Authors: Magnus T L Hsu, Daniel A. Shaddock, Ian C M Littler, Jan Herrmann, R B Warrington, Malcolm B Gray
    Abstract:

    We present an all-digital phase meter for precision length measurements using heterodyne laser interferometry. Our phase meter has a phase Sensitivity of 3μrad/√Hz at signal frequencies of 1Hz and above. We test the performance of our phase meter in an optical heterodyne interferometric configuration, using an active Sagnac interferometer test bed that is flexible and low noise. We demonstrate more than 70dB of laser frequency noise suppression to achieve an optical phase Sensitivity of 5μrad/√Hz and a corresponding Displacement Sensitivity of 0.5pm/√Hz at signal frequencies above 10Hz. In addition, we demonstrate the ability of our phase meter to follow full fringe signals accurately at 100Hz and to track large signal excursions in excess of 105 fringes without cycle slipping. Finally, we demonstrate a cyclic error of ≤1pm/√Hz, above 10Hz.

Olav Solgaard - One of the best experts on this subject based on the ideXlab platform.

  • fabry perot fiber sensors with reproducible Displacement sensitivities
    International Conference on Optical MEMS and Nanophotonics, 2011
    Co-Authors: Onur Can Akkaya, Onur Kilic, Gordon S. Kino, Michael J. F. Digonnet, Olav Solgaard
    Abstract:

    An all-silica design and silicate bonding are used to demonstrate a Fabry-Perot acoustic fiber sensor for large-scale array applications with a high Sensitivity, high thermal stability, and excellent reproducibility in Displacement Sensitivity (±0.6 dB).

  • Displacement sensing using evanescent tunneling between guided resonances in photonic crystal slabs
    Journal of Applied Physics, 2005
    Co-Authors: Olav Solgaard
    Abstract:

    Using both analytic theory and first-principles finite-difference time-domain simulations, we introduce a Displacement sensing mechanism using photonic crystal slabs coupled in the near-field regime. In this regime, the operating characteristics are completely different from conventional resonant optical sensors, and high Sensitivity can be obtained without the use of highly reflecting mirrors. This enables high Displacement Sensitivity combined with low Sensitivity to wavelength and to structural disorders, thereby simplifying operation and fabrication of high-Sensitivity Displacement sensors.

Mansoo Choi - One of the best experts on this subject based on the ideXlab platform.

  • ultrasensitive mechanical crack based sensor inspired by the spider sensory system
    Nature, 2014
    Co-Authors: Daeshik Kang, Linfeng Piao, Byeonghak Park, Sung Soo Shin, Yong Whan Choi, Peter V Pikhitsa, Mansoo Choi
    Abstract:

    A mechanical crack-based sensor inspired by the mechanism spiders use to sense minute variations in stress offers ultrahigh Sensitivity to pressure and vibration and can easily be mounted on human skin for the purposes of speech recognition and the monitoring of physiological signals. Usually when spiders are mentioned in a biomimetic context the remarkable tensile strength of spider silk is discussed. But in this study, Mansoo Choi and colleagues take inspiration from the slit sensory organs that a spider uses to detect vibrations in its web. The authors have developed a nanoscale mechanical crack-based sensor consisting of a thin platinum layer, in which tiny cracks are produced in a controlled way, on a flexible polymer sheet. Vibrations and changes in pressure are measured as changes in conductivity in the platinum sheet as the cracks open and close. The potential of the device is demonstrated with a variety of examples such as with a pixelated sensor that can detect a flapping ladybird and a flexible sensor that can measure and replay music. It can easily be mounted on human skin for purposes such as speech recognition and the monitoring of physiological signals. Recently developed flexible mechanosensors based on inorganic silicon1,2,3, organic semiconductors4,5,6, carbon nanotubes7, graphene platelets8, pressure-sensitive rubber9 and self-powered devices10,11 are highly sensitive and can be applied to human skin. However, the development of a multifunctional sensor satisfying the requirements of ultrahigh mechanoSensitivity, flexibility and durability remains a challenge. In nature, spiders sense extremely small variations in mechanical stress using crack-shaped slit organs near their leg joints12. Here we demonstrate that sensors based on nanoscale crack junctions and inspired by the geometry of a spider’s slit organ can attain ultrahigh Sensitivity and serve multiple purposes. The sensors are sensitive to strain (with a gauge factor of over 2,000 in the 0–2 per cent strain range) and vibration (with the ability to detect amplitudes of approximately 10 nanometres). The device is reversible, reproducible, durable and mechanically flexible, and can thus be easily mounted on human skin as an electronic multipixel array. The ultrahigh mechanoSensitivity is attributed to the disconnection–reconnection process undergone by the zip-like nanoscale crack junctions under strain or vibration. The proposed theoretical model is consistent with experimental data that we report here. We also demonstrate that sensors based on nanoscale crack junctions are applicable to highly selective speech pattern recognition and the detection of physiological signals. The nanoscale crack junction-based sensory system could be useful in diverse applications requiring ultrahigh Displacement Sensitivity.

  • Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system
    Nature, 2014
    Co-Authors: Daeshik Kang, Linfeng Piao, Byeonghak Park, Sung Soo Shin, Kahp Yang Suh, Yong Whan Choi, Chanseok Lee, Peter V Pikhitsa, Tae Il Kim, Mansoo Choi
    Abstract:

    Recently developed flexible mechanosensors based on inorganic silicon, organic semiconductors, carbon nanotubes, graphene platelets, pressure-sensitive rubber and self-powered devices are highly sensitive and can be applied to human skin. However, the development of a multifunctional sensor satisfying the requirements of ultrahigh mechanoSensitivity, flexibility and durability remains a challenge. In nature, spiders sense extremely small variations in mechanical stress using crack-shaped slit organs near their leg joints. Here we demonstrate that sensors based on nanoscale crack junctions and inspired by the geometry of a spider's slit organ can attain ultrahigh Sensitivity and serve multiple purposes. The sensors are sensitive to strain (with a gauge factor of over 2,000 in the 0-2 per cent strain range) and vibration (with the ability to detect amplitudes of approximately 10 nanometres). The device is reversible, reproducible, durable and mechanically flexible, and can thus be easily mounted on human skin as an electronic multipixel array. The ultrahigh mechanoSensitivity is attributed to the disconnection-reconnection process undergone by the zip-like nanoscale crack junctions under strain or vibration. The proposed theoretical model is consistent with experimental data that we report here. We also demonstrate that sensors based on nanoscale crack junctions are applicable to highly selective speech pattern recognition and the detection of physiological signals. The nanoscale crack junction-based sensory system could be useful in diverse applications requiring ultrahigh Displacement Sensitivity.

Audrey K Ellerbee - One of the best experts on this subject based on the ideXlab platform.

Evan D Morris - One of the best experts on this subject based on the ideXlab platform.

  • positron emission tomography Displacement Sensitivity predicting binding potential change for positron emission tomography tracers based on their kinetic characteristics
    Journal of Cerebral Blood Flow and Metabolism, 2007
    Co-Authors: Evan D Morris, Karmen K Yoder
    Abstract:

    There is great interest in positron emission tomography (PET) as a noninvasive assay of fluctuations in synaptic neurotransmitter levels, but questions remain regarding the optimal choice of tracer for such a task. A mathematical method is proposed for predicting the utility of any PET tracer as a detector of changes in the concentration of an endogenous competitor via Displacement of the tracer (a.k.a., its ‘vulnerability’ to competition). The method is based on earlier theoretical work by Endres and Carson and by the authors. A tracer-specific predictor, the PET Displacement Sensitivity (PDS), is calculated from compartmental model simulations of the uptake and retention of dopaminergic radiotracers in the presence of transient elevations of dopamine (DA). The PDS predicts the change in binding potential (DBP) for a given change in receptor occupancy because of binding by the endogenous competitor. Simulations were performed using estimates of tracer kinetic parameters derived from the literature. For D2/D3 tracers, the calculated PDS indices suggest a rank order for Sensitivity to Displacement by DA as follows: raclopride (highest Sensitivity), followed by fallypride, FESP, FLB, NMSP, and epidepride (lowest). Although the PDS takes into account the affinity constant for the tracer at the binding site, its predictive value cannot be matched by either a single equilibrium constant, or by any one rate constant of the model. Values for DBP have been derived from published studies that employed comparable Displacement paradigms with amphetamine and a D2/D3 tracer. The values are in good agreement with the PDS-predicted rank order of Sensitivity to Displacement.