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Sample records for absolute optical frequency

  1. Absolute distance measurement using frequency-sweeping heterodyne interferometer calibrated by an optical frequency comb.

    PubMed

    Wu, Xuejian; Wei, Haoyun; Zhang, Hongyuan; Ren, Libing; Li, Yan; Zhang, Jitao

    2013-04-01

    We present a frequency-sweeping heterodyne interferometer to measure an absolute distance based on a frequency-tunable diode laser calibrated by an optical frequency comb (OFC) and an interferometric phase measurement system. The laser frequency-sweeping process is calibrated by the OFC within a range of 200 GHz and an accuracy of 1.3 kHz, which brings about a precise temporal synthetic wavelength of 1.499 mm. The interferometric phase measurement system consisting of the analog signal processing circuit and the digital phase meter achieves a phase difference resolution better than 0.1 deg. As the laser frequency is sweeping, the absolute distance can be determined by measuring the phase difference variation of the interference signals. In the laboratory condition, our experimental scheme realizes micrometer accuracy over meter distance.

  2. Absolute frequency stabilization of an injection-seeded optical parametric oscillator

    SciTech Connect

    Plusquellic, D.F.; Votava, O.; Nesbitt, D.J.

    1996-03-01

    A method is described that provides absolute frequency stabilization and calibration of the signal and idler waves generated by an injection-seeded optical parametric oscillator (OPO). The method makes use of a He{endash}Ne stabilized transfer cavity (TC) to control the frequencies of the cw sources used to seed both the pump laser and OPO cavity. The TC serves as a stable calibration source for the signal and idler waves by providing marker fringes as the seed laser is scanned. Additionally, an acoustic-optic modulator (AOM) is used to shift the OPO seed laser{close_quote}s frequency before locking it onto the TC. The sidebands of the AOM are tunable over more than one free spectral range of the TC, thereby permitting stabilization of the signal and idler waves at any frequency. A {plus_minus}25-MHz residual error in the absolute frequency stabilities of the pump, signal, and idler waves is experimentally demonstrated, which is roughly 30{percent} of the 160-MHz near-transform-limited linewidths of the signal and idler pulses. {copyright} {ital 1996 Optical Society of America.}

  3. High-accuracy absolute distance measurement with a mode-resolved optical frequency comb

    NASA Astrophysics Data System (ADS)

    Voigt, Dirk; van den Berg, Steven A.; Lešundák, Adam; van Eldik, Sjoerd; Bhattacharya, Nandini

    2016-04-01

    Optical interferometry enables highly accurate non-contact displacement measurement. The optical phase ambiguity needs to be resolved for absolute distance ranging. In controlled laboratory conditions and for short distances it is possible to track a non-interrupted displacement from a reference position to a remote target. With large distances covered in field applications this may not be feasible, e.g. in structure monitoring, large scale industrial manufacturing or aerospace navigation and attitude control. We use an optical frequency comb source to explore absolute distance measurement by means of a combined spectral and multi-wavelength homodyne interferometry. This relaxes the absolute distance ambiguity to a few tens of centimeters, covered by simpler electronic distance meters, while maintaining highly accurate optical phase measuring capability. A virtually imaged phased array spectrometer records a spatially dispersed interferogram in a single exposure and allows for resolving the modes of our near infrared comb source with 1 GHz mode separation. This enables measurements with direct traceability of the atomic clock referenced comb source. We observed agreement within 500 nm in comparison with a commercial displacement interferometer for target distances up to 50 m. Furthermore, we report on current work toward applicability in less controlled conditions. A filter cavity decimates the comb source to an increased mode separation larger than 20 GHz. A simple grating spectrometer then allows to record mode-resolved interferograms.

  4. Measuring absolute frequencies beyond the GPS limit via long-haul optical frequency dissemination.

    PubMed

    Clivati, Cecilia; Cappellini, Giacomo; Livi, Lorenzo F; Poggiali, Francesco; de Cumis, Mario Siciliani; Mancini, Marco; Pagano, Guido; Frittelli, Matteo; Mura, Alberto; Costanzo, Giovanni A; Levi, Filippo; Calonico, Davide; Fallani, Leonardo; Catani, Jacopo; Inguscio, Massimo

    2016-05-30

    Global Positioning System (GPS) dissemination of frequency standards is ubiquitous at present, providing the most widespread time and frequency reference for the majority of industrial and research applications worldwide. On the other hand, the ultimate limits of the GPS presently curb further advances in high-precision, scientific and industrial applications relying on this dissemination scheme. Here, we demonstrate that these limits can be reliably overcome even in laboratories without a local atomic clock by replacing the GPS with a 642-km-long optical fiber link to a remote primary caesium frequency standard. Through this configuration we stably address the 1S0-3P0 clock transition in an ultracold gas of 173Yb, with a precision that exceeds the possibilities of a GPS-based measurement, dismissing the need for a local clock infrastructure to perform beyond-GPS high-precision tasks. We also report an improvement of two orders of magnitude in the accuracy on the transition frequency reported in literature.

  5. Monolithically integrated absolute frequency comb laser system

    SciTech Connect

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  6. High-resolution absolute frequency referenced fiber optic sensor for quasi-static strain sensing

    SciTech Connect

    Lam, Timothy T.-Y.; Chow, Jong H.; Shaddock, Daniel A.; Littler, Ian C. M.; Gagliardi, Gianluca; Gray, Malcolm B.; McClelland, David E.

    2010-07-20

    We present a quasi-static fiber optic strain sensing system capable of resolving signals below nanostrain from 20 mHz. A telecom-grade distributed feedback CW diode laser is locked to a fiber Fabry-Perot sensor, transferring the detected signals onto the laser. An H{sup 13}C{sup 14}N absorption line is then used as a frequency reference to extract accurate low-frequency strain signals from the locked system.

  7. Auto-elimination of fiber optical path-length drift in a frequency scanning interferometer for absolute distance measurements

    NASA Astrophysics Data System (ADS)

    Tao, Long; Liu, Zhigang; Zhang, Weibo

    2015-09-01

    Because of its compact size and portability, optical fiber has been wildly used as optical paths in frequency-scanning interferometers for high-precision absolute distance measurements. However, since the fiber is sensitive to ambient temperature, its length and refractive index change with temperature, resulting in an optical path length drift that influences the repeatability of measurements. To improve the thermal stability of the measurement system, a novel frequency-scanning interferometer composed of two Michelson-type interferometers sharing a common fiber optical path is proposed. One interferometer defined as origin interferometer is used to monitor the drift of the measurement origin due to the optical path length drift of the optical fiber under on-site environment. The other interferometer defined as measurement interferometer is used to measure the distance to the target. Because the optical path length drift of the fiber appears in both interferometers, its influence can be eliminated by subtracting the optical path difference of the origin interferometer from the optical path difference of the measurement interferometer. A prototype interferometer was developed in our research, and experimental results demonstrate its robustness and stability. Under on-site environment, an accuracy about 4 μm was achieved for a distance of about 1 m.

  8. Absolute frequency measurement of the 674-nm {sup 88}Sr{sup +} clock transition using a femtosecond optical frequency comb

    SciTech Connect

    Margolis, H.S.; Huang, G.; Barwood, G.P.; Lea, S.N.; Klein, H.A.; Rowley, W.R.C.; Gill, P.; Windeler, R.S.

    2003-03-01

    The frequency of the 5s {sup 2}S{sub 1/2}-4d {sup 2}D{sub 5/2} electric quadrupole transition at 674 nm in a single, trapped, laser-cooled {sup 88}Sr{sup +} ion has been measured with respect to the Systeme International (SI) second using a femtosecond laser optical frequency comb. The measured frequency of 444 779 044 095.52 kHz, with an estimated standard uncertainty of 0.10 kHz, is more accurate than, and in agreement with, the value previously measured using a conventional frequency chain.

  9. Absolute Frequency Measurements with a Set of Transportable HE-NE/CH4 Optical Frequency Standards and Prospects for Future Design and Applications

    NASA Astrophysics Data System (ADS)

    Gubin, M.; Kovalchuk, E.; Petrukhin, E.; Shelkovnikov, A.; Tyurikov, D.; Gamidov, R.; Erdogan, C.; Sahin, E.; Felder, R.; Gill, P.; Lea, S. N.; Kramer, G.; Lipphardt, B.

    2002-04-01

    The accumulated results of absolute frequency measurements (AFM) carried out in 1997-2000 with transportable double-mode He-Ne/CH4 optical frequency standards (λ = 3 .39μm) in a collaboration of several laboratories are presented. The performance of this secondary optical frequency standard is estimated on the level of 10-13 (in repeatability), and 1 × 10-14/s (in stability). The next steps towards He-Ne/CH4 standards with one order of magnitude better performance, including devices based on monolithic zerodur resonators, are discussed. Important applications of transportable He-Ne/CH4 optical frequency standards have appeared now due to dramatic progress in the field of optical frequency measurements. Used to stabilize the repetition rate of a Ti:Sa fs laser, these compact secondary standards can transfer their performance into the whole optical range covered by a fs comb. Thus they can play the role of a narrow spectrum interrogative oscillator for super-accurate optical or microwave frequency standards substituting in some tasks a H-maser or oscillators based on cryogenic sapphire resonators.

  10. Absolute calibration of optical flats

    DOEpatents

    Sommargren, Gary E.

    2005-04-05

    The invention uses the phase shifting diffraction interferometer (PSDI) to provide a true point-by-point measurement of absolute flatness over the surface of optical flats. Beams exiting the fiber optics in a PSDI have perfect spherical wavefronts. The measurement beam is reflected from the optical flat and passed through an auxiliary optic to then be combined with the reference beam on a CCD. The combined beams include phase errors due to both the optic under test and the auxiliary optic. Standard phase extraction algorithms are used to calculate this combined phase error. The optical flat is then removed from the system and the measurement fiber is moved to recombine the two beams. The newly combined beams include only the phase errors due to the auxiliary optic. When the second phase measurement is subtracted from the first phase measurement, the absolute phase error of the optical flat is obtained.

  11. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N.

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  12. Magnifying absolute instruments for optically homogeneous regions

    SciTech Connect

    Tyc, Tomas

    2011-09-15

    We propose a class of magnifying absolute optical instruments with a positive isotropic refractive index. They create magnified stigmatic images, either virtual or real, of optically homogeneous three-dimensional spatial regions within geometrical optics.

  13. Absolute optical metrology : nanometers to kilometers

    NASA Technical Reports Server (NTRS)

    Dubovitsky, Serge; Lay, O. P.; Peters, R. D.; Liebe, C. C.

    2005-01-01

    We provide and overview of the developments in the field of high-accuracy absolute optical metrology with emphasis on space-based applications. Specific work on the Modulation Sideband Technology for Absolute Ranging (MSTAR) sensor is described along with novel applications of the sensor.

  14. Arbitrary optical frequency synthesis traced to an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun

    2016-11-01

    An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and <3 kHz, respectively. The arbitrary optical frequency synthesizer will be a versatile tool in diverse applications, such as synthetic wavelength based absolute distance measurement and frequency-stabilized Cavity Ring-Down Spectroscopy.

  15. Observation and Absolute Frequency Measurements of the {sup 1}S{sub 0}-{sup 3}P{sub 0} Optical Clock Transition in Neutral Ytterbium

    SciTech Connect

    Hoyt, C.W.; Barber, Z.W.; Oates, C.W.; Fortier, T.M.; Diddams, S.A.; Hollberg, L.

    2005-08-19

    We report the direct excitation of the highly forbidden (6s{sup 2}){sup 1}S{sub 0}{r_reversible}(6s6p){sup 3}P{sub 0} optical transition in two odd isotopes of neutral ytterbium. As the excitation laser frequency is scanned, absorption is detected by monitoring the depletion from an atomic cloud at {approx}70 {mu}K in a magneto-optical trap. The measured frequency in {sup 171}Yb (F=1/2) is 518 295 836 591.6{+-}4.4 kHz. The measured frequency in {sup 173}Yb (F=5/2) is 518 294 576 847.6{+-}4.4 kHz. Measurements are made with a femtosecond-laser frequency comb calibrated by the National Institute of Standards and Technology cesium fountain clock and represent nearly a 10{sup 6}-fold reduction in uncertainty. The natural linewidth of these J=0 to J=0 transitions is calculated to be {approx}10 mHz, making them well suited to support a new generation of optical atomic clocks based on confinement in an optical lattice.

  16. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  17. Absolute frequency measurement of rubidium 5S-7S two-photon transitions.

    PubMed

    Morzyński, Piotr; Wcisło, Piotr; Ablewski, Piotr; Gartman, Rafał; Gawlik, Wojciech; Masłowski, Piotr; Nagórny, Bartłomiej; Ozimek, Filip; Radzewicz, Czesław; Witkowski, Marcin; Ciuryło, Roman; Zawada, Michał

    2013-11-15

    We report the absolute frequency measurements of rubidium 5S-7S two-photon transitions with a cw laser digitally locked to an atomic transition and referenced to an optical frequency comb. The narrow, two-photon transition, 5S-7S (760 nm), insensitive to first-order in a magnetic field, is a promising candidate for frequency reference. The performed tests yielded more accurate transition frequencies than previously reported.

  18. High-precision absolute distance and vibration measurement with frequency scanned interferometry

    SciTech Connect

    Yang, H.-J.; Deibel, Jason; Nyberg, Sven; Riles, Keith

    2005-07-01

    We report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of {approx}50 nm was achieved for absolute distances ranging from 0.1 to 0.7 m by use of the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 to 100 Hz with an amplitude as small as a few nanometers without a priori knowledge.

  19. High-precision absolute distance and vibration measurement with frequency scanned interferometry.

    PubMed

    Yang, Hai-Jun; Deibel, Jason; Nyberg, Sven; Riles, Keith

    2005-07-01

    We report high-precision absolute distance and vibration measurements performed with frequency scanned interferometry using a pair of single-mode optical fibers. Absolute distance was determined by counting the interference fringes produced while scanning the laser frequency. A high-finesse Fabry-Perot interferometer was used to determine frequency changes during scanning. Two multiple-distance-measurement analysis techniques were developed to improve distance precision and to extract the amplitude and frequency of vibrations. Under laboratory conditions, measurement precision of approximately 50 nm was achieved for absolute distances ranging from 0.1 to 0.7 m by use of the first multiple-distance-measurement technique. The second analysis technique has the capability to measure vibration frequencies ranging from 0.1 to 100 Hz with an amplitude as small as a few nanometers without a priori knowledge.

  20. Absolute frequency measurement at 10-16 level based on the international atomic time

    NASA Astrophysics Data System (ADS)

    Hachisu, H.; Fujieda, M.; Kumagai, M.; Ido, T.

    2016-06-01

    Referring to International Atomic Time (TAI), we measured the absolute frequency of the 87Sr lattice clock with its uncertainty of 1.1 x 10-15. Unless an optical clock is continuously operated for the five days of the TAI grid, it is required to evaluate dead time uncertainty in order to use the available five-day average of the local frequency reference. We homogeneously distributed intermittent measurements over the five-day grid of TAI, by which the dead time uncertainty was reduced to low 10-16 level. Three campaigns of the five (or four)-day consecutive measurements have resulted in the absolute frequency of the 87Sr clock transition of 429 228 004 229 872.85 (47) Hz, where the systematic uncertainty of the 87Sr optical frequency standard amounts to 8.6 x 10-17.

  1. Dual frequency optical cavity

    DOEpatents

    George, E.V.; Schipper, J.F.

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a T configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  2. Dual frequency optical cavity

    DOEpatents

    George, E. Victor; Schipper, John F.

    1985-01-01

    Method and apparatus for generating two distinct laser frequencies in an optical cavity, using a "T" configuration laser cavity and means for intermittently increasing or decreasing the index of refraction n of an associated transmission medium in one arm of the optical cavity to enhance laser action in one arm or the second arm of the cavity.

  3. Frequency-scanning interferometry for dynamic absolute distance measurement using Kalman filter.

    PubMed

    Tao, Long; Liu, Zhigang; Zhang, Weibo; Zhou, Yangli

    2014-12-15

    We propose a frequency-scanning interferometry using the Kalman filtering technique for dynamic absolute distance measurement. Frequency-scanning interferometry only uses a single tunable laser driven by a triangle waveform signal for forward and backward optical frequency scanning. The absolute distance and moving speed of a target can be estimated by the present input measurement of frequency-scanning interferometry and the previously calculated state based on the Kalman filter algorithm. This method not only compensates for movement errors in conventional frequency-scanning interferometry, but also achieves high-precision and low-complexity dynamic measurements. Experimental results of dynamic measurements under static state, vibration and one-dimensional movement are presented.

  4. Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor

    SciTech Connect

    Stalnaker, Jason E.; Mbele, Vela; Gerginov, Vladislav; Fortier, Tara M.; Diddams, Scott A.; Hollberg, Leo; Tanner, Carol E.

    2010-04-15

    We report measurements of absolute transition frequencies and hyperfine coupling constants for the 8S{sub 1/2}, 9S{sub 1/2}, 7D{sub 3/2}, and 7D{sub 5/2} states in {sup 133}Cs vapor. The stepwise excitation through either the 6P{sub 1/2} or 6P{sub 3/2} intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the 7P{sub 1/2,3/2{yields}}6S{sub 1/2} branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the 8S state and provide improvement by 2 orders of magnitude over previously published results for the 9S and 7D states.

  5. C2H2 absolutely optical frequency-stabilized and 40 GHz repetition-rate-stabilized, regeneratively mode-locked picosecond erbium fiber laser at 1.53 microm.

    PubMed

    Nakazawa, Masataka; Kasai, Keisuke; Yoshida, Masato

    2008-11-15

    We have succeeded in the simultaneous stabilization of the optical frequency and repetition rate of a regeneratively mode-locked picosecond erbium-doped fiber ring laser. The optical frequency was locked to the molecular absorption of C2H2 in the 1.5 microm band, and the repetition rate was stabilized to a 40 GHz synthesizer by using a microwave phase-locked loop. The optical frequency stability of the pulse train reached 2x10(-11) for tau=10-100 s. The key to success is the independent control of the repetition rate without disturbing the optical cavity condition.

  6. Absolute flux calibration of optical spectrophotometric standard stars

    NASA Technical Reports Server (NTRS)

    Colina, Luis; Bohlin, Ralph C.

    1994-01-01

    A method based on Landolt photometry in B and V is developed to correct for a wavelength independent offset of the absolute flux level of optical spectrophotometric standards. The method is based on synthetic photometry techniques in B and V and is accurate to approximately 1%. The correction method is verified by Hubble Space Telescope Faint Object Spectrograph absolute fluxes for five calibration stars, which agree with Landolt photometry to 0.5% in B and V.

  7. Precision optical reference frequencies

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz; Schnatz, Harald; Zinner, G.; Trebst, Tilmann; Helmcke, Juergen

    1999-05-01

    Optical reference frequencies are provided by lasers of which the frequencies are stabilized to suitable absorption lines. Presently, twelve reference frequencies/wavelengths within the wavelengths range from 243 nm to 10.3 micrometers are recommended by the International Committee of Weights and Measures as references for the realization of the meter and scientific applications. As typical examples, we describe a diode-pumped, frequency doubled YAG-laser stabilized to an absorption line of molecular iodine and a Ca-stabilized laser. The latter one has been developed in two versions, a transportable system utilizing a small beam of thermal Ca atoms and a stationary standard based on laser cooled and trapped Ca atoms. The frequency of the Ca standard based on cold Ca atoms has been measured by a frequency chain allowing a phase-coherent comparison against the primary standard of time and frequency, the caesium clock. Its value is vCa equals 455 986 240 494.13 kHz with a relative standard uncertainty of 2.5 (DOT) 10-13.

  8. Absolute calibration for complex-geometry biomedical diffuse optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Mastanduno, Michael A.; Jiang, Shudong; El-Ghussein, Fadi; diFlorio-Alexander, Roberta; Pogue, Brian W.; Paulsen, Keith D.

    2013-03-01

    We have presented methodology to calibrate data in NIRS/MRI imaging versus an absolute reference phantom and results in both phantoms and healthy volunteers. This method directly calibrates data to a diffusion-based model, takes advantage of patient specific geometry from MRI prior information, and generates an initial guess without the need for a large data set. This method of calibration allows for more accurate quantification of total hemoglobin, oxygen saturation, water content, scattering, and lipid concentration as compared with other, slope-based methods. We found the main source of error in the method to be derived from incorrect assignment of reference phantom optical properties rather than initial guess in reconstruction. We also present examples of phantom and breast images from a combined frequency domain and continuous wave MRI-coupled NIRS system. We were able to recover phantom data within 10% of expected contrast and within 10% of the actual value using this method and compare these results with slope-based calibration methods. Finally, we were able to use this technique to calibrate and reconstruct images from healthy volunteers. Representative images are shown and discussion is provided for comparison with existing literature. These methods work towards fully combining the synergistic attributes of MRI and NIRS for in-vivo imaging of breast cancer. Complete software and hardware integration in dual modality instruments is especially important due to the complexity of the technology and success will contribute to complex anatomical and molecular prognostic information that can be readily obtained in clinical use.

  9. The assessment of protective behavioral strategies: comparing the absolute frequency and contingent frequency response scales.

    PubMed

    Kite, Benjamin A; Pearson, Matthew R; Henson, James M

    2013-12-01

    The purpose of the present studies was to examine the effects of response scale on the observed relationships between protective behavioral strategies (PBS) measures and alcohol-related outcomes. We reasoned that an "absolute frequency" scale (stem: "how many times …"; response scale: 0 times to 11+ times) conflates the frequency of using PBS with the frequency of consuming alcohol; thus, we hypothesized that the use of an absolute frequency response scale would result in positive relationships between types of PBS and alcohol-related outcomes. Alternatively, a "contingent frequency" scale (stem: "When drinking … how often …"; response scale: never to always) does not conflate frequency of alcohol use with use of PBS; therefore, we hypothesized that use of a contingent frequency scale would result in negative relationships between use of PBS and alcohol-related outcomes. Two published measures of PBS were used across studies: the Protective Behavioral Strategies Survey (PBSS) and the Strategy Questionnaire (SQ). Across three studies, we demonstrate that when measured using a contingent frequency response scale, PBS measures relate negatively to alcohol-related outcomes in a theoretically consistent manner; however, when PBS measures were measured on an absolute frequency response scale, they were nonsignificantly or positively related to alcohol-related outcomes. We discuss the implications of these findings for the assessment of PBS.

  10. Subnanometer absolute displacement measurement using a frequency comb referenced dual resonance tracking Fabry-Perot interferometer.

    PubMed

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

    2015-05-10

    Fabry-Perot (F-P) interferometry is a traceable high-resolution method for displacement metrology that has no nonlinearity. Compared with the single resonance tracking F-P interferometry, the dual resonance tracking (DRT) F-P interferometer system is able to realize tens of millimeters measurement range while maintaining the intrinsic high resolution. A DRT F-P system is thus developed for absolute displacement measurement in metrology applications. Two external cavity diode lasers (ECDLs) are simultaneously locked to two resonances of a high-finesse F-P cavity using the Pound-Drever-Hall locking scheme. The absolute optical frequencies of the locked ECDLs are measured using a reference diode laser, with the frequency stabilized and controlled by an optical frequency comb. The absolute cavity resonance order numbers are investigated. The measurement range is experimentally tested to achieve 20 mm, while the resolution reaches ~10 pm level, mainly limited by the mechanical stability of the F-P cavity. Compared with the measurement results from a self-developed displacement-angle heterodyne interferometer, the displacement residuals are within 10 nm in the range of 20 mm. This high-resolution interferometer may become a candidate for length metrology such as in Watt balance or Joule balance projects.

  11. Frequency domain nonlinear optics

    NASA Astrophysics Data System (ADS)

    Legare, Francois

    2016-05-01

    The universal dilemma of gain narrowing occurring in fs amplifiers prevents ultra-high power lasers from delivering few-cycle pulses. This problem is overcome by a new amplification concept: Frequency domain Optical Parametric Amplification - FOPA. It enables simultaneous up-scaling of peak power and amplified spectral bandwidth and can be performed at any wavelength range of conventional amplification schemes, however, with the capability to amplify single cycles of light. The key idea for amplification of octave-spanning spectra without loss of spectral bandwidth is to amplify the broad spectrum ``slice by slice'' in the frequency domain, i.e. in the Fourier plane of a 4f-setup. The striking advantages of this scheme, are its capability to amplify (more than) one octave of bandwidth without shorting the corresponding pulse duration. This is because ultrabroadband phase matching is not defined by the properties of the nonlinear crystal employed but the number of crystals employed. In the same manner, to increase the output energy one simply has to increase the spectral extension in the Fourier plane and to add one more crystal. Thus, increasing pulse energy and shortening its duration accompany each other. A proof of principle experiment was carried out at ALLS on the sub-two cycle IR beam line and yielded record breaking performance in the field of few-cycle IR lasers. 100 μJ two-cycle pulses from a hollow core fibre compression setup were amplified to 1.43mJ without distorting spatial or temporal properties. Pulse duration at the input of FOPA and after FOPA remains the same. Recently, we have started upgrading this system to be pumped by 250 mJ to reach 40 mJ two-cycle IR few-cycle pulses and latest results will be presented at the conference. Furthermore, the extension of the concept of FOPA to other nonlinear optical processes will be discussed. Frequency domain nonlinear optics.

  12. Noninvasive absolute cerebral oximetry with frequency-domain near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Hallacoglu, Bertan

    Near-infrared spectroscopy (NIRS) measurements of absolute concentrations of oxy-hemoglobin and deoxy-hemoglobin in the human brain can provide critical information about cerebral physiology in terms of cerebral blood volume, blood flow, oxygen delivery, and metabolic rate of oxygen. We developed several frequency domain NIRS data acquisition and analysis methods aimed at absolute measurements of hemoglobin concentration and saturation in cerebral tissue of adult human subjects. Extensive experimental investigations were carried out in various homogenous and two-layered tissue-mimicking phantoms, and biological tissues. The advantages and limitations of commonly used homogenous models and inversion strategies were thoroughly investigated. Prior to human subjects, extensive studies were carried out in in vivo animal models. In rabbits, absolute hemoglobin oxygen desaturation was shown to depend strongly on surgically induced testicular torsion. Methods developed in this study were then adapted for measurements in the rat brain. Absolute values were demonstrated to discern cerebrovascular impairment in a rat model of diet-induced vascular cognitive impairment. These results facilitated the development of clinically useful optical measures of cerebrovascular health. In a large group of human subjects, employing a homogeneous model for absolute measurements was shown to be reliable and robust. However, it was also shown to be limited due to the relatively thick extracerebral tissue. The procedure we develop in this work and the thesis thereof performs a nonlinear inversion procedure with six unknown parameters with no other prior knowledge for the retrieval of the optical coefficients and top layer thickness with high accuracy on two-layered media. Our absolute measurements of cerebral hemoglobin concentration and saturation are based on the discrimination of extracerebral and cerebral tissue layers, and they can enhance the impact of NIRS for cerebral hemodynamics and

  13. Absolute distance sensing by two laser optical interferometry.

    PubMed

    Thurner, Klaus; Braun, Pierre-François; Karrai, Khaled

    2013-11-01

    We have developed a method for absolute distance sensing by two laser optical interferometry. A particularity of this technique is that a target distance is determined in absolute and is no longer limited to within an ambiguity range affecting usually multiple wavelength interferometers. We implemented the technique in a low-finesse Fabry-Pérot miniature fiber based interferometer. We used two diode lasers, both operating in the 1550 nm wavelength range. The wavelength difference is chosen to create a 25 μm long periodic beating interferometric pattern allowing a nanometer precise position measurement but limited to within an ambiguity range of 25 μm. The ambiguity is then eliminated by scanning one of the wavelengths over a small range (3.4 nm). We measured absolute distances in the sub-meter range and this with just few nanometer repeatability.

  14. Method and apparatus for two-dimensional absolute optical encoding

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    2004-01-01

    This invention presents a two-dimensional absolute optical encoder and a method for determining position of an object in accordance with information from the encoder. The encoder of the present invention comprises a scale having a pattern being predetermined to indicate an absolute location on the scale, means for illuminating the scale, means for forming an image of the pattern; and detector means for outputting signals derived from the portion of the image of the pattern which lies within a field of view of the detector means, the field of view defining an image reference coordinate system, and analyzing means, receiving the signals from the detector means, for determining the absolute location of the object. There are two types of scale patterns presented in this invention: grid type and starfield type.

  15. Fiber optic frequency transfer link

    NASA Technical Reports Server (NTRS)

    Primas, Lori E. (Inventor); Sydnor, Richard L. (Inventor); Lutes, George F. (Inventor)

    1991-01-01

    A reference frequency distribution system is disclosed for transmitting a reference frequency from a reference unit to a remote unit while keeping the reference frequency at the reference unit and the remote unit in phase. A fiber optic cable connects the reference unit to the remote unit. A frequency source at the reference unit produces a reference frequency having an adjustable phase. A fiber optic transmitter at the reference unit modulates a light beam with the reference frequency and transmits the light beam into the fiber optic cable. A 50/50 reflector at the remote unit reflects a first portion of the light beam from the reference unit back into the fiber optic cable to the reference unit. A first fiber optic receiver disposed at the remote unit receives a second portion of the light beam and demodulates the reference frequency to be used at the remote unit. A second fiber optic receiver disposed at the reference unit receives the first portion of the light beam and demodulates a reference frequency component. A phase conjugator is connected to the frequency source for comparing the phase of the reference frequency component to the phase of the reference frequency modulating the light beam being transmitted from the reference unit to maintain a conjugate (anti-symmetric) relationship between the reference frequency component and the reference frequency modulating the light beam where virtually no phase difference exists between the phase of the reference frequency component and the phase of the reference frequency modulating the light beam.

  16. A novel absolute measurement for the low-frequency figure correction of aspheric surfaces

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Cheng; Chang, Shenq-Tsong; Ho, Cheng-Fang; Kuo, Ching-Hsiang; Chung, Chien-Kai; Hsu, Wei-Yao; Tseng, Shih-Feng; Sung, Cheng-Kuo

    2015-07-01

    This study proposes an absolute measurement method with a computer-generated hologram (CGHs) to assist the identification of manufacturing form error, and gravity and mounting resulted distortions for a 300 mm aspherical mirror. This method adopts the frequency of peaks and valleys of each Zernike coefficient grabbed by the measurement with various orientations of the mirror in horizontal optical-axis configuration. In addition, the rotational-symmetric aberration (spherical aberration) is calibrated with random ball test method. According to the measured absolute surface figure, a high accuracy aspherical surface with peak to valley (P-V) value of 1/8 wave @ 632.8 nm was fabricated after surface figure correction with the reconstructed error map.

  17. Calibration method of absolute orientation of camera optical axis

    NASA Astrophysics Data System (ADS)

    Xu, Yong; Guo, Pengyu; Zhang, Xiaohu; Ding, Shaowen; Su, Ang; Li, Lichun

    2013-08-01

    Camera calibration is one of the most basic and important processes in optical measuring field. Generally, the objective of camera calibration is to estimate the internal and external parameters of object cameras, while the orientation error of optical axis is not included yet. Orientation error of optical axis is a important factor, which seriously affects measuring precision in high-precision measurement field, especially for those distant aerospace measurement in which object distance is much longer than focal length, that lead to magnifying the orientation errors to thousands times. In order to eliminate the influence of orientation error of camera optical axis, the imaging model of camera is analysed and established in this paper, and the calibration method is also introduced: Firstly, we analyse the reasons that cause optical axis error and its influence. Then, we find the model of optical axis orientation error and imaging model of camera basing on it's practical physical meaning. Furthermore, we derive the bundle adjustment algorithm which could compute the internal and external camera parameters and absolute orientation of camera optical axis simultaneously at high precision. In numeric simulation, we solve the camera parameters by using bundle adjustment optimization algorithm, then we correct the image points by calibration results according to the model of optical axis error, and the simulation result shows that our calibration model is reliable, effective and precise.

  18. Absolute distance measurement with an optical feedback interferometer.

    PubMed

    Gouaux, F; Servagent, N; Bosch, T

    1998-10-01

    An important use of the self-mixing effect inside a frequency-modulated single-mode laser diode is in laser velocimetry and range-finding applications. The optical beam reflected by a target and injected into the laser diode cavity modulated by a reshaped current is mixed with the light inside the cavity, causing variations of the optical output power. A theoretical analysis of this effect is proposed, based on the determination of the beat frequencies of the optical power variations, to improve the accuracy of laser distance measurement. A resolution of ?1.5 mm from 50 cm to 2 m is obtained when thermal effects are taken into account.

  19. Active Faraday optical frequency standard.

    PubMed

    Zhuang, Wei; Chen, Jingbiao

    2014-11-01

    We propose the mechanism of an active Faraday optical clock, and experimentally demonstrate an active Faraday optical frequency standard based on narrow bandwidth Faraday atomic filter by the method of velocity-selective optical pumping of cesium vapor. The center frequency of the active Faraday optical frequency standard is determined by the cesium 6 (2)S(1/2) F=4 to 6 (2)P(3/2) F'=4 and 5 crossover transition line. The optical heterodyne beat between two similar independent setups shows that the frequency linewidth reaches 281(23) Hz, which is 1.9×10(4) times smaller than the natural linewidth of the cesium 852-nm transition line. The maximum emitted light power reaches 75 μW. The active Faraday optical frequency standard reported here has advantages of narrow linewidth and reduced cavity pulling, which can readily be extended to other atomic transition lines of alkali and alkaline-earth metal atoms trapped in optical lattices at magic wavelengths, making it useful for new generation of optical atomic clocks.

  20. Single-track absolute position encoding method based on spatial frequency of stripes

    NASA Astrophysics Data System (ADS)

    Xiang, Xiansong; Lu, Yancong; Wei, Chunlong; Zhou, Changhe

    2014-11-01

    A new method of single-track absolute position encoding based on spatial frequency of stripes is proposed. Instead of using pseudorandom-sequence arranged stripes as in conventional situations, this kind of encoding method stores the location information in the frequency space of the stripes, which means the spatial frequency of stripes varies with position and indicates position. This encoding method has a strong fault-tolerant capability with single-stripe detecting errors. The method can be applied to absolute linear encoders, absolute photoelectric angle encoders or two-dimensional absolute linear encoders. The measuring apparatus includes a CCD image sensor and a microscope system, and the method of decoding this frequency code is based on FFT algorithm. This method should be highly interesting for practical applications as an absolute position encoding method.

  1. Colloidal Metamaterials at Optical Frequencies

    DTIC Science & Technology

    2014-07-18

    AFRL-OSR-VA-TR-2014-0184 Colloidal Metamaterials at Optical Frequencies Jennifer Dionne LELAND STANFORD JUNIOR UNIV CA Final Report 07/18/2014...Prescribed by ANSI Std. Z39.18 Colloidal Metamaterials at Optical Frequencies Annual Report, June 30, 2014 A. Investigators PI: Jennifer Dionne...team has combined theoretical and experimental methods to produce a colloidally -synthesized metamaterial fluid, or “metafluid,” exhibiting strong

  2. Length measurement in absolute scale via low-dispersion optical cavity

    NASA Astrophysics Data System (ADS)

    Pravdova, Lenka; Lesundak, Adam; Smid, Radek; Hrabina, Jan; Rerucha, Simon; Cip, Ondrej

    2016-12-01

    We report on the length measuring instrument with the absolute scale that was based on the combination of an optical frequency comb and a passive optical cavity. The time spacing of short femtosecond pulses, generated by the optical frequency comb, is optically phase locked onto the cavity free spectral range with a derivative spectroscopy technique so that the value of the repetition frequency of the femtosecond laser is tied to and determines the measured displacement. The instantaneous value of the femtosecond pulse train frequency is counted by a frequency counter. This counted value corresponds to the length given by the spacing between the two mirrors of the passive cavity. The phase lock between the femtosecond pulsed beam and the passive cavity is possible due to the low-dispersion of the cavity mirrors, where the silver coating on the mirrors was used to provide the low dispersion for the broadband radiation of the comb. Every reflection on the output mirror feeds a portion of the beam back to the cavity so that the output beam is a result of multiple interfering components. The parameters of the output beam are given not only by the parameters of the mirrors but mainly by the absolute distance between the mirror surfaces. Thus, one cavity mirror can be considered as the reference starting point of the distance to be measured and the other mirror is the measuring probe surveying the unknown distance. The measuring mirror of the experimental setup of the low-dispersion cavity is mounted on a piezoelectric actuator which provides small changes in the cavity length we used to test the length measurement method. For the verification of the measurement accuracy a reference incremental interferometer was integrated into our system so that the displacement of the piezoelectric actuator could be obtained with both measuring methods simultaneously.

  3. Absolute frequency measurement of the {{}^{1}}{{\\text{S}}_{0}} – {{}^{3}}{{\\text{P}}_{0}} transition of 171Yb

    NASA Astrophysics Data System (ADS)

    Pizzocaro, Marco; Thoumany, Pierre; Rauf, Benjamin; Bregolin, Filippo; Milani, Gianmaria; Clivati, Cecilia; Costanzo, Giovanni A.; Levi, Filippo; Calonico, Davide

    2017-02-01

    We report the absolute frequency measurement of the unperturbed transition {{}1}{{\\text{S}}0} – {{}3}{{\\text{P}}0} at 578 nm in 171Yb realized in an optical lattice frequency standard relative to a cryogenic caesium fountain. The measurement result is 518 295 836 590 863.59(31) Hz with a relative standard uncertainty of 5.9× {{10}-16} . This value is in agreement with the ytterbium frequency recommended as a secondary representation of the second in the International System of Units.

  4. Enhanced Lamb dip for absolute laser frequency stabilization

    NASA Technical Reports Server (NTRS)

    Siegman, A. E.; Byer, R. L.; Wang, S. C.

    1972-01-01

    Enhanced Lamb dip width is 5 MHz and total depth is 10 percent of peak power. Present configuration is useful as frequency standard in near infrared. Technique extends to other lasers, for which low pressure narrow linewidth gain tubes can be constructed.

  5. Absolute Measurements of Optical Oscillator Strengths of Xe

    NASA Astrophysics Data System (ADS)

    Gibson, N. D.

    1998-05-01

    The dramatically increased interest in Xe as a discharge medium for the efficient generation of UV radiation, and Xe use in high technology applications such as flat panel displays for laptop computer screens and home TV and theater applications, has created the need for significantly more accurate oscillator strength data. Modeling of plasma processing systems and lighting discharges critically depends on accurate, precise atomic data. We are measuring the optical oscillator strengths of several Xe resonance lines. These measurements use a 900 eV collimated electron beam to excite the Xe atoms. In the method of self absorption used here, the transmission of the emitted radiation is measured as a function of the gas density. The measured oscillator strengths are proportional to the distance between the electron beam and the fixed aperture of the spectrometer-detector system. Since the theoretical form of the transmission function is well understood, there are few systematic errors. Absolute errors as low as 3-4% can be obtained.

  6. Frequency Measurements of Al+ and Hg+ Optical Standards

    NASA Astrophysics Data System (ADS)

    Itano, W. M.; Bergquist, J. C.; Rosenband, T.; Wineland, D. J.; Hume, D.; Chou, C.-W.; Jefferts, S. R.; Heavner, T. P.; Parker, T. E.; Diddams, S. A.; Fortier, T. M.

    2010-02-01

    Frequency standards based on narrow optical transitions in 27Al+ and 199Hg+ ions have been developed at NIST. Both standards have absolute reproducibilities of a few parts in 1017. This is about an order of magnitude better than the fractional uncertainty of the SI second, which is based on the 133Cs hyperfine frequency. Use of femtosecond laser frequency combs makes it possible to compare the optical frequency standards to microwave frequency standards or to each other. The ratio of the Al+ and Hg+ frequencies can be measured more accurately than the reproducibility of the primary cesium frequency standards. Frequency measurements made over time can be used to set limits on the time variation of fundamental constants, such as the fine structure constant α or the quark masses.

  7. Dynamic optical frequency domain reflectometry.

    PubMed

    Arbel, Dror; Eyal, Avishay

    2014-04-21

    We describe a dynamic Optical Frequency Domain Reflectometry (OFDR) system which enables real time, long range, acoustic sensing at high sampling rate. The system is based on a fast scanning laser and coherent detection scheme. Distributed sensing is obtained by probing the Rayleigh backscattered light. The system was tested by interrogation of a 10 km communication type single mode fiber and successfully detected localized impulse and sinusoidal excitations.

  8. Absolute frequency list of the ν3-band transitions of methane at a relative uncertainty level of 10(-11).

    PubMed

    Okubo, Sho; Nakayama, Hirotaka; Iwakuni, Kana; Inaba, Hajime; Sasada, Hiroyuki

    2011-11-21

    We determine the absolute frequencies of 56 rotation-vibration transitions of the ν(3) band of CH(4) from 88.2 to 90.5 THz with a typical uncertainty of 2 kHz corresponding to a relative uncertainty of 2.2 × 10(-11) over an average time of a few hundred seconds. Saturated absorption lines are observed using a difference-frequency-generation source and a cavity-enhanced absorption cell, and the transition frequencies are measured with a fiber-laser-based optical frequency comb referenced to a rubidium atomic clock linked to the international atomic time. The determined value of the P(7) F(2)((2)) line is consistent with the International Committee for Weights and Measures recommendation within the uncertainty.

  9. Different ways to active optical frequency standards

    NASA Astrophysics Data System (ADS)

    Pan, Duo; Xue, Xiaobo; Zhang, Xiaogang; Chen, Jingbiao

    2016-06-01

    Active optical frequency standard, or active optical clock, is a new concept of optical frequency standard, where a weak feedback with phase coherence information in optical bad-cavity limitation is formed, and the continuous self-sustained coherent stimulated emission between two atomic transition levels with population inversion is realized. Through ten years of both theoretical and experimental exploration, the narrow linewidth and suppression of cavity pulling effect of active optical frequency standard have been initially proved. In this paper, after a simple review, we will mainly present the most recent experimental progresses of active optical frequency standards in Peking University, including 4-level cesium active optical frequency standards and active Faraday optical frequency standards. The future development of active optical frequency standards is also discussed.

  10. Quantifying discipline practices using absolute versus relative frequencies: clinical and research implications for child welfare.

    PubMed

    Lindhiem, Oliver; Shaffer, Anne; Kolko, David J

    2014-01-01

    In the parent intervention outcome literatures, discipline practices are generally quantified as absolute frequencies or, less commonly, as relative frequencies. These differences in methodology warrant direct comparison as they have critical implications for study results and conclusions among treatments targeted at reducing parental aggression and harsh discipline. In this study, we directly compared the absolute frequency method and the relative frequency method for quantifying physically aggressive, psychologically aggressive, and nonaggressive discipline practices. Longitudinal data over a 3-year period came from an existing data set of a clinical trial examining the effectiveness of a psychosocial treatment in reducing parental physical and psychological aggression and improving child behavior (N = 139). Discipline practices (aggressive and nonaggressive) were assessed using the Conflict Tactics Scale. The two methods yielded different patterns of results, particularly for nonaggressive discipline strategies. We suggest that each method makes its own unique contribution to a more complete understanding of the association between parental aggression and intervention effects.

  11. Metrology with AN Optical Feedback Frequency Stabilized Crds

    NASA Astrophysics Data System (ADS)

    Kassi, Samir; Burkart, Johannes

    2015-06-01

    We will present a metrological application of our recently developed Optical Feedback Frequency Stabilized - Cavity Ring Down Spectrometer (OFFS-CRDS). This instrument, which ideally fits with an optical frequency comb for absolute frequency calibration, relies on the robust lock of a steady cavity ring down resonator against a highly stable, radiofrequency tuned optical source. At 1.6 μm, over 7 nm, we demonstrate Lamb dip spectroscopy of CO_2 with line frequency retrieval at the kHz level, a dynamic in excess of 700,000 on the absorption scale and a detectivity of 4x10-13cm-1Hz-1/2. Such an instrument nicely meets the requirements for the most demanding spectroscopy spanning from accurate isotopic ratio determination and very precise lineshape recordings to Boltzmann constant redefinition.

  12. Dynamic frequency-domain interferometer for absolute distance measurements with high resolution.

    PubMed

    Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

    2014-11-01

    A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

  13. Dynamic frequency-domain interferometer for absolute distance measurements with high resolution

    SciTech Connect

    Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

    2014-11-15

    A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

  14. Frequency comb metrology with an optical parametric oscillator.

    PubMed

    Balskus, K; Schilt, S; Wittwer, V J; Brochard, P; Ploetzing, T; Jornod, N; McCracken, R A; Zhang, Z; Bartels, A; Reid, D T; Südmeyer, T

    2016-04-18

    We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-µm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the 87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb = 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-µm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser.

  15. Femtosecond frequency combs for optical clocks and timing transfer

    NASA Astrophysics Data System (ADS)

    Foreman, Seth M.

    The rapid development of femtosecond optical frequency combs over the last decade has brought together ultrastable phase control of both cw and mode-locked lasers and ultrafast time-domain applications. Frequency-domain laser stabilization techniques applied to the ultrashort-pulse trains emitted by a mode-locked laser result in a level of optical phase control previously achievable only for radio frequencies and microwaves. I present our work extending such control to mode-locked lasers for both timing and frequency stabilization applications of optical frequency combs. I first present a microwave technique for synchronizing two independent modelocked lasers at a level of timing precision less than the duration of an optical cycle, below 1 fs of residual rms timing jitter. Using these synchronized pulses, simultaneous sum- and difference-frequency generation of 400-nm and tunable mid-infrared fs pulses is demonstrated, opening the door for broadband coherent control of atomic and molecular systems. For frequency metrology, I report on an offset-free clockwork for an optical clock based on the 3.39-mum transition in methane. The clockwork's simplicity leads to a robust and reliable table-sized optical frequency reference with instability approaching a few parts in 1014. Then I describe a directly-octave-spanning, self-referenced Ti:sapphire laser employed as the robustly-running phase-coherent clockwork for an 87Sr optical lattice clock. The optical comb distributes the 2-s coherence time of the 698-nm ultrastable clock laser to its modes spanning the visible and near-IR spectrum, and is therefore simultaneously used as a hub for measuring absolute frequencies or frequency ratios between the Sr clock and other remotely-located microwave and optical atomic standards. Finally, I report on the transfer of ultrastable frequency references, both microwave and optical, through 10-km-scale optical fiber links. Actively stabilizing the optical phase delay of such a fiber

  16. Frequency domain optical parametric amplification

    PubMed Central

    Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

    2014-01-01

    Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 μm wavelength. PMID:24805968

  17. Absolute distance measurement by multi-heterodyne interferometry using a frequency comb and a cavity-stabilized tunable laser.

    PubMed

    Wu, Hanzhong; Zhang, Fumin; Liu, Tingyang; Balling, Petr; Qu, Xinghua

    2016-05-20

    In this paper, we develop a multi-heterodyne system capable of absolute distance measurement using a frequency comb and a tunable diode laser locked to a Fabry-Perot cavity. In a series of subsequent measurements, numerous beat components can be obtained by downconverting the optical frequency into the RF region with multi-heterodyne interferometry. The distances can be measured via the mode phases with a series of synthetic wavelengths. The comparison with the reference interferometer shows an agreement within 1.5 μm for the averages of five measurements and 2.5 μm for the single measurement, which is at the 10-8 relative precision level.

  18. Optical Frequency Synthesizer for Precision Spectroscopy

    NASA Astrophysics Data System (ADS)

    Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Knight, J. C.; Wadsworth, W. J.; Russell, P. St. J.

    2000-09-01

    We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the uncertainty of this new approach to 5.1×10-16. This opens the door for measurement and synthesis of virtually any optical frequency and is ready to revolutionize frequency metrology.

  19. Absolute positioning by multi-wavelength interferometry referenced to the frequency comb of a femtosecond laser.

    PubMed

    Wang, Guochao; Jang, Yoon-Soo; Hyun, Sangwon; Chun, Byung Jae; Kang, Hyun Jay; Yan, Shuhua; Kim, Seung-Woo; Kim, Young-Jin

    2015-04-06

    A multi-wavelength interferometer utilizing the frequency comb of a femtosecond laser as the wavelength ruler is tested for its capability of ultra-precision positioning for machine axis control. The interferometer uses four different wavelengths phase-locked to the frequency comb and then determines the absolute position through a multi-channel scheme of detecting interference phases in parallel so as to enable fast, precise and stable measurements continuously over a few meters of axis-travel. Test results show that the proposed interferometer proves itself as a potential candidate of absolute-type position transducer needed for next-generation ultra-precision machine axis control, demonstrating linear errors of less than 61.9 nm in peak-to-valley over a 1-meter travel with an update rate of 100 Hz when compared to an incremental-type He-Ne laser interferometer.

  20. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

    2012-10-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  1. Using neuromorphic optical sensors for spacecraft absolute and relative navigation

    NASA Astrophysics Data System (ADS)

    Shake, Christopher M.

    We develop a novel attitude determination system (ADS) for use on nano spacecraft using neuromorphic optical sensors. The ADS intends to support nano-satellite operations by providing low-cost, low-mass, low-volume, low-power, and redundant attitude determination capabilities with quick and straightforward onboard programmability for real time spacecraft operations. The ADS is experimentally validated with commercial-off-the-shelf optical devices that perform sensing and image processing on the same circuit board and are biologically inspired by insects' vision systems, which measure optical flow while navigating in the environment. The firmware on the devices is modified to both perform the additional biologically inspired task of tracking objects and communicate with a PC/104 form-factor embedded computer running Real Time Application Interface Linux used on a spacecraft simulator. Algorithms are developed for operations using optical flow, point tracking, and hybrid modes with the sensors, and the performance of the system in all three modes is assessed using a spacecraft simulator in the Advanced Autonomous Multiple Spacecraft (ADAMUS) laboratory at Rensselaer. An existing relative state determination method is identified to be combined with the novel ADS to create a self-contained navigation system for nano spacecraft. The performance of the method is assessed in simulation and found not to match the results from its authors using only conditions and equations already published. An improved target inertia tensor method is proposed as an update to the existing relative state method, but found not to perform as expected, but is presented for others to build upon.

  2. REVIEW: Optical frequency standards and femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Baklanov, E. V.; Pokasov, P. V.

    2003-05-01

    A review is presented of the state of the art in a new direction in quantum electronics based on the use of femtosecond lasers for precision frequency measurements and the development of optical frequency and time standards.

  3. Absolute frequency measurement with uncertainty below 1× 10^{-15} using International Atomic Time

    NASA Astrophysics Data System (ADS)

    Hachisu, Hidekazu; Petit, Gérard; Ido, Tetsuya

    2017-01-01

    The absolute frequency of the ^{87}Sr clock transition measured in 2015 (Jpn J Appl Phys 54:112401, 2015) was reevaluated using an improved frequency link to the SI second. The scale interval of International Atomic Time (TAI) that we used as the reference was calibrated for an evaluation interval of 5 days instead of the conventional interval of 1 month which is regularly employed in Circular T. The calibration on a 5-day basis removed the uncertainty in assimilating the TAI scale of the 5-day mean to that of the 1-month mean. The reevaluation resulted in the total uncertainty of 10^{-16} level for the first time without local cesium fountains. Since there are presumably no correlations among systematic shifts of cesium fountains worldwide, the measurement is not limited by the systematic uncertainty of a specific primary frequency standard.

  4. Utilization of coincidence criteria in absolute length measurements by optical interferometry in vacuum and air

    NASA Astrophysics Data System (ADS)

    Schödel, R.

    2015-08-01

    Traceability of length measurements to the international system of units (SI) can be realized by using optical interferometry making use of well-known frequencies of monochromatic light sources mentioned in the Mise en Pratique for the realization of the metre. At some national metrology institutes, such as Physikalisch-Technische Bundesanstalt (PTB) in Germany, the absolute length of prismatic bodies (e.g. gauge blocks) is realized by so-called gauge-block interference comparators. At PTB, a number of such imaging phase-stepping interference comparators exist, including specialized vacuum interference comparators, each equipped with three highly stabilized laser light sources. The length of a material measure is expressed as a multiple of each wavelength. The large number of integer interference orders can be extracted by the method of exact fractions in which the coincidence of the lengths resulting from the different wavelengths is utilized as a criterion. The unambiguous extraction of the integer interference orders is an essential prerequisite for correct length measurements. This paper critically discusses coincidence criteria and their validity for three modes of absolute length measurements: 1) measurements under vacuum in which the wavelengths can be identified with the vacuum wavelengths, 2) measurements under air in which the air refractive index is obtained from environmental parameters using an empirical equation, and 3) measurements under air in which the air refractive index is obtained interferometrically by utilizing a vacuum cell placed along the measurement pathway. For case 3), which corresponds to PTB’s Kösters-Comparator for long gauge blocks, the unambiguous determination of integer interference orders related to the air refractive index could be improved by about a factor of ten when an ‘overall dispersion value,’ suggested in this paper, is used as coincidence criterion.

  5. Precise Stabilization of the Optical Frequency of WGMRs

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Matsko, Andrey; Matsko, Andrey; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir

    2009-01-01

    Crystalline whispering gallery mode resonators (CWGMRs) made of crystals with axial symmetry have ordinary and extraordinary families of optical modes. These modes have substantially different thermo-refractive constants. This results in a very sharp dependence of differential detuning of optical frequency on effective temperature. This frequency difference compared with clock gives an error signal for precise compensation of the random fluctuations of optical frequency. Certain crystals, like MgF2, have turnover points where the thermo-refractive effect is completely nullified. An advantage for applications using WGMRs for frequency stabilization is in the possibility of manufacturing resonators out of practically any optically transparent crystal. It is known that there are crystals with negative and zero thermal expansion at some specific temperatures. Doping changes properties of the crystals and it is possible to create an optically transparent crystal with zero thermal expansion at room temperature. With this innovation s stabilization technique, the resultant WGMR will have absolute frequency stability The expansion of the resonator s body can be completely compensated for by nonlinear elements. This results in compensation of linear thermal expansion (see figure). In three-mode, the MgF2 resonator, if tuned at the turnover thermal point, can compensate for all types of random thermal-related frequency drift. Simplified dual-mode method is also available. This creates miniature optical resonators with good short- and long-term stability for passive secondary frequency ethalon and an active resonator for active secondary frequency standard (a narrowband laser with long-term stability).

  6. Use of the absolute phase in frequency modulated continuous wave plasma reflectometry

    SciTech Connect

    Cunningham, G.

    2008-08-15

    In frequency modulated continuous wave reflectometry, used for density profile measurement in fusion plasmas, it is usual to measure the beat frequency between the launched wave and the reflected wave, and from this to calculate the position of the reflecting layer in the plasma. The absolute phase of the beat signal is usually neglected. The reason is that the phase shift between sweeps is usually comparable with or more than 2{pi}, leading to an ambiguity that is impossible to resolve. However, recent observations on the MAST tokamak have shown that, under quiet plasma conditions (this term has to be defined), the phase shift between sweeps is small compared with 2{pi} and the phase ambiguity can be readily resolved. The reflectometer signal is then being analyzed as an interferometer signal would normally be, and there is a substantial improvement in spatial resolution. The method is illustrated by application to small edge localized mode precursor and allows what is believed to be the first quantitative measurement of the displacement of the plasma boundary by such a precursor mode. The errors in both the absolute phase measurement and the more conventional frequency measurement are also estimated.

  7. A dedicated pistonphone for absolute calibration of infrasound sensors at very low frequencies

    NASA Astrophysics Data System (ADS)

    He, Wen; He, Longbiao; Zhang, Fan; Rong, Zuochao; Jia, Shushi

    2016-02-01

    Aimed at the absolute calibration of infrasound sensors at very low frequencies, an upgraded and improved infrasonic pistonphone has been developed. The pistonphone was designed such that a very narrow clearance between the piston and its guide was realized based on an automatically-centered clearance-sealing structure, and a large volume rigid-walled chamber was also adopted, which improved the leakage time-constant of the chamber. A composite feedback control system was applied to the electromagnetic vibrator to control the precise motion of the piston. Performance tests and uncertainty analysis show that the leakage time-constant is so large, and the distortion of the sound pressure is so small, that the pistonphone can be used as a standard infrasound source in the frequency range from 0.001 Hz to 20 Hz. The low frequency property of the pistonphone has been verified through calibrating low frequency microphones. Comparison tests with the reciprocity method have shown that the pressure sensitivities from the pistonphone are not only reliable at common frequencies but also have smaller uncertainties at low frequencies.

  8. Frequency-Domain Optical Mammography

    DTIC Science & Technology

    2001-10-01

    optical measurements on breast-like phantoms (Months 19-24) a. Prepare the breast-like phantoms (optical inhomogeneities + strongly scattering...reveals contralateral hemodynamic changes upon hemi- imaging of solid phantoms for optical mammography. Appl Opt field paradigm. Vision Res 41: 97...1064 nm for the Nd:YAG, 660-1180 nm (tunable) for the Ti:sapphire, and 625-780 nm (tunable) for dye lasers using DCM or oxanine 1 dyes. A unique

  9. Mosher Amides: Determining the Absolute Stereochemistry of Optically-Active Amines

    ERIC Educational Resources Information Center

    Allen, Damian A.; Tomaso, Anthony E., Jr.; Priest, Owen P.; Hindson, David F.; Hurlburt, Jamie L.

    2008-01-01

    The use of chiral reagents for the derivatization of optically-active amines and alcohols for the purpose of determining their enantiomeric purity or absolute configuration is a tool used by many chemists. Among the techniques used, Mosher's amide and Mosher's ester analyses are among the most reliable and one of the most often used. Despite this,…

  10. A distance meter using a terahertz intermode beat in an optical frequency comb.

    PubMed

    Yokoyama, Shuko; Yokoyama, Toshiyuki; Hagihara, Yuki; Araki, Tsutomu; Yasui, Takeshi

    2009-09-28

    We propose a distance meter that utilizes an intermode beat of terahertz frequency in an optical frequency comb to perform high resolution and high dynamic range absolute distance measurements. The proposed system is based on a novel method, called multiheterodyne cross-correlation detection, in which intermode beat frequencies are scaled down to radio frequencies by optical mixing of two detuned optical frequency combs with a nonlinear optical crystal. Using this method, we obtained a 1.056 THz intermode beat and achieved a distance resolution of 0.820 microm from its phase measurement. Absolute distance measurement using 1.056 THz and 8.187 GHz intermode beats was also demonstrated in the range of 10 mm, resulting in a precision of 0.688 microm.

  11. Absolute measurements of the high-frequency magnetic dynamics in high-{Tc} superconductors

    SciTech Connect

    Hayden, S.M.; Aeppli, G.; Dai, P.; Mook, H.A.; Perring, T.G.; Cheong, S.W.; Fisk, Z.; Dogan, F.; Mason, T.E.

    1997-08-07

    The authors review recent measurements of the high-frequency dynamic magnetic susceptibility in the high-T{sub c} superconducting systems La{sub 2{minus}x}Sr{sub x}CuO{sub 4} and YBa{sub 2}Cu{sub 3}O{sub 6+x}. Experiments were performed using the chopper spectrometers HET and MARI at the ISIS spallation source. The authors have placed their measurements on an absolute intensity scale, this allows systematic trends to be seen and comparisons with theory to be made. They find that the insulating S = 1/2 antiferromagnetic parent compounds show a dramatic renormalization in the spin wave intensity. The effect of doping on the response is to cause broadenings in wave vector and large redistributions of spectral weight in frequency.

  12. Absolute and relative surface profile interferometry using multiple frequency-scanned lasers

    NASA Astrophysics Data System (ADS)

    Peca, Marek; Psota, Pavel; Vojtíšek, Petr; Lédl, Vít.

    2016-11-01

    An interferometer has been used to measure the surface profile of generic object. Frequency scanning interferometry has been employed to provide unambiguous phase readings, to suppress etalon fringes, and to supersede phase-shifting. The frequency scan has been performed in three narrow wavelength bands, each generated by a temperature tuned laser diode. It is shown, that for certain portions of measured object, it was possible to get absolute phase measurement, counting all wave periods from the point of zero path difference, yielding precision of 2.7nm RMS over 11.75mm total path difference. For the other areas where steep slopes were present in object geometry, a relative measurement is still possible, at measured surface roughness comparable to that of machining process (the same 2.7nm RMS). It is concluded, that areas containing steep slopes exhibit systematic error, attributed to a combined factors of dispersion and retrace error.

  13. Exact Theory of Optical Tweezers and Its Application to Absolute Calibration.

    PubMed

    Dutra, Rafael S; Viana, Nathan B; Neto, Paulo A Maia; Nussenzveig, H Moysés

    2017-01-01

    Optical tweezers have become a powerful tool for basic and applied research in cell biology. Here, we describe an experimentally verified theory for the trapping forces generated by optical tweezers based on first principles that allows absolute calibration. For pedagogical reasons, the steps that led to the development of the theory over the past 15 years are outlined. The results are applicable to a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Protocols for implementing absolute calibration are given, explaining how to measure all required experimental parameters, and including a link to an applet for stiffness calculations.

  14. Optical scanning extrinsic Fabry-Perot interferometer for absolute microdisplacement measurement.

    PubMed

    Li, T; May, R G; Wang, A; Claus, R O

    1997-12-01

    We report an optical-scanning, dual-fiber, extrinsic Fabry-Perot interferometer system for absolute measurement of microdisplacement. The system involves two air-gapped Fabry-Perot cavities, formed by fiber end faces, functioning as sensing and reference elements. Taking the scanning wavelength as an interconverter to compare the gap length of the sensing head with the reference-cavity length yields the absolute measurement of the sensing-cavity length. The measurement is independent of the wavelength-scanning accuracy, and the reference-cavity length can be self-calibrated simply by one's changing the sensing-head length by an accurate value.

  15. Time-frequency spectrograms of optical pulses

    SciTech Connect

    Beck, M.

    1995-11-01

    The authors present a discussion of several different types of joint time-frequency distributions of optical pulses. Particular attention is paid to the Wigner distribution W(t,{omega}), as it is the fundamental distribution from which all others can be derived. They elucidate the relationship between the Wigner distribution and other spectrograms of current-interest, such as that obtained from frequency-resolved optical gating (FROG).

  16. Digitally enhanced optical fiber frequency reference.

    PubMed

    McRae, Terry G; Ngo, Silvie; Shaddock, Daniel A; Hsu, Magnus T L; Gray, Malcolm B

    2014-04-01

    We use digitally enhanced heterodyne interferometry to measure the stability of optical fiber laser frequency references. Suppression of laser frequency noise by over four orders of magnitude is achieved using post processing time delay interferometry, allowing us to measure the mechanical stability for frequencies as low as 100 μHz. The performance of the digitally enhanced heterodyne interferometer platform used here is not practically limited by the dynamic range or bandwidth issues that can occur in feedback stabilization systems. This allows longer measurement times, better frequency discrimination, a reduction in spatially uncorrelated noise sources and an increase in interferometer sensitivity. An optical fiber frequency reference with the stability reported here, over a signal band of 20 mHz-1 Hz, has potential for use in demanding environments, such as space-based interferometry missions and optical flywheel applications.

  17. Reference frequency transmission over optical fiber

    NASA Technical Reports Server (NTRS)

    Lutes, G.; Kirk, A.

    1986-01-01

    A 100-MHz reference frequency from a hydrogen maser frequency standard has been transmitted via optical fiber over a 14-km distance with a measured stability of 1.5 X 10 to the-15 power for 1000 seconds averaging time. This capability was demonstrated in a frequency distribution experiment performed in April, 1986. The reference frequency was transmitted over a single-mode fiber-optic link from Deep Space Station (DSS) 13 to DSS 12 and back. The background leading up to the experiment and the significance of stable reference frequency distribution in the Deep Space Network (DSN) is discussed. Also described are the experiment, including the fiber-optic link, the measurement method and equipment, and finally the results of the experiment.

  18. Absolute group refractive index measurement of air by dispersive interferometry using frequency comb.

    PubMed

    Yang, L J; Zhang, H Y; Li, Y; Wei, H Y

    2015-12-28

    The absolute group refractive index of air at 1563 nm is measured by dispersive interferometry, and a combined uncertainty of 1.2 × 10(-8) is achieved. The group refractive index of air is calculated from the dispersive interferograms of the two beams passing through the inner and outer regions of a vacuum cell by fast-Fourier-transform. Experimental results show that the discrepancies between our method and modified Edlén equation are less than 3.43 × 10(-8) and 4.4 × 10(-8) for short-term and long-term experiments, respectively. The interferogram update rate is 15 ms, which makes it suitable for application of real-time monitoring. Furthermore, it is promising to improve the measurement uncertainty to 3.0 × 10(-9) by changing the material of the vacuum cell and measuring its length more accurately through optical interferometry.

  19. Semiconductor laser gyro with optical frequency dithering

    SciTech Connect

    Prokof'eva, L P; Sakharov, V K; Shcherbakov, V V

    2014-04-28

    The semiconductor laser gyro is described, in which the optical frequency dithering implemented by intracavity phase modulation suppresses the frequency lock-in and provides the interference of multimode radiation. The sensitivity of the device amounted to 10–20 deg h{sup -1}. (laser gyroscopes)

  20. Frequency Selective Volumes for Optical Spatial Filters

    SciTech Connect

    E Topsakal; JL Volakis

    2004-04-15

    A new model is proposed for modeling metallic losses at optical frequencies and is used in the analysis of Frequency Selective Surfaces (FSSs) and Volumes (FSVs). Conventional methods for simulating metallic losses are also outlined and a comparison with those models is given for a patch FSS. Measured data for a slot-ring FSS are also given for model validation.

  1. Atomically referenced 1-GHz optical parametric oscillator frequency comb.

    PubMed

    McCracken, Richard A; Balskus, Karolis; Zhang, Zhaowei; Reid, Derryck T

    2015-06-15

    The visible to mid-infrared coverage of femtosecond optical parametric oscillator (OPO) frequency combs makes them attractive resources for high-resolution spectroscopy and astrophotonic spectrograph calibration. Such applications require absolute traceability and wide comb-tooth spacing, attributes which until now have remained unavailable from any single OPO frequency comb. Here, we report a 1-GHz Ti:sapphire pumped OPO comb whose repetition and offset frequencies are referenced to Rb-stabilised microwave and laser oscillators respectively. This technique simultaneously achieves fully stabilized combs from both the Ti:sapphire laser and the OPO with sub-MHz comb-tooth linewidths, multi-hour locking stability and without the need for super-continuum generation.

  2. Simplified fringe order correction for absolute phase maps recovered with multiple-spatial-frequency fringe projections

    NASA Astrophysics Data System (ADS)

    Ding, Yi; Peng, Kai; Lu, Lei; Zhong, Kai; Zhu, Ziqi

    2017-02-01

    Various kinds of fringe order errors may occur in the absolute phase maps recovered with multi-spatial-frequency fringe projections. In existing methods, multiple successive pixels corrupted by fringe order errors are detected and corrected pixel-by-pixel with repeating searches, which is inefficient for applications. To improve the efficiency of multiple successive fringe order corrections, in this paper we propose a method to simplify the error detection and correction by the stepwise increasing property of fringe order. In the proposed method, the numbers of pixels in each step are estimated to find the possible true fringe order values, repeating the search in detecting multiple successive errors can be avoided for efficient error correction. The effectiveness of our proposed method is validated by experimental results.

  3. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography

    PubMed Central

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2016-01-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365

  4. Frequency agile optical parametric oscillator

    DOEpatents

    Velsko, Stephan P.

    1998-01-01

    The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy.

  5. Frequency agile optical parametric oscillator

    DOEpatents

    Velsko, S.P.

    1998-11-24

    The frequency agile OPO device converts a fixed wavelength pump laser beam to arbitrary wavelengths within a specified range with pulse to pulse agility, at a rate limited only by the repetition rate of the pump laser. Uses of this invention include Laser radar, LIDAR, active remote sensing of effluents/pollutants, environmental monitoring, antisensor lasers, and spectroscopy. 14 figs.

  6. Frequency-Domain Optical Mammogram

    DTIC Science & Technology

    2002-10-01

    spectral features of all the tumors. Task 2. Perform the optical measurements on breast-like phantoms (Months 19-24) a. Prepare the breast-like phantoms ...a tur- ygen saturation measurements to within 15% of the bid medium can be modeled with the first-order actual values in phantoms and have reported...31. Y. Yamashita and M. Kaneko, "Visible and infrared diaphanog- ized abnormalities embedded within tissuelike phantoms ," raphy for medical diagnosis

  7. Cavity ring-down spectroscopy of Doppler-broadened absorption line with sub-MHz absolute frequency accuracy.

    PubMed

    Cheng, C-F; Sun, Y R; Pan, H; Lu, Y; Li, X-F; Wang, J; Liu, A-W; Hu, S-M

    2012-04-23

    A continuous-wave cavity ring-down spectrometer has been built for precise determination of absolute frequencies of Doppler-broadened absorption lines. Using a thermo-stabilized Fabry-Pérot interferometer and Rb frequency references at the 780 nm and 795 nm, 0.1 - 0.6 MHz absolute frequency accuracy has been achieved in the 775-800 nm region. A water absorption line at 12579 cm(-1) is studied to test the performance of the spectrometer. The line position at zero-pressure limit is determined with an uncertainty of 0.3 MHz (relative accuracy of 0.8 × 10(-9)).

  8. Comparing a mercury optical lattice clock with microwave and optical frequency standards

    NASA Astrophysics Data System (ADS)

    Tyumenev, R.; Favier, M.; Bilicki, S.; Bookjans, E.; Le Targat, R.; Lodewyck, J.; Nicolodi, D.; Le Coq, Y.; Abgrall, M.; Guéna, J.; De Sarlo, L.; Bize, S.

    2016-11-01

    In this paper we report the evaluation of an optical lattice clock based on neutral mercury with a relative uncertainty of 1.7× {10}-16. Comparing this characterized frequency standard to a 133Cs atomic fountain we determine the absolute frequency of the {}1{{{S}}}0\\to {}3{{{P}}}0 transition of 199Hg as {ν }{Hg}=1128 575 290 808 154.62 {Hz}+/- 0.19 {Hz}({statistical})+/- 0.38 {Hz} (systematic), limited solely by the realization of the SI second. Furthermore, by comparing the mercury optical lattice clock to a 87Rb atomic fountain, we determine for the first time to our knowledge the ratio between the 199Hg clock transition and the 87Rb ground state hyperfine transition. Finally we present a direct optical to optical measurement of the 199Hg/87Sr frequency ratio. The obtained value of {ν }{Hg}/{ν }{Sr} = 2.629 314 209 898 909 15 with a fractional uncertainty of 1.8× {10}-16 is in excellent agreement with a similar measurement obtained by Yamanaka et al (2015 Phys. Rev. Lett. 114 230801). This makes this frequency ratio one of the few physical quantities agreed upon by different laboratories to this level of uncertainty. Frequency ratio measurements of the kind reported in this paper have a strong impact for frequency metrology and fundamental physics as they can be used to monitor putative variations of fundamental constants.

  9. Correlation of symptom clusters of schizophrenia with absolute powers of main frequency bands in quantitative EEG

    PubMed Central

    Gross, Andres; Joutsiniemi, Sirkka-Liisa; Rimon, Ranan; Appelberg, Björn

    2006-01-01

    Background Research of QEEG activity power spectra has shown intriguing results in patients with schizophrenia. Different symptom clusters have been correlated to QEEG frequency bands. The findings have been to some extent inconsistent. Replication of the findings of previous research is thus an important task. In the current study we investigated the correlations between the absolute powers of delta, theta, alpha, and beta frequency bands over the fronto-central scalp area (FC) with the PANSS subscales and the Liddle's factors in 16 patients with schizophrenia. The authors hypothesised a priori the correlations reported by Harris et al (1999) of PANSS negative subscale with delta power, Liddle's psychomotor poverty with delta and beta powers, disorganisation with delta power and reality distortion with alpha power on the midline FC. Methods The sample consisted of 16 patients with chronic schizophrenia considered as having insufficient clinical response to conventional antipsychotic treatment and evidencing a relapse. The correlations between quantitative electroencephalography (QEEG) absolute powers of delta (1.5–3.0 Hz), theta (3.0–7.5 Hz), alpha (7.5–12.5 Hz), and beta (12.5–20.0 Hz) frequency bands over the fronto-central scalp area (FC) with PANSS subscales and Liddle's factors (reality distortion, disorganisation, psychomotor poverty) were investigated. Results Significant positive correlations were found between the beta and psychomotor poverty (p < 0.05). Trends towards positive correlations (p < 0.1) were observed between delta and PANSS negative subscale and psychomotor poverty. Alpha did not correlate with reality distortion and delta did not correlate with disorganisation. Post hoc analysis revealed correlations of the same magnitude between beta and psychopathology generally over FC. Conclusion The a priori hypothesis was partly supported by the correlation of the beta and psychomotor poverty. Liddle's factors showed correlations of the same

  10. Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight

    PubMed Central

    Elyas, Eli; Grimwood, Alex; Erler, Janine T.; Robinson, Simon P.; Cox, Thomas R.; Woods, Daniel; Clowes, Peter; De Luca, Ramona; Marinozzi, Franco; Fromageau, Jérémie; Bamber, Jeffrey C.

    2017-01-01

    Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms. PMID:28107368

  11. Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight.

    PubMed

    Elyas, Eli; Grimwood, Alex; Erler, Janine T; Robinson, Simon P; Cox, Thomas R; Woods, Daniel; Clowes, Peter; De Luca, Ramona; Marinozzi, Franco; Fromageau, Jérémie; Bamber, Jeffrey C

    2017-01-01

    Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms.

  12. Optical frequency standards for time and length applications

    NASA Astrophysics Data System (ADS)

    Hong, Feng-Lei

    2017-01-01

    The last decade has witnessed tremendous progress in research on optical frequency metrology. Optical frequency standards using optical lattice and single-ion trap technologies have reached levels of stability and accuracy that surpass the performance of the best Cs fountain atomic clocks by orders of magnitude. Optical frequency standards are also used for various applications including length metrology. Optical frequency measurement and links using optical frequency combs and optical fibres play important roles in the development of optical frequency standards. This article introduces optical frequency standards recommended by the International Committee for Weights and Measures (CIPM) along with updates provided by recent research results. Frequency ratio measurements and remote frequency comparisons are addressed in relation to the work whose goal is to redefine the second. Optical frequency standard and optical frequency comb applications are also described.

  13. Nobel Lecture: Defining and measuring optical frequencies

    NASA Astrophysics Data System (ADS)

    Hall, John L.

    2006-10-01

    Four long-running currents in laser technology met and merged in 1999-2000. Two of these were the quest toward a stable repetitive sequence of ever-shorter optical pulses and, on the other hand, the quest for the most time-stable, unvarying optical frequency possible. The marriage of UltraFast and UltraStable lasers was brokered mainly by two international teams and became exciting when a special “designer” microstructure optical fiber was shown to be nonlinear enough to produce “white light” from the femtosecond laser pulses, such that the output spectrum embraced a full optical octave. Then, for the first time, one could realize an optical frequency interval equal to the comb’s lowest frequency, and count out this interval as a multiple of the repetition rate of the femtosecond pulse laser. This “gear-box” connection between the radio frequency standard and any/all optical frequency standards came just as Sensitivity-Enhancing ideas were maturing. The four-way Union empowered an explosion of accurate frequency measurement results in the standards field and prepares the way for refined tests of some of our cherished physical principles, such as the time-stability of some of the basic numbers in physics (e.g., the “fine-structure” constant, the speed of light, certain atomic mass ratios etc.), and the equivalence of time-keeping by clocks based on different physics. The stable laser technology also allows time-synchronization between two independent femtosecond lasers so exact they can be made to appear as if the source were a single laser. By improving pump/probe experiments, one important application will be in bond-specific spatial scanning of biological samples. This next decade in optical physics should be a blast.

  14. Absolute Retinal Blood Flow Measurement With a Dual-Beam Doppler Optical Coherence Tomography

    PubMed Central

    Dai, Cuixia; Liu, Xiaojing; Zhang, Hao F.; Puliafito, Carmen A.; Jiao, Shuliang

    2013-01-01

    Purpose. To test the capability of a novel dual-beam Doppler optical coherence tomography (OCT) technique for simultaneous in vivo measurement of the Doppler angle and, thus, the absolute retinal blood velocity and the retinal flow rate, without the influence of motion artifacts. Methods. A novel dual-beam Doppler spectral domain OCT (SD-OCT) was developed. The two probing beams are separated with a controllable distance along an arbitrary direction, both of which are controlled by two independent 2D optical scanners. Two sets of optical Doppler tomography (ODT) images are acquired simultaneously. The Doppler angle of each blood vessel segment is calculated from the relative coordinates of the centers of the blood vessel in the two corresponding ODT images. The absolute blood flow velocity and the volumetric blood flow rate can then be calculated. To measure the total retinal blood flow, we used a circular scan pattern centered at the optic disc to obtain two sets of concentric OCT/ODT images simultaneously. Results. We imaged two normal human subjects at ages of 48 and 34 years. The total retinal blood flow rates of the two human subjects were calculated to be 47.01 μL/min (older subject) and 51.37 μL/min (younger subject), respectively. Results showed that the performance of this imaging system is immune to eye movement, since the two sets of ODT images were acquired simultaneously. Conclusions. The dual-beam OCT/ODT system is successful in measuring the absolute retinal blood velocity and the volumetric flow rate. The advantage of the technique is that the two sets of ODT images used for the calculation are acquired simultaneously, which eliminates the influence of eye motion and ensures the accuracy of the calculated hemodynamic parameters. PMID:24222303

  15. Absolute Spatially- and Temporally-Resolved Optical Emission Measurements of rf Glow Discharges in Argon

    PubMed Central

    Djurović, S.; Roberts, J. R.; Sobolewski, M. A.; Olthoff, J. K.

    1993-01-01

    Spatially- and temporally-resolved measurements of optical emission intensities are presented from rf discharges in argon over a wide range of pressures (6.7 to 133 Pa) and applied rf voltages (75 to 200 V). Results of measurements of emission intensities are presented for both an atomic transition (Ar I, 750.4 nm) and an ionic transition (Ar II, 434.8 nm). The absolute scale of these optical emissions has been determined by comparison with the optical emission from a calibrated standard lamp. All measurements were made in a well-defined rf reactor. They provide detailed characterization of local time-resolved plasma conditions suitable for the comparison with results from other experiments and theoretical models. These measurements represent a new level of detail in diagnostic measurements of rf plasmas, and provide insight into the electron transport properties of rf discharges. PMID:28053464

  16. Absolute distance measurement by dual-comb nonlinear asynchronous optical sampling.

    PubMed

    Zhang, Hongyuan; Wei, Haoyun; Wu, Xuejian; Yang, Honglei; Li, Yan

    2014-03-24

    A dual-comb nonlinear asynchronous optical sampling method is proposed to simplify determination of the time interval and extend the non-ambiguity range in absolute length measurements. Type II second harmonic generation facilitates curve fitting in determining the time interval between adjacent pulses. Meanwhile, the non-ambiguity range is extended by adjusting the repetition rate of the signal laser. The performance of the proposed method is compared with a heterodyne interferometer. Results show that the system achieves a maximum residual of 100.6 nm and an uncertainty of 1.48 μm in a 0.5 ms acquisition time. With longer acquisition time, the uncertainty can be reduced to 166.6 nm for 50 ms and 82.9 nm for 500 ms. Moreover, the extension of the non-ambiguity range is demonstrated by measuring an absolute distance beyond the inherent range determined by the fixed repetition rate.

  17. Sensitive and absolute absorption measurements in optical materials and coatings by laser-induced deflection technique

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon

    2012-12-01

    The laser-induced deflection (LID) technique, a photo-thermal deflection setup with transversal pump-probe-beam arrangement, is applied for sensitive and absolute absorption measurements of optical materials and coatings. Different LID concepts for bulk and transparent coating absorption measurements, respectively, are explained, focusing on providing accurate absorption data with only one measurement and one sample. Furthermore, a new sandwich concept is introduced that allows transferring the LID technique to very small sample geometries and to significantly increase the sensitivity for materials with weak photo-thermal responses. For each of the different concepts, a representative application example is given. Particular emphasis is placed on the importance of the calibration procedure for providing absolute absorption data. The validity of an electrical calibration procedure for the LID setup is proven using specially engineered surface absorbing samples. The electrical calibration procedure is then applied to evaluate two other approaches that use either doped samples or highly absorptive reference samples.

  18. Calibration-free absolute quantification of optical absorption coefficients using acoustic spectra in 3D photoacoustic microscopy of biological tissue.

    PubMed

    Guo, Zijian; Hu, Song; Wang, Lihong V

    2010-06-15

    Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.

  19. Stabilized fiber-optic frequency distribution system

    NASA Technical Reports Server (NTRS)

    Primas, L. E.; Lutes, G. F.; Sydnor, R. L.

    1989-01-01

    A technique for stabilizing reference frequencies transmitted over fiber-optic cable in a frequency distribution system is discussed. The distribution system utilizes fiber-optic cable as the transmission medium to distribute precise reference signals from a frequency standard to remote users. The stability goal of the distribution system is to transmit a 100-MHz signal over a 22-km fiber-optic cable and maintain a stability of 1 part in 10(17) for 1000-second averaging times. Active stabilization of the link is required to reduce phase variations produced by environmental effects, and is achieved by transmitting the reference signal from the frequency standard to the remote unit and then reflecting back to the reference unit over the same optical fiber. By comparing the phase of the transmitted and reflected signals at the reference unit, phase variations of the remote signal can be measured. An error voltage derived from the phase difference between the two signals is used to add correction phase.

  20. Intercomparison of the LBIR Absolute Cryogenic Radiometers to the NIST Optical Power Measurement Standard

    PubMed Central

    Fedchak, James A.; Carter, Adriaan C.; Datla, Raju

    2006-01-01

    The Low Background Infrared calibration (LBIR) facility at the National Institute of Standards and Technology (NIST) presently maintains four absolute cryogenic radiometers (ACRs) which serve as standard reference detectors for infrared calibrations performed by the facility. The primary standard for optical power measurements at NIST-Gaithersburg has been the High Accuracy Cryogenic Radiometer (HACR). Recently, an improved radiometer, the Primary Optical Watt Radiometer (POWR), has replaced the HACR as the primary standard. In this paper, we present the results of comparisons between the radiometric powers measured by the four ACRs presently maintained by the LBIR facility to that measured by the HACR and POWR. This was done by using a Si photodiode light-trapping detector as a secondary transfer standard to compare the primary national standards to the ACRs maintained by the LBIR facility. The technique used to compare an ACR to the trap detector is described in detail. The absolute optical power measurements are found to be within 0.1 % of the primary standard for all the ACRs examined in this study. PMID:27274936

  1. A simple setup to simultaneously measure the resonant frequency and the absolute dissipation factor of a quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Rodahl, Michael; Kasemo, Bengt

    1996-09-01

    An experimental setup is described that can simultaneously measure the absolute dissipation factor and the resonant frequency of a short-circuited quartz crystal microbalance. The crystal is driven at approximately its resonant frequency by a signal generator which is intermittently disconnected by a relay, causing the crystal oscillation amplitude to decay exponentially. The decay is measured using a ferrite toroid transformer. One of the crystal leads is fed through the center of the ferrite toroid and thereby acts as the primary winding of the transformer. The secondary winding of the transformer is connected to a digitizing oscilloscope which records the decay of the crystal oscillation. From the recorded decay curve, the absolute dissipation factor (calculated from the decay time constant) and the series resonant frequency of the freely oscillating crystal are obtained. Alternatively, the dissipation factor and resonant frequency can be measured for the crystal oscillating under open-circuit conditions, i.e., in the parallel mode. The measurements are automated.

  2. Method and apparatus for ultra-high-sensitivity, incremental and absolute optical encoding

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B. (Inventor)

    1999-01-01

    An absolute optical linear or rotary encoder which encodes the motion of an object (3) with increased resolution and encoding range and decreased sensitivity to damage to the scale includes a scale (5), which moves with the object and is illuminated by a light source (11). The scale carries a pattern (9) which is imaged by a microscope optical system (13) on a CCD array (17) in a camera head (15). The pattern includes both fiducial markings (31) which are identical for each period of the pattern and code areas (33) which include binary codings of numbers identifying the individual periods of the pattern. The image of the pattern formed on the CCD array is analyzed by an image processor (23) to locate the fiducial marking, decode the information encoded in the code area, and thereby determine the position of the object.

  3. Determination of absolute configuration of chiral molecules using vibrational optical activity: a review.

    PubMed

    He, Yanan; Wang, Bo; Dukor, Rina K; Nafie, Laurence A

    2011-07-01

    Determination of the absolute handedness, known as absolute configuration (AC), of chiral molecules is an important step in any field related to chirality, especially in the pharmaceutical industry. Vibrational optical activity (VOA) has become a powerful tool for the determination of the AC of chiral molecules in the solution state after nearly forty years of evolution. VOA offers a novel alternative, or supplement, to X-ray crystallography, permitting AC determinations on neat liquid, oil, and solution samples without the need to grow single crystals of the pure chiral sample molecules as required for X-ray analysis. By comparing the sign and intensity of the measured VOA spectrum with the corresponding ab initio density functional theory (DFT) calculated VOA spectrum of a chosen configuration, one can unambiguously assign the AC of a chiral molecule. Comparing measured VOA spectra with calculated VOA spectra of all the conformers can also provide solution-state conformational populations. VOA consists of infrared vibrational circular dichroism (VCD) and vibrational Raman optical activity (ROA). Currently, VCD is used routinely by researchers in a variety of backgrounds, including molecular chirality, asymmetric synthesis, chiral catalysis, drug screening, pharmacology, and natural products. Although the application of ROA in AC determination lags behind that of VCD, with the recent implementation of ROA subroutines in commercial quantum chemistry software, ROA will in the future complement VCD for AC determination. In this review, the basic principles of the application of VCD to the determination of absolute configuration in chiral molecules are described. The steps required for VCD spectral measurement and calculation are outlined, followed by brief descriptions of recently published papers reporting the determination of AC in small organic, pharmaceutical, and natural product molecules.

  4. On the Color Indices and Absolute Brightnesses of the Optical Afterglows of GRB

    NASA Astrophysics Data System (ADS)

    Šimon, V.; Hudec, R.; Masetti, N.; Pizzichini, G.

    2003-04-01

    The study of the color indices and luminosities of 17 optical afterglows (OAs) of GRBs, including the most recent one, GRB010222, showed that the color variations during the decline of OAs are quite small during t - T0 < 10 days and allow a comparison among them, even for the less densely sampled OAs. The colors in the observer frame concentrate at (V - R)0 = 0.40+/-0.13, (R - I)0 = 0.46+/-0.18, (B - V)0 = 0.47+/-0.17, except for GRB000131 and GRB980425. However, large scatter is observed in (U - B)0. The color evolution of the OAs is negligible although their brightness declines by several magnitudes during t - T0 < 10 days. Such a strong concentration of the color indices also suggests that the intrinsic reddening (inside their host galaxies) must be quite similar and relatively small for all these events. The absolute brightness of OAs in the observer frame lies within MR0 = -26.5 to -22.2 for (t - T0)rest = 0.25 days. The general decline rate of the OA sample considered here seems to be independent of the absolute optical brightness of the OA, measured at some t - T0 identical for all OAs, and the light curves of all events are almost parallel, when corrected for the redshift-induced time dilation.

  5. Nonlinear optical protection against frequency agile lasers

    SciTech Connect

    McDowell, V.P.

    1988-08-04

    An eye-protection or equipment-filter device for protection from laser energy is disclosed. The device may be in the form of a telescope, binoculars, goggles, constructed as part of equipment such as image intensifiers or range designators. Optical elements focus the waist of the beam within a nonlinear frequency-doubling crystal or nonlinear optical element or fiber. The nonlinear elements produce a harmonic outside the visible spectrum in the case of crystals, or absorb the laser energy in the case of nonlinear fibers. Embodiments include protectors for the human eye as well as filters for sensitive machinery such as TV cameras, FLIR systems or other imaging equipment.

  6. Optical wire guided lumpectomy: frequency domain measurements

    NASA Astrophysics Data System (ADS)

    Dayton, A. L.; Keränen, V. T.; Prahl, S. A.

    2009-02-01

    In practice, complete removal of the tumor during a lumpectomy is difficult; the published rates of positive margins range from 10% to 50%. A spherical lumpectomy specimen with tumor directly in the middle may improve the success rate. A light source placed within the tumor may accomplish this goal by creating a sphere surrounding the tumor that can serve as a guide for resection. In an optical phantom and a prophylactic mastectomy specimen, sinusoidally modulated light within the medium was collected by optical fiber(s) at fixed distance(s) from the source and used to measure the optical properties. These optical properties were then used to calculate the distance the light had traveled through the medium. The fiber was coupled to an 830nm diode laser that was modulated at 100, 200 and 300 MHz. A handheld optical probe collected the modulated light and a network analyzer measured the phase lag. This data was used to calculate the distance the light traveled from the emitting fiber tip to the probe. The optical properties were μa = 0.004mm-1 and μ1s = 0.38mm-1 in the phantom. The optical properties for the tissue were μa = 0.005mm-1 and μ1s = 0.20mm-1. The prediction of distance from the source was within 4mm of the actual distance at 30mm in the phantom and within 3mm of the actual distance at 25mm in the tissue. The feasibility of a frequency domain system that makes measurements of local optical properties and then extrapolates those optical properties to make measurements of distance with a separate probe was demonstrated.

  7. Frequency measurement of a Sr lattice clock using an SI-second-referenced optical frequency comb linked by a global positioning system (GPS).

    PubMed

    Hong, Feng-Lei; Takamoto, Masao; Higashi, Ryoichi; Fukuyama, Yasuhiro; Jiang, Jie; Katori, Hidetoshi

    2005-07-11

    We have established a transportable frequency measurement system using an optical frequency comb linked to a commercial Cs atomic clock, which is in turn linked to international atomic time (TAI) through global positioning system (GPS) time. An iodine-stabilized Nd:YAG laser is used as a flywheel in the frequency measurement system. This system is used to measure the absolute frequency of the clock transition of (87)Sr in an optical lattice. We obtained a fractional uncertainty of 2x10(-14) in the frequency measurement with a total averaging time of ~ 10(5) s over 9 days.

  8. Absolute position calculation for a desktop mobile rehabilitation robot based on three optical mouse sensors.

    PubMed

    Zabaleta, Haritz; Valencia, David; Perry, Joel; Veneman, Jan; Keller, Thierry

    2011-01-01

    ArmAssist is a wireless robot for post stroke upper limb rehabilitation. Knowing the position of the arm is essential for any rehabilitation device. In this paper, we describe a method based on an artificial landmark navigation system. The navigation system uses three optical mouse sensors. This enables the building of a cheap but reliable position sensor. Two of the sensors are the data source for odometry calculations, and the third optical mouse sensor takes very low resolution pictures of a custom designed mat. These pictures are processed by an optical symbol recognition algorithm which will estimate the orientation of the robot and recognize the landmarks placed on the mat. The data fusion strategy is described to detect the misclassifications of the landmarks in order to fuse only reliable information. The orientation given by the optical symbol recognition (OSR) algorithm is used to improve significantly the odometry and the recognition of the landmarks is used to reference the odometry to a absolute coordinate system. The system was tested using a 3D motion capture system. With the actual mat configuration, in a field of motion of 710 × 450 mm, the maximum error in position estimation was 49.61 mm with an average error of 36.70 ± 22.50 mm. The average test duration was 36.5 seconds and the average path length was 4173 mm.

  9. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    DOE PAGES

    Gregor, M. C.; Boni, R.; Sorce, A.; ...

    2016-11-29

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology–traceable tungsten-filament lamp through various narrowband (40 nm-wide) filters. The integrated signal over the SOP’s ~250-nm operating range ismore » then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. As a result, error estimates indicate that brightness temperature can be inferred to a precision of <5%.« less

  10. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    NASA Astrophysics Data System (ADS)

    Gregor, M. C.; Boni, R.; Sorce, A.; Kendrick, J.; McCoy, C. A.; Polsin, D. N.; Boehly, T. R.; Celliers, P. M.; Collins, G. W.; Fratanduono, D. E.; Eggert, J. H.; Millot, M.

    2016-11-01

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology-traceable tungsten-filament lamp through various narrowband (40-nm-wide) filters. The integrated signal over the SOP's ˜250-nm operating range is then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. Error estimates indicate that brightness temperature can be inferred to a precision of <5%.

  11. Absolute calibration of the OMEGA streaked optical pyrometer for temperature measurements of compressed materials

    SciTech Connect

    Gregor, M. C.; Boni, R.; Sorce, A.; Kendrick, J.; McCoy, C. A.; Polsin, D. N.; Boehly, T. R.; Celliers, P. M.; Collins, G. W.; Fratanduono, D. E.; Eggert, J. H.; Millot, M.

    2016-11-29

    Experiments in high-energy-density physics often use optical pyrometry to determine temperatures of dynamically compressed materials. In combination with simultaneous shock-velocity and optical-reflectivity measurements using velocity interferometry, these experiments provide accurate equation-of-state data at extreme pressures (P > 1 Mbar) and temperatures (T > 0.5 eV). This paper reports on the absolute calibration of the streaked optical pyrometer (SOP) at the Omega Laser Facility. The wavelength-dependent system response was determined by measuring the optical emission from a National Institute of Standards and Technology–traceable tungsten-filament lamp through various narrowband (40 nm-wide) filters. The integrated signal over the SOP’s ~250-nm operating range is then related to that of a blackbody radiator using the calibrated response. We present a simple closed-form equation for the brightness temperature as a function of streak-camera signal derived from this calibration. As a result, error estimates indicate that brightness temperature can be inferred to a precision of <5%.

  12. Silicon-Chip-Based Optical Frequency Combs

    DTIC Science & Technology

    2015-10-26

    generated sideband. Considering the phase mismatch equation with only the GVD contribution, the detuning is inversely proportional to the square root...lower than expected due to resist polymerization issues during fabrication. Since the optical parametric oscillation threshold is inversely proportional...portion around 1360 nm is frequency doubled in a periodically poled lithium niobate (PPLN) crystal and then collinearly recombined in space and time

  13. Multipulse interferometric frequency-resolved optical gating

    SciTech Connect

    Siders, C.W.; Siders, J.L.W.; Omenetto, F.G.; Taylor, A.J.

    1999-04-01

    The authors review multipulse interferometric frequency-resolved optical gating (MI-FROG) as a technique, uniquely suited for pump-probe coherent spectroscopy using amplified visible and near-infrared short-pulse systems and/or emissive targets, for time-resolving ultrafast phase shifts and intensity changes. Application of polarization-gate MI-FROG to the study of ultrafast ionization in gases is presented.

  14. Design of a cryogenic absolute prism refractometer for infrared optical materials

    NASA Astrophysics Data System (ADS)

    Liao, Sheng; Ni, Lei; Ren, Qi-feng

    2011-12-01

    In order to enable high quality infrared lens designs at cryogenic temperature, we decided to study the IR materials" optical properties, such as the refractive index, the thermo-optic coefficient (dn/dT) etc. As a matter of fact, accurate precision refractive index data for infrared optical materials at cryogenic temperatures is scarce, so we decided to design a cryogenic absolute prism refractometer for infrared optical materials. Considering the most accurate and precise measurements of the real part of the refractive index, n, optical materials are obtained through minimum deviation refractometry, we decided to choose this classic refractometer for our cryogenic IR materials index measuring. Given the thermo-optic coefficient of many IR materials, which was reported by NASA, the measurement precision is at least 10-3. In order to achieve this precision, the error of apex angle of sample prism and deviation angle must be less than 20 arc-second. The thermal stress of the prism must be in control, or the volume change of the prism may lead to stress birefringence (photo-elastic effect). The bandwidth of IR source must be less than 20nm and the error caused by dispersion (dn/dλ) will generally be negligible in our system. The hardware system consists of 5 subsystems: the rotating sample chamber subsystem, the rotating plat mirror subsystem, the cryogenic vacuum subsystem, auto control subsystem, exit image collimation subsystem. Finally, the system is designed to measure IR materials" indices between 1-4, at the wavelength of 1.0-12μm, at room (300K) and cryogenic temperature (100K), with a precision of 10-4.

  15. Dissemination of optical-comb-based ultra-broadband frequency reference through a fiber network.

    PubMed

    Nagano, Shigeo; Kumagai, Motohiro; Li, Ying; Ido, Tetsuya; Ishii, Shoken; Mizutani, Kohei; Aoki, Makoto; Otsuka, Ryohei; Hanado, Yuko

    2016-08-22

    We disseminated an ultra-broadband optical frequency reference based on a femtosecond (fs)-laser optical comb through a kilometer-scale fiber link. Its spectrum ranged from 1160 nm to 2180 nm without additional fs-laser combs at the end of the link. By employing a fiber-induced phase noise cancellation technique, the linewidth and fractional frequency instability attained for all disseminated comb modes were of order 1 Hz and 10-18 in a 5000 s averaging time. The ultra-broad optical frequency reference, for which absolute frequency is traceable to Japan Standard Time, was applied in the frequency stabilization of an injection-seeded Q-switched 2051 nm pulse laser for a coherent light detection and ranging LIDAR system.

  16. Frequency ratio measurement of 171Yb and 87Sr optical lattice clocks.

    PubMed

    Akamatsu, Daisuke; Yasuda, Masami; Inaba, Hajime; Hosaka, Kazumoto; Tanabe, Takehiko; Onae, Atsushi; Hong, Feng-Lei

    2014-04-07

    The frequency ratio of the (1)S(0)(F = 1/2)-(3)P(0)(F = 1/2) clock transition in (171)Yb and the (1)S(0)(F = 9/2)-(3)P(0)(F = 9/2) clock transition in (87)Sr is measured by an optical-optical direct frequency link between two optical lattice clocks. We determined the ratio (ν(Yb)/ν(Sr)) to be 1.207 507 039 343 341 2(17) fractional standard uncertainty of 1.4 × 10(-15) [corrected]. The measurement uncertainty of the frequency ratio is smaller than that obtained from absolute frequency measurements using the International Atomic Time (TAI) link. The measured ratio agrees well with that derived from the absolute frequency measurement results obtained at NIST and JILA, Boulder, CO using their Cs-fountain clock. Our measurement enables the first international comparison of the frequency ratios of optical clocks. The measured frequency ratio will be reported to the International Committee for Weights and Measures for a discussion related to the redefinition of the second.

  17. NRZ versus RZ over Absolute Added Correlative coding in optical metro-access networks

    NASA Astrophysics Data System (ADS)

    Dong-Nhat, Nguyen; Elsherif, Mohamed A.; Le Minh, Hoa; Malekmohammadi, Amin

    2017-03-01

    This paper comparatively investigates the transmission performance of absolute added correlative coding (AACC) using non-return-to-zero (NRZ) and return-to-zero (RZ) pulse shapes with a binary intensity modulation direct detection receiver in 40 Gb/s optical metro-access networks operating at 1550 nm. It is shown that, for AACC transmission, the NRZ impulse shaping is superior in comparison to RZ in spectral efficiency, dispersion tolerance, residual dispersion and self-phase modulation (SPM) tolerance. However, RZ-AACC experiences a 1-2 dB advantage in receiver sensitivity over NRZ-AACC for back-to-back configuration as well as after 300-km single-mode fiber delivery.

  18. Assessment of absolute added correlative coding in optical intensity modulation and direct detection channels

    NASA Astrophysics Data System (ADS)

    Dong-Nhat, Nguyen; Elsherif, Mohamed A.; Malekmohammadi, Amin

    2016-06-01

    The performance of absolute added correlative coding (AACC) modulation format with direct detection has been numerically and analytically reported, targeting metro data center interconnects. Hereby, the focus lies on the performance of the bit error rate, noise contributions, spectral efficiency, and chromatic dispersion tolerance. The signal space model of AACC, where the average electrical and optical power expressions are derived for the first time, is also delineated. The proposed modulation format was also compared to other well-known signaling, such as on-off-keying (OOK) and four-level pulse-amplitude modulation, at the same bit rate in a directly modulated vertical-cavity surface-emitting laser-based transmission system. The comparison results show a clear advantage of AACC in achieving longer fiber delivery distance due to the higher dispersion tolerance.

  19. Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

    PubMed Central

    Morzyński, Piotr; Bober, Marcin; Bartoszek-Bober, Dobrosława; Nawrocki, Jerzy; Krehlik, Przemysław; Śliwczyński, Łukasz; Lipiński, Marcin; Masłowski, Piotr; Cygan, Agata; Dunst, Piotr; Garus, Michał; Lisak, Daniel; Zachorowski, Jerzy; Gawlik, Wojciech; Radzewicz, Czesław; Ciuryło, Roman; Zawada, Michał

    2015-01-01

    We report a stability below 7 × 10−17 of two independent optical lattice clocks operating with bosonic 88Sr isotope. The value (429 228 066 418 008.3(1.9)syst (0.9)stat Hz) of the absolute frequency of the 1S0 – 3P0 transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures. PMID:26639347

  20. Absolute measurement of the 1S0 - 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link.

    PubMed

    Morzyński, Piotr; Bober, Marcin; Bartoszek-Bober, Dobrosława; Nawrocki, Jerzy; Krehlik, Przemysław; Śliwczyński, Łukasz; Lipiński, Marcin; Masłowski, Piotr; Cygan, Agata; Dunst, Piotr; Garus, Michał; Lisak, Daniel; Zachorowski, Jerzy; Gawlik, Wojciech; Radzewicz, Czesław; Ciuryło, Roman; Zawada, Michał

    2015-12-07

    We report a stability below 7 × 10(-17) of two independent optical lattice clocks operating with bosonic (88)Sr isotope. The value (429 228 066 418 008.3(1.9)(syst) (0.9)(stat) Hz) of the absolute frequency of the (1)S(0) - (3)P(0) transition was measured with an optical frequency comb referenced to the local representation of the UTC by the 330 km-long stabilized fibre optical link. The result was verified by series of measurements on two independent optical lattice clocks and agrees with recommendation of Bureau International des Poids et Mesures.

  1. Optical and Radio Properties of QSOS as a Function of Absolute Luminosity.

    NASA Astrophysics Data System (ADS)

    Pica, Andrew Joseph

    1982-03-01

    Photometric data for nearly 250 quasars, BL Lacertids, and active galaxies have been obtained at the Rosemary Hill Observatory during a continuous 13-year monitoring program. Long-term optical records for 130 of these sources are employed in an effort to assess the physical and cosmological properties of quasi-stellar objects. Photographic P and B magnitudes were obtained with the 76- and 46-cm telescopes at Rosemary Hill. Corrections for galactic absorption, emission lines, and the K-term are applied to the raw data yielding monochromatic flux densities at a standard emitted wavelength of 2500 (ANGSTROM). Long -term light curves are compiled for all objects and 3 levels of activity are determined for each individual source. The MEAN, BASE, and MAX brightness levels are then used to study QSOs in their average, quiescent, and active phases, respectively. Absolute intrinsic luminosities of all sources in the sample are computed from the monochromatic flux densities based on relativistic cosmological models. Radio -emitting quasars, radio-quiet QSOs, and active galaxies fall into 3 distinct groups and are examined separately. The cosmological properties of QSOs are studied by plotting apparent magnitude vs. redshift, the so-called Hubble diagram. Scatter in the diagram due to variability is substantially reduced by plotting log z vs. the MEAN, BASE, and MAX flux densities. The brightest QSOs at each redshift are then chosen as "standard candles" in an effort to determine if quasars obey Hubble's law for expanding universe. It is found that they fit the Hubble relation quite well if certain selection effects are accounted for. Other evidence for the cosmological origin of QSOs is briefly discussed. Variability provides a test as to whether individual quasars are essentially multiple in nature (the "Christmas Tree" model), or are single coherent sources (such as a massive black hole). The amplitude of variability vs. absolute luminosity relation is used to discriminate

  2. Investigations of high-speed optical transmission systems employing Absolute Added Correlative Coding (AACC)

    NASA Astrophysics Data System (ADS)

    Dong-Nhat, Nguyen; Elsherif, Mohamed A.; Malekmohammadi, Amin

    2016-07-01

    A novel multilevel modulation format based on partial-response signaling called Absolute Added Correlative Coding (AACC) is proposed and numerically demonstrated for high-speed fiber-optic communication systems. A bit error rate (BER) estimation model for the proposed multilevel format has also been developed. The performance of AACC is examined and compared against other prevailing On-Off-Keying and multilevel modulation formats e.g. non-return-to-zero (NRZ), 50% return-to-zero (RZ), 67% carrier-suppressed return-to-zero (CS-RZ), duobinary and four-level pulse-amplitude modulation (4-PAM) in terms of receiver sensitivity, spectral efficiency and dispersion tolerance. Calculated receiver sensitivity at a BER of 10-9 and chromatic dispersion tolerance of the proposed system are ˜-28.3 dBm and ˜336 ps/nm, respectively. The performance of AACC is delineated to be improved by 7.8 dB in terms of receiver sensitivity compared to 4-PAM in back-to-back scenario. The comparison results also show a clear advantage of AACC in achieving longer fiber transmission distance due to the higher dispersion tolerance in optical access networks.

  3. Behavioral studies on the enantiomers of butaclamol demonstrating absolute optical specificity for neuroleptic activity.

    PubMed

    Voith, K; Cummings, J R

    1976-08-01

    Butaclamol is a member of a new chemical class for which antipsychotic activity in humans has been demonstrated. Butaclamol, a racemate, has been resolved into its optical isomers and a separation of activities was found to occur between the (+) and (-) enantiomers. The present experiments show that at doses ranging from 0.1 to 0.3 mg/kg the (+) enantiomer abolished amphetamine-induced (a) stereotyped behavior and (b) rotational behavior in rats with unilateral lesions in the substantia nigra. It also inhibited the lever-pressing response in the continuous (Sidman) avoidance procedure, blocked discriminated avoidance behavior, and decreased ambulation and rearing in the open field. In contrast, the (-) enantiomer was devoid of behavioral activity at 100-500 times larger doses. At considerably higher doses (+)-butaclamol antagonized epinephrine-induced mortality. Again, the (-)-butaclamol was devoid of this activity as well. The significance of absolute optical specifity manifested by a neuroleptic drug is discussed in the light of dopaminergic and adrenergic mechanisms.

  4. Fiber-based femtosecond optical frequency comb stabilized to iodine frequency standard

    NASA Astrophysics Data System (ADS)

    Bagayev, S. N.; Denisov, V. I.; Dychkov, A. S.; Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Farnosov, S. A.; Antropov, A. A.

    2017-01-01

    A fiber-based femtosecond optical frequency comb spanning wavelengths from 1 to 2 μm was stabilized precisely to an iodine frequency standard by means of heterodyne optical phase-locked loops. It enables transfer of frequency stability across electromagnetic spectrum and implementation of compact optical clocks with ∼10-15 long-term instability.

  5. The optical frequency comb fibre spectrometer.

    PubMed

    Coluccelli, Nicola; Cassinerio, Marco; Redding, Brandon; Cao, Hui; Laporta, Paolo; Galzerano, Gianluca

    2016-10-03

    Optical frequency comb sources provide thousands of precise and accurate optical lines in a single device enabling the broadband and high-speed detection required in many applications. A main challenge is to parallelize the detection over the widest possible band while bringing the resolution to the single comb-line level. Here we propose a solution based on the combination of a frequency comb source and a fibre spectrometer, exploiting all-fibre technology. Our system allows for simultaneous measurement of 500 isolated comb lines over a span of 0.12 THz in a single acquisition; arbitrarily larger span are demonstrated (3,500 comb lines over 0.85 THz) by doing sequential acquisitions. The potential for precision measurements is proved by spectroscopy of acetylene at 1.53 μm. Being based on all-fibre technology, our system is inherently low-cost, lightweight and may lead to the development of a new class of broadband high-resolution spectrometers.

  6. The optical frequency comb fibre spectrometer

    NASA Astrophysics Data System (ADS)

    Coluccelli, Nicola; Cassinerio, Marco; Redding, Brandon; Cao, Hui; Laporta, Paolo; Galzerano, Gianluca

    2016-10-01

    Optical frequency comb sources provide thousands of precise and accurate optical lines in a single device enabling the broadband and high-speed detection required in many applications. A main challenge is to parallelize the detection over the widest possible band while bringing the resolution to the single comb-line level. Here we propose a solution based on the combination of a frequency comb source and a fibre spectrometer, exploiting all-fibre technology. Our system allows for simultaneous measurement of 500 isolated comb lines over a span of 0.12 THz in a single acquisition; arbitrarily larger span are demonstrated (3,500 comb lines over 0.85 THz) by doing sequential acquisitions. The potential for precision measurements is proved by spectroscopy of acetylene at 1.53 μm. Being based on all-fibre technology, our system is inherently low-cost, lightweight and may lead to the development of a new class of broadband high-resolution spectrometers.

  7. The optical frequency comb fibre spectrometer

    PubMed Central

    Coluccelli, Nicola; Cassinerio, Marco; Redding, Brandon; Cao, Hui; Laporta, Paolo; Galzerano, Gianluca

    2016-01-01

    Optical frequency comb sources provide thousands of precise and accurate optical lines in a single device enabling the broadband and high-speed detection required in many applications. A main challenge is to parallelize the detection over the widest possible band while bringing the resolution to the single comb-line level. Here we propose a solution based on the combination of a frequency comb source and a fibre spectrometer, exploiting all-fibre technology. Our system allows for simultaneous measurement of 500 isolated comb lines over a span of 0.12 THz in a single acquisition; arbitrarily larger span are demonstrated (3,500 comb lines over 0.85 THz) by doing sequential acquisitions. The potential for precision measurements is proved by spectroscopy of acetylene at 1.53 μm. Being based on all-fibre technology, our system is inherently low-cost, lightweight and may lead to the development of a new class of broadband high-resolution spectrometers. PMID:27694981

  8. Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry.

    PubMed

    Wang, G; Wu, K; Hu, H; Li, G; Wang, L J

    2016-10-01

    To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

  9. Ultra-low-frequency vertical vibration isolator based on a two-stage beam structure for absolute gravimetry

    NASA Astrophysics Data System (ADS)

    Wang, G.; Wu, K.; Hu, H.; Li, G.; Wang, L. J.

    2016-10-01

    To reduce seismic and environmental vibration noise, ultra-low-frequency vertical vibration isolation systems play an important role in absolute gravimetry. For this purpose, an isolator based on a two-stage beam structure is proposed and demonstrated. The isolator has a simpler and more robust structure than the present ultra-low-frequency vertical active vibration isolators. In the system, two beams are connected to a frame using flexural pivots. The upper beam is suspended from the frame with a normal hex spring and the lower beam is suspended from the upper one using a zero-length spring. The pivot of the upper beam is not vertically above the pivot of the lower beam. With this special design, the attachment points of the zero-length spring to the beams can be moved to adjust the effective stiffness. A photoelectric detector is used to detect the angle between the two beams, and a voice coil actuator attached to the upper beam is controlled by a feedback circuit to keep the angle at a fixed value. The system can achieve a natural period of 100 s by carefully moving the attachment points of the zero-length spring to the beams and tuning the feedback parameters. The system has been used as an inertial reference in the T-1 absolute gravimeter. The experiment results demonstrate that the system has significant vibration isolation performance that holds promise in applications such as absolute gravimeters.

  10. Frequency domain optical tomography in human tissue

    NASA Astrophysics Data System (ADS)

    Yao, Yuqi; Wang, Yao; Pei, Yaling; Zhu, Wenwu; Hu, Jenhun; Barbour, Randall L.

    1995-10-01

    In this paper, a reconstruction algorithm for frequency-domain optical tomography in human tissue is presented. A fast and efficient multigrid finite difference (MGFD) method is adopted as a forward solver to obtain the simulated detector responses and the required imaging operator. The solutions obtained form MGFD method for 3D problems with weakly discontinuous cocoefficients are compared with analyzed solutions to determine the accuracy of the numerical method. Simultaneous reconstruction of both absorption and scattering coefficients for tissue-like media is accomplished by solving a perturbation equation using the Born approximation. This solution is obtained by a conjugate gradient descent method with Tikhonov regularization. Two examples are given to show the quality of the reconstruction results. Both involve the examination of anatomically accurate optical models of tissue derived from segmented 3D magnetic resonance images to which have been assigned optical coefficients to the designated tissue types. One is a map of a female breast containing two small 'added pathologies', such as tumors. The other is a map of the brain containing a 'local bleeding' area, representing a hemorrhage. The reconstruction results show that the algorithm is computationally practical and can yield qualitatively correct geometry of the objects embedded in the simulated human tissue. Acceptable results are obtaiend even when 10% noise is present in the data.

  11. Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems

    NASA Astrophysics Data System (ADS)

    Johnston, Mark D.; Oliver, Bryan V.; Droemer, Darryl W.; Frogget, Brent; Crain, Marlon D.; Maron, Yitzhak

    2012-08-01

    This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm2/steradian/nm). Error analysis shows this method to be accurate to within +/- 20%, which represents a high level of accuracy for this type of measurement.

  12. Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems.

    PubMed

    Johnston, Mark D; Oliver, Bryan V; Droemer, Darryl W; Frogget, Brent; Crain, Marlon D; Maron, Yitzhak

    2012-08-01

    This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm(2)/steradian/nm). Error analysis shows this method to be accurate to within +∕- 20%, which represents a high level of accuracy for this type of measurement.

  13. Intermittent optical frequency measurements to reduce the dead time uncertainty of frequency link

    NASA Astrophysics Data System (ADS)

    Hachisu, Hidekazu; Ido, Tetsuya

    2015-11-01

    The absolute frequency of the 87Sr lattice clock transition was evaluated with an uncertainty of 1.1 × 10-15 using a frequency link to the international atomic time (TAI). The frequency uncertainty of a hydrogen maser used as a transfer oscillator was reduced by homogeneously distributed intermittent measurement over a five-day grid of TAI. Three sets of four or five days measurements as well as systematic uncertainty of the clock at 8.6 × 10-17 have resulted in an absolute frequency of 87Sr 1S0-3P0 clock transition to be 429 228 004 229 872.85 (47) Hz.

  14. Space position measurement using long-path heterodyne interferometer with optical frequency comb.

    PubMed

    Wang, Xiaonan; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

    2012-01-30

    A heterodyne interference system was developed for position measurement. A stabilized optical-frequency comb is used as the laser source. The preliminary experiment to measure a distance of 22.478 m shows a drift of 1.6 μm in 20 minutes after the temperature compensation. Comparison and frequency shift experiments have been done for a distance of about 7.493 m. The experimental results show that the drift is mainly caused by environmental condition changes and the vibration of the table and floor also has some effects. It was verified that the absolute distance measurement can be realized by fringe scanning and frequency-shifting methods.

  15. 3D absolute shape measurement of live rabbit hearts with a superfast two-frequency phase-shifting technique

    PubMed Central

    Wang, Yajun; Laughner, Jacob I.; Efimov, Igor R.; Zhang, Song

    2013-01-01

    This paper presents a two-frequency binary phase-shifting technique to measure three-dimensional (3D) absolute shape of beating rabbit hearts. Due to the low contrast of the cardiac surface, the projector and the camera must remain focused, which poses challenges for any existing binary method where the measurement accuracy is low. To conquer this challenge, this paper proposes to utilize the optimal pulse width modulation (OPWM) technique to generate high-frequency fringe patterns, and the error-diffusion dithering technique to produce low-frequency fringe patterns. Furthermore, this paper will show that fringe patterns produced with blue light provide the best quality measurements compared to fringe patterns generated with red or green light; and the minimum data acquisition speed for high quality measurements is around 800 Hz for a rabbit heart beating at 180 beats per minute. PMID:23482151

  16. All optical measurement of an unknown wideband microwave frequency

    NASA Astrophysics Data System (ADS)

    Kumar, A.; Priye, V.; Raj Singh, R.

    2016-12-01

    A novel all optical measurement scheme is proposed to measure wideband microwave frequencies up to 30 GHz. The proposed method is based on a four-wave mixing (FWM) approach in a semiconductor optical amplifier (SOA) of both even order side-bands generated by an unknown microwave frequency modulating an optical carrier. The optical power of a generated FWM signal depends on frequency spacing between extracted side-bands. A mathematical relation is established between FWM power and frequency of an unknown signal. A calibration curve is drawn based on the mathematical relation which predicts the unknown frequency from power withdrawn after FWM.

  17. Optical Tunable-Based Transmitter for Multiple Radio Frequency Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Hung (Inventor); Simons, Rainee N. (Inventor); Wintucky, Edwin G. (Inventor); Freeman, Jon C. (Inventor)

    2016-01-01

    An optical tunable transmitter is used to transmit multiple radio frequency bands on a single beam. More specifically, a tunable laser is configured to generate a plurality of optical wavelengths, and an optical tunable transmitter is configured to modulate each of the plurality of optical wavelengths with a corresponding radio frequency band. The optical tunable transmitter is also configured to encode each of the plurality of modulated optical wavelengths onto a single laser beam for transmission of a plurality of radio frequency bands using the single laser beam.

  18. Characterization of an atmospheric helium plasma jet by relative and absolute optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiong, Qing; Nikiforov, Anton Yu; González, Manuel Á.; Leys, Christophe; Pei Lu, Xin

    2013-02-01

    The characteristics of plasma temperatures (gas temperature and electron excitation temperature) and electron density in a pulsed-dc excited atmospheric helium plasma jet are studied by relative and absolute optical emission spectroscopy (OES). High-resolution OES is performed for the helium and hydrogen lines for the determination of electron density through the Stark broadening mechanism. A superposition fitting method composed of two component profiles corresponding to two different electron densities is developed to fit the investigated lines. Electron densities of the orders of magnitude of 1021 and 1020 m-3 are characterized for the center and edge regions in the jet discharge when the applied voltage is higher than 13.0 kV. The atomic state distribution function (ASDF) of helium demonstrates that the discharge deviates from the Boltzmann-Saha equilibrium state, especially for the helium lower levels, which are significantly overpopulated. Local electron excitation temperatures T13 and Tspec corresponding to the lower and upper parts of the helium ASDF are defined and found to range from 1.2 eV to 1.4 eV and 0.2 eV to 0.3 eV, respectively. A comparative analysis shows that the Saha balance is valid in the discharge for helium atoms at high excited states.

  19. Field Measurement of Sand Dune Bidirectional Reflectance Characteristics for Absolute Radiometric Calibration of Optical Remote Sensing Data.

    NASA Astrophysics Data System (ADS)

    Coburn, C. A.; Logie, G.; Beaver, J.; Helder, D.

    2015-12-01

    The use of Pseudo Invariant Calibration Sites (PICS) for establishing the radiometric trending of optical remote sensing systems has a long history of successful implementation. Past studies have shown that the PICS method is useful for evaluating the trend of sensors over time or cross-calibration of sensors but was not considered until recently for deriving absolute calibration. Current interest in using this approach to establish absolute radiometric calibration stems from recent research that indicates that with empirically derived models of the surface properties and careful atmospheric characterisation Top of Atmosphere (TOA) reflectance values can be predicted and used for absolute sensor radiometric calibration. Critical to the continued development of this approach is the accurate characterization of the Bidirectional Reflectance Distribution Function (BRDF) of PICS sites. This paper presents the field data collected by a high-performance portable goniometer system in order to develop a BRDF model for the Algodones Dunes in California. These BRDF data are part of a larger study that is seeking to evaluate and quantify all aspects of this dune system (from regional effects to the micro scale optical properties of the sand) in order to provide an absolute radiometric calibration PICS. This paper presents the results of a dense temporal measurement sequence (several measurements per hour with high angular resolution), to yield detailed information on the nature of the surface reflectance properties. The BRDF data were collected covering typical view geometry of space borne sensors and will be used to close the loop on the calibration to create an absolute calibration target for optical satellite absolute radiometric calibration.

  20. Tomographic imaging of absolute optical absorption coefficient in turbid media using combined photoacoustic and diffusing light measurements.

    PubMed

    Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei

    2007-09-01

    We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected.

  1. The orbit of Phi Cygni measured with long-baseline optical interferometry - Component masses and absolute magnitudes

    NASA Technical Reports Server (NTRS)

    Armstrong, J. T.; Hummel, C. A.; Quirrenbach, A.; Buscher, D. F.; Mozurkewich, D.; Vivekanand, M.; Simon, R. S.; Denison, C. S.; Johnston, K. J.; Pan, X.-P.

    1992-01-01

    The orbit of the double-lined spectroscopic binary Phi Cygni, the distance to the system, and the masses and absolute magnitudes of its components are presented via measurements with the Mar III Optical Interferometer. On the basis of a reexamination of the spectroscopic data of Rach & Herbig (1961), the values and uncertainties are adopted for the period and the projected semimajor axes from the present fit to the spectroscopic data and the values of the remaining elements from the present fit to the Mark III data. The elements of the true orbit are derived, and the masses and absolute magnitudes of the components, and the distance to the system are calculated.

  2. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata

    NASA Astrophysics Data System (ADS)

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.20, respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  3. Radio frequency cavity analysis, measurement, and calibration of absolute Dee voltage for K-500 superconducting cyclotron at VECC, Kolkata.

    PubMed

    Som, Sumit; Seth, Sudeshna; Mandal, Aditya; Paul, Saikat; Duttagupta, Anjan

    2013-02-01

    Variable Energy Cyclotron Centre has commissioned a K-500 superconducting cyclotron for various types of nuclear physics experiments. The 3-phase radio-frequency system of superconducting cyclotron has been developed in the frequency range 9-27 MHz with amplitude and phase stability of 100 ppm and ±0.2(0), respectively. The analysis of the RF cavity has been carried out using 3D Computer Simulation Technology (CST) Microwave Studio code and various RF parameters and accelerating voltages ("Dee" voltage) are calculated from simulation. During the RF system commissioning, measurement of different RF parameters has been done and absolute Dee voltage has been calibrated using a CdTe X-ray detector along with its accessories and known X-ray source. The present paper discusses about the measured data and the simulation result.

  4. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  5. Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.

    PubMed

    Dale, John; Hughes, Ben; Lancaster, Andrew J; Lewis, Andrew J; Reichold, Armin J H; Warden, Matthew S

    2014-10-06

    We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10⁻⁶ at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm.

  6. Measurement of the absolute Raman cross section of the optical phonon in silicon

    NASA Astrophysics Data System (ADS)

    Aggarwal, R. L.; Farrar, L. W.; Saikin, S. K.; Aspuru-Guzik, A.; Stopa, M.; Polla, D. L.

    2011-04-01

    The absolute Raman cross section σ of the first-order 519 cm -1 optical phonon in silicon was measured using a small temperature-controlled blackbody for the signal calibration of the Raman system. Measurements were made with a 25-mil thick (001) silicon sample located in the focal plane of a 20-mm effective focal length (EFL) lens using 785-, 1064-, and 1535-nm CW pump lasers for the excitation of Raman scattering. The pump beam was polarized along the [100] axis of the silicon sample. Values of 1.0±0.2×10 -27, 3.6±0.7×10 -28, and 1.1±0.2×10 -29 cm 2 were determined for σ for 785-, 1064-, and 1535-nm excitation, respectively. The corresponding values of the Raman scattering efficiency S are 4.0±0.8×10 -6, 1.4±0.3×10 -6, and 4.4±0.8×10 -8 cm -1 sr -1.The values of the Raman polarizability |d| for 785-, 1064-, and 1535-nm excitation are 4.4±0.4×10 -15, 5.1±0.5×10 -15, and 1.9±0.2×10 -15 cm 2, respectively. The values of 4.4±0.4×10 -15 and 5.1±0.5×10 -15 cm 2 for |d| for 785- and 1064-nm excitation, respectively, are 1.3 and 2.0 times larger than the values of 3.5×10 -15 and 2.5×10 -15 cm 2 calculated by Wendel. The Raman polarizability |d| computed using the density functional theory in the long-wavelength limit is consistent with the general trend of the measured data and Wendel's model.

  7. Absolute frequency of cesium 6S-8S 822 nm two-photon transition by a high-resolution scheme.

    PubMed

    Wu, Chien-Ming; Liu, Tze-Wei; Wu, Ming-Hsuan; Lee, Ray-Kuang; Cheng, Wang-Yau

    2013-08-15

    We present an alternative scheme for determining the frequencies of cesium (Cs) atom 6S-8S Doppler-free transitions. With the use of a single electro-optical crystal, we simultaneously narrow the laser linewidth, lock the laser frequency, and resolve a narrow spectrum point by point. The error budget for this scheme is presented, and we prove that the transition frequency obtained from the Cs cell at room temperature and with one-layer μ-metal shielding is already very near that for the condition of zero collision and zero magnetic field. We point out that a sophisticated linewidth measurement could be a good guidance for choosing a suitable Cs cell for better frequency accuracy.

  8. Stabilisation of a fibre frequency synthesiser using acousto-optical and electro-optical modulators

    NASA Astrophysics Data System (ADS)

    Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Dychkov, A. S.; Farnosov, S. A.; Denisov, V. I.; Bagayev, S. N.

    2016-12-01

    A fibre-optic frequency synthesiser is developed that is stabilised to the optical frequency standard based on molecular iodine ({\\text{Nd : YAG/I}}2). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1 - 2 \\unicode{956}{\\text{m}} and to the RF range by using synthesiser phase-locked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10-13 for 1 {\\text{s}} and 5 × 10-15 for 1000 {\\text{s}}).

  9. Precision Spectroscopy, Diode Lasers, and Optical Frequency Measurement Technology

    NASA Technical Reports Server (NTRS)

    Hollberg, Leo (Editor); Fox, Richard (Editor); Waltman, Steve (Editor); Robinson, Hugh

    1998-01-01

    This compilation is a selected set of reprints from the Optical Frequency Measurement Group of the Time and Frequency Division of the National Institute of Standards and Technology, and consists of work published between 1987 and 1997. The two main programs represented here are (1) development of tunable diode-laser technology for scientific applications and precision measurements, and (2) research toward the goal of realizing optical-frequency measurements and synthesis. The papers are organized chronologically in five, somewhat arbitrarily chosen categories: Diode Laser Technology, Tunable Laser Systems, Laser Spectroscopy, Optical Synthesis and Extended Wavelength Coverage, and Multi-Photon Interactions and Optical Coherences.

  10. Effect of laser frequency noise on fiber-optic frequency reference distribution

    NASA Technical Reports Server (NTRS)

    Logan, R. T., Jr.; Lutes, G. F.; Maleki, L.

    1989-01-01

    The effect of the linewidth of a single longitude-mode laser on the frequency stability of a frequency reference transmitted over a single-mode optical fiber is analyzed. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation (square root of the Allan variance) of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit of the ultimate stability possible for frequency reference transmission on optical fiber, but is not a serious limitation to present system performance.

  11. The realization of the dipole (γ, γ) method and its application to determine the absolute optical oscillator strengths of helium

    PubMed Central

    Xu, Long-Quan; Liu, Ya-Wei; Kang, Xu; Ni, Dong-Dong; Yang, Ke; Hiraoka, Nozomu; Tsuei, Ku-Ding; Zhu, Lin-Fan

    2015-01-01

    The dipole (γ, γ) method, which is the inelastic x-ray scattering operated at a negligibly small momentum transfer, is proposed and realized to determine the absolute optical oscillator strengths of the vanlence-shell excitations of atoms and molecules. Compared with the conventionally used photoabsorption method, this new method is free from the line saturation effect, which can seriously limit the accuracies of the measured photoabsorption cross sections for discrete transitions with narrow natural linewidths. Furthermore, the Bethe-Born conversion factor of the dipole (γ, γ) method varies much more slowly with the excitation energy than does that of the dipole (e, e) method. Absolute optical oscillator strengths for the excitations of 1s2 → 1 snp(n = 3 − 7) of atomic helium have been determined using the high-resolution dipole (γ, γ) method, and the excellent agreement of the present measurements with both those measured by the dipole (e, e) method and the previous theoretical calculations indicates that the dipole (γ, γ) method is a powerful tool to measure the absolute optical oscillator strengths of the valence-shell excitations of atoms and molecules. PMID:26678298

  12. Method and apparatus for optical communication by frequency modulation

    DOEpatents

    Priatko, Gordon J.

    1988-01-01

    Laser optical communication according to this invention is carried out by producing multi-frequency laser beams having different frequencies, splitting one or more of these constituent beams into reference and signal beams, encoding information on the signal beams by frequency modulation and detecting the encoded information by heterodyne techniques. Much more information can be transmitted over optical paths according to the present invention than with the use of only one path as done previously.

  13. Frequency Comparison of [Formula: see text] Ion Optical Clocks at PTB and NPL via GPS PPP.

    PubMed

    Leute, J; Huntemann, N; Lipphardt, B; Tamm, Christian; Nisbet-Jones, P B R; King, S A; Godun, R M; Jones, J M; Margolis, H S; Whibberley, P B; Wallin, A; Merimaa, M; Gill, P; Peik, E

    2016-07-01

    We used precise point positioning, a well-established GPS carrier-phase frequency transfer method to perform a direct remote comparison of two optical frequency standards based on single laser-cooled [Formula: see text] ions operated at the National Physical Laboratory (NPL), U.K. and the Physikalisch-Technische Bundesanstalt (PTB), Germany. At both institutes, an active hydrogen maser serves as a flywheel oscillator which is connected to a GPS receiver as an external frequency reference and compared simultaneously to a realization of the unperturbed frequency of the (2)S1/2(F=0)-(2)D3/2(F=2) electric quadrupole transition in [Formula: see text] via an optical femtosecond frequency comb. To profit from long coherent GPS-link measurements, we extrapolate the fractional frequency difference over the various data gaps in the optical clock to maser comparisons which introduces maser noise to the frequency comparison but improves the uncertainty from the GPS-link instability. We determined the total statistical uncertainty consisting of the GPS-link uncertainty and the extrapolation uncertainties for several extrapolation schemes. Using the extrapolation scheme with the smallest combined uncertainty, we find a fractional frequency difference [Formula: see text] of -1.3×10(-15) with a combined uncertainty of 1.2×10(-15) for a total measurement time of 67 h. This result is consistent with an agreement of the frequencies realized by both optical clocks and with recent absolute frequency measurements against caesium fountain clocks within the corresponding uncertainties.

  14. Drug Treated Schizophrenia, Schizoaffective and Bipolar Disorder Patients Evaluated by qEEG Absolute Spectral Power and Mean Frequency Analysis

    PubMed Central

    Wix-Ramos, Richard; Moreno, Xiomara; Capote, Eduardo; González, Gilbert; Uribe, Ezequiel

    2014-01-01

    Objective Research of electroencephalograph (EEG) power spectrum and mean frequency has shown inconsistent results in patients with schizophrenic, schizoaffective and bipolar disorders during medication when compared to normal subjects thus; the characterization of these parameters is an important task. Methods We applied quantitative EEG (qEEG) to investigate 38 control, 15 schizophrenic, 7 schizoaffective and 11 bipolar disorder subjects which remaine under the administration of psychotropic drugs (except control group). Absolute spectral power (ASP), mean frequency and hemispheric electrical asymmetry were measured by 19 derivation qEEG. Group mean values were compared with non parametrical Mann-Whitney test and spectral EEG maps with z-score method at p < 0.05. Results Most frequent drug treatments for schizophrenic patients were neuroleptic+antiepileptic (40% of cases) or 2 neuroleptics (33.3%). Schizoaffective patients received neuroleptic+benzodiazepine (71.4%) and for bipolar disorder patients neuroleptic+antiepileptic (81.8%). Schizophrenic (at all derivations except for Fp1, Fp2, F8 and T6) and schizoaffective (only at C3) show higher values of ASP (+57.7% and +86.1% respectively) compared to control group. ASP of bipolar disorder patients did not show differences against control group. The mean frequency was higher at Fp1 (+14.2%) and Fp2 (+17.4%) in bipolar disorder patients than control group, but no differences were found in frequencies between schizophrenic or schizoaffective patients against the control group. Majority of spectral differences were found at the left hemisphere in schizophrenic and schizoaffective but not in bipolar disorder subjects. Conclusion The present report contributes to characterize quantitatively the qEEG in drug treated schizophrenic, schizoaffective or bipolar disorder patients. PMID:24851121

  15. Frequency Resolution of an Acousto-Optical Spectrometer

    DTIC Science & Technology

    1993-08-03

    AD-A267 822 FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER DTIC S ELECTE AUG 111993 D FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER by... D ~t• i,5"t~o’• A i +’- 1 Av.:+l +,O ,J Dist Avi! .. DTIC QUALITY I1V’PEMTED 3 FREQUENCY RESOLUTION OF AN ACOUSTO - OPTICAL SPECTROMETER... optical spectrometer (AOS) system as affected by the acousto - optical deflector and the coherent light beam truncation ratio, and examines the response

  16. Optical frequency tripling with improved suppression and sideband selection.

    PubMed

    Thakur, Manoj P; Medeiros, Maria C R; Laurêncio, Paula; Mitchell, John E

    2011-12-12

    A novel optical dispersion tolerant millimetre-wave radio-over-fibre system using optical frequency tripling technique with enhanced and selectable sideband suppression is demonstrated. The implementation utilises cascaded optical modulators to achieve either an optical single sideband (OSSB) or double sideband-suppressed carrier (DSB-SC) signal with high sideband suppression. Our analysis and simulation results indicate that the achievable suppression ratio of this configuration is only limited by other system factors such as optical noise and drifting of the operational conditions. The OSSB transmission system performance is assessed experimentally by the transport of 4 WiMax channels modulating a 10 GHz optical upconverted RF carrier as well as for optical frequency doubling and tripling. The 10 GHz and tripled carrier at 30 GHz are dispersion tolerant resulting both in an average relative constellation error (RCE) of -28.7 dB after 40 km of fibre.

  17. Synthesis, absolute configuration and conformation of optically active 1,2-homoheptafulvalene.

    PubMed

    Ito, Shunji; Kurita, Mitsuhiro; Kikuchi, Sigeru; Asao, Toyonobu; Ito, Yoshitora; Oda, Masaji; Sotokawa, Hideo; Tajiri, Akio; Morita, Noboru

    2003-02-07

    An optically active 1,2-homoheptafulvalene was successfully synthesized and subjected to spectroscopic investigation. The cycloaddition of the optically active hydrocarbon with tetracyanoethylene (TCNE) and 4-phenyl-1,2,4-triazoline-3,5-dione(PTAD) gave a [4 + 2] cycloadduct and a mixture of [8 + 2] cycloadducts, respectively, which are both optically active.

  18. Robust interferometric frequency lock between cw lasers and optical frequency combs.

    PubMed

    Benkler, Erik; Rohde, Felix; Telle, Harald R

    2013-02-15

    A transfer interferometer is presented which establishes a versatile and robust optical frequency locking link between a tunable single frequency laser and an optical frequency comb. It enables agile and continuous tuning of the frequency difference between both lasers while fluctuations and drift effects of the transfer interferometer itself are widely eliminated via common mode rejection. Experimental results will be presented for a tunable extended-cavity 1.5 μm laser diode locked to an Er-fiber based frequency comb.

  19. An optical frequency standard based on ultracold magnesium atoms

    NASA Astrophysics Data System (ADS)

    Goncharov, A. N.; Bonert, A. E.; Brazhnikov, D. V.; Prudnikov, O. N.; Tropnikov, M. A.; Kuznetsov, S. A.; Taichenachev, A. V.; Bagayev, S. N.

    2017-01-01

    This paper presents the recent experimental results on development of an optical frequency standard based on ultra cold magnesium atoms with relative frequency uncertainty and long term stability at the level of Δv/v <10‑16. We stabilized the frequency of our clock laser system at 655 THz to narrow Ramsey fringes in a time separated laser fields interacting with cooled Mg atoms localized in a magneto-optical trap (MOT). The intercombination line 1S0→3P1 was used as the reference for frequency stabilization. The results of stabilization were studied with femtosecond comb based on Ti:Sa laser.

  20. 10-GHz Self-Referenced Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Bartels, Albrecht; Heinecke, Dirk; Diddams, Scott A.

    2009-10-01

    The femtosecond laser-based frequency comb has played a key role in high-precision optical frequency metrology for a decade. Although often referred to as a precise optical frequency ruler, its tick marks are in fact too densely spaced for direct observation and individual use, limiting important applications in spectroscopy, astronomy, and ultrafast electromagnetic waveform control. We report on a femtosecond laser frequency comb with a 10-gigahertz repetition rate that creates a stabilized output spectrum with coverage from 470 to 1130 nanometers. The individual modes can be directly resolved with a grating spectrometer and are visible by eye.

  1. Stable radio-frequency transfer over optical fiber by phase-conjugate frequency mixing.

    PubMed

    He, Yabai; Orr, Brian J; Baldwin, Kenneth G H; Wouters, Michael J; Luiten, Andre N; Aben, Guido; Warrington, R Bruce

    2013-08-12

    We demonstrate long-distance (≥100-km) synchronization of the phase of a radio-frequency reference over an optical-fiber network without needing to actively stabilize the optical path length. Frequency mixing is used to achieve passive phase-conjugate cancellation of fiber-length fluctuations, ensuring that the phase difference between the reference and synchronized oscillators is independent of the link length. The fractional radio-frequency-transfer stability through a 100-km "real-world" urban optical-fiber network is 6 × 10(-17) with an averaging time of 10(4) s. Our compensation technique is robust, providing long-term stability superior to that of a hydrogen maser. By combining our technique with the short-term stability provided by a remote, high-quality quartz oscillator, this system is potentially applicable to transcontinental optical-fiber time and frequency dissemination where the optical round-trip propagation time is significant.

  2. T-shaped cavity dual-frequency Nd:YAG laser with electro-optical modulation

    NASA Astrophysics Data System (ADS)

    Xing, Junhong; Jiao, Mingxing; Liu, Yun

    2016-05-01

    A T-shaped cavity dual-frequency Nd:YAG laser with electro-optical modulation is proposed, which consists of both p- and s-cavities sharing the same gain medium of Nd:YAG. Each cavity was not only able to select longitudinal mode but also tune frequency using an electro-optic birefringent filter polarization beam splitter + lithium niobate. The frequency difference of dual frequency was tuned through the whole gain bandwidth of Nd:YAG, which is far above the usually accepted free spectral range value in the case of a single-axis laser. As a result, the simultaneous operation of orthogonally and linearly polarized dual-frequency laser was obtained, which coincides with the theoretical analysis based on Jones matrices. The obtained frequency difference ranges from 0 to 132 GHz. This offers a simple and widely tunable source with potential for portable frequency reference applications in terahertz-wave generation and absolute-distance interferometry measurement areas.

  3. Frequency Measurement System of Optical Clocks Without a Flywheel Oscillator.

    PubMed

    Fujieda, Miho; Ido, Tetsuya; Hachisu, Hidekazu; Gotoh, Tadahiro; Takiguchi, Hiroshi; Hayasaka, Kazuhiro; Toyoda, Kenji; Yonegaki, Kenji; Tanaka, Utako; Urabe, Shinji

    2016-12-01

    We developed a system for the remote frequency comparison of optical clocks. The system does not require a flywheel oscillator at the remote end, making it possible to evaluate optical frequencies even in laboratories, where no stable microwave reference, such as an Rb clock, a Cs clock, or a hydrogen maser exists. The system is established by the integration of several systems: a portable carrier-phase two-way satellite frequency transfer station and a microwave signal generation system by an optical frequency comb from an optical clock. The measurement was as quick as a conventional method that employs a local microwave reference. We confirmed the system uncertainty and instability to be at the low 10(-15) level using an Sr lattice clock.

  4. Frequency-resolved optical grating using third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; Delong, K.W.

    1995-12-01

    We demonstrate the first frequency-resolved optical gating measurement of an laser oscillator without the time ambiguity using third-harmonic generation. The experiment agrees well with the phase-retrieved spectrograms.

  5. Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle

    PubMed Central

    Gurley, Katelyn; Shang, Yu

    2012-01-01

    Abstract. This study investigates a method using novel hybrid diffuse optical spectroscopies [near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS)] to obtain continuous, noninvasive measurement of absolute blood flow (BF), blood oxygenation, and oxygen consumption rate (V˙O2) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and V˙O2 in forearm flexor muscles, while a hybrid optical probe on the skin surface directly monitored oxy-, deoxy-, and total hemoglobin concentrations ([HbO2], [Hb], and THC), tissue oxygen saturation (StO2), relative BF (rBF), and relative oxygen consumption rate (rV˙O2). The rBF and rV˙O2 signals were calibrated with absolute baseline BF and V˙O2 obtained through venous and arterial occlusions, respectively. Known problems with muscle-fiber motion artifacts in optical measurements during exercise were mitigated using a novel gating algorithm that determined muscle contraction status based on control signals from a dynamometer. Results were consistent with previous findings in the literature. This study supports the application of NIRS/DCS technology to quantitatively evaluate hemodynamic and metabolic parameters in exercising skeletal muscle and holds promise for improving diagnosis and treatment evaluation for patients suffering from diseases affecting skeletal muscle and advancing fundamental understanding of muscle and exercise physiology. PMID:22894482

  6. Noninvasive optical quantification of absolute blood flow, blood oxygenation, and oxygen consumption rate in exercising skeletal muscle

    NASA Astrophysics Data System (ADS)

    Gurley, Katelyn; Shang, Yu; Yu, Guoqiang

    2012-07-01

    This study investigates a method using novel hybrid diffuse optical spectroscopies [near-infrared spectroscopy (NIRS) and diffuse correlation spectroscopy (DCS)] to obtain continuous, noninvasive measurement of absolute blood flow (BF), blood oxygenation, and oxygen consumption rate (\\Vdot O2) in exercising skeletal muscle. Healthy subjects (n=9) performed a handgrip exercise to increase BF and \\Vdot O2 in forearm flexor muscles, while a hybrid optical probe on the skin surface directly monitored oxy-, deoxy-, and total hemoglobin concentrations ([HbO2], [Hb], and THC), tissue oxygen saturation (StO2), relative BF (rBF), and relative oxygen consumption rate (r\\Vdot O2). The rBF and r\\Vdot O2 signals were calibrated with absolute baseline BF and \\Vdot O2 obtained through venous and arterial occlusions, respectively. Known problems with muscle-fiber motion artifacts in optical measurements during exercise were mitigated using a novel gating algorithm that determined muscle contraction status based on control signals from a dynamometer. Results were consistent with previous findings in the literature. This study supports the application of NIRS/DCS technology to quantitatively evaluate hemodynamic and metabolic parameters in exercising skeletal muscle and holds promise for improving diagnosis and treatment evaluation for patients suffering from diseases affecting skeletal muscle and advancing fundamental understanding of muscle and exercise physiology.

  7. Real-time frequency-domain fiber optic sensor for intra-arterial blood oxygen measurements

    NASA Astrophysics Data System (ADS)

    Alcala, J. R.; Scott, Ian L.; Parker, Jennifer W.; Atwater, Beauford W.; Yu, Clement; Fischer, Russell; Bellingrath, K.

    1993-05-01

    A real time frequency domain phosphorimeter capable of measuring precise and accurate excited state lifetimes for determining oxygen is described. This frequency domain instrument does not make use of cross correlation techniques traditionally used in frequency domain fluorometers. Instead, the electrical signal from the detector is filtered to contain only the first several harmonics. This filtered signal is then sampled and averaged over a few thousand cycles. The absolute phase and absolute modulation of each sampled harmonic of the excitation and of the luminescence is computed by employing fast Fourier transform algorithms. The phase delay and the modulation ratio is then calculated at each harmonic frequency. A least squares fit is performed in the frequency domain to obtain the lifetimes of discrete exponentials. Oxygen concentrations are computed from these lifetimes. Prototypes based on these techniques were built employing commercially available components. Results from measurements in saline solution and in the arterial blood of dogs show that oxygen concentrations can be determined reproducibly. The system drift is less than 1% in over 100 hours of continuous operation. The performance of fiber optic sensors was evaluated in dogs over a period of 10 hours. The sensors tracked changes in arterial oxygen tension over the course of the experiment without instabilities. The overall response of the system was about 90 seconds. The update time was 3 seconds.

  8. High resolution kilometric range optical telemetry in air by radio frequency phase measurement

    NASA Astrophysics Data System (ADS)

    Guillory, Joffray; Šmíd, Radek; García-Márquez, Jorge; Truong, Daniel; Alexandre, Christophe; Wallerand, Jean-Pierre

    2016-07-01

    We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances up to 1.2 km.

  9. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  10. The Optically Pumped Cs Frequency Standard at the NRLM

    DTIC Science & Technology

    1987-12-01

    References 1. J.L. Picqu6, "Hyperfine optical pumping of a cesium atomic beam, and applications," Metrologia, vo1.13, pp.115-119, 1977. 2. M. Arditi and... Arditi , "A caesium beam atomic clock with laser optical pumping, as a potential frequency standard," Metrologia, vo1.18, pp.59-66, 1982. 4. G

  11. Spectroscopy of Metamaterials from Infrared to Optical Frequencies

    DTIC Science & Technology

    2006-03-01

    negative permeability,” Phys. Rev. Lett. 94, 37402 (2005). 14. F . Wooten , Optical Properties of Solids (Academic, 1972). 15. For example, see M. Born...for materials with differ- ent symmetry properties of the constitutive relations. The terms and are called the magneto- optical permittivi- ties...Spectroscopy of metamaterials from infrared to optical frequencies Willie J. Padilla Materials Science and Technology Division, Center for Integrated

  12. Improved optical frequency standards at 612 nm

    SciTech Connect

    Bertinetto, F.; Cordiale, P.; Fontana, S.

    1994-12-31

    Using FM Spectroscopy as the detection method in an experiment of optical saturation absorption, a fractional stability (Allan variance) of 5 x 10{sup -14} has been observed for an integration time of 10{sup 3} s, and a reproducibility better than 1 part in 10{sup 11} has been achieved.

  13. Temporal dynamics of sand dune bidirectional reflectance characteristics for absolute radiometric calibration of optical remote sensing data

    NASA Astrophysics Data System (ADS)

    Coburn, Craig A.; Logie, Gordon; Beaver, Jason

    2016-09-01

    The use of Pseudo Invariant Calibration Sites (PICS) for establishing the radiometric trending of optical remote sensing systems has a long history of successful implementation. Past studies have shown that the PICS method is useful for evaluating the trend of sensors over time or cross-calibration of sensors but was not considered until recently for deriving absolute calibration. Current interest in using this approach to establish absolute radiometric calibration stems from recent research that indicates that with empirically derived models of the surface properties and careful atmospheric characterisation Top of Atmosphere (TOA) reflectance values can be predicted and used for absolute sensor radiometric calibration. Critical to the continued development of this approach is the accurate characterization of the Bidirectional Reflectance Distribution Function (BRDF) of PICS sites. This paper presents BRDF data collected by a high-performance portable goniometer system in order to develop a temporal BRDF model for the Algodones Dunes in California. The results demonstrated that the BRDF of a reasonably simple sand surface was complex with changes in anisotropy taking place in response to changing solar zenith angles. The nature of these complex interactions would present challenges to future model development.

  14. Measurement of absolute CO number densities in CH3F/O2 plasmas by optical emission self-actinometry

    NASA Astrophysics Data System (ADS)

    Karakas, Erdinc; Kaler, Sanbir; Lou, Qiaowei; Donnelly, Vincent M.; Economou, Demetre J.

    2014-02-01

    CH3F/O2 inductively coupled plasmas at 10 mTorr were investigated using optical emission spectroscopy. A ‘self-actinometry’ method was developed to measure the absolute number density of CO that formed in reactions following dissociation of CH3F and O2 in the plasma. In this method, small amounts of CO were added to the plasma, leading to small increases in the CO emission intensity. By carefully accounting for small perturbations to the plasma electron density and/or electron energy distribution, and by showing that very little of the CO added to the plasma was decomposed by electron impact or other reactions, it was possible to derive absolute number densities for the CO content of the plasma. With equal fractions (0.50) of CH3F and O2 in the feed gas, the CO mole fraction as a function of plasma power saturated at a value of 0.20-0.25. As O2 in the feed gas was varied at a constant power of 100 W, the CO mole fraction went through a maximum of about 0.25 near an O2 feed gas fraction of 0.5. The relative CO number densities determined by ‘standard’ actinometry followed the same functional dependence as the absolute mole fractions determined by self-actinometry, aided by the fact that electron temperature did not change appreciably with power or feed gas composition.

  15. Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

    DOEpatents

    Georgiades, Nikos P.; Polzik, Eugene S.; Kimble, H. Jeff

    1999-02-02

    An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100's THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 .mu.m to 1.66 .mu.m for fiber optics can be accomplished with a nearly continuous frequency coverage.

  16. Opto-electronic device for frequency standard generation and terahertz-range optical demodulation based on quantum interference

    DOEpatents

    Georgiades, N.P.; Polzik, E.S.; Kimble, H.J.

    1999-02-02

    An opto-electronic system and technique for comparing laser frequencies with large frequency separations, establishing new frequency standards, and achieving phase-sensitive detection at ultra high frequencies are disclosed. Light responsive materials with multiple energy levels suitable for multi-photon excitation are preferably used for nonlinear mixing via quantum interference of different excitation paths affecting a common energy level. Demodulation of a carrier with a demodulation frequency up to 100`s THZ can be achieved for frequency comparison and phase-sensitive detection. A large number of materials can be used to cover a wide spectral range including the ultra violet, visible and near infrared regions. In particular, absolute frequency measurement in a spectrum from 1.25 {micro}m to 1.66 {micro}m for fiber optics can be accomplished with a nearly continuous frequency coverage. 7 figs.

  17. Near infrared standard sources, generated by electro-optic frequency comb, using injection-locked DFB laser

    NASA Astrophysics Data System (ADS)

    Lee, Sung Hun; Suh, Ho Suhng

    2014-02-01

    Stable, near-infrared laser sources were generated by an electro-optic modulator with selected comb-mode seeding. The single comb mode was selected from the fiber laser comb using a Fabry-Pèrot cavity (FPC) of 1.25 GHz spacing, and injection locking technique. An electro-optic frequency comb (EOFC) with spacing of 25 GHz was generated as the side mode of the injection-locked comb mode. Using a single mode of the EOFC, we measured the frequency of the acetylene stabilized laser used as the calibration reference frequency light source for optical communication. The absolute frequency and estimated stability of the acetylene stabilized laser were 194 369 569 384.6 kHz and 2.3×10-12 (average time 1 s), respectively.

  18. Modal Frequency Detection in Composite Beams Using Fiber Optic Sensors

    DTIC Science & Technology

    2011-07-28

    optic sensors showed more sensitivity and better signal-to-noise ratios. The analytical classical beam theory and a finite element model validated the...61 C. INPUT AND OUTPUT FOR THE FINITE ELEMENT MODEL ..... 88 B IB LIO G RA PH Y...beam compared to MATLAB generated frequencies of classical beam theory and frequencies calculated using a finite element model (FEM

  19. Absolute Calibration of Optical Satellite Sensors Using Libya 4 Pseudo Invariant Calibration Site

    NASA Technical Reports Server (NTRS)

    Mishra, Nischal; Helder, Dennis; Angal, Amit; Choi, Jason; Xiong, Xiaoxiong

    2014-01-01

    The objective of this paper is to report the improvements in an empirical absolute calibration model developed at South Dakota State University using Libya 4 (+28.55 deg, +23.39 deg) pseudo invariant calibration site (PICS). The approach was based on use of the Terra MODIS as the radiometer to develop an absolute calibration model for the spectral channels covered by this instrument from visible to shortwave infrared. Earth Observing One (EO-1) Hyperion, with a spectral resolution of 10 nm, was used to extend the model to cover visible and near-infrared regions. A simple Bidirectional Reflectance Distribution function (BRDF) model was generated using Terra Moderate Resolution Imaging Spectroradiometer (MODIS) observations over Libya 4 and the resulting model was validated with nadir data acquired from satellite sensors such as Aqua MODIS and Landsat 7 (L7) Enhanced Thematic Mapper (ETM+). The improvements in the absolute calibration model to account for the BRDF due to off-nadir measurements and annual variations in the atmosphere are summarized. BRDF models due to off-nadir viewing angles have been derived using the measurements from EO-1 Hyperion. In addition to L7 ETM+, measurements from other sensors such as Aqua MODIS, UK-2 Disaster Monitoring Constellation (DMC), ENVISAT Medium Resolution Imaging Spectrometer (MERIS) and Operational Land Imager (OLI) onboard Landsat 8 (L8), which was launched in February 2013, were employed to validate the model. These satellite sensors differ in terms of the width of their spectral bandpasses, overpass time, off-nadir-viewing capabilities, spatial resolution and temporal revisit time, etc. The results demonstrate that the proposed empirical calibration model has accuracy of the order of 3% with an uncertainty of about 2% for the sensors used in the study.

  20. On the Absolute Age of the Metal-rich Globular M71 (NGC 6838). I. Optical Photometry

    NASA Astrophysics Data System (ADS)

    Di Cecco, A.; Bono, G.; Prada Moroni, P. G.; Tognelli, E.; Allard, F.; Stetson, P. B.; Buonanno, R.; Ferraro, I.; Iannicola, G.; Monelli, M.; Nonino, M.; Pulone, L.

    2015-08-01

    We investigated the absolute age of the Galactic globular cluster M71 (NGC 6838) using optical ground-based images (u\\prime ,g\\prime ,r\\prime ,i\\prime ,z\\prime ) collected with the MegaCam camera at the Canada-France-Hawaii Telescope (CFHT). We performed a robust selection of field and cluster stars by applying a new method based on the 3D (r\\prime ,u\\prime -g\\prime ,g\\prime -r\\prime ) color-color-magnitude diagram. A comparison between the color-magnitude diagram (CMD) of the candidate cluster stars and a new set of isochrones at the locus of the main sequence turn-off (MSTO) suggests an absolute age of 12 ± 2 Gyr. The absolute age was also estimated using the difference in magnitude between the MSTO and the so-called main sequence knee, a well-defined bending occurring in the lower main sequence. This feature was originally detected in the near-infrared bands and explained as a consequence of an opacity mechanism (collisionally induced absorption of molecular hydrogen) in the atmosphere of cool low-mass stars. The same feature was also detected in the r‧, u\\prime -g\\prime , and in the r\\prime ,g\\prime -r\\prime CMD, thus supporting previous theoretical predictions by Borysow et al. The key advantage in using the {{{Δ }}}{TO}{Knee} as an age diagnostic is that it is independent of uncertainties affecting the distance, the reddening, and the photometric zero point. We found an absolute age of 12 ± 1 Gyr that agrees, within the errors, with similar age estimates, but the uncertainty is on average a factor of two smaller. We also found that the {{{Δ }}}{TO}{Knee} is more sensitive to the metallicity than the MSTO, but the dependence vanishes when using the difference in color between the MSK and the MSTO.

  1. Water wave frequency detection by optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyi; Bao, Xiaoyi; Rennie, Colin D.; Nistor, Ioan; Cornett, Andrew

    2008-12-01

    An optical fiber sensor has been developed and applied to measure frequency of water waves based on wave induced polarization change of the light. The fiber sensor can accurately detect water wave frequency for regular and irregular waves. The optimum sag of sensing fiber to the sensor output's linearity has been studied. The agreement of the fiber sensor and wave gauge in frequency and time domain suggests that the fiber sensor has great potential for passive acoustic sensing and wave monitoring.

  2. Compensated Fiber-Optic Frequency Distribution Equipment

    DTIC Science & Technology

    2010-11-01

    availability of long- haul components at 1550 nm. If installing a new system with new fiber, it may also make sense to use dispersion-shifted fiber, which...selected the 1550 nm (C-Band) for the optical wavelength. Although this wavelength requires CD correction in long haul systems, it makes good sense for...CD, we place both lasers on the same ITU channel, and adjust their center wavelengths to within a few GHz of each other. Ideally, the two signals

  3. Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue

    NASA Astrophysics Data System (ADS)

    Kienle, Alwin; Lilge, Lothar; Patterson, Michael S.; Hibst, Raimund; Steiner, Rudolf; Wilson, Brian C.

    1996-05-01

    The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm-1 and absorption coefficients between 0.002 and 0.1 mm -1 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle (breast), were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam. Carlo, neural network.

  4. Optical Frequency Standards Based on Neutral Atoms and Molecules

    NASA Astrophysics Data System (ADS)

    Riehle, Fritz; Helmcke, Juergen

    The current status and prospects of optical frequency standards based on neutral atomic and molecular absorbers are reviewed. Special attention is given to an optical frequency standard based on cold Ca atoms which are interrogated with a pulsed excitation scheme leading to resolved line structures with a quality factor Q > 10^12. The optical frequency was measured by comparison with PTB's primary clock to be νCa = 455 986 240 494.13 kHz with a total relative uncertainty of 2.5 x10^-13. After a recent recommendation of the International Committee of Weights and Measures (CIPM), this frequency standard now represents one of the most accurate realizations of the length unit.

  5. Photon frequency-mode matching using acousto-optic frequency beam splitters

    SciTech Connect

    Jones, Nick S.; Stace, T. M.

    2006-03-15

    It is a difficult engineering task to create distinct solid state single photon sources which nonetheless emit photons at the same frequency. It is also hard to create entangled photon pairs from quantum dots. In the spirit of quantum engineering we propose a simple optical circuit which can, in the right circumstances, make frequency distinguishable photons frequency indistinguishable. Our circuit can supply a downstream solution to both problems, opening up a large window of allowed frequency mismatches between physical mechanisms. The only components used are spectrum analysers or prisms and an acousto-optic modulator. We also note that an acousto-optic modulator can be used to obtain Hong-Ou-Mandel two photon interference effects from the frequency distinguishable photons generated by distinct sources.

  6. Absolute measurement of cerebral optical coefficients, hemoglobin concentration and oxygen saturation in old and young adults with near-infrared spectroscopy.

    PubMed

    Hallacoglu, Bertan; Sassaroli, Angelo; Wysocki, Michael; Guerrero-Berroa, Elizabeth; Schnaider Beeri, Michal; Haroutunian, Vahram; Shaul, Merav; Rosenberg, Irwin H; Troen, Aron M; Fantini, Sergio

    2012-08-01

    We present near-infrared spectroscopy measurement of absolute cerebral hemoglobin concentration and saturation in a large sample of 36 healthy elderly (mean age, 85 ± 6 years) and 19 young adults (mean age, 28 ± 4 years). Non-invasive measurements were obtained on the forehead using a commercially available multi-distance frequency-domain system and analyzed using a diffusion theory model for a semi-infinite, homogeneous medium with semi-infinite boundary conditions. Our study included repeat measurements, taken five months apart, on 16 elderly volunteers that demonstrate intra-subject reproducibility of the absolute measurements with cross-correlation coefficients of 0.9 for absorption coefficient (μa), oxy-hemoglobin concentration ([HbO2]), and total hemoglobin concentration ([HbT]), 0.7 for deoxy-hemoglobin concentration ([Hb]), 0.8 for hemoglobin oxygen saturation (StO2), and 0.7 for reduced scattering coefficient (μ's). We found significant differences between the two age groups. Compared to young subjects, elderly subjects had lower cerebral [HbO2], [Hb], [HbT], and StO2 by 10 ± 4 μM, 4 ± 3 μM, 14 ± 5 μM, and 6%±5%, respectively. Our results demonstrate the reliability and robustness of multi-distance near-infrared spectroscopy measurements based on a homogeneous model in the human forehead on a large sample of human subjects. Absolute, non-invasive optical measurements on the brain, such as those presented here, can significantly advance the development of NIRS technology as a tool for monitoring resting/basal cerebral perfusion, hemodynamics, oxygenation, and metabolism.

  7. Fast frequency hopping codes applied to SAC optical CDMA network

    NASA Astrophysics Data System (ADS)

    Tseng, Shin-Pin

    2015-06-01

    This study designed a fast frequency hopping (FFH) code family suitable for application in spectral-amplitude-coding (SAC) optical code-division multiple-access (CDMA) networks. The FFH code family can effectively suppress the effects of multiuser interference and had its origin in the frequency hopping code family. Additional codes were developed as secure codewords for enhancing the security of the network. In considering the system cost and flexibility, simple optical encoders/decoders using fiber Bragg gratings (FBGs) and a set of optical securers using two arrayed-waveguide grating (AWG) demultiplexers (DeMUXs) were also constructed. Based on a Gaussian approximation, expressions for evaluating the bit error rate (BER) and spectral efficiency (SE) of SAC optical CDMA networks are presented. The results indicated that the proposed SAC optical CDMA network exhibited favorable performance.

  8. Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms

    PubMed Central

    Zhang, S. Y.; Wu, J. T.; Zhang, Y. L.; Leng, J. X.; Yang, W. P.; Zhang, Z. G.; Zhao, J. Y.

    2015-01-01

    Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios. PMID:26459877

  9. Direct frequency comb optical frequency standard based on two-photon transitions of thermal atoms.

    PubMed

    Zhang, S Y; Wu, J T; Zhang, Y L; Leng, J X; Yang, W P; Zhang, Z G; Zhao, J Y

    2015-10-13

    Optical clocks have been the focus of science and technology research areas due to their capability to provide highest frequency accuracy and stability to date. Their superior frequency performance promises significant advances in the fields of fundamental research as well as practical applications including satellite-based navigation and ranging. In traditional optical clocks, ultrastable optical cavities, laser cooling and particle (atoms or a single ion) trapping techniques are employed to guarantee high stability and accuracy. However, on the other hand, they make optical clocks an entire optical tableful of equipment, and cannot work continuously for a long time; as a result, they restrict optical clocks used as very convenient and compact time-keeping clocks. In this article, we proposed, and experimentally demonstrated, a novel scheme of optical frequency standard based on comb-directly-excited atomic two-photon transitions. By taking advantage of the natural properties of the comb and two-photon transitions, this frequency standard achieves a simplified structure, high robustness as well as decent frequency stability, which promise widespread applications in various scenarios.

  10. A method of developing frequency encoded multi-bit optical data comparator using semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Garai, Sisir Kumar

    2011-02-01

    Optical data comparator is the part and parcel of arithmetic and logical unit of any optical data processor and it is working as a building block in a larger optical circuit, as an optical switch in all optical header processing and optical packet switching based all optical telecommunications system. In this article the author proposes a method of developing an all optical single bit comparator unit and subsequently extending the proposal to develop a n-bit comparator exploiting the nonlinear rotation of the state of polarization of the probe beam in semiconductor optical amplifier (SOA). Here the dataset to be compared are taken in frequency encoded/decoded form throughout the communication. The major advantages of frequency encoding over all other conventional techniques are that as the frequency of any signal is fundamental one so it can preserve its identity throughout the communication of optical signal and minimizes the probability of bit error problem. For frequency routing purpose optical add/drop multiplexer (ADM) is used which not only route the pump beams properly but also to amplify the pump beams efficiently. Switching speed of 'MZI-SOA switch' as well as SOA based switches are very fast with good on-off contrast ratio and as a result it is possible to obtain very fast action of optical data comparator.

  11. Positioning, alignment and absolute pointing of the ANTARES neutrino telescope

    NASA Astrophysics Data System (ADS)

    Fehr, F.; Distefano, C.; Antares Collaboration

    2010-01-01

    A precise detector alignment and absolute pointing is crucial for point-source searches. The ANTARES neutrino telescope utilises an array of hydrophones, tiltmeters and compasses for the relative positioning of the optical sensors. The absolute calibration is accomplished by long-baseline low-frequency triangulation of the acoustic reference devices in the deep-sea with a differential GPS system at the sea surface. The absolute pointing can be independently verified by detecting the shadow of the Moon in cosmic rays.

  12. Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system

    NASA Astrophysics Data System (ADS)

    Baltzer, M. M.; Craig, D.; Den Hartog, D. J.; Nishizawa, T.; Nornberg, M. D.

    2016-11-01

    An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

  13. Absolute wavelength calibration of a Doppler spectrometer with a custom Fabry-Perot optical system.

    PubMed

    Baltzer, M M; Craig, D; Den Hartog, D J; Nishizawa, T; Nornberg, M D

    2016-11-01

    An Ion Doppler Spectrometer (IDS) is used for fast measurements of C VI line emission (343.4 nm) in the Madison Symmetric Torus. Absolutely calibrated flow measurements are difficult because the IDS records data within 0.25 nm of the line. Commercial calibration lamps do not produce lines in this narrow range. A light source using an ultraviolet LED and etalon was designed to provide a fiducial marker 0.08 nm wide. The light is coupled into the IDS at f/4, and a holographic diffuser increases homogeneity of the final image. Random and systematic errors in data analysis were assessed. The calibration is accurate to 0.003 nm, allowing for flow measurements accurate to 3 km/s. This calibration is superior to the previous method which used a time-averaged measurement along a chord believed to have zero net Doppler shift.

  14. Frequency domain optical tomography using a Monte Carlo perturbation method

    NASA Astrophysics Data System (ADS)

    Yamamoto, Toshihiro; Sakamoto, Hiroki

    2016-04-01

    A frequency domain Monte Carlo method is applied to near-infrared optical tomography, where an intensity-modulated light source with a given modulation frequency is used to reconstruct optical properties. The frequency domain reconstruction technique allows for better separation between the scattering and absorption properties of inclusions, even for ill-posed inverse problems, due to cross-talk between the scattering and absorption reconstructions. The frequency domain Monte Carlo calculation for light transport in an absorbing and scattering medium has thus far been analyzed mostly for the reconstruction of optical properties in simple layered tissues. This study applies a Monte Carlo calculation algorithm, which can handle complex-valued particle weights for solving a frequency domain transport equation, to optical tomography in two-dimensional heterogeneous tissues. The Jacobian matrix that is needed to reconstruct the optical properties is obtained by a first-order "differential operator" technique, which involves less variance than the conventional "correlated sampling" technique. The numerical examples in this paper indicate that the newly proposed Monte Carlo method provides reconstructed results for the scattering and absorption coefficients that compare favorably with the results obtained from conventional deterministic or Monte Carlo methods.

  15. Fiber optic reference frequency distribution to remote beam waveguide antennas

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Kuhnle, Paul; Law, Julius

    1995-01-01

    In the NASA/JPL Deep Space Network (DSN), radio science experiments (probing outer planet atmospheres, rings, gravitational waves, etc.) and very long-base interferometry (VLBI) require ultra-stable, low phase noise reference frequency signals at the user locations. Typical locations for radio science/VLBI exciters and down-converters are the cone areas of the 34 m high efficiency antennas or the 70 m antennas, located several hundred meters from the reference frequency standards. Over the past three years, fiber optic distribution links have replaced coaxial cable distribution for reference frequencies to these antenna sites. Optical fibers are the preferred medium for distribution because of their low attenuation, immunity to EMI/IWI, and temperature stability. A new network of Beam Waveguide (BWG) antennas presently under construction in the DSN requires hydrogen maser stability at tens of kilometers distance from the frequency standards central location. The topic of this paper is the design and implementation of an optical fiber distribution link which provides ultra-stable reference frequencies to users at a remote BWG antenna. The temperature profile from the earth's surface to a depth of six feet over a time period of six months was used to optimize the placement of the fiber optic cables. In-situ evaluation of the fiber optic link performance indicates Allan deviation on the order of parts in 10(exp -15) at 1000 and 10,000 seconds averaging time; thus, the link stability degradation due to environmental conditions still preserves hydrogen maser stability at the user locations. This paper reports on the implementation of optical fibers and electro-optic devices for distributing very stable, low phase noise reference signals to remote BWG antenna locations. Allan deviation and phase noise test results for a 16 km fiber optic distribution link are presented in the paper.

  16. A scheme of developing frequency encoded tristate-optical logic operations using semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Garai, Sisir Kumar

    2010-03-01

    The ever increasing demand for very fast and agile optical networks requires very fast execution of different optical and logical operations as well as large information handling capacities at the same time. In conventional binary logic based operations the information is represented by two distinct states only (0 and 1 state). It limits the large information handling capacity and speed of different arithmetic and optical logic operations. Tristate based logic operations can be accommodated with optics successfully in data processing, as this type of operation can enhance the speed of operation as well as increase the information handling capacity. Here in this communication the author proposes a new method to implement all-optical different logic gates with tristate logic using the frequency-encoding principle. The frequency encoding/decoding based optical communication has distinctly great advantages because the frequency is the fundamental character of an optical signal and it preserves its identity throughout the communication. The principle of the rotation of the state of polarization of a probe beam through semiconductor optical amplifier (SOA), frequency routing property of an optical add/drop multiplexer (AD) and high frequency conversion property of reflecting semiconductor optical amplifiers (RSOA) have been exploited here to implement the desired AND, OR, NAND and NOR logic operations with tristate logic.

  17. Mounting system for optical frequency reference cavities

    NASA Technical Reports Server (NTRS)

    Notcutt, Mark (Inventor); Hall, John L. (Inventor); Ma, Long-Sheng (Inventor)

    2008-01-01

    A technique for reducing the vibration sensitivity of laser-stabilizing optical reference cavities is based upon an improved design and mounting method for the cavity, wherein the cavity is mounted vertically. It is suspended at one plane, around the spacer cylinder, equidistant from the mirror ends of the cavity. The suspension element is a collar of an extremely low thermal expansion coefficient material, which surrounds the spacer cylinder and contacts it uniformly. Once the collar has been properly located, it is cemented in place so that the spacer cylinder is uniformly supported and does not have to be squeezed at all. The collar also includes a number of cavities partially bored into its lower flat surface, around the axial bore. These cavities are support points, into which mounting base pins will be inserted. Hence the collar is supported at a minimum of three points.

  18. Frequency noise processes in a strontium ion optical clock

    NASA Astrophysics Data System (ADS)

    Barwood, G. P.; Huang, G.; King, S. A.; Klein, H. A.; Gill, P.

    2015-02-01

    A recent comparison of the frequencies of a pair of optical clocks based on the 674 nm 2S1/2-2D5/2 optical clock transition in 88Sr+ has highlighted the need to understand factors affecting frequency instability. We have developed statistical models to show that our clock is capable of reaching the quantum projection noise limit; for our clock using 100 ms probe pulses, this is ˜3 × 10-15/√τ. However, this optical clock uses atomic transitions with a linear Zeeman shift, which can lead to a degradation in stability in the presence of magnetic field noise. We show that this generally leads to an increase in white frequency noise, even in cases dominated by magnetic field flicker or random walk noise. By taking into account both the quantum projection and magnetic field noise we are able to explain our observed frequency instabilities. This analysis will relate to any optical clock with a linear Zeeman shift where cancellation of this shift is achieved by interrogating pairs of components. Furthermore, implementing automatic control of lasers and minimization of micromotion requires pausing of the frequency servo occasionally; this leads to only a small degradation of frequency stability.

  19. Phase and frequency tracking considerations for heterodyne optical communications

    NASA Astrophysics Data System (ADS)

    Kaufmann, J. E.

    Heterodyne optical communications systems represent a potential for substantial performance improvement over direct detection systems. Certain difficulties can arise, however, in heterodyne systems, in connection with a frequency instability of the employed laser. In general, frequency or phase tracking will be needed at the receiver to avoid significant degradations in communications performance and requirements for increased transmitter power unless very stable lasers are available. The present investigation is concerned with receiver phase and frequency tracking schemes suitable for heterodyne PSK and MFSK (multilevel frequency-shift-keying) systems in a space communications context, although this work is also applicable to fiberoptic systems.

  20. Optical techniques for time and frequency transfer

    NASA Technical Reports Server (NTRS)

    Baumont, Francoise; Gaignebet, Jean

    1994-01-01

    Light has been used as a means for time synchronization for a long time. The flight time was supposed to be negligible. The first scientific determination of the velocity of the light was done by measuring a round trip flight time on a given distance. The well known flying clock experiment leading to Einstein's General Relativity is another example. The advent of lasers, particularly short pulse and modulated ones, as well as the improvements of the timing equipments have led to new concepts for time and frequency transfer. We describe some experiments using different techniques and configurations which have been proposed and tested in this field since the beginning of the space age. Added to that, we set out advantages, drawbacks, and performances achieved in the different cases.

  1. Ultra-broadband microwave frequency down-conversion based on optical frequency comb.

    PubMed

    Fang, Xiao; Bai, Ming; Ye, Xiuzhu; Miao, Jungang; Zheng, Zheng

    2015-06-29

    Based on optical frequency comb (OFC), a photonic-assisted ultra-broadband microwave signal down-converting method is proposed. In the proposed scheme, microwave signal at 2~20GHz can be down-converted to 0~1GHz intermediate frequency (IF) signals by an OFC of 2GHz frequency space at different order of comb lines. By slightly switching the frequency space of OFC, the frequency of the signal to be measured can be retrieved through the frequency shift of the down-converted IF signal. The validity of this proposed unknown signal detection method is verified by the experiments. The proposed method is proven to be flexible, low-cost and easily implemented, which requires only a low-frequency tunable microwave source while provides ultra-broadband down-converting frequency range.

  2. Revealing carrier-envelope phase through frequency mixing and interference in frequency resolved optical gating.

    PubMed

    Snedden, E W; Walsh, D A; Jamison, S P

    2015-04-06

    We demonstrate that full temporal characterisation of few-cycle electromagnetic pulses, including retrieval of the carrier envelope phase (CEP), can be directly obtained from Frequency Resolved Optical Gating (FROG) techniques in which the interference between non-linear frequency mixing processes is resolved. We derive a framework for this scheme, defined Real Domain FROG (ReD-FROG), for the cases of interference between sum and difference frequency components and between fundamental and sum / difference frequency components. A successful numerical demonstration of ReD-FROG as applied to the case of a self-referenced measurement is provided. A proof-of-principle experiment is performed in which the CEP of a single-cycle THz pulse is accurately obtained and demonstrates the possibility for THz detection beyond optical probe duration limitations inherent to electro-optic sampling.

  3. Femtosecond fibre laser stabilisation to an optical frequency standard using a KTP electro-optic crystal

    SciTech Connect

    Nyushkov, B N; Pivtsov, V S; Koliada, N A; Kaplun, A B; Meshalkin, A B

    2015-05-31

    A miniature intracavity KTP-based electro-optic phase modulator has been developed which can be used for effective stabilisation of an optical frequency comb of a femtosecond erbiumdoped fibre laser to an optical frequency standard. The use of such an electro-optic modulator (EOM) has made it possible to extend the working frequency band of a phase-locked loop system for laser stabilisation to several hundred kilohertz. We demonstrate that the KTP-based EOM is sufficiently sensitive even at a small optical length, which allows it to be readily integrated into cavities of femtosecond fibre lasers with high mode frequency spacings (over 100 MHz). (extreme light fields and their applications)

  4. Optical-fiber frequency domain interferometer with nanometer resolution and centimeter measuring range.

    PubMed

    Weng, Jidong; Tao, Tianjiong; Liu, Shenggang; Ma, Heli; Wang, Xiang; Liu, Cangli; Tan, Hua

    2013-11-01

    A new optical-fiber frequency domain interferometer (OFDI) device for accurate measurement of the absolute distance between two stationary objects, with centimeter measuring range and nanometer resolution, has been developed. Its working principle and on-line data processing method were elaborated. The new OFDI instrument was constructed all with currently available commercial communication products. It adopted the wide-spectrum amplified spontaneous emission light as the light source and optical-fiber tip as the test probe. Since this device consists of only fibers or fiber coupled components, it is very compact, convenient to operate, and easy to carry. By measuring the single-step length of a translation stage and the thickness of standard gauge blocks, its ability in implementing nanometer resolution and centimeter measuring range on-line measurements was validated.

  5. Measurement of absolute transition frequencies of {sup 87}Rb to nS and nD Rydberg states by means of electromagnetically induced transparency

    SciTech Connect

    Mack, Markus; Karlewski, Florian; Hattermann, Helge; Hoeckh, Simone; Jessen, Florian; Cano, Daniel; Fortagh, Jozsef

    2011-05-15

    We report the measurement of absolute excitation frequencies of {sup 87}Rb to nS and nD Rydberg states. The Rydberg transition frequencies are obtained by observing electromagnetically induced transparency on a rubidium vapor cell. The accuracy of the measurement of each state is < or approx. 1 MHz, which is achieved by frequency stabilizing the two diode lasers employed for the spectroscopy to a frequency comb and a frequency comb calibrated wavelength meter, respectively. Based on the spectroscopic data we determine the quantum defects of {sup 87}Rb, and compare it with previous measurements on {sup 85}Rb. We determine the ionization frequency from the 5S{sub 1/2}(F=1) ground state of {sup 87}Rb to 1010.029 164 6(3)THz, providing the binding energy of the ground state with an accuracy improved by two orders of magnitude.

  6. One-way quantum computing in the optical frequency comb.

    PubMed

    Menicucci, Nicolas C; Flammia, Steven T; Pfister, Olivier

    2008-09-26

    One-way quantum computing allows any quantum algorithm to be implemented easily using just measurements. The difficult part is creating the universal resource, a cluster state, on which the measurements are made. We propose a scalable method that uses a single, multimode optical parametric oscillator (OPO). The method is very efficient and generates a continuous-variable cluster state, universal for quantum computation, with quantum information encoded in the quadratures of the optical frequency comb of the OPO.

  7. Optical frequency comb interference profilometry using compressive sensing.

    PubMed

    Pham, Quang Duc; Hayasaki, Yoshio

    2013-08-12

    We describe a new optical system using an ultra-stable mode-locked frequency comb femtosecond laser and compressive sensing to measure an object's surface profile. The ultra-stable frequency comb laser was used to precisely measure an object with a large depth, over a wide dynamic range. The compressive sensing technique was able to obtain the spatial information of the object with two single-pixel fast photo-receivers, with no mechanical scanning and fewer measurements than the number of sampling points. An optical experiment was performed to verify the advantages of the proposed method.

  8. Differential processing for frequency chirp measurement using optical pulse synthesizer

    NASA Astrophysics Data System (ADS)

    Kashiwagi, Ken; Seki, Satoshi; Tsuda, Hiroyuki; Takenouchi, Hirokazu; Kurokawa, Takashi

    2017-03-01

    In this study, we introduced an optical pulse synthesizer (OPS) to measure frequency chirps of optical pulses by differential processing. The OPS has a single-chip integrated structure of all elements for the differential filtering and enables stable measurement. Because the exact filter causes a large loss, we employed a phase-only filter, whose frequency response was only in phase. We measured chirp rates of pulses which were induced by propagating standard single mode fibers with different lengths. The retrieved chirp rates were comparable to calculated results. We simulated accuracy of the method and concluded that our experiment had phase control accuracy within 0.07π.

  9. Rectennas at optical frequencies: How to analyze the response

    SciTech Connect

    Joshi, Saumil; Moddel, Garret

    2015-08-28

    Optical rectennas, antenna-coupled diode rectifiers that receive optical-frequency electromagnetic radiation and convert it to DC output, have been proposed for use in harvesting electromagnetic radiation from a blackbody source. The operation of these devices is qualitatively different from that of lower-frequency rectennas, and their design requires a new approach. To that end, we present a method to determine the rectenna response to high frequency illumination. It combines classical circuit analysis with classical and quantum-based photon-assisted tunneling response of a high-speed diode. We demonstrate the method by calculating the rectenna response for low and high frequency monochromatic illumination, and for radiation from a blackbody source. Such a blackbody source can be a hot body generating waste heat, or radiation from the sun.

  10. Rectennas at optical frequencies: How to analyze the response

    NASA Astrophysics Data System (ADS)

    Joshi, Saumil; Moddel, Garret

    2015-08-01

    Optical rectennas, antenna-coupled diode rectifiers that receive optical-frequency electromagnetic radiation and convert it to DC output, have been proposed for use in harvesting electromagnetic radiation from a blackbody source. The operation of these devices is qualitatively different from that of lower-frequency rectennas, and their design requires a new approach. To that end, we present a method to determine the rectenna response to high frequency illumination. It combines classical circuit analysis with classical and quantum-based photon-assisted tunneling response of a high-speed diode. We demonstrate the method by calculating the rectenna response for low and high frequency monochromatic illumination, and for radiation from a blackbody source. Such a blackbody source can be a hot body generating waste heat, or radiation from the sun.

  11. Multiplexed sub-Doppler spectroscopy with an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Long, D. A.; Fleisher, A. J.; Plusquellic, D. F.; Hodges, J. T.

    2016-12-01

    An optical frequency comb generated with an electro-optic phase modulator and a chirped radio-frequency waveform is used to perform pump-probe spectroscopy on the D1 and D2 transitions of atomic potassium at 770.1 and 766.7 nm, respectively. With a comb tooth spacing of 200 kHz and an optical bandwidth of 2 GHz the hyperfine transitions can be observed simultaneously. Interferograms are recorded in as little as 5 µs (a timescale corresponding to the inverse of the comb tooth spacing). Importantly, the sub-Doppler features can be measured as long as the laser carrier frequency lies within the Doppler profile, thus removing the need for slow scanning or a priori knowledge of the frequencies of the sub-Doppler features. Sub-Doppler optical frequency comb spectroscopy has the potential to dramatically reduce acquisition times and allow for rapid and accurate assignment of complex molecular and atomic spectra which are presently intractable.

  12. Optically transparent frequency selective surfaces on flexible thin plastic substrates

    SciTech Connect

    Dewani, Aliya A. O’Keefe, Steven G.; Thiel, David V.; Galehdar, Amir

    2015-02-15

    A novel 2D simple low cost frequency selective surface was screen printed on thin (0.21 mm), flexible transparent plastic substrate (relative permittivity 3.2). It was designed, fabricated and tested in the frequency range 10-20 GHz. The plane wave transmission and reflection coefficients agreed with numerical modelling. The effective permittivity and thickness of the backing sheet has a significant effect on the frequency characteristics. The stop band frequency reduced from 15GHz (no backing) to 12.5GHz with polycarbonate. The plastic substrate thickness beyond 1.8mm has minimal effect on the resonant frequency. While the inner element spacing controls the stop-band frequency, the substrate thickness controls the bandwidth. The screen printing technique provided a simple, low cost FSS fabrication method to produce flexible, conformal, optically transparent and bio-degradable FSS structures which can find their use in electromagnetic shielding and filtering applications in radomes, reflector antennas, beam splitters and polarizers.

  13. Frequency ratios of optical lattice clocks at the 17th decimal place

    NASA Astrophysics Data System (ADS)

    Katori, Hidetoshi

    2016-05-01

    Optical lattice clocks benefit from a low quantum-projection noise by simultaneously interrogating a large number of atoms, which are trapped in an optical lattice tuned to the ``magic wavelength'' to largely cancel out light shift perturbation in the clock transition. About a thousand atoms enable the clocks to achieve 10-18 instability in a few hours of operation, allowing intensive investigation and control of systematic uncertainties. As optical lattice clocks have reached inaccuracies approaching 10-18, it is now the uncertainty of the SI second (~ 10-16) itself that restricts the measurement of the absolute frequencies of such optical clocks. Direct comparisons of optical clocks are, therefore, the only way to investigate and utilize their superb performance beyond the SI second. In this presentation, we report on frequency comparisons of optical lattice clocks with neutral strontium (87 Sr), ytterbium (171 Yb) and mercury (199 Hg) atoms. By referencing cryogenic Sr clocks, we determine frequency ratios, νYb/νSr and νHg/νSr, of a cryogenic Yb clock and a Hg clock with uncertainty at the mid 10-17 level. Such ratios provide an access to search for temporal variation of the fundamental constants. We also present remote comparisons between cryogenic Sr clocks located at RIKEN and the University of Tokyo over a 30-km-long phase-stabilized fiber link. The gravitational red shift Δν /ν0 ~ 1.1× 10-18 Δh cm-1 reads out the height difference of Δh ~ 15 m between the two clocks with uncertainty of 5 cm, which demonstrates a step towards relativistic geodesy. ERATO, JST.

  14. Frequency-noise measurements of optical frequency combs by multiple fringe-side discriminator

    PubMed Central

    Coluccelli, Nicola; Cassinerio, Marco; Gambetta, Alessio; Laporta, Paolo; Galzerano, Gianluca

    2015-01-01

    The frequency noise of an optical frequency comb is routinely measured through the hetherodyne beat of one comb tooth against a stable continuous-wave laser. After frequency-to-voltage conversion, the beatnote is sent to a spectrum analyzer to retrive the power spectral density of the frequency noise. Because narrow-linewidth continuous-wave lasers are available only at certain wavelengths, heterodyning the comb tooth can be challenging. We present a new technique for direct characterization of the frequency noise of an optical frequency comb, requiring no supplementary reference lasers and easily applicable in all spectral regions from the terahertz to the ultraviolet. The technique is based on the combination of a low finesse Fabry-Perot resonator and the so-called “fringe-side locking” method, usually adopted to characterize the spectral purity of single-frequency lasers, here generalized to optical frequency combs. The effectiveness of this technique is demonstrated with an Er-fiber comb source across the wavelength range from 1 to 2 μm. PMID:26548900

  15. Optoelectronic Infrastructure for Radio Frequency and Optical Phased Arrays

    NASA Technical Reports Server (NTRS)

    Cai, Jianhong

    2015-01-01

    Optoelectronic integrated circuits offer radiation-hardened solutions for satellite systems in addition to improved size, weight, power, and bandwidth characteristics. ODIS, Inc., has developed optoelectronic integrated circuit technology for sensing and data transfer in phased arrays. The technology applies integrated components (lasers, amplifiers, modulators, detectors, and optical waveguide switches) to a radio frequency (RF) array with true time delay for beamsteering. Optical beamsteering is achieved by controlling the current in a two-dimensional (2D) array. In this project, ODIS integrated key components to produce common RF-optical aperture operation.

  16. Novel phase-locking schemes for the carrier envelope offset frequency of an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Okubo, Sho; Onae, Atsushi; Hosaka, Kazumoto; Sera, Hideyuki; Inaba, Hajime; Hong, Feng-Lei

    2015-11-01

    We propose simple schemes to phase-lock the carrier envelope offset frequency (fceo) referring to the repetition rate (frep) of an optical frequency comb. We demonstrate the locking of fceo such that fceo = (1/2)frep, (1/3)frep, and (2/3)frep. The Allan deviation and signal-to-noise ratio of the coherent δ-function peak for the in-loop beat signal are 5.3 × 10-17/τ and 80-85 dB·Hz, respectively, where τ is the averaging time of the frequency measurement. These new locking schemes simplify the sign and mode-number determination in frequency measurements.

  17. Kerr optical frequency combs: theory, applications and perspectives

    NASA Astrophysics Data System (ADS)

    Chembo, Yanne K.

    2016-06-01

    The optical frequency comb technology is one of the most important breakthrough in photonics in recent years. This concept has revolutionized the science of ultra-stable lightwave and microwave signal generation. These combs were originally generated using ultrafast mode-locked lasers, but in the past decade, a simple and elegant alternativewas proposed,which consisted in pumping an ultra-high-Q optical resonator with Kerr nonlinearity using a continuous-wave laser. When optimal conditions are met, the intracavity pump photons are redistributed via four-wave mixing to the neighboring cavity modes, thereby creating the so-called Kerr optical frequency comb. Beyond being energy-efficient, conceptually simple, and structurally robust, Kerr comb generators are very compact devices (millimetric down to micrometric size) which can be integrated on a chip. They are, therefore, considered as very promising candidates to replace femtosecond mode-locked lasers for the generation of broadband and coherent optical frequency combs in the spectral domain, or equivalently, narrow optical pulses in the temporal domain. These combs are, moreover, expected to provide breakthroughs in many technological areas, such as integrated photonics, metrology, optical telecommunications, and aerospace engineering. The purpose of this review article is to present a comprehensive survey of the topic of Kerr optical frequency combs.We provide an overview of the main theoretical and experimental results that have been obtained so far. We also highlight the potential of Kerr combs for current or prospective applications, and discuss as well some of the open challenges that are to be met at the fundamental and applied level.

  18. WGM Resonators for Terahertz-to-Optical Frequency Conversion

    NASA Technical Reports Server (NTRS)

    Strekalov,Dmitry; Savchenkov, Anatoliy; Matsko, Andrey; Nu, Nan

    2008-01-01

    Progress has been made toward solving some practical problems in the implementation of terahertz-to-optical frequency converters utilizing whispering-gallery-mode (WGM) resonators. Such frequency converters are expected to be essential parts of non-cryogenic terahertz- radiation receivers that are, variously, under development or contemplated for a variety of applications in airborne and spaceborne instrumentation for astronomical and military uses. In most respects, the basic principles of terahertz-to-optical frequency conversion in WGM resonators are the same as those of microwave (sub-terahertz)-to-optical frequency conversion in WGM resonators, various aspects of which were discussed in the three preceeding articles. To recapitulate: In a receiver following this approach, a preamplified incoming microwave signal (in the present case, a terahertz signal) is up-converted to an optical signal by a technique that exploits the nonlinearity of the electromagnetic response of a whispering-gallery-mode (WGM) resonator made of LiNbO3 or another suitable electro-optical material. Upconversion takes place by three-wave mixing in the resonator. To ensure the required interaction among the optical and terahertz signals, the WGM resonator must be designed and fabricated to function as an electro-optical modulator while simultaneously exhibiting (1) resonance at the required microwave and optical operating frequencies and (2) phase matching among the microwave and optical signals circulating in the resonator. Downstream of the WGM resonator, the up-converted signal is processed photonically by use of a tunable optical filter or local oscillator and is then detected. The practical problems addressed in the present development effort are the following: Satisfaction of the optical and terahertz resonance-frequency requirement is a straightforward matter, inasmuch as the optical and terahertz spectra can be measured. However, satisfaction of the phase-matching requirement is

  19. Flux of optical meteors down to M sub pg = +12. [photographic absolute magnitude

    NASA Technical Reports Server (NTRS)

    Cook, A. F.; Weekes, T. C.; Williams, J. T.; Omongain, E.

    1980-01-01

    Observations of the flux of optical meteors down to photographic magnitudes of +12 are reported. The meteors were detected by photometry using a 10-m optical reflector from December 12-15, 1974, during the Geminid shower. A total of 2222 light pulses is identified as coming from meteors within the 1 deg field of view of the detector, most of which correspond to sporadic meteors traversing the detector beam at various angles and velocities and do not differ with the date, indicating that the Geminid contribution at faint luminosities is small compared to the sporadic contribution. A rate of 1.1 to 3.3 x 10 to the -12th meteors/sq cm per sec is obtained together with a power law meteor spectrum which is used to derive a relationship between cumulative meteor flux and magnitude which is linear for magnitudes from -2.4 through +12. Expressions for the cumulative flux upon the earth's atmosphere and at a test surface at 1 AU far from the earth as a function of magnitude are also obtained along with an estimate of the cumulative number density of particles.

  20. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    PubMed

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  1. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    PubMed Central

    Shaddad, R. Q.; Mohammad, A. B.; Al-Gailani, S. A.; Al-Hetar, A. M.

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. PMID:24772009

  2. Frequency-domain single-shot optical frequency comb tomography using VIPA

    NASA Astrophysics Data System (ADS)

    Miyaoka, Takumi; Shioda, Tatsutoshi

    2016-03-01

    Novel two-dimensional single-shot imaging optical system based on Frequency-domain interferometry using a virtually imaged phased array is proposed. The VIPA simultaneously outputs incoherent optical frequency combs (OFCs) whose teeth interval are scanned as a function of its output angle. Teeth intervals of the OFCs only in a reference are spatially swept by using of a VIPA whose advantage compared to an optical resonator. Thus, the single-shot imaging system can be realized with the FSR scanned frequency-domain OFC interference monitored by CCD. This system enable high speed 2-dimensional tomographic image without mechanical moving part. And the axial measurement range is not limited by using multi-order interference that is generated by OFCs interferometry. We will present the operation principle with its confirmed results in terms of both simulation and experiment.

  3. Squeezing Alters Frequency Tuning of WGM Optical Resonator

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Maleki, Lute

    2010-01-01

    Mechanical squeezing has been found to alter the frequency tuning of a whispering-gallery-mode (WGM) optical resonator that has an elliptical shape and is made of lithium niobate. It may be possible to exploit this effect to design reconfigurable optical filters for optical communications and for scientific experiments involving quantum electrodynamics. Some background information is prerequisite to a meaningful description of the squeezing-induced alteration of frequency tuning: The spectrum of a WGM resonator is represented by a comblike plot of intensity versus frequency. Each peak of the comblike plot corresponds to an electromagnetic mode represented by an integer mode number, and the modes are grouped into sets represented by integer mode indices. Because lithium niobate is an electro-optically active material, the WGM resonator can be tuned (that is, the resonance frequencies can be shifted) by applying a suitable bias potential. The frequency shift of each mode is quantified by a tuning rate defined as the ratio between the frequency shift and the applied potential. In the absence of squeezing, all modes exhibit the same tuning rate. This concludes the background information. It has been demonstrated experimentally that when the resonator is squeezed along part of either of its two principal axes, tuning rates differ among the groups of modes represented by different indices (see figure). The differences in tuning rates could be utilized to configure the resonance spectrum to obtain a desired effect; for example, through a combination of squeezing and electrical biasing, two resonances represented by different mode indices could be set at a specified frequency difference something that could not be done through electrical biasing alone.

  4. Time division approach to separate overlapped interference fringes of multiple pulse trains of femtosecond optical frequency comb for length measurement

    NASA Astrophysics Data System (ADS)

    Wei, Dong; Aketagawa, Masato

    2017-01-01

    In this study, we attempt the separation of overlapped interference fringes arising from multiple pulse trains of a femtosecond optical frequency comb for length measurement. Based on an optical experiment, we test the performance of the separation of two overlapped interference fringes by time division for an absolute length measurement, which is about one adjacent pulse repetition interval length. We compare our results with those of a commercial He-Ne interferometer system. The two sets of results show an agreement within 0.7 μm.

  5. Optical isotropy at terahertz frequencies using anisotropic metamaterials

    NASA Astrophysics Data System (ADS)

    Lee, In-Sung; Sohn, Ik-Bu; Kang, Chul; Kee, Chul-Sik; Yang, Jin-Kyu; Lee, Joong Wook

    2016-07-01

    We demonstrate optically isotropic filters in the terahertz (THz) frequency range using structurally anisotropic metamaterials. The proposed metamaterials with two-dimensional arrangements of anisotropic H-shaped apertures show polarization-independent transmission due to the combined effects of the dipole resonances of resonators and antennas. Our results may offer the potential for the design and realization of versatile THz devices and systems.

  6. Stabilized Fiber-Optic Distribution of Reference Frequency

    NASA Technical Reports Server (NTRS)

    Calhoun, Malcolm; Tjoelker, Robert; Diener, William; Dick, G. John; Wang, Rabi; Kirk, Albert

    2003-01-01

    An optoelectronic system distributes a reference signal of low noise and highly stabilized phase and frequency (100 MHz) from an atomic frequency standard to a remote facility at a distance up to tens of kilometers. The reference signal is transmitted to the remote station as amplitude modulation of an optical carrier signal propagating in an optical fiber. The stabilization scheme implemented in this system is intended particularly to suppress phase and frequency fluctuations caused by vibrations and by expansion and contraction of the optical fiber and other components in diurnal and seasonal heating and cooling cycles. The system (see figure) comprises several subsystems, the main one being (1) a hydrogen-maser or linear-ion-trap frequency standard in an environmentally controlled room in a signal-processing center (SPC), (2) a stabilized fiber-optic distribution assembly (SFODA), (3) a compensated sapphire oscillator (CSO) in an environmentally controlled room in the remote facility, (4) thermally stabilized distribution amplifiers and cabling from the environmentally controlled room to end users, and (5) performance- measuring equipment.

  7. An optical beam frequency reference with 10{sup -14} range frequency instability

    SciTech Connect

    McFerran, J. J.; Hartnett, J. G.; Luiten, A. N.

    2009-07-20

    The authors report on a thermal beam optical frequency reference with a fractional frequency instability of 9.2x10{sup -14} at 1 s reducing to 2.0x10{sup -14} at 64 s before slowly rising. The {sup 1}S{sub 0}{r_reversible}{sup 3}P{sub 1} intercombination line in neutral {sup 40}Ca is used as a frequency discriminator. A diode laser at 423 nm probes the ground state population after a Ramsey-Borde sequence of 657 nm light-field interactions on the atoms. The measured fractional frequency instability is an order of magnitude improvement on previously reported thermal beam optical clocks. The photon shot-noise of the read-out produces a limiting square root {lambda}-variance of 7x10{sup -14}/{radical}({tau})

  8. Frequency Comparison of Two High-Accuracy Al+ Optical Clocks

    NASA Astrophysics Data System (ADS)

    Chou, C. W.; Hume, D. B.; Koelemeij, J. C. J.; Wineland, D. J.; Rosenband, T.

    2010-02-01

    We have constructed an optical clock with a fractional frequency inaccuracy of 8.6×10-18, based on quantum logic spectroscopy of an Al+ ion. A simultaneously trapped Mg+ ion serves to sympathetically laser cool the Al+ ion and detect its quantum state. The frequency of the S01↔P03 clock transition is compared to that of a previously constructed Al+ optical clock with a statistical measurement uncertainty of 7.0×10-18. The two clocks exhibit a relative stability of 2.8×10-15τ-1/2, and a fractional frequency difference of -1.8×10-17, consistent with the accuracy limit of the older clock.

  9. A rare gas optics-free absolute photon flux and energy analyzer for solar and planetary observations

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    We have developed a prototype spectrometer for space applications requiring long term absolute EUV photon flux measurements. In this recently developed spectrometer, the energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  10. Phase-coherent all-optical frequency division by three

    SciTech Connect

    Lee, Dong-Hoon; Klein, Marvin E.; Meyn, Jan-Peter; Wallenstein, Richard; Gross, Petra; Boller, Klaus-Jochen

    2003-01-01

    The properties of all-optical phase-coherent frequency division by 3, based on a self-phase-locked continuous-wave (cw) optical parametric oscillator (OPO), are investigated theoretically and experimentally. The frequency to be divided is provided by a diode laser master-oscillator power-amplifier system operated at a wavelength of 812 nm and used as the pump source of the OPO. Optical self-phase-locking of the OPO signal and idler waves is achieved by mutual injection locking of the signal wave and the intracavity frequency-doubled idler wave. The OPO process and the second-harmonic generation of the idler wave are simultaneously phase matched through quasi-phase-matching using two periodically poled sections of different period manufactured within the same LiNbO{sub 3} crystal. An optical self-phase-locking range of up to 1 MHz is experimentally observed. The phase coherence of frequency division by three is measured via the phase stability of an interference pattern formed by the input and output waves of the OPO. The fractional frequency instability of the divider is measured to be smaller than 7.6x10{sup -14} for a measurement time of 10 s (resolution limited). The self-phase-locking characteristics of the cw OPO are theoretically investigated by analytically solving the coupled field equations in the steady-state regime. For the experimental parameters of the OPO, the calculations predict a locking range of 1.3 MHz and a fractional frequency instability of 1.6x10{sup -15}, in good agreement with the experimental results.

  11. New optical frequency domain differential mode delay measurement method for a multimode optical fiber.

    PubMed

    Ahn, T; Moon, S; Youk, Y; Jung, Y; Oh, K; Kim, D

    2005-05-30

    A novel mode analysis method and differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.

  12. Optical Frequency Measurements Relying on a Mid-Infrared Frequency Standard

    NASA Astrophysics Data System (ADS)

    Rovera, G. Daniele; Acef, Ouali

    Only a small number of groups are capable of measuring optical frequencies throughout the world. In this contribution we present some of the underlying philosophy of such frequency measurement systems, including some important theoretical hints. In particular, we concentrate on the approach that has been used with the BNM-LPTF frequency chain, where a separate secondary frequency standard in the mid-infrared has been used. The low-frequency section of the chain is characterized by a measurement of the phase noise spectral density Sφ at 716GHz.Most of the significant measurements performed in the last decade are briefly presented, together with a report on the actual stability and reproducibility of the CO2/ OsO4 frequency standard.Measuring the frequency of an optical frequency standard by direct comparison with the signal available at the output of a primary frequency standard (usually between 5MHz and 100MHz) requires a multiplication factor greater than 107. A number of possible configurations, using harmonic generation, sum or difference frequency generation, have been proposed and realized in the past [1,2,3,4,5,6] and in more recent times [7]. A new technique, employing a femtosecond laser, is presently giving its first impressive results [8].All of the classical frequency chains require a large amount of manpower, together with a great deal of simultaneously operating hardware. This has the consequence that only a very few systems are actually in an operating condition throughout the world.

  13. Frequency-range discriminations and absolute pitch in black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata).

    PubMed

    Lee, Tiffany T Y; Charrier, Isabelle; Bloomfield, Laurie L; Weisman, Ronald G; Sturdy, Christopher B

    2006-08-01

    The acoustic frequency ranges in birdsongs provide important absolute pitch cues for the recognition of conspecifics. Black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata) were trained to sort tones contiguous in frequency into 8 ranges on the basis of associations between response to the tones in each range and reward. All 3 species acquired accurate frequency-range discriminations, but zebra finches acquired the discrimination in fewer trials and to a higher standard than black-capped or mountain chickadees, which did not differ appreciably in the discrimination. Chickadees' relatively poorer accuracy was traced to poorer discrimination of tones in the higher frequency ranges. During transfer tests, the discrimination generalized to novel tones when the training tones were included, but not when they were omitted.

  14. Parametric frequency upconversion, optical fiber transmission, and streak camera recording

    SciTech Connect

    Lowry, M.E.; Rotter, M.D.

    1987-01-30

    The use of optical fiber for the transmission of information over relatively long distances is being recognized as the only viable solution to many data transmission problems, particularly those requiring high information density and faithful temporal content. This necessary reliance upon the optical carrier has meant that the image-tube based optical streak camera is often the instrument of choice for recording single-shot multi-parameter events with high temporal resolution. However, current photocathode technology is incompatible with the trend of the optical fiber industry toward the use of the 1300 to 1600 nm wavelength regime. To retain the advantages of optical streak-camera recording and optical fiber transmission, a way must be found to ''upconvert'' the optical carrier to higher energy. This report describes the use of an intense lazer pump beam coincident with the IR signal into a non-linear crystal (LiIO/sub 3/) to increase the signal's frequency. A beam splitter is used to separate the signal from the pump beam at the detector. The physical theory underlying this process is described. (JDH)

  15. Evaluating the thermal stability of multi-pass cells' effective optical path length using optical frequency domain reflectometer

    NASA Astrophysics Data System (ADS)

    Gao, Hong; Cao, Xiuhan; Li, Jinyi; Du, Zhenhui

    2016-10-01

    Multi-pass cells (MPCs) are commonly used to improve the sensitivity for trace gas detection using spectroscopy technologies. The determination of Effective Optical Path Length (EOPL) of a MPC is very important and challenging in applications which aim at absolute measurements. It is well-known that the temperature changing will exercise some influence on the MPCs' spatial structure, however, measurements of the influence haven't been reported which might due to the limitation of measuring method. In this paper, we used a direct high-precision measuring method with Optical Frequency Domain Reflectometer (OFDR) to evaluate the thermal stability of a multi-pass cell. To simulate the environment with a large range of temperature changing, this paper gave a series of experiments by setting the temperature control unit in system from 25 to 175 degree Celsius, and the MPC's EOPL was measured simultaneously for the investigation of temperature response. The results showed that the effective optical path length increase monotonically along with the variation of the temperature, and the rising rate is 0.5 mm/ºC with the total length of about 3 meters which should be pay attention to when the ultra-high accuracy results are demanded. To stabilize the EOPL of the system, if it is possible, the environment temperature of gas cell can be controlled with a constant temperature. In practical applications, the real-time monitoring of EOPL with a direct measuring method may be necessary.

  16. Ratio of the AL+ and HG+ Optical Clock Frequencies to 17 Decimal Places

    NASA Astrophysics Data System (ADS)

    Itano, W. M.; Rosenband, T.; Hume, D. B.; Schmidt, P. O.; Chou, C. W.; Brusch, A.; Lorini, L.; Oskay, W. H.; Drullinger, R. E.; Bickman, S.; Fortier, T. M.; Stalnaker, J. E.; Diddams, S. A.; Swann, W. C.; Newbury, N. R.; Wineland, D. J.; Bergquist, J. C.

    2009-06-01

    Frequency standards (atomic clocks) based on narrow optical transitions in 27Al+ and 199Hg+ have been developed over the past several years at NIST. Both types of standards are based on single ions confined in Paul traps, but differ in the methods used to prepare and detect the internal atomic states. Al+ lacks a strong, laser-accessible transition for laser-cooling and for state preparation and detection. Coupling with a Be+ ion, trapped simultaneously with the Al+ ion, enables state manipulation, detection, and cooling of the Al+ ion. Both standards have achieved absolute reproducibilities of a few parts in 1017. Development of femtosecond laser frequency combs makes it possible to directly compare optical frequencies. The present determination of fAl/fHg is 1.052 871 833 148 990 438 (55), where the uncertainty is expressed in units of the least significant digit. Measurements of fAl/fHg made over about one year show a drift rate consistent with zero. This result can be used to place limits on time variations of fundamental constants such as the fine structure constant α.

  17. Generation of frequency-chirped optical pulses with felix

    SciTech Connect

    Knippels, G.M.H.; Meer, A.F.G. van der; Mols, R.F.X.A.M.

    1995-12-31

    Frequency-chirped optical pulses have been produced in the picosecond regime by varying the energy of the electron beam on a microsecond time scale. These pulses were then compressed close to their bandwidth limit by an external pulse compressor. The amount of chirp can be controlled by varying the sweep rate on the electron beam energy and by cavity desynchronisation. To examine the generated chirp we used the following diagnostics: a pulse compressor, a crossed beam autocorrelator, a multichannel electron spectrometer and multichannel optical spectrometer. The compressor is build entirely using reflective optics to permit broad band operation. The autocorrelator is currently operating from 6 {mu}m to 30 {mu}m with one single crystal. It has been used to measure pulses as short as 500 fs. All diagnostics are evacuated to prevent pulse shape distortion or pulse lengthening caused by absorption in ambient water vapour. Pulse length measurements and optical spectra will be presented for different electron beam sweep rates, showing the presence of a frequency chirp. Results on the compression of the optical pulses to their bandwidth limit are given for different electron sweep rates. More experimental results showing the dependence of the amount of chirp on cavity desynchronisation will be presented.

  18. Fibre optics wavemeters calibration using a self-referenced optical frequency comb

    SciTech Connect

    Galindo-Santos, J.; Velasco, A. V.; Corredera, P.

    2015-01-15

    Self-referenced optical frequency combs enable the measurement of optical frequencies with a very high accuracy, achieving uncertainties close to the atomic clock used as reference (<10{sup −13} s). In this paper, we present the technique for the measurement of laser frequencies for optical communications followed at IO-CSIC and its application to the calibration of two wavemeters in the 1.5 μm optical communication window. Calibration uncertainties down to 12 MHz and 59 MHz were obtained, respectively, for each of the devices. Furthermore, the long-term behaviour of the higher resolution wavemeter was studied during a 750 h period of sustained operation, exhibiting a dispersion in the measurements of 7.72 MHz. Temperature dependence of the device was analysed, enabling to further reduce dispersion down to a 2.15 MHz range, with no significant temporal deviations.

  19. Enhanced link availability for free space optical time-frequency transfer using adaptive optic terminals

    NASA Astrophysics Data System (ADS)

    Petrillo, Keith G.; Dennis, Michael L.; Juarez, Juan C.; Souza, Katherine T.; Baumann, Esther; Bergeron, Hugo; Coddington, Ian; Deschenes, Jean-Daniel; Giorgetta, Fabrizio R.; Newbury, Nathan R.; Sinclair, Laura C.; Swann, William C.

    2016-05-01

    Optical time and frequency transfer offers extremely high precision wireless synchronization across multiple platforms for untethered distributed systems. While large apertures provide antenna gain for wireless systems which leads to robust link budgets and operation over increased distance, turbulence disrupts the beam and limits the full realization of the antenna gain. Adaptive optics can correct for phase distortions due to turbulence which potentially increases the total gain of the aperture to that for diffraction-limited operation. Here, we explore the use of adaptive optics terminals for free-space time and frequency transfer. We find that the requirement of reciprocity in a two-way time and frequency transfer link is maintained during the phase compensation of adaptive optics, and that the enhanced link budget due to aperture gain allows for potential system operation over ranges of at least tens of kilometers.

  20. Frequency converter implementing an optical analogue of the cosmological redshift.

    PubMed

    Ginis, Vincent; Tassin, Philippe; Craps, Ben; Veretennicoff, Irina

    2010-03-01

    According to general relativity, the frequency of electromagnetic radiation is altered by the expansion of the universe. This effect-commonly referred to as the cosmological redshift--is of utmost importance for observations in cosmology. Here we show that this redshift can be reproduced on a much smaller scale using an optical analogue inside a dielectric metamaterial with time-dependent material parameters. To this aim, we apply the framework of transformation optics to the Robertson-Walker metric. We demonstrate theoretically how perfect redshifting or blueshifting of an electromagnetic wave can be achieved without the creation of sidebands with a device of finite length.

  1. Frequency-dependent optical steering from subwavelength plasmonic structures.

    PubMed

    Djalalian-Assl, A; Gómez, D E; Roberts, A; Davis, T J

    2012-10-15

    We show theoretically and with numerical simulations that the direction of the in-plane scattering from a subwavelength optical antenna system can be controlled by the frequency of the incident light. This optical steering effect does not rely on propagation phase shifts or diffraction but arises from phase shifts in the localized surface plasmon modes of the antenna. An analytical model is developed to optimize the parameters for the configuration, showing good agreement with a rigorous numerical simulation. The simulation predicts a 25° angular shift in the direction of the light scattered from two gold nanorods for a wavelength change of 12 nm.

  2. Offset-free broadband Yb:fiber optical frequency comb for optical clocks.

    PubMed

    Nakamura, Takuma; Ito, Isao; Kobayashi, Yohei

    2015-07-27

    We demonstrate a passively offset-frequency stabilized optical frequency comb centered at 1060 nm. The offset-free comb was achieved through difference frequency generation (DFG) between two portions of a supercontinuum based on a Yb:fiber laser. As the DFG comb had only one degree of freedom, repetition frequency, full stabilization was achieved via locking one of the modes to an ultra-stable continuous wave (CW) laser. The DFG comb provided sufficient average power to enable further amplification, using Yb-doped fiber amplifier, and spectral broadening. The spectrum spanned from 690 nm to 1300 nm and the average power was of several hundred mW, which could be ideal for the comparison of optical clocks, such as optical lattice clocks operated with Sr (698 nm) and Hg (1063 nm) reference atoms.

  3. Nonlinear optics at low powers: Alternative mechanism of on-chip optical frequency comb generation

    NASA Astrophysics Data System (ADS)

    Rogov, Andrei S.; Narimanov, Evgenii E.

    2016-12-01

    Nonlinear optical effects provide a natural way of light manipulation and interaction and form the foundation of applied photonics, from high-speed signal processing and telecommunication to ultrahigh-bandwidth interconnects and information processing. However, relatively weak nonlinear response at optical frequencies calls for operation at high optical powers or boosting efficiency of nonlinear parametric processes by enhancing local-field intensity with high-quality-factor resonators near cavity resonance, resulting in reduced operational bandwidth and increased loss due to multiphoton absorption. We present an alternative to this conventional approach, with strong nonlinear optical effects at low local intensities, based on period-doubling bifurcations near nonlinear cavity antiresonance and apply it to low-power optical frequency comb generation in a silicon chip.

  4. Routes to spatiotemporal chaos in Kerr optical frequency combs

    SciTech Connect

    Coillet, Aurélien; Chembo, Yanne K.

    2014-03-15

    We investigate the various routes to spatiotemporal chaos in Kerr optical frequency combs, obtained through pumping an ultra-high Q-factor whispering-gallery mode resonator with a continuous-wave laser. The Lugiato–Lefever model is used to build bifurcation diagrams with regards to the parameters that are externally controllable, namely, the frequency and the power of the pumping laser. We show that the spatiotemporal chaos emerging from Turing patterns and solitons display distinctive dynamical features. Experimental spectra of chaotic Kerr combs are also presented for both cases, in excellent agreement with theoretical spectra.

  5. A distributed fiber optic sensor system for dike monitoring using Brillouin optical frequency domain analysis

    NASA Astrophysics Data System (ADS)

    Nöther, Nils; Wosniok, Aleksander; Krebber, Katerina; Thiele, Elke

    2008-03-01

    We report on the development of a complete system for spatially resolved detection of critical soil displacement in river embankments. The system uses Brillouin frequency domain analysis (BOFDA) for distributed measurement of strain in silica optical fibers. Our development consists of the measurement unit, an adequate coating for the optical fibers and a technique to integrate the coated optical fibers into geotextiles as they are commonly used in dike construction. We present several laboratory and field tests that prove the capability of the system to detect areas of soil displacement as small as 2 meters. These are the first tests of truly distributed strain measurements on optical fibers embedded into geosynthetics.

  6. Charge Transfer Plasmons: Optical Frequency Conductances and Tunable Infrared Resonances.

    PubMed

    Wen, Fangfang; Zhang, Yue; Gottheim, Samuel; King, Nicholas S; Zhang, Yu; Nordlander, Peter; Halas, Naomi J

    2015-06-23

    A charge transfer plasmon (CTP) appears when an optical-frequency conductive pathway between two metallic nanoparticles is established, enabling the transfer of charge between nanoparticles when the plasmon is excited. Here we investigate the properties of the CTP in a nanowire-bridged dimer geometry. Varying the junction geometry controls its conductance, which modifies the resonance energies and scattering intensities of the CTP while also altering the other plasmon modes of the nanostructure. Reducing the junction conductance shifts this resonance to substantially lower energies in the near- and mid-infrared regions of the spectrum. The CTP offers both a high-information probe of optical frequency conductances in nanoscale junctions and a new, unique approach to controllably engineering tunable plasmon modes at infrared wavelengths.

  7. Cascade frequency generation regime in an optical parametric oscillator

    SciTech Connect

    Kolker, D B; Dmitriev, Aleksandr K; Gorelik, P; Vong, Franko; Zondy, J J

    2009-05-31

    In a parametric oscillator of a special two-sectional design based on a lithium niobate periodic structure, a cascade frequency generation regime was observed in which a signal wave pumped a secondary parametric oscillator, producing secondary signal and idler waves. The secondary parametric oscillator can be tuned in a broad range of {approx}200 nm with respect to a fixed wavelength of the primary idler wave. (nonlinear optical phenomena)

  8. Ultrasensitive high resolution laser spectroscopy and its application to optical frequency standards

    NASA Astrophysics Data System (ADS)

    Ye, Jun

    1997-09-01

    Advanced laser stabilization techniques now enable one to lock laser frequencies onto line centers of natural atomic/molecular resonances with unprecedented precision and accuracy. In this dissertation we discuss our effort in utilizing these techniques to establish visible optical frequency standards. By summarizing our earlier results on frequency measurements of the 87Rb D2 line at 780 nm 127I2 hyperfine transitions at 532 nm, we show the advantage of using a higher quality reference line, usually characterized by its narrower linewidth, higher attainable signal-to-noise ratio and lower sensitivity toward external perturbations. We then present a novel approach of cavity-enhanced frequency modulation spectroscopy for ultra-sensitive detections. The powerful utility of this new technique in the field of frequency standards is demonstrated by probing saturated molecular overtone transitions in the visible and near infrared. Weakly-absorbing gases such as C2H2 and C2HD are placed inside an external high-finesse resonator to enhance their detection sensitivities. A frequency modulation technique is employed to achieve a shot noise limited signal-to- noise ratio. The rf modulation frequency is chosen to match the cavity's free spectral range in order to avoid the cavity-induced conversion of laser frequency noise into amplitude noise. The molecular saturated dispersion signal is directly recovered after demodulation of the cavity transmitted light. A record high integrated absorption sensitivity of 5× 10-13/ (1× 10-14/cm) (at 1 second averaging time) has been obtained. Systematic studies on this new technique are presented on topics of detection sensitivity, signal line shape, signal size and slope, and pressure dependent linewidth broadening and linecenter shift. A Nd:YAG laser is stabilized on the P(5) transition in the (ν2+3/ ν3) overtone band of C2HD at 1.064 μm. Its absolute frequency is established. The excellent signal- to-noise ratio produces a frequency

  9. Conformation, optical properties, and absolute configuration of 2‧,3‧-isopropylideneadenosines: Theoretical vs. experimental study

    NASA Astrophysics Data System (ADS)

    Ivanova, Bojidarka; Spiteller, Michael

    2011-10-01

    The conformational analysis, determination of absolute configurations (ACs) as well as elucidation of the electronic absorption and CD spectra of chiral molecules 2',3'-O-isopropylideneadenosine ( 1), 5'-carboxy-2',3'-O-isopropylidene-D-adenosine ( 2), 2-chloro-2',3'-O-isopropylideneadenosine-5'-N- ethylcarboxamide ( 3) and 1-[6-(6-Amino-2-methyl-purin-9-yl)-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethyl]-3-carbamoyl-pyridinium chloride ( 4), 9-(6-aminomethyl-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-yl)-9H-purin-6-ylamine ( 5) and acetic acid 6-(6-amino-purin-9-yl)-2,2-dimethyl-tetrahydro-furo[3,4-d][1,3]dioxol-4-ylmethyl ester ( 6) are performer. The methods such as electronic absorption (EAs), diffuse reflectance (DSs) spectroscopy as well as electronic circular dichroism (ECD) are applied. The theoretical density functional theory (DFT) calculations are carried out to evaluate the optical phenomena of isolated molecules as well as dimeric associates. We are demonstrated the significance and the advances of the stereo chemical experimental and theoretical characterization of natural products and their functional synthetic derivatives, vitha a view to further elucidation of unknown extracts of same chemical class. Special attention is devoted to the role of intermolecular interactions in condense phases on the theoretical and experimental optical properties, studying the corresponding dimeric associates. These results are a key in the drug discovery, and structure-based design of functionalized nucleosides. The methods as single crystal X-ray diffraction and MALDI Orbitrap mass spectrometric imaging (MALDI Orbitrap MSI) are also applied.

  10. Broadband ultrasonic sensor array via optical frequency domain reflectometry

    NASA Astrophysics Data System (ADS)

    Gabai, Haniel; Steinberg, Idan; Eyal, Avishay

    2015-03-01

    We introduce a new approach for multiplexing fiber-based ultrasound sensors using Optical Frequency Domain Reflectometry (OFDR). In the present demonstration of the method, each sensor was a short section of Polyimide-coated single-mode fiber. One end of the sensing fiber was pigtailed to a mirror and the other end was connected, via a fiber optic delay line, to a 1X4 fiber coupler. The multiplexing was enabled by using a different delay to each sensor. Ultrasonic excitation was performed by a 1MHz transducer which transmitted 4μs tone-bursts above the sensor array. The ultrasound waves generated optical phase variations in the fibers which were detected using the OFDR method. The ultrasound field at the sensors was successfully reconstructed without any noticeable cross-talk.

  11. Frequency-domain optical tomographic imaging of arthritic finger joints.

    PubMed

    Hielscher, Andreas H; Kim, Hyun Keol; Montejo, Ludguier D; Blaschke, Sabine; Netz, Uwe J; Zwaka, Paul A; Illing, Gerd; Muller, Gerhard A; Beuthan, Jürgen

    2011-10-01

    We are presenting data from the largest clinical trial on optical tomographic imaging of finger joints to date. Overall we evaluated 99 fingers of patients affected by rheumatoid arthritis (RA) and 120 fingers from healthy volunteers. Using frequency-domain imaging techniques we show that sensitivities and specificities of 0.85 and higher can be achieved in detecting RA. This is accomplished by deriving multiple optical parameters from the optical tomographic images and combining them for the statistical analysis. Parameters derived from the scattering coefficient perform slightly better than absorption derived parameters. Furthermore we found that data obtained at 600 MHz leads to better classification results than data obtained at 0 or 300 MHz.

  12. Simultaneous transfer of optical frequency and time over 306 km long-haul optical fibre link

    NASA Astrophysics Data System (ADS)

    Hucl, Vaclav; Cizek, Martin; Pravdova, Lenka; Rerucha, Simon; Hrabina, Jan; Mikel, Bretislav; Smotlacha, Vladimir; Vojtech, Josef; Lazar, Josef; Cip, Ondrej

    2016-12-01

    Optical fibre links for distributing optical frequencies and time stamps were researched and experimentally tested in the past fifteen years. They have been used mainly for stability comparison of experimental optical clocks. But recent development puts demands on a technology transfer from laboratory experiments to the real industry. The remote calibration of interrogators of Fibre Bragg Grating strain sensory networks is one of important examples. The first step of the adoption the time and frequency broadcasting should be the drop-out free long-term operation of this technology between research laboratories connected via long-haul fibre links. We present a 306 km long-haul optical fibre link between the cities of Prague and Brno in the Czech Republic where a coherent transfer of stable optical frequency and a stable time signal has been firstly demonstrated. The link between ISI CAS Brno and CESNET Prague uses an internet communication fibre where a window of 1540-1546 nm is dedicated for the coherent transfer and 1PPS signal. The link is equipped with 6 bidirectional EDFA amplifiers. The optical frequency standard based on the highly-coherent laser Koheras Adjustik working at 1540.5 nm and stabilized with a saturation absorption spectroscopy technique was used for the coherent wave transfer. The suppression of the Doppler shift induced by the optical fibre was based on an accoustooptical modulator with a servo-loop including a fast PID controller processing the beat-note frequency given by mixing of the Adjustik laser (Brno) and the reflected frequency of this laser from the far end of 306 km long-haul fibre link (Prague). We verified the Doppler shift suppression for the coherent wave with a measuring method analysing the transport delay of the 1PPS signal.

  13. Synthesis of Optical Frequencies and Ultrastable Femtosecond Pulse Trains from an Optical Reference Oscillator

    NASA Astrophysics Data System (ADS)

    Bartels, A.; Ramond, T. M.; Diddams, S. A.; Hollberg, L.

    Recently, atomic clocks based on optical frequency standards have been demonstrated [1,2]. A key element in these clocks is a femtosecond laser that downconverts the petahertz oscillation rate into countable ticks at 1 GHz. When compared to current microwave standards, these new optical clocks are expected to yield an improvement in stability and accuracy by roughly a factor of 1000. Furthermore, it is possible that the lowest noise microwave sources will soon be based on atomically-stabilized optical oscillators that have their frequency converted to the microwave domain via a femtosecond laser. Here, we present tests of the ability of femtosecond lasers to transfer stability from an optical oscillator to their repetition rates as well as to the associated broadband frequency comb. In a first experiment, we phase-lock two lasers to a stabilized laser diode and find that the relative timing jitter in their pulse trains can be on the order of 1 femtosecond in a 100 kHz bandwidth. It is important to distinguish this technique from previous work where a femtosecond laser has been stabilized to a microwave standard [3,4] or another femtosecond laser [5]. Furthermore, we extract highly stable microwave signals with a fractional frequency instability of 2×10-14 in 1 s by photodetection of the laser pulse trains. In a second experiment, we similarly phase-lock the femtosecond laser to an optical oscillator with linewidth less than 1 Hz [6]. The precision with which we can make the femtosecond frequency comb track this reference oscillator is then tested by a heterodyne measurement between a second stable optical oscillator and a mode of the frequency comb that is displaced 76 THz from the 1 Hz-wide reference. From this heterodyne signal we place an upper limit of 150 Hz on the linewidth of the elements of the frequency comb, limited by the noise in the measurement itself.

  14. Frequency-time coherence for all-optical sampling without optical pulse source

    PubMed Central

    Preußler, Stefan; Raoof Mehrpoor, Gilda; Schneider, Thomas

    2016-01-01

    Sampling is the first step to convert an analogue optical signal into a digital electrical signal. The latter can be further processed and analysed by well-known electrical signal processing methods. Optical pulse sources like mode-locked lasers are commonly incorporated for all-optical sampling, but have several drawbacks. A novel approach for a simple all-optical sampling is to utilise the frequency-time coherence of each signal. The method is based on only using two coupled modulators driven with an electrical sine wave. Since no optical source is required, a simple integration in appropriate platforms, such as Silicon Photonics might be possible. The presented method grants all-optical sampling with electrically tunable bandwidth, repetition rate and time shift. PMID:27687495

  15. An Optical Frequency Comb Tied to GPS for Laser Frequency/Wavelength Calibration

    PubMed Central

    Stone, Jack A.; Egan, Patrick

    2010-01-01

    Optical frequency combs can be employed over a broad spectral range to calibrate laser frequency or vacuum wavelength. This article describes procedures and techniques utilized in the Precision Engineering Division of NIST (National Institute of Standards and Technology) for comb-based calibration of laser wavelength, including a discussion of ancillary measurements such as determining the mode order. The underlying purpose of these calibrations is to provide traceable standards in support of length measurement. The relative uncertainty needed to fulfill this goal is typically 10−8 and never below 10−12, very modest requirements compared to the capabilities of comb-based frequency metrology. In this accuracy range the Global Positioning System (GPS) serves as an excellent frequency reference that can provide the traceable underpinning of the measurement. This article describes techniques that can be used to completely characterize measurement errors in a GPS-based comb system and thus achieve full confidence in measurement results. PMID:27134794

  16. Spectrometer employing optical fiber time delays for frequency resolution

    DOEpatents

    Schuss, Jack J.; Johnson, Larry C.

    1979-01-01

    This invention provides different length glass fibers for providing a broad range of optical time delays for short incident chromatic light pulses for the selective spatial and frequency analysis of the light with a single light detector. To this end, the frequencies of the incident light are orientated and matched with the different length fibers by dispersing the separate frequencies in space according to the respective fiber locations and lengths at the input terminal of the glass fibers. This makes the different length fibers useful in the field of plasma physics. To this end the short light pulses can be scattered by a plasma and then passed through the fibers for analyzing and diagnosing the plasma while it varies rapidly with time.

  17. Measurement of plasma wave frequency from absolute stimulated Raman scattering near the quarter-critical surface in a laser plasma

    NASA Astrophysics Data System (ADS)

    Villeneuve, D. M.; Bernard, J. E.; Baldis, H. A.

    1987-12-01

    Thomson scattering techniques were used to measure the frequency of plasma waves near the quarter-critical surface in a well-diagnosed plasma irradiated by a nanosecond CO2 laser with intensity ˜1014 W/cm2. The frequency ωp was shown to be less than ω0/2, in disagreement with the commonly used estimate ωp=ω0/2+ (9)/(8) (ve/c)2ω0. The theory of Afeyan and Williams [Phys. Fluids 28, 3397 (1985)] gives better agreement, and shows that the density scale length is more important than the temperature in determining the frequency shift.

  18. Dispersive white light combined with a frequency-modulated continuous-wave interferometer for high-resolution absolute measurements of distance.

    PubMed

    Rovati, L; Minoni, U; Docchio, F

    1997-06-15

    A nonincremental interferometer for the absolute measurement of distances is presented. The measuring technique is based on both dispersive white-light (DWL) interferometry and frequency-modulated continuous-wave (FMCW) interferometry. The proposed configuration integrates both techniques in the same interferometer by use of a single laser diode. This solution enables the results from the coarse measurements from the FMCW interferometer to be combined with the fine readouts from the DWL interferometer. Preliminary experimental results confirm the capability of the system to combine the advantages of the two techniques.

  19. Accurate absolute frequencies of the {nu}{sub 1}+{nu}{sub 3} band of {sup 13}C{sub 2}H{sub 2} determined using an infrared mode-locked Cr:YAG laser frequency comb

    SciTech Connect

    Madej, Alan A.; Bernard, John E.; John Alcock, A.; Czajkowski, Andrzej; Chepurov, Sergei

    2006-04-15

    Absolute frequency measurements, with up to 1x10{sup -11} level accuracies, are presented for 60 lines of the P and R branches for the {nu}{sub 1}+{nu}{sub 3} band of {sup 13}C{sub 2}H{sub 2} at 1.5 {mu}m (194 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line and a second laser system stabilized to the line whose frequency was to be determined, a Cr:YAG frequency comb was employed to accurately measure the tetrahertz level frequency intervals. The results are compared with recent work from other groups and indicate that these lines would form a basis for a high-quality atlas of reference frequencies for this region of the spectrum.

  20. Absolute Distance Measurement with the MSTAR Sensor

    NASA Technical Reports Server (NTRS)

    Lay, Oliver P.; Dubovitsky, Serge; Peters, Robert; Burger, Johan; Ahn, Seh-Won; Steier, William H.; Fetterman, Harrold R.; Chang, Yian

    2003-01-01

    The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. The sensor uses a single laser in conjunction with fast phase modulators and low frequency detectors. We describe the design of the system - the principle of operation, the metrology source, beamlaunching optics, and signal processing - and show results for target distances up to 1 meter. We then demonstrate how the system can be scaled to kilometer-scale distances.

  1. 1-GHz harmonically pumped femtosecond optical parametric oscillator frequency comb.

    PubMed

    Balskus, K; Leitch, S M; Zhang, Z; McCracken, R A; Reid, D T

    2015-01-26

    We present the first example of a femtosecond optical parametric oscillator frequency comb harmonically-pumped by a 333-MHz Ti:sapphire laser to achieve a stabilized signal comb at 1-GHz mode spacing in the 1.1-1.6-µm wavelength band. Simultaneous locking of the comb carrier-envelope-offset and repetition frequencies is achieved with uncertainties over 1 s of 0.27 Hz and 5 mHz respectively, which are comparable with those of 0.27 Hz and 1.5 mHz achieved for 333-MHz fundamental pumping. The phase-noise power-spectral density of the CEO frequency integrated from 1 Hz-64 kHz was 2.8 rad for the harmonic comb, 1.0 rad greater than for fundamental pumping. The results show that harmonic operation does not substantially compromise the frequency-stability of the comb, which is shown to be limited only by the Rb atomic frequency reference used.

  2. Optimal light harvesting structures at optical and infrared frequencies.

    PubMed

    Villate-Guío, F; López-Tejeira, F; García-Vidal, F J; Martín-Moreno, L; de León-Pérez, F

    2012-11-05

    One-dimensional light harvesting structures with a realistic geometry nano-patterned on an opaque metallic film are optimized to render high transmission efficiencies at optical and infrared frequencies. Simple design rules are developed for the particular case of a slit-groove array with a given number of grooves that are symmetrically distributed with respect to a central slit. These rules take advantage of the hybridization of Fabry-Perot modes in the slit and surface modes of the corrugated metal surface. Same design rules apply for optical and infrared frequencies. The parameter space of the groove array is also examined with a conjugate gradient optimization algorithm that used as a seed the geometries optimized following physical intuition. Both uniform and nonuniform groove arrays are considered. The largest transmission enhancement, with respect to a uniform array, is obtained for a chirped groove profile. Such relative enhancement is a function of the wavelength. It decreases from 39 % in the optical part of the spectrum to 15 % at the long wavelength infrared.

  3. Frequency-domain optical mammography: edge effect corrections.

    PubMed

    Fantini, S; Franceschini, M A; Gaida, G; Gratton, E; Jess, H; Mantulin, W W; Moesta, K T; Schlag, P M; Kaschke, M

    1996-01-01

    We have investigated the problem of edge effects in laser-beam transillumination scanning of the human breast. Edge effects arise from tissue thickness variability along the scanned area, and from lateral photon losses through the sides of the breast. Edge effects can be effectively corrected in frequency-domain measurements by employing a two-step procedure: (1) use of the phase information to calculate an effective tissue thickness for each pixel location; (2) application of the knowledge of tissue thickness to calculate an edge-corrected optical image from the ac signal image. The measurements were conducted with a light mammography apparatus (LIMA) designed for feasibility tests in the clinical environment. Operating in the frequency-domain (110 MHz), this instrument performs a transillumination optical scan at two wavelengths (685 and 825 nm). We applied the proposed two-step procedure to data from breast phantoms and from human breasts. The processed images provide higher contrast and detectability in optical mammography with respect to raw data breast images.

  4. Frequency comparison of optical lattice clocks beyond the Dick limit

    NASA Astrophysics Data System (ADS)

    Takamoto, Masao; Takano, Tetsushi; Katori, Hidetoshi

    2011-05-01

    The supreme accuracy of atomic clocks relies on the universality of atomic transition frequencies. The stability of a clock, meanwhile, measures how quickly the clock's statistical uncertainties are reduced. The ultimate measure of stability is provided by the quantum projection noise, which improves as 1/√N by measuring N uncorrelated atoms. Quantum projection noise limited stabilities have been demonstrated in caesium clocks and in single-ion optical clocks, where the quantum noise overwhelms the Dick effect attributed to local oscillator noise. Here, we demonstrate a synchronous frequency comparison of two optical lattice clocks using 87Sr and 88Sr atoms, respectively, for which the Allan standard deviation reached 1 × 10-17 in an averaging time of 1,600 s by cancelling out the Dick effect to approach the quantum projection noise limit. The scheme demonstrates the advantage of using a large number (N ~ 1,000) of atoms in optical clocks and paves the way to investigating the inherent uncertainties of clocks and relativistic geodesy on a timescale of tens of minutes.

  5. Effect of soil temperature on optical frequency transfer through unidirectional dense-wavelength-division-multiplexing fiber-optic links.

    PubMed

    Pinkert, T J; Böll, O; Willmann, L; Jansen, G S M; Dijck, E A; Groeneveld, B G H M; Smets, R; Bosveld, F C; Ubachs, W; Jungmann, K; Eikema, K S E; Koelemeij, J C J

    2015-02-01

    Results of optical frequency transfer over a carrier-grade dense-wavelength-division-multiplexing (DWDM) optical fiber network are presented. The relation between soil temperature changes on a buried optical fiber and frequency changes of an optical carrier through the fiber is modeled. Soil temperatures, measured at various depths by the Royal Netherlands Meteorology Institute (KNMI) are compared with observed frequency variations through this model. A comparison of a nine-day record of optical frequency measurements through the 2×298  km fiber link with soil temperature data shows qualitative agreement. A soil temperature model is used to predict the link stability over longer periods (days-months-years). We show that optical frequency dissemination is sufficiently stable to distribute and compare, e.g., rubidium frequency standards over standard DWDM optical fiber networks using unidirectional fibers.

  6. Invited Article: A compact optically coherent fiber frequency comb.

    PubMed

    Sinclair, L C; Deschênes, J-D; Sonderhouse, L; Swann, W C; Khader, I H; Baumann, E; Newbury, N R; Coddington, I

    2015-08-01

    We describe the design, fabrication, and performance of a self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, saturable absorbers for mode-locking, high signal-to-noise ratio (SNR) detection of the control signals, and digital feedback control for frequency stabilization. The output is phase-coherent over a 1-2 μm octave-spanning spectrum with a pulse repetition rate of ∼200 MHz and a residual pulse-to-pulse timing jitter <3 fs well within the requirements of most frequency-comb applications. Digital control enables phase coherent operation for over 90 h, critical for phase-sensitive applications such as timekeeping. We show that this phase-slip free operation follows the fundamental limit set by the SNR of the control signals. Performance metrics from three nearly identical combs are presented. This laptop-sized comb should enable a wide-range of applications beyond the laboratory.

  7. Invited Article: A compact optically coherent fiber frequency comb

    NASA Astrophysics Data System (ADS)

    Sinclair, L. C.; Deschênes, J.-D.; Sonderhouse, L.; Swann, W. C.; Khader, I. H.; Baumann, E.; Newbury, N. R.; Coddington, I.

    2015-08-01

    We describe the design, fabrication, and performance of a self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, saturable absorbers for mode-locking, high signal-to-noise ratio (SNR) detection of the control signals, and digital feedback control for frequency stabilization. The output is phase-coherent over a 1-2 μm octave-spanning spectrum with a pulse repetition rate of ˜200 MHz and a residual pulse-to-pulse timing jitter <3 fs well within the requirements of most frequency-comb applications. Digital control enables phase coherent operation for over 90 h, critical for phase-sensitive applications such as timekeeping. We show that this phase-slip free operation follows the fundamental limit set by the SNR of the control signals. Performance metrics from three nearly identical combs are presented. This laptop-sized comb should enable a wide-range of applications beyond the laboratory.

  8. Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rutkowski, Lucile; Khodabakhsh, Amir; Johanssson, Alexandra C.; Foltynowicz, Aleksandra

    2015-06-01

    We present noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), a recently developed technique for sensitive, broadband, and high resolution spectroscopy. In NICE-OFCS an optical frequency comb (OFC) is locked to a high finesse cavity and phase-modulated at a frequency precisely equal to (a multiple of) the cavity free spectral range. Since each comb line and sideband is transmitted through a separate cavity mode in exactly the same way, any residual frequency noise on the OFC relative to the cavity affects each component in an identical manner. The transmitted intensity contains a beat signal at the modulation frequency that is immune to frequency-to-amplitude noise conversion by the cavity, in a way similar to continuous wave noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS). The light transmitted through the cavity is detected with a fast-scanning Fourier-transform spectrometer (FTS) and the NICE-OFCS signal is obtained by fast Fourier transform of the synchronously demodulated interferogram. Our NICE-OFCS system is based on an Er:fiber femtosecond laser locked to a cavity with a finesse of ˜9000 and a fast-scanning FTS equipped with a high-bandwidth commercial detector. We measured NICE-OFCS signals from the 3νb{1}+νb{3} overtone band of CO_2 around 1.57 μm and achieved absorption sensitivity 6.4×10-11cm-1 Hz-1/2 per spectral element, corresponding to a minimum detectable CO_2 concentration of 25 ppb after 330 s integration time. We will describe the principles of the technique and its technical implementation, and discuss the spectral lineshapes of the NICE-OFCS signals. A. Khodabakhsh, C. Abd Alrahman, and A. Foltynowicz, Opt. Lett. 39, 5034-5037 (2014). J. Ye, L. S. Ma, and J. L. Hall, J. Opt. Soc. Am. B 15, 6-15 (1998). A. Khodabakhsh, A. C. Johansson, and A. Foltynowicz, Appl. Phys. B (2015) doi:10.1007/s00340-015-6010-7.

  9. Optical frequency comb based multi-band microwave frequency conversion for satellite applications.

    PubMed

    Yang, Xinwu; Xu, Kun; Yin, Jie; Dai, Yitang; Yin, Feifei; Li, Jianqiang; Lu, Hua; Liu, Tao; Ji, Yuefeng

    2014-01-13

    Based on optical frequency combs (OFC), we propose an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. By optically channelizing the mixed OFCs, the converted signal in different bands can be obtained in different channels. Alternatively, the scheme can be configured to generate multi-band local oscillators (LO) for widely distribution. Moreover, the scheme realizes simultaneous inter- and intra-band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources. We carry out a proof of concept experiment in which multiple LOs with 2 GHz, 10 GHz, 18 GHz, and 26 GHz are generated. A C-band signal of 6.1 GHz input to the proposed scheme is successfully converted to 4.1 GHz (C band), 3.9 GHz (C band) and 11.9 GHz (X band), etc. Compared with the back-to-back (B2B) case measured at 0 dBm input power, the proposed scheme shows a 9.3% error vector magnitude (EVM) degradation at each output channel. Furthermore, all channels satisfy the EVM limit in a very wide input power range.

  10. Absolute airborne gravimetry

    NASA Astrophysics Data System (ADS)

    Baumann, Henri

    This work consists of a feasibility study of a first stage prototype airborne absolute gravimeter system. In contrast to relative systems, which are using spring gravimeters, the measurements acquired by absolute systems are uncorrelated and the instrument is not suffering from problems like instrumental drift, frequency response of the spring and possible variation of the calibration factor. The major problem we had to resolve were to reduce the influence of the non-gravitational accelerations included in the measurements. We studied two different approaches to resolve it: direct mechanical filtering, and post-processing digital compensation. The first part of the work describes in detail the different mechanical passive filters of vibrations, which were studied and tested in the laboratory and later in a small truck in movement. For these tests as well as for the airborne measurements an absolute gravimeter FG5-L from Micro-G Ltd was used together with an Inertial navigation system Litton-200, a vertical accelerometer EpiSensor, and GPS receivers for positioning. These tests showed that only the use of an optical table gives acceptable results. However, it is unable to compensate for the effects of the accelerations of the drag free chamber. The second part describes the strategy of the data processing. It is based on modeling the perturbing accelerations by means of GPS, EpiSensor and INS data. In the third part the airborne experiment is described in detail, from the mounting in the aircraft and data processing to the different problems encountered during the evaluation of the quality and accuracy of the results. In the part of data processing the different steps conducted from the raw apparent gravity data and the trajectories to the estimation of the true gravity are explained. A comparison between the estimated airborne data and those obtained by ground upward continuation at flight altitude allows to state that airborne absolute gravimetry is feasible and

  11. RA diagnostics applying optical tomography in frequency domain

    NASA Astrophysics Data System (ADS)

    Klose, Alexander D.; Prapavat, Viravuth; Minet, Olaf; Beuthan, Juergen; Mueller, Gerhard J.

    1998-01-01

    Our aim is to reconstruct the optical parameters in a slice of a finger joint phantom for further investigations about rheumatoid arthritis (RA). Therefore, we have developed a flexible NIR scanning system in order to collect amplitude and phase delay of photon density waves in frequency-domain. A cylindrical finger joint phantom was embedded in a container of Intralipid solution due to the application of an inverse method for infinite geometry. The joint phantom was investigated by a laser beam obtaining several projections. The average optical parameters of each projection was calculated. Using different reconstruction techniques, e.g. ART and SIRT with a special projection operator, we reconstructed the optical parameters in a slice. The projection operator can be heuristically described by a photon path density function of a homogeneous media with infinite geometry. Applied to an object with an unknown distribution of optical parameters it calculates the expectation value of the investigated object. The potentials and limits of these fast reconstruction methods will be presented.

  12. Multiphoton Raman Atom Optics with Frequency-Swept Adiabatic Passage

    NASA Astrophysics Data System (ADS)

    Kotru, Krish; Butts, David; Kinast, Joseph; Stoner, Richard

    2016-05-01

    Light-pulse atom interferometry is a promising candidate for future inertial navigators, gravitational wave detectors, and measurements of fundamental physical constants. The sensitivity of this technique, however, is often limited by the small momentum separations created between interfering atom wave packets (typically ~ 2 ℏk) . We address this issue using light-pulse atom optics derived from stimulated Raman transitions and frequency-swept adiabatic rapid passage (ARP). In experiments, these Raman ARP atom optics have generated up to 30 ℏk photon recoil momenta in an acceleration-sensitive atom interferometer, thereby enhancing the phase shift per unit acceleration by a factor of 15. Since this approach forgoes evaporative cooling and velocity selection, it could enable large-area atom interferometry at higher data rates, while also lowering the atom shot-noise-limited measurement uncertainty.

  13. Software reconfigurable highly flexible gain switched optical frequency comb source.

    PubMed

    Pascual, M Deseada Gutierrez; Zhou, Rui; Smyth, Frank; Anandarajah, Prince M; Barry, Liam P

    2015-09-07

    The authors present the performance and noise properties of a software reconfigurable, FSR and wavelength tunable gain switched optical frequency comb source. This source, based on the external injection of a temperature tuned Fabry-Pérot laser diode, offers quasi-continuous wavelength tunability over the C-band (30nm) and FSR tunability ranging from 6 to 14GHz. The results achieved demonstrate the excellent spectral quality of the comb tones (RIN ~-130dB/Hz and low phase noise of 300kHz) and its outstanding stability (with fluctuations of the individual comb tones of less than 0.5dB in power and 5pm in wavelength, characterized over 24hours) highlighting its suitability for employment in next generation flexible optical transmission networks.

  14. Tunable radio frequency photonics filter using a comb-based optical tapped delay line with an optical nonlinear multiplexer.

    PubMed

    Ziyadi, Morteza; Mohajerin-Ariaei, Amirhossein; Chitgarha, Mohammad Reza; Khaleghi, Salman; Almaiman, Ahmed; Cao, Yinwen; Abouzaid, Amin; Shamee, Bishara; Tur, Moshe; Paraschis, Loukas; Langrock, Carsten; Fejer, Martin M; Touch, Joseph D; Willner, Alan E

    2015-07-15

    A radio frequency (RF) photonic filter is experimentally demonstrated using an optical tapped delay line (TDL) based on an optical frequency comb and a periodically poled lithium niobate (PPLN) waveguide as multiplexer. The approach is used to implement RF filters with variable bandwidth, shape, and center-frequency.

  15. Lattice-induced nonadiabatic frequency shifts in optical lattice clocks

    SciTech Connect

    Beloy, K.

    2010-09-15

    We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

  16. All-optical stabilization of a soliton frequency comb in a crystalline microresonator.

    PubMed

    Jost, J D; Lucas, E; Herr, T; Lecaplain, C; Brasch, V; Pfeiffer, M H P; Kippenberg, T J

    2015-10-15

    We demonstrate the all-optical stabilization of a low-noise temporal soliton based microresonator based optical frequency comb in a crystalline resonator via a new technique to control the repetition rate. This is accomplished by thermally heating the microresonator with an additional probe laser coupled to an auxiliary optical resonator mode. The carrier-envelope offset frequency is controlled by stabilizing the pump laser frequency to a reference optical frequency comb. We analyze the stabilization by performing an out-of-loop comparison and measure the overlapping Allan deviation. This all-optical stabilization technique can prove useful as an actuator for self-referenced microresonator frequency combs.

  17. Accurate absolute reference frequencies from 1511 to 1545 nm of the {nu}{sub 1}+{nu}{sub 3} band of {sup 12}C{sub 2}H{sub 2} determined with laser frequency comb interval measurements

    SciTech Connect

    Madej, Alan A.; Alcock, A. John; Czajkowski, Andrzej; Bernard, John E.; Chepurov, Sergei

    2006-10-15

    Absolute frequency measurements, with uncertainties as low as 2 kHz (1x10{sup -11}), are presented for the {nu}{sub 1}+{nu}{sub 3} band of {sup 12}C{sub 2}H{sub 2} at 1.5 {mu}m (194-198 THz). The measurements were made using cavity-enhanced, diode-laser-based saturation spectroscopy. With one laser system stabilized to the P(16) line of {sup 13}C{sub 2}H{sub 2} and a system stabilized to the line in {sup 12}C{sub 2}H{sub 2} whose frequency was to be determined, a Cr:YAG laser-based frequency comb was employed to measure the frequency intervals. The systematic uncertainty is notably reduced relative to that of previous studies, and the region of measured lines has been extended. Improved molecular constants are obtained.

  18. Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs.

    PubMed

    Posada-Roman, Julio E; Garcia-Souto, Jose A; Poiana, Dragos A; Acedo, Pablo

    2016-11-26

    Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz). Measurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal.

  19. Frequency Comparison of Two (40)Ca(+) Optical Clocks with an Uncertainty at the 10(-17) Level.

    PubMed

    Huang, Y; Guan, H; Liu, P; Bian, W; Ma, L; Liang, K; Li, T; Gao, K

    2016-01-08

    Based upon an over-one-month frequency comparison of two (40)Ca(+) optical clocks, the frequency difference between the two clocks is measured to be 3.2×10(-17) with a measurement uncertainty of 5.5×10(-17), considering both the statistic (1.9×10(-17)) and the systematic (5.1×10(-17)) uncertainties. This is the first performance of a (40)Ca(+) clock better than that of Cs fountains. A fractional stability of 7×10(-17) in 20,000 s of averaging time is achieved. The evaluation of the two clocks shows that the shift caused by the micromotion in one of the two clocks limits the uncertainty of the comparison. By carefully compensating the micromotion, the absolute frequency of the clock transition is measured to be 411 042 129 776 401.7(1.1) Hz.

  20. Pulse-to-pulse alignment based on interference fringes and the second-order temporal coherence function of optical frequency combs for distance measurement.

    PubMed

    Zhu, Jigui; Cui, Pengfei; Guo, Yin; Yang, Linghui; Lin, Jiarui

    2015-05-18

    A pulse-to-pulse alignment method based on interference fringes and the second-order temporal coherence function of optical frequency combs is proposed for absolute distance measurement. The second-order temporal coherence function of the pulse train emitted from optical frequency combs is studied. A numerical model of the function is developed with an assumption of Gaussian pulse and has good agreement with experimental measurements taken by an ordinary Michelson interferometer. The experimental results show an improvement of standard deviation of peak finding results from 27.3 nm to 8.5 nm by the method in ordinary laboratory conditions. The absolute distance measurement with the pulse-to-pulse alignment method is also proposed and experimentally proved.

  1. Automatic analysis of ciliary beat frequency using optical flow

    NASA Astrophysics Data System (ADS)

    Figl, Michael; Lechner, Manuel; Werther, Tobias; Horak, Fritz; Hummel, Johann; Birkfellner, Wolfgang

    2012-02-01

    Ciliary beat frequency (CBF) can be a useful parameter for diagnosis of several diseases, as e.g. primary ciliary dyskinesia. (PCD). CBF computation is usually done using manual evaluation of high speed video sequences, a tedious, observer dependent, and not very accurate procedure. We used the OpenCV's pyramidal implementation of the Lukas-Kanade algorithm for optical flow computation and applied this to certain objects to follow the movements. The objects were chosen by their contrast applying the corner detection by Shi and Tomasi. Discrimination between background/noise and cilia by a frequency histogram allowed to compute the CBF. Frequency analysis was done using the Fourier transform in matlab. The correct number of Fourier summands was found by the slope in an approximation curve. The method showed to be usable to distinguish between healthy and diseased samples. However there remain difficulties in automatically identifying the cilia, and also in finding enough high contrast cilia in the image. Furthermore the some of the higher contrast cilia are lost (and sometimes found) by the method, an easy way to distinguish the correct sub-path of a point's path have yet to be found in the case where the slope methods doesn't work.

  2. Acousto-optical combined frequency splitters and shifters as components of a ring optical gyroscope

    SciTech Connect

    Kotov, V M

    1999-03-31

    An analysis is made of the task of symmetrisation of a Y-type directional coupler and of shifting the frequency of counterpropagating waves in a ring gyroscope by means of the relatively recently discovered new type of acousto-optical diffraction when the incident radiation is diffracted simultaneously into two orders. Anisotropic and isotropic acousto-optical diffraction in a uniaxial crystal is considered and expressions convenient for calculations are derived. Experiments carried out on isotropic diffraction in LiNbO{sub 3} confirm, on the whole, the theoretical predictions. (laser applications and other topics in quantum electronics)

  3. Optical frequency domain reflectometry: principles and applications in fiber optic sensing

    NASA Astrophysics Data System (ADS)

    Kreger, Stephen T.; Rahim, Nur Aida Abdul; Garg, Naman; Klute, Sandra M.; Metrey, Daniel R.; Beaty, Noah; Jeans, James W.; Gamber, Robert

    2016-05-01

    Optical Frequency Domain Reflectometry (OFDR) is the basis of an emerging high-definition distributed fiber optic sensing (HD-FOS) technique that provides an unprecedented combination of resolution and sensitivity. OFDR employs swept laser interferometry to produce strain or temperature vs. sensor length with fiber Bragg gratings (FBGs) or Rayleigh scatter as the source signal. We look at the influence of HD-FOS on design and test of new, lighter weight, stronger and more fuel efficient vehicles. Examples include defect detection, model verification and structural health monitoring of composites, and temperature distribution monitoring of battery packs and inverters in hybrid and electric powertrains.

  4. Low-frequency rTMS over the Parieto-frontal network during a sensorimotor task: The role of absolute beta power in the sensorimotor integration.

    PubMed

    Gongora, Mariana; Bittencourt, Juliana; Teixeira, Silmar; Basile, Luis F; Pompeu, Fernando; Droguett, Enrique López; Arias-Carrion, Oscar; Budde, Henning; Cagy, Mauricio; Velasques, Bruna; Nardi, Antonio Egídio; Ribeiro, Pedro

    2016-01-12

    Several studies have demonstrated that Repetitive Transcranial Magnetic Stimulation (rTMS) promotes alterations in the Central Nervous System circuits and networks. The focus of the present study is to examine the absolute beta power patterns in the Parieto-frontal network. We hypothesize that rTMS alters the mechanisms of the sensorimotor integration process during a visuomotor task. Twelve young healthy volunteers performed a visuomotor task involving decision making recorded (Catch a ball in a free fall) by Electroencephalography. rTMS was applied on the Superior Parietal Cortex (SPC; Brodmann area [BA] 7) with low-frequency (1 Hz - 15 min - 80% Resting Motor Threshold). For each Frontal and Parietal region, a two-way ANOVA was used to compare the absolute beta power before and after TMS for each condition of the study (Rest 1, Task and Rest 2). The results demonstrated interactions (TMS vs. Condition) for the Frontal electrodes: Fp1, Fp2 and F7 and an effect of TMS (before and after) for F4.The results for the Parietal region showed a main effect of Condition for the P3, PZ and P4 electrodes. Thus, our paradigm was useful to better understand the reorganization and neural plasticity mechanisms in the parieto-frontal network during the sensorimotor integration process.

  5. Fast, precise, and widely tunable frequency control of an optical parametric oscillator referenced to a frequency comb

    NASA Astrophysics Data System (ADS)

    Prehn, Alexander; Glöckner, Rosa; Rempe, Gerhard; Zeppenfeld, Martin

    2017-03-01

    Optical frequency combs (OFCs) provide a convenient reference for the frequency stabilization of continuous-wave lasers. We demonstrate a frequency control method relying on tracking over a wide range and stabilizing the beat note between the laser and the OFC. The approach combines fast frequency ramps on a millisecond timescale in the entire mode-hop free tuning range of the laser and precise stabilization to single frequencies. We apply it to a commercially available optical parametric oscillator (OPO) and demonstrate tuning over more than 60 GHz with a ramping speed up to 3 GHz/ms. Frequency ramps spanning 15 GHz are performed in less than 10 ms, with the OPO instantly relocked to the OFC after the ramp at any desired frequency. The developed control hardware and software are able to stabilize the OPO to sub-MHz precision and to perform sequences of fast frequency ramps automatically.

  6. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    SciTech Connect

    Niemi, K.; O'Connell, D.; Gans, T.; Oliveira, N. de; Joyeux, D.; Nahon, L.; Booth, J. P.

    2013-07-15

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N{sub 2}/O{sub 2} (4:1) admixtures. A maximum in the O-atom concentration of (9.1 {+-} 0.7) Multiplication-Sign 10{sup 20} m{sup -3} was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 {+-} 0.4) Multiplication-Sign 10{sup 19} m{sup -3} at 0.1 vol. %.

  7. Development of a prototype compact fibre frequency synthesiser for mobile femtosecond optical clocks

    SciTech Connect

    Pivtsov, V S; Korel', I I; Koliada, N A; Farnosov, S A; Denisov, V I; Nyushkov, B N

    2014-06-30

    A prototype compact fibre frequency synthesiser based on a femtosecond erbium fibre laser and an original hybrid highly nonlinear fibre is developed and preliminarily studied. This synthesiser will ensure an extremely low relative instability of synthesised frequencies (down to 10{sup -17}) with the use of a corresponding optical standard and will be used in mobile optical clocks. The realised frequency stabilisation principle makes the synthesiser universal and allows it to transfer the frequency stability of various types of optical standards to the synthesised radio- and optical frequencies. (extreme light fields and their applications)

  8. Material candidates for optical frequency comb generation in microspheres.

    PubMed

    Riesen, Nicolas; Afshar V, Shahraam; François, Alexandre; Monro, Tanya M

    2015-06-01

    This paper evaluates the opportunities for using materials other than silica for optical frequency comb generation in whispering gallery mode microsphere resonators. Different materials are shown to satisfy the requirement of dispersion compensation in interesting spectral regions such as the visible or mid-infrared and for smaller microspheres. This paper also analyses the prospects of comb generation in microspheres within aqueous solution for potential use in applications such as biosensing. It is predicted that to achieve comb generation with microspheres in aqueous solution the visible low-loss wavelength window of water needs to be exploited. This is because efficient comb generation necessitates ultra-high Q-factors, which are only possible for cavities with low absorption of the evanescent field outside the cavity. This paper explores the figure of merit for nonlinear interaction efficiency and the potential for dispersion compensation at unique wavelengths for a host of microsphere materials and dimensions and in different surroundings.

  9. Demonstration of optical multicasting using Kerr frequency comb lines.

    PubMed

    Bao, Changjing; Liao, Peicheng; Kordts, Arne; Karpov, Maxim; Pfeiffer, Martin H P; Zhang, Lin; Yan, Yan; Xie, Guodong; Cao, Yinwen; Almaiman, Ahmed; Ziyadi, Morteza; Li, Long; Zhao, Zhe; Mohajerin-Ariaei, Amirhossein; Wilkinson, Steven R; Tur, Moshe; Fejer, Martin M; Kippenberg, Tobias J; Willner, Alan E

    2016-08-15

    We experimentally demonstrate optical multicasting using Kerr frequency combs generated from a Si3N4 microresonator. We obtain Kerr combs in two states with different noise properties by varying the pump wavelength in the resonator and investigate the effect of Kerr combs on multicasting. Seven-fold multicasting of 20 Gbaud quadrature phase-shift-keyed signals and four-fold multicasting of 16-quadrature amplitude modulation signals have been achieved when low-phase-noise combs are input into a periodically poled lithium niobate waveguide. In addition, we find that the wavelength conversion efficiency in the PPLN waveguide for chaotic combs with high noise is similar to that for low-noise combs, while the signal quality of the multicast copy is significantly degraded.

  10. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, M. C.; Muggli, Patric; Yakimenko, Vitaly; Babzien, Marcus; Kusche, Karl; Fedurin, Mikhail

    2010-11-01

    Beam-driven plasma wakefield accelerators (PWFA), such as the ``plasma afterburner,'' are a promising approach for significantly increasing the particle energies of conventional accelerators. The study and optimization of PWFA would benefit from an experimental correlation between the parameters of the drive bunch, the accelerated bunch and the corresponding, accelerating plasma wave structure. However, the plasma wave structure has not yet been observed directly in PWFA. We will report our current work on noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) visualization of beam-driven plasma waves. Both techniques employ two laser pulses (probe and reference) co-propagating with the particle drive-beam and its plasma wake. The reference pulse precedes the drive bunch, while the probe overlaps the plasma wave and maps its longitudinal and transverse structure. The experiment is being developed at the BNL/ATF Linac to visualize wakes generated by two and multi-bunch drive beams.

  11. Time-delay interferometry with optical frequency comb

    NASA Astrophysics Data System (ADS)

    Tinto, Massimo; Yu, Nan

    2015-08-01

    Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises, it has previously been suggested that additional interspacecraft phase measurements must be performed by modulating the laser beams. With the advent of self-referenced optical frequency combs, it is possible to generate a heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be canceled directly by applying modified second-generation time-delay interferometric combinations to the heterodyne phase measurements. This approach avoids the use of modulated laser beams as well as the need for additional ultrastable oscillator clocks.

  12. Holographic frequency resolved optical gating for spatio-temporal characterization of ultrashort optical pulse

    NASA Astrophysics Data System (ADS)

    Mehta, Nikhil; Yang, Chuan; Xu, Yong; Liu, Zhiwen

    2014-09-01

    We introduce a novel method for characterizing the spatio-temporal evolution of ultrashort optical field by recording the spectral hologram of frequency resolved optical gating (FROG) trace. We show that FROG holography enables the measurement of phase (up to an overall constant) and group delay of the pulse which cannot be measured by conventional FROG method. To illustrate our method, we perform numerical simulation to generate holographic collinear FROG (cFROG) trace of a chirped optical pulse and retrieve its complex profile at multiple locations as it propagates through a hypothetical dispersive medium. Further, we experimentally demonstrate our method by retrieving a 67 fs pulse at three axial locations in the vicinity of focus of an objective lens and compute its group delay.

  13. Towards chip-scale optical frequency synthesis based on optical heterodyne phase-locked loop.

    PubMed

    Arafin, Shamsul; Simsek, Arda; Kim, Seong-Kyun; Dwivedi, Sarvagya; Liang, Wei; Eliyahu, Danny; Klamkin, Jonathan; Matsko, Andrey; Johansson, Leif; Maleki, Lute; Rodwell, Mark; Coldren, Larry

    2017-01-23

    An integrated heterodyne optical phase-locked loop was designed and demonstrated with an indium phosphide based photonic integrated circuit and commercial off-the-shelf electronic components. As an input reference, a stable microresonator-based optical frequency comb with a 50-dB span of 25 nm (~3 THz) around 1550 nm, having a spacing of ~26 GHz, was used. A widely-tunable on-chip sampled-grating distributed-Bragg-reflector laser is offset locked across multiple comb lines. An arbitrary frequency synthesis between the comb lines is demonstrated by tuning the RF offset source, and better than 100Hz tuning resolution with ± 5 Hz accuracy is obtained. Frequency switching of the on-chip laser to a point more than two dozen comb lines away (~5.6 nm) and simultaneous locking to the corresponding nearest comb line is also achieved in a time ~200 ns. A low residual phase noise of the optical phase-locking system is successfully achieved, as experimentally verified by the value of -80 dBc/Hz at an offset of as low as 200 Hz.

  14. Coherent Magnetic Response at Optical Frequencies Using Atomic Transitions

    NASA Astrophysics Data System (ADS)

    Brewer, Nicholas R.; Buckholtz, Zachary N.; Simmons, Zachary J.; Mueller, Eli A.; Yavuz, Deniz D.

    2017-01-01

    In optics, the interaction of atoms with the magnetic field of light is almost always ignored since its strength is many orders of magnitude weaker compared to the interaction with the electric field. In this article, by using a magnetic-dipole transition within the 4 f shell of europium ions, we show a strong interaction between a green laser and an ensemble of atomic ions. The electrons move coherently between the ground and excited ionic levels (Rabi flopping) by interacting with the magnetic field of the laser. By measuring the Rabi flopping frequency as the laser intensity is varied, we report the first direct measurement of a magnetic-dipole matrix element in the optical region of the spectrum. Using density-matrix simulations of the ensemble, we infer the generation of coherent magnetization with magnitude 5.5 ×10-3 A /m , which is capable of generating left-handed electromagnetic waves of intensity 1 nW /cm2 . These results open up the prospect of constructing left-handed materials using sharp transitions of atoms.

  15. Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs

    PubMed Central

    Posada-Roman, Julio E.; Garcia-Souto, Jose A.; Poiana, Dragos A.; Acedo, Pablo

    2016-01-01

    Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz). Measurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal. PMID:27898043

  16. Precision Calculation of Blackbody Radiation Shifts for Optical Frequency Metrology

    SciTech Connect

    Safronova, M. S.; Kozlov, M. G.; Clark, Charles W.

    2011-09-30

    We show that three group IIIB divalent ions, B{sup +}, Al{sup +}, and In{sup +}, have anomalously small blackbody radiation (BBR) shifts of the ns{sup 2} {sup 1}S{sub 0}-nsnp {sup 3}P{sub 0}{sup o} clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration-interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al{sup +} clock to 4x10{sup -19} at T=300 K. We also reduce the uncertainties due to this effect at room temperature to 10{sup -18} level for B{sup +} and In{sup +} to facilitate further development of these systems for metrology and quantum sensing.

  17. Absolute measurement of subnanometer scale vibration of cochlear partition of an excised guinea pig cochlea using spectral-domain phase-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Subhash, Hrebesh M.; Choudhury, Niloy; Jacques, Steven L.; Wang, Ruikang K.; Chen, Fangyi; Zha, Dingjun; Nuttall, Alfred L.

    2012-01-01

    Direct measurement of absolute vibration parameters from different locations within the mammalian organ of Corti is crucial for understanding the hearing mechanics such as how sound propagates through the cochlea and how sound stimulates the vibration of various structures of the cochlea, namely, basilar membrane (BM), recticular lamina, outer hair cells and tectorial membrane (TM). In this study we demonstrate the feasibility a modified phase-sensitive spectral domain optical coherence tomography system to provide subnanometer scale vibration information from multiple angles within the imaging beam. The system has the potential to provide depth resolved absolute vibration measurement of tissue microstructures from each of the delay-encoded vibration images with a noise floor of ~0.3nm at 200Hz.

  18. Measurement of the binding energy of ultracold 87Rb133Cs molecules using an offset-free optical frequency comb

    NASA Astrophysics Data System (ADS)

    Molony, Peter K.; Kumar, Avinash; Gregory, Philip D.; Kliese, Russell; Puppe, Thomas; Le Sueur, C. Ruth; Aldegunde, Jesus; Hutson, Jeremy M.; Cornish, Simon L.

    2016-08-01

    We report the binding energy of 87Rb133Cs molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of ˜5 kHz over an energy-level difference of more than 114 T Hz ; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of h ×114 268 135.24 (4 )(3 )M Hz . To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule.

  19. Frequency-resolved optical grating using surface third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; Delong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1995-11-01

    We demonstrate the frequency-resolved optical grating technique using third-harmonic generation on the surface of a cover glass with ultra-short optical pulses and compare that with the phase-retrieved spectrogram.

  20. Photonic radio-frequency dissemination via optical fiber with high-phase stability.

    PubMed

    Wang, Xiaocheng; Liu, Zhangweiyi; Wang, Siwei; Sun, Dongning; Dong, Yi; Hu, Weisheng

    2015-06-01

    We demonstrate a photonic radio-frequency transmission system via optical fiber. Optical radio-frequency signal is generated utilizing a Mach-Zehnder modulator based on double-side-band with carrier suppression modulation scheme. The phase error induced by optical fiber transmission is transferred to an intermediate frequency signal by the dual-heterodyne phase error transfer scheme, and then canceled by a phase locked loop. With precise phase compensation, a radio frequency with high-phase stability can be obtained at the remote end. We performed 20.07-GHz radio-frequency transfer over 100-km optical fiber, and achieved residual phase noise of -65  dBc/Hz at 1-Hz offset frequency, and the RMS timing jitter in the frequency range from 0.01 Hz to 1 MHz reaches 110 fs. The long-term frequency stability also achieves 8×10(-17) at 10,000 s averaging time.

  1. Nonlinear Dynamics of Photonics for Optical Signal Processing - Optical Frequency Conversion and Optical DSB-to-SSB Conversion

    DTIC Science & Technology

    2015-09-17

    Multiplexing, Optical Amplifier , Terahertz Electronics, Four-wave mixing, Radio-over-fiber networks, Intensity-asymmetry 16. SECURITY CLASSIFICATION OF: 17...structure and operation. For the photonic microwave amplification, we have demonstrated that microwaves can be amplified “photonically” by up to 30 dB for...linewidth and stability. 3. Photonic microwave amplification: Goals: To “photonically” amplify microwaves for a broad frequency range, from a few tens

  2. Continued analysis of optical frequency-modulated continuous-wave interference.

    PubMed

    Zheng, Jesse

    2005-02-10

    I continue to analyze systematically the theory of optical frequency-modulated continuous-wave (FMCW) interference. Two special cases, multiple-beam optical FMCW interference and multiple-wavelength optical FMCW interference, are discussed in detail. Multiple-beam optical FMCW interference generates a signal with multiple frequencies because of mutual interference among the waves. Multiple-wavelength optical FMCW interference produces a signal whose amplitude is modulated by a synthetic wave. The applications of both types of optical FMCW interference are also discussed.

  3. Absolute Zero

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell J.; Sheibley, D.; Belloni, M.; Stamper-Kurn, D.; Vinen, W. F.

    2006-12-01

    Absolute Zero is a two hour PBS special attempting to bring to the general public some of the advances made in 400 years of thermodynamics. It is based on the book “Absolute Zero and the Conquest of Cold” by Tom Shachtman. Absolute Zero will call long-overdue attention to the remarkable strides that have been made in low-temperature physics, a field that has produced 27 Nobel Prizes. It will explore the ongoing interplay between science and technology through historical examples including refrigerators, ice machines, frozen foods, liquid oxygen and nitrogen as well as much colder fluids such as liquid hydrogen and liquid helium. A website has been established to promote the series: www.absolutezerocampaign.org. It contains information on the series, aimed primarily at students at the middle school level. There is a wealth of material here and we hope interested teachers will draw their student’s attention to this website and its substantial contents, which have been carefully vetted for accuracy.

  4. Generation of Flat Optical Frequency Comb based on Mach-Zehnder Modulator and Recirculating Frequency Shifter Loop

    NASA Astrophysics Data System (ADS)

    Wu, Shibao; Li, Yulong; Fei, Yue; Hu, Faze

    2014-06-01

    We propose a novel scheme to generate optical frequency comb by using Mach-Zehnder modulator and recirculating frequency shifter loop based on IQ modulator driven by radio frequency clock signals. A system of 4 flat and stable comb lines generation based on Mach-Zehnder modulator is set as the seed light source of the recirculating loop. Through theorical analysis and simulation it is shown that the proposed theoretical model is proved in good agreement with simulation results.

  5. Time-frequency analysis of functional optical mammographic images

    NASA Astrophysics Data System (ADS)

    Barbour, Randall L.; Graber, Harry L.; Schmitz, Christoph H.; Tarantini, Frank; Khoury, Georges; Naar, David J.; Panetta, Thomas F.; Lewis, Theophilus; Pei, Yaling

    2003-07-01

    We have introduced working technology that provides for time-series imaging of the hemoglobin signal in large tissue structures. In this study we have explored our ability to detect aberrant time-frequency responses of breast vasculature for subjects with Stage II breast cancer at rest and in response to simple provocations. The hypothesis being explored is that time-series imaging will be sensitive to the known structural and functional malformations of the tumor vasculature. Mammographic studies were conducted using an adjustable hemisheric measuring head containing 21 source and 21 detector locations (441 source-detector pairs). Simultaneous dual-wavelength studies were performed at 760 and 830 nm at a framing rate of ~2.7 Hz. Optical measures were performed on women lying prone with the breast hanging in a pendant position. Two class of measures were performed: (1) 20- minute baseline measure wherein the subject was at rest; (2) provocation studies wherein the subject was asked to perform some simple breathing maneuvers. Collected data were analyzed to identify the time-frequency structure and central tendencies of the detector responses and those of the image time series. Imaging data were generated using the Normalized Difference Method (Pei et al., Appl. Opt. 40, 5755-5769, 2001). Results obtained clearly document three classes of anomalies when compared to the normal contralateral breast. 1) Breast tumors exhibit altered oxygen supply/demand imbalance in response to an oxidative challenge (breath hold). 2) The vasomotor response of the tumor vasculature is mainly depressed and exhibits an altered modulation. 3) The affected area of the breast wherein the altered vasomotor signature is seen extends well beyond the limits of the tumor itself.

  6. Ultra-stable long distance optical frequency distribution using the Internet fiber network.

    PubMed

    Lopez, Olivier; Haboucha, Adil; Chanteau, Bruno; Chardonnet, Christian; Amy-Klein, Anne; Santarelli, Giorgio

    2012-10-08

    We report an optical link of 540 km for ultrastable frequency distribution over the Internet fiber network. The stable frequency optical signal is processed enabling uninterrupted propagation on both directions. The robustness and the performance of the link are enhanced by a cost effective fully automated optoelectronic station. This device is able to coherently regenerate the return optical signal with a heterodyne optical phase locking of a low noise laser diode. Moreover the incoming signal polarization variation are tracked and processed in order to maintain beat note amplitudes within the operation range. Stable fibered optical interferometer enables optical detection of the link round trip phase signal. The phase-noise compensated link shows a fractional frequency instability in 10 Hz bandwidth of 5 × 10(-15) at one second measurement time and 2 × 10(-19) at 30,000 s. This work is a significant step towards a sustainable wide area ultrastable optical frequency distribution and comparison network.

  7. Non-contact precision profile measurement to rough-surface objects with optical frequency combs

    NASA Astrophysics Data System (ADS)

    Onoe, Taro; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

    2016-12-01

    In this research, we developed a new method for the high precision and contactless profile measurement of rough-surfaced objects using optical frequency combs. The uncertainty of the frequency beats of an optical frequency comb is very small (relative uncertainty is 10-10 in our laboratory). In addition, the wavelengths corresponding to these frequency beats are long enough to measure rough-surfaced objects. We can conduct high-precision measurement because several GHz frequency beats can be used if the capability of the detector permits. Moreover, two optical frequency combs with Rb-stabilized repetition frequencies are used for the measurement instead of an RF frequency oscillator; thus, we can avoid the cyclic error caused by the RF frequency oscillator. We measured the profile of a wood cylinder with a rough surface (diameter is approximately 113.2 mm) and compared the result with that of coordinate measuring machine (CMM).

  8. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    SciTech Connect

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-04

    Bunch driven plasma wakefield accelerators (PWFA), such as the 'plasma afterburner', are a promising emerging method for significantly increasing the energy output of conventional particle accelerators. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) and Holographic (FDH) diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two and multi-bunch drive beams.

  9. Optical Frequency Domain Visualization of Electron Beam Driven Plasma Wakefields

    NASA Astrophysics Data System (ADS)

    Zgadzaj, Rafal; Downer, Michael C.; Muggli, Patric; Yakimenko, Vitaly; Kusche, Karl; Fedurin, Michhail; Babzien, Marcus

    2010-11-01

    Bunch driven plasma wakefield accelerators (PWFA), such as the "plasma afterburner," are a promising emerging method for significantly increasing the energy output of conventional particle accelerators [1]. The study and optimization of this method would benefit from an experimental correlation of the drive bunch parameters and the accelerated particle parameters with the corresponding plasma wave structure. However, the plasma wave structure has not been observed directly so far. We will report ongoing development of a noninvasive optical Frequency Domain Interferometric (FDI) [2] and Holographic (FDH) [3] diagnostics of bunch driven plasma wakes. Both FDI and FDH have been previously demonstrated in the case of laser driven wakes. These techniques employ two laser pulses co-propagating with the drive particle bunch and the trailing plasma wave. One pulse propagates ahead of the drive bunch and serves as a reference, while the second is overlapped with the plasma wave and probes its structure. The multi-shot FDI and single-shot FDH diagnostics permit direct noninvasive observation of longitudinal and transverse structure of the plasma wakes. The experiment is being developed at the 70 MeV Linac in the Accelerator Test Facility at Brookhaven National Laboratory to visualize wakes generated by two [4] and multi-bunch [5] drive beams.

  10. Electronic Absolute Cartesian Autocollimator

    NASA Technical Reports Server (NTRS)

    Leviton, Douglas B.

    2006-01-01

    An electronic absolute Cartesian autocollimator performs the same basic optical function as does a conventional all-optical or a conventional electronic autocollimator but differs in the nature of its optical target and the manner in which the position of the image of the target is measured. The term absolute in the name of this apparatus reflects the nature of the position measurement, which, unlike in a conventional electronic autocollimator, is based absolutely on the position of the image rather than on an assumed proportionality between the position and the levels of processed analog electronic signals. The term Cartesian in the name of this apparatus reflects the nature of its optical target. Figure 1 depicts the electronic functional blocks of an electronic absolute Cartesian autocollimator along with its basic optical layout, which is the same as that of a conventional autocollimator. Referring first to the optical layout and functions only, this or any autocollimator is used to measure the compound angular deviation of a flat datum mirror with respect to the optical axis of the autocollimator itself. The optical components include an illuminated target, a beam splitter, an objective or collimating lens, and a viewer or detector (described in more detail below) at a viewing plane. The target and the viewing planes are focal planes of the lens. Target light reflected by the datum mirror is imaged on the viewing plane at unit magnification by the collimating lens. If the normal to the datum mirror is parallel to the optical axis of the autocollimator, then the target image is centered on the viewing plane. Any angular deviation of the normal from the optical axis manifests itself as a lateral displacement of the target image from the center. The magnitude of the displacement is proportional to the focal length and to the magnitude (assumed to be small) of the angular deviation. The direction of the displacement is perpendicular to the axis about which the

  11. Absolute and relative emission spectroscopy study of 3 cm wide planar radio frequency atmospheric pressure bio-plasma source

    SciTech Connect

    Deng, Xiaolong; Nikiforov, Anton Yu Leys, Christophe; Ionita, Eusebiu-Rosini; Dinescu, Gheorghe

    2015-08-03

    The dynamics of low power atmospheric pressure radio frequency discharge generated in Ar gas in long gap of 3 cm is investigated. This plasma source is characterized and analyzed for possible large scale biomedical applications where low gas temperature and potential-less effluent are required. The discharge forms a homogenous glow-like afterglow in ambient air at input power of 30 W with low gas temperature of 330 K, which is desirable in biomedical applications. With absolute calibrated spectroscopy of the discharge, electron density of 0.4 × 10{sup 18} m{sup −3} and electron temperature of 1.5 eV are obtained from continuum Bremsstrahlung radiation of the source. Time and spatial resolved emission spectroscopy is used to analyze discharge generation mechanism and active species formation. It is found that discharge dynamics strongly correlates with the discharge current waveform. Strong Ar(2p) excited states emission is observed nearby the electrodes surface on a distance up to 200 μm in the plasma sheath region at 10 ns after the current peak, whereas OH(A) emission is uniform along of the interelectrode gap.

  12. Design-oriented analytic model of phase and frequency modulated optical links

    NASA Astrophysics Data System (ADS)

    Monsurrò, Pietro; Saitto, Antonio; Tommasino, Pasquale; Trifiletti, Alessandro; Vannucci, Antonello; Cimmino, Rosario F.

    2016-07-01

    An analytic design-oriented model of phase and frequency modulated microwave optical links has been developed. The models are suitable for design of broadband high dynamic range optical links for antenna remoting and optical beamforming, where noise and linearity of the subsystems are a concern Digital filter design techniques have been applied to the design of optical filters working as frequency discriminator, that are the bottleneck in terms of linearity for these systems. The models of frequency modulated, phase modulated, and coherent I/Q link have been used to compare performance of the different architectures in terms of linearity and SFDR.

  13. Frequency-shifted interferometry for fiber-optic sensing

    NASA Astrophysics Data System (ADS)

    Ye, Fei

    This thesis studies frequency-shifted interferometry (FSI), a useful and versatile technique for fiber-optic sensing. I first present FSI theory by describing practical FSI configurations and discussing the parameters that affect system performance. Then, I demonstrate the capabilities of FSI in fiber-optic sensor multiplexing and high sensitivity chemical analysis. We implemented a cryogenic liquid level sensing system in which an array of 3 fiber Bragg grating (FBG) based sensors was interrogated by FSI. Despite sensors' spectral overlap, FSI is able to separate sensor signals according to their spatial locations and to measure their spectra, from which whether a sensor is in liquid or air can be unambiguously determined. I showed that a broadband source paired with a fast tunable filter can be used in FSI systems as the light source. An array of 9 spectrally overlapping FBGs was successfully measured by such a system, indicating the potential of system cost reduction as well as measurement speed improvement. I invented the the FSI-CRD technique, a highly sensitive FSI-based fiber cavity ring-down (CRD) method capable of deducing minuscule loss change in a fiber cavity from the intensity decay rate of continuous-wave light circulating in the cavity. As a proof-of-principle experiment, I successfully measured the fiber bend loss introduced in the fiber cavity with FSI-CRD, which was found to be 0.172 dB/m at a bend radius of 12.5 mm. We then applied FSI-CRD to evanescent-field sensing. We incorporated fiber tapers as the sensor head in the system and measured the concentration of 1-octyne solutions. A minimum detectable 1-octyne concentration of 0.29% was achieved with measurement sensitivity of 0.0094 dB/% 1-octyne. The same system also accurately detected the concentration change of sodium chloride (NaCl) and glucose solutions. Refractive index sensitivity of 1 dB/RIU with a measurement error of 1x10-4 dB was attined for NaCl solutions. Finally, I proposed a

  14. Frequency interleaving towards spectrally efficient directly detected optical OFDM for next-generation optical access networks.

    PubMed

    Mehedy, Lenin; Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai

    2010-10-25

    In this paper, we theoretically analyze and demonstrate that spectral efficiency of a conventional direct detection based optical OFDM system (DDO-OFDM) can be improved significantly using frequency interleaving of adjacent DDO-OFDM channels where OFDM signal band of one channel occupies the spectral gap of other channel and vice versa. We show that, at optimum operating condition, the proposed technique can effectively improve the spectral efficiency of the conventional DDO-OFDM system as much as 50%. We also show that such a frequency interleaved DDO-OFDM system, with a bit rate of 48 Gb/s within 25 GHz bandwidth, achieves sufficient power budget after transmission over 25 km single mode fiber to be used in next-generation time-division-multiplexed passive optical networks (TDM-PON). Moreover, by applying 64- quadrature amplitude modulation (QAM), the system can be further scaled up to 96 Gb/s with a power budget sufficient for 1:16 split TDM-PON.

  15. Recent developments in fiber-based optical frequency comb and its applications

    NASA Astrophysics Data System (ADS)

    Xia, Wei; Chen, Xuzong

    2016-04-01

    Fiber-based optical frequency combs, characterized by compact configuration and outstanding optical properties, have been developed into state-of-the-art precision instruments which are no longer used just for optical frequency metrology, but for a number of applications, including optical clocks, attosecond science, exoplanet searches, medical diagnostics, physicochemical processes control and advanced manufacturing. This short perspective presents some of the milestones and highlights in the evolution of fiber-based optical frequency combs and the technical revolution that are brought by them for a wide range of applications. Along the way, both the challenges and opportunities in the future development of the fiber-based optical frequency comb technology have been described as well.

  16. Absolute Summ

    NASA Astrophysics Data System (ADS)

    Phillips, Alfred, Jr.

    Summ means the entirety of the multiverse. It seems clear, from the inflation theories of A. Guth and others, that the creation of many universes is plausible. We argue that Absolute cosmological ideas, not unlike those of I. Newton, may be consistent with dynamic multiverse creations. As suggested in W. Heisenberg's uncertainty principle, and with the Anthropic Principle defended by S. Hawking, et al., human consciousness, buttressed by findings of neuroscience, may have to be considered in our models. Predictability, as A. Einstein realized with Invariants and General Relativity, may be required for new ideas to be part of physics. We present here a two postulate model geared to an Absolute Summ. The seedbed of this work is part of Akhnaton's philosophy (see S. Freud, Moses and Monotheism). Most important, however, is that the structure of human consciousness, manifest in Kenya's Rift Valley 200,000 years ago as Homo sapiens, who were the culmination of the six million year co-creation process of Hominins and Nature in Africa, allows us to do the physics that we do. .

  17. Progress in optical frequency standards: ultracold Thulium, ions, and passive resonators

    NASA Astrophysics Data System (ADS)

    Kolachevsky, N.; Khabarova, K.; Semerikov, I.; Zalivako, I.; Borisenko, A.

    2017-01-01

    We report on different types of optical clocks and passive frequency references which are under development in our laboratories: optical lattice clock based on the inner-shell transition in the Tm atom at λ = 1.14μm, optical ion clock on single 27Al+ ion, and a family of lasers referenced to ultra-stable ULE and cryogenic silicon cavities.

  18. Baseband integrated acousto-optic frequency shifter/modulator module for fiber optic at 1.3 mum.

    PubMed

    Tsai, C S; Cheng, Z Y

    1993-01-01

    A baseband integrated acoustooptic (AO) frequency shifter/modulator module that consists of a pair of titanium-indiffused proton-exchanged (TIPE) waveguide lenses and a pair of cascaded guided-wave AO Bragg cells has been realized in a Y-cut LiNbO(3) waveguide substrate 0.1 cmx1.0 cmx2.0 cm in size. A device module operating at the optical wavelength of 1.3 mum has provided a -3-dB tunable bandwidth of 120 MHz at baseband. The frequency-shifted or -modulated light propagates in a fixed direction, irrespective of the magnitude of frequency shift or modulation, and is focused into a spot (FWHM) of 6.2-mum size on the output edge of the waveguide. Accordingly, this optical frequency shifter/module can be directly interfaced with single-mode optical fibers to facilitate applications in fiber optic systems.

  19. Frequency-dependent linewidth enhancement factor of optical injection-locked quantum dot/dash lasers.

    PubMed

    Wang, Cheng; Chaibi, Mohamed E; Huang, Heming; Erasme, Didier; Poole, Philip; Even, Jacky; Grillot, Frédéric

    2015-08-24

    Combining theoretical and experimental studies show that optical injection strongly changes the behavior of the linewidth enhancement factor (α(H)-factor) and the FM-to-AM indices ratio (FAIR) in quantum dash/dot semiconductor lasers. In contrast to solitary lasers, both the α(H)-factor and the FAIR at low-frequency modulation are reduced by optical injection. At high modulation frequency, however, the phase-amplitude coupling characteristics are little influenced by optical injection.

  20. Note: Laser frequency shifting by using two novel triple-pass acousto-optic modulator configurations

    SciTech Connect

    Carlos-Lopez, E. de; Lopez, J. M.; Lopez, S.; Espinosa, M. G.; Lizama, L. A.

    2012-11-15

    We report the design of two novel triple-pass acousto-optic modulator systems. These designs are extensions of the well known acousto-optic modulator (AOM) double-pass configuration, which eliminates the angle dependence of the diffracted beam with respect to the modulation frequency. In a triple-pass system, however, the frequency dependence of the angle does not disappear but the frequency shift is larger, spanning 3 times the AOM central frequency. In some applications, such as optically pumped Cesium-beam frequency standards, the frequencies of the two laser beams remain fixed and a triple-pass optical system can be used to reduce to one the number of lasers used in such atomic clocks. The two triple-pass configurations use either a retro-reflecting mirror, or a right angle prism to pass for third time the laser beam through the AOM, obtaining diffraction efficiencies of about 27% and 44%, respectively.

  1. Inter-satellite coherent optical communication locked frequency analysis and method

    NASA Astrophysics Data System (ADS)

    Guo, Haichao; She, Shang; Xiaojun, Li; Song, Dawei

    2014-10-01

    In free space optical homodyne receiver that analyze Residual carrier COSTAS loop, Inter-satellite LEO-GEO laser communication link frequency analysis, result from Doppler frequency shift 10GHz in the maximum range, LEO-GEO inter-satellite laser links between Doppler rate of change in the 20MHz/s. The optical homodyne COSTAS receiver is the application in inter-satellite optical link coherent communication system. The homodyne receiver is the three processes: Scanning frequency, Locked frequency and Locked phase, before the homodyne coherent communication. The processes are validated in lab., and the paper presents the locked frequency data and chart, LO laser frequency with triangle control scanning and receiving optical frequency is mixed less 100MHz intermediate frequency, locked frequency range between 100MHz and 1MHz basically, discriminator method determines mixing intermediate frequency less 1MHz between the signal laser and the LO laser with the low-pass filter due to frequency loop and phase loop noise. When two loops are running, the boundary frequency of laser tuning is fuzzy, so that we must be decoupling internal PID parameters. In the Locked frequency and phase COSTAS loop homodyne receiver gave the eye-diagram with Bit error rate 10E-7.

  2. Optical frequency combs generated by four-wave mixing in optical fibers for astrophysical spectrometer calibration and metrology.

    PubMed

    Cruz, Flavio C

    2008-08-18

    Optical frequency combs generated by multiple four-wave mixing in short and highly nonlinear optical fibers are proposed for use as high precision frequency markers, calibration of astrophysical spectrometers, broadband spectroscopy and metrology. Implementations can involve two optical frequency standards as input lasers, or one standard and a second laser phase-locked to it using a stable microwave reference oscillator. Energy and momentum conservation required by the parametric generation assures phase coherence among comb frequencies, while fibers with short lengths can avoid linewidth broadening and stimulated Brillouin scattering. In contrast to combs from mode-locked lasers or microcavities, the absence of a resonator allows large tuning of the frequency spacing from tens of gigahertz to beyond teraHertz.

  3. Generation of optical frequency combs in fibres: an optical pulse analysis

    NASA Astrophysics Data System (ADS)

    Zajnulina, Marina; Böhm, Michael; Blow, Keith; Chavez Boggio, José M.; Rieznik, Andres A.; Haynes, Roger; Roth, Martin M.

    2014-07-01

    The innovation of optical frequency combs (OFCs) generated in passive mode-locked lasers has provided astronomy with unprecedented accuracy for wavelength calibration in high-resolution spectroscopy in research areas such as the discovery of exoplanets or the measurement of fundamental constants. The unique properties of OCFs, namely a highly dense spectrum of uniformly spaced emission lines of nearly equal intensity over the nominal wavelength range, is not only beneficial for high-resolution spectroscopy. Also in the low- to medium-resolution domain, the OFCs hold the promise to revolutionise the calibration techniques. Here, we present a novel method for generation of OFCs. As opposed to the mode-locked laser-based approach that can be complex, costly, and difficult to stabilise, we propose an all optical fibre-based system that is simple, compact, stable, and low-cost. Our system consists of three optical fibres where the first one is a conventional single-mode fibre, the second one is an erbium-doped fibre and the third one is a highly nonlinear low-dispersion fibre. The system is pumped by two equally intense continuous-wave (CW) lasers. To be able to control the quality and the bandwidth of the OFCs, it is crucial to understand how optical solitons arise out of the initial modulated CW field in the first fibre. Here, we numerically investigate the pulse evolution in the first fibre using the technique of the solitons radiation beat analysis. Having applied this technique, we realised that formation of higherorder solitons is supported in the low-energy region, whereas, in the high-energy region, Kuznetsov-Ma solitons appear.

  4. Optical frequency standards based on mercury and aluminum ions

    NASA Astrophysics Data System (ADS)

    Itano, W. M.; Bergquist, J. C.; Brusch, A.; Diddams, S. A.; Fortier, T. M.; Heavner, T. P.; Hollberg, L.; Hume, D. B.; Jefferts, S. R.; Lorini, L.; Parker, T. E.; Rosenband, T.; Stalnaker, J. E.

    2007-09-01

    Single-trapped-ion frequency standards based on a 282 nm transition in 199Hg+ and on a 267 nm transition in 27Al + have been developed at NIST over the past several years. Their frequencies are measured relative to each other and to the NIST primary frequency standard, the NIST-F1 cesium fountain, by means of a self-referenced femtosecond laser frequency comb. Both ion standards have demonstrated instabilities and inaccuracies of less than 1 × 10 -16.

  5. Absolute Photometry

    NASA Astrophysics Data System (ADS)

    Hartig, George

    1990-12-01

    The absolute sensitivity of the FOS will be determined in SV by observing 2 stars at 3 epochs, first in 3 apertures (1.0", 0.5", and 0.3" circular) and then in 1 aperture (1.0" circular). In cycle 1, one star, BD+28D4211 will be observed in the 1.0" aperture to establish the stability of the sensitivity and flat field characteristics and improve the accuracy obtained in SV. This star will also be observed through the paired apertures since these are not calibrated in SV. The stars will be observed in most detector/grating combinations. The data will be averaged to form the inverse sensitivity functions required by RSDP.

  6. Frequency Comparison of Al+ and Hg+ Optical Standards

    NASA Astrophysics Data System (ADS)

    Rosenband, T.; Hume, D. B.; Brusch, A.; Lorini, L.; Schmidt, P. O.; Fortier, T. M.; Stalnaker, J. E.; Diddams, S. A.; Newbury, N. R.; Swann, W. C.; Oskay, W. H.; Itano, W. M.; Wineland, D. J.; Bergquist, J. C.

    2008-04-01

    We compare the frequencies of two single ion frequency standards: 27Al+ and 199Hg+. Systematic fractional frequency uncertainties of both standards are below 10-16, and the statistical measurement uncertainty is below 5 × 10-17. Recent ratio measurements show a reproducibility that is better than 10-16.

  7. Optical frequency measurement of the 1S-3S two-photon transition in hydrogen

    NASA Astrophysics Data System (ADS)

    Arnoult, O.; Nez, F.; Julien, L.; Biraben, F.

    2010-11-01

    This article reports the first optical frequency measurement of the 1S-3S transition in hydrogen. The excitation of this transition occurs at a wavelength of 205 nm which is obtained with two frequency doubling stages of a titanium sapphire laser at 820 nm. Its frequency is measured with an optical frequency comb. The second-order Doppler effect is evaluated from the observation of the motional Stark effect due to a transverse magnetic field perpendicular to the atomic beam. The measured value of the 1S_{1/2}( F = 1)-3S1/2( F = 1) frequency splitting is 2 922 742 936.729(13) MHz with a relative uncertainty of 4.5 × 10-12. After the measurement of the 1S-2S frequency, this result is the most precise of the optical frequencies in hydrogen.

  8. Offset-Free Gigahertz Midinfrared Frequency Comb Based on Optical Parametric Amplification in a Periodically Poled Lithium Niobate Waveguide

    NASA Astrophysics Data System (ADS)

    Mayer, A. S.; Phillips, C. R.; Langrock, C.; Klenner, A.; Johnson, A. R.; Luke, K.; Okawachi, Y.; Lipson, M.; Gaeta, A. L.; Fejer, M. M.; Keller, U.

    2016-11-01

    We report the generation of an optical-frequency comb in the midinfrared region with 1-GHz comb-line spacing and no offset with respect to absolute-zero frequency. This comb is tunable from 2.5 to 4.2 μ m and covers a critical spectral region for important environmental and industrial applications, such as molecular spectroscopy of trace gases. We obtain such a comb using a highly efficient frequency conversion of a near-infrared frequency comb. The latter is based on a compact diode-pumped semiconductor saturable absorber mirror-mode-locked ytterbium-doped calcium-aluminum gadolynate (Yb:CALGO) laser operating at 1 μ m . The frequency-conversion process is based on optical parametric amplification (OPA) in a periodically poled lithium niobate (PPLN) chip containing buried waveguides fabricated by reverse proton exchange. The laser with a repetition rate of 1 GHz is the only active element of the system. It provides the pump pulses for the OPA process as well as seed photons in the range of 1.4 - 1.8 μ m via supercontinuum generation in a silicon-nitride (Si3 N4 ) waveguide. Both the PPLN and Si3 N4 waveguides represent particularly suitable platforms for low-energy nonlinear interactions; they allow for mid-IR comb powers per comb line at the microwatt level and signal amplification levels up to 35 dB, with 2 orders of magnitude less pulse energy than reported in OPA systems using bulk devices. Based on numerical simulations, we explain how high amplification can be achieved at low energy using the interplay between mode confinement and a favorable group-velocity mismatch configuration where the mid-IR pulse moves at the same velocity as the pump.

  9. Comment on the Paper "Absolute Motion Determined from Michelson- Type Experiments in Optical Media" by V. P. Dmitriyev

    NASA Astrophysics Data System (ADS)

    Sfarti, Adrian

    2011-12-01

    Alternative explanations to the Michelson-Morley experiment exist and continue to be produced. In the current paper, we will correct a recently published paper concerning a reenactment of the famous experiment. The author of the paper in cause claims the presence of a non-null result though he did not run any experiment himself. Dmitriyev bases his paper on a paper by Demjanov that has already been retracted by the journal where he originally published (V. V. Demjanov, Phys. Lett. A 374, 1110 (2010)). Our paper is organized as follows: in the background section we will give the correct expressions for the relativistic light speed in arbitrary media as opposed to the incorrect ones given in V. P. Dmitriyev, Z. Naturforsch. 66a, 228 (2011). We will follow by explaining the correct equations of the Michelson-Morley experiment in a refractive medium with n > 1, and we will outline the errors in V. P. Dmitriyev, Z. Naturforsch. 66a, 228 (2011). The non-mainstream claims of detecting `absolute motion' are refuted by both theoretical and experimental data.

  10. Tracking performance of optical phase locking loop with frequency discrimination and control subloop

    NASA Astrophysics Data System (ADS)

    Wang, Yunxiang; Li, Biao; Guo, Yong; Wang, Zhiyong; Shi, Shuangjin; Su, Jun; Qiu, Qi

    2016-05-01

    Optical phase locking is a key technique in homodyne coherent optical communication, coherent optical detection, and active coherent laser beam combination. In these applications, environmental temperature variation and mechanical vibration would affect the accuracy of phase locking, or even cause losing lock. These disturbances are generally equivalent to introducing phase jitter, phase step, frequency ramp, and frequency step in the loop. A frequency discrimination and control subloop is introduced to improve the frequency acquisition, and the tracking performance is studied experimentally. The loop can track phase step in 0.2 ms, and precisely track ±π/2 sine phase jitter for jittering frequency lower than 1 kHz. For frequency ramp, the residual phase error is unaffected for ramping rates slower than 40 MHz/s. The frequency discrimination and control subloop makes the loop lock quickly under a frequency step larger than the pull-in frequency. The mean tracking time is 31 ms for a 1 MHz frequency step. The maximum trackable frequency step is around 160 MHz. Continuous or step variation of phase and frequency could be tracked by the loop with the frequency discrimination and control subloop.

  11. On the absolute accuracy of Zernike polynomials to characterize the corneal surface and the optical aberrations of the human eye

    NASA Astrophysics Data System (ADS)

    Carvalho, Luis A.

    2005-06-01

    Zernike Polynomials have been successfully used for many years in optics. Nevertheless there are some recent discussions regarding their accuracy when applied to surfaces such as the human cornea. A set of synthetic surfaces resembling several common corneal anomalies was sampled and was also used to compute the optical path difference using a simple ray-tracing procedure. The Root Mean Square Error between the Zernike Polynomials fit and the theoretical elevation and WF error surface was computed for both surfaces and for all number of Zernike terms. We have found that RMSE for the simplest, most symmetric corneal surface (spherical shape) and for the most complex shape (post-radial keratotomy) both the optical path difference and surface elevation, for 1 through 36 Zernike terms, range from: 421.4 to 0.8 microns, and 421.4 to 8.2 microns, respectively; mean RMSE for maximum Zernike terms for both surfaces were 4.5 microns. Computations in this work suggest that, for surfaces such as post-RK, keratoconus or post-keratoplasty, even more than 36 terms may be necessary in order to obtain minimum precision requirements. We suggest that the number of Zernike Polynomial should not be a global fixed conventional value but rather based on specific surface properties.

  12. A deep-UV optical frequency comb at 205 nm.

    PubMed

    Peters, E; Diddams, S A; Fendel, P; Reinhardt, S; Hänsch, T W; Udem, Th

    2009-05-25

    By frequency quadrupling a picosecond pulse train from a Ti:sapphire laser at 820 nm we generate a frequency comb at 205 nm with nearly bandwidth-limited pulses. The nonlinear frequency conversion is accomplished by two successive frequency doubling stages that take place in resonant cavities that are matched to the pulse repetition rate of 82 MHz. This allows for an overall efficiency of 4.5 % and produces an output power of up to 70 mW for a few minutes and 25 mW with continuous operation for hours. Such a deep UV frequency comb may be employed for direct frequency comb spectroscopy in cases where it is less efficient to convert to these short wavelengths with continuous wave lasers.

  13. Self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators.

    PubMed

    Dai, Jian; Xu, Xingyuan; Wu, Zhongle; Dai, Yitang; Yin, Feifei; Zhou, Yue; Li, Jianqiang; Xu, Kun

    2015-11-16

    An ultraflat self-oscillating optical frequency comb generator based on an optoelectronic oscillator employing cascaded modulators was proposed and experimentally demonstrated. By incorporating the optoelectronic oscillation loop with cascaded modulators into the optical frequency comb generator, 11 ultraflat comb lines would be generated, and the frequency spacing is equal to the oscillation frequency of the OEO. 10 and 12GHz optical frequency combs are demonstrated with the spectral power variation below 0.82dB and 0.93dB respectively. The corresponding spectral pure microwave source are also generated and evaluated. The corresponding single-sideband phase noise are as low as -122dBc/Hz and -115 dBc/Hz at 10 kHz offset frequency.

  14. Measurement of absolute frequency of continuous-wave terahertz radiation in real time using a free-running, dual-wavelength mode-locked, erbium-doped fibre laser

    NASA Astrophysics Data System (ADS)

    Hu, Guoqing; Mizuguchi, Tatsuya; Zhao, Xin; Minamikawa, Takeo; Mizuno, Takahiko; Yang, Yuli; Li, Cui; Bai, Ming; Zheng, Zheng; Yasui, Takeshi

    2017-02-01

    A single, free-running, dual-wavelength mode-locked, erbium-doped fibre laser was exploited to measure the absolute frequency of continuous-wave terahertz (CW-THz) radiation in real time using dual THz combs of photo-carriers (dual PC-THz combs). Two independent mode-locked laser beams with different wavelengths and different repetition frequencies were generated from this laser and were used to generate dual PC-THz combs having different frequency spacings in photoconductive antennae. Based on the dual PC-THz combs, the absolute frequency of CW-THz radiation was determined with a relative precision of 1.2 × 10‑9 and a relative accuracy of 1.4 × 10‑9 at a sampling rate of 100 Hz. Real-time determination of the absolute frequency of CW-THz radiation varying over a few tens of GHz was also demonstrated. Use of a single dual-wavelength mode-locked fibre laser, in place of dual mode-locked lasers, greatly reduced the size, complexity, and cost of the measurement system while maintaining the real-time capability and high measurement precision.

  15. Measurement of absolute frequency of continuous-wave terahertz radiation in real time using a free-running, dual-wavelength mode-locked, erbium-doped fibre laser

    PubMed Central

    Hu, Guoqing; Mizuguchi, Tatsuya; Zhao, Xin; Minamikawa, Takeo; Mizuno, Takahiko; Yang, Yuli; Li, Cui; Bai, Ming; Zheng, Zheng; Yasui, Takeshi

    2017-01-01

    A single, free-running, dual-wavelength mode-locked, erbium-doped fibre laser was exploited to measure the absolute frequency of continuous-wave terahertz (CW-THz) radiation in real time using dual THz combs of photo-carriers (dual PC-THz combs). Two independent mode-locked laser beams with different wavelengths and different repetition frequencies were generated from this laser and were used to generate dual PC-THz combs having different frequency spacings in photoconductive antennae. Based on the dual PC-THz combs, the absolute frequency of CW-THz radiation was determined with a relative precision of 1.2 × 10−9 and a relative accuracy of 1.4 × 10−9 at a sampling rate of 100 Hz. Real-time determination of the absolute frequency of CW-THz radiation varying over a few tens of GHz was also demonstrated. Use of a single dual-wavelength mode-locked fibre laser, in place of dual mode-locked lasers, greatly reduced the size, complexity, and cost of the measurement system while maintaining the real-time capability and high measurement precision. PMID:28186148

  16. Midinfrared frequency comb from self-stable degenerate GaAs optical parametric oscillator.

    PubMed

    Lee, Kevin F; Mohr, C; Jiang, J; Schunemann, Peter G; Vodopyanov, K L; Fermann, M E

    2015-10-05

    We pump a degenerate frequency-divide-by-two optical parametric oscillator (OPO) based on orientation-patterned GaAs with a stable Tm frequency comb at 2 micrometer wavelength and measure the OPO comb offset frequency and linewidth. We show frequency division by two with sub-Hz relative linewidth of the comb teeth. The OPO thermally self-stabilizes and oscillates for nearly an hour without any active control.

  17. Study of the cortical representation of whisker frequency selectivity using voltage-sensitive dye optical imaging

    PubMed Central

    Tsytsarev, Vassiliy; Pumbo, Elena; Tang, Qinggong; Chen, Chao-Wei; Kalchenko, Vyacheslav; Chen, Yu

    2016-01-01

    ABSTRACT The facial whiskers of rodents act as a high-resolution tactile apparatus that allow the animal to detect the finest details of its environment. Previously it was shown that whisker-sensitive neurons in the somatosensory cortex show frequency selectivity to small amplitude stimuli, An intravital voltage-sensitive dye optical imaging (VSDi) method in combination with the different frequency whisker stimulation was used in order to visualize neural activity in the mice somatosensory cortex in response to the stimulation of a single whisker by different frequencies. Using the intravital voltage-sensitive dye optical imaging (VSDi) method in combination with the different frequency whisker stimulation we visualized neural activity in the mice somatosensory cortex in response to the stimulation of a single whisker by different frequencies. We found that whisker stimuli with different frequencies led to different optical signals in the barrel field. Our results provide evidence that different neurons of the barrel cortex have different frequency preferences. This supports prior research that whisker deflections cause responses in cortical neurons within the barrel field according to the frequency of the stimulation. Many studies of the whisker frequency selectivity were performed using unit recording but to map spatial organization, imaging methods are essential. In the work described in the present paper, we take a serious step toward detailed functional mapping of the somatosensory cortex using VSDi. To our knowledge, this is the first demonstration of whisker frequency sensitivity and selectivity of barrel cortex neurons with optical imaging methods. PMID:28243518

  18. Measurement of the Yb I S10-P11 transition frequency at 399 nm using an optical frequency comb

    NASA Astrophysics Data System (ADS)

    Kleinert, Michaela; Gold Dahl, M. E.; Bergeson, Scott

    2016-11-01

    We determine the frequency of the Yb I S10-P11 transition at 399 nm using an optical frequency comb. Although this transition was measured previously using an optical transfer cavity [D. Das et al., Phys. Rev. A 72, 032506 (2005), 10.1103/PhysRevA.72.032506], recent work has uncovered significant errors in that method. We compare our result of 751 526 533.49 ± 0.33 MHz for the 174Yb isotope with those from the literature and discuss observed differences. We verify the correctness of our method by measuring the frequencies of well-known transitions in Rb and Cs, and by demonstrating proper control of systematic errors in both laser metrology and atomic spectroscopy. We also demonstrate the effect of quantum interference due to hyperfine structure in a divalent atomic system and present isotope shift measurements for all stable isotopes.

  19. Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

    NASA Astrophysics Data System (ADS)

    Fat'yanov, O. V.; Asimow, P. D.

    2015-10-01

    We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

  20. Contributed Review: Absolute spectral radiance calibration of fiber-optic shock-temperature pyrometers using a coiled-coil irradiance standard lamp

    SciTech Connect

    Fat’yanov, O. V. Asimow, P. D.

    2015-10-15

    We describe an accurate and precise calibration procedure for multichannel optical pyrometers such as the 6-channel, 3-ns temporal resolution instrument used in the Caltech experimental geophysics laboratory. We begin with a review of calibration sources for shock temperatures in the 3000-30 000 K range. High-power, coiled tungsten halogen standards of spectral irradiance appear to be the only practical alternative to NIST-traceable tungsten ribbon lamps, which are no longer available with large enough calibrated area. However, non-uniform radiance complicates the use of such coiled lamps for reliable and reproducible calibration of pyrometers that employ imaging or relay optics. Careful analysis of documented methods of shock pyrometer calibration to coiled irradiance standard lamps shows that only one technique, not directly applicable in our case, is free of major radiometric errors. We provide a detailed description of the modified Caltech pyrometer instrument and a procedure for its absolute spectral radiance calibration, accurate to ±5%. We employ a designated central area of a 0.7× demagnified image of a coiled-coil tungsten halogen lamp filament, cross-calibrated against a NIST-traceable tungsten ribbon lamp. We give the results of the cross-calibration along with descriptions of the optical arrangement, data acquisition, and processing. We describe a procedure to characterize the difference between the static and dynamic response of amplified photodetectors, allowing time-dependent photodiode correction factors for spectral radiance histories from shock experiments. We validate correct operation of the modified Caltech pyrometer with actual shock temperature experiments on single-crystal NaCl and MgO and obtain very good agreement with the literature data for these substances. We conclude with a summary of the most essential requirements for error-free calibration of a fiber-optic shock-temperature pyrometer using a high-power coiled tungsten halogen

  1. A 920-kilometer optical fiber link for frequency metrology at the 19th decimal place.

    PubMed

    Predehl, K; Grosche, G; Raupach, S M F; Droste, S; Terra, O; Alnis, J; Legero, Th; Hänsch, T W; Udem, Th; Holzwarth, R; Schnatz, H

    2012-04-27

    Optical clocks show unprecedented accuracy, surpassing that of previously available clock systems by more than one order of magnitude. Precise intercomparisons will enable a variety of experiments, including tests of fundamental quantum physics and cosmology and applications in geodesy and navigation. Well-established, satellite-based techniques for microwave dissemination are not adequate to compare optical clocks. Here, we present phase-stabilized distribution of an optical frequency over 920 kilometers of telecommunication fiber. We used two antiparallel fiber links to determine their fractional frequency instability (modified Allan deviation) to 5 × 10(-15) in a 1-second integration time, reaching 10(-18) in less than 1000 seconds. For long integration times τ, the deviation from the expected frequency value has been constrained to within 4 × 10(-19). The link may serve as part of a Europe-wide optical frequency dissemination network.

  2. Effect of coherence and polarization on frequency resolution in optical Fourier transforming system.

    PubMed

    Ostrovsky, Andrey S; Olvera-Santamaría, Miguel Á; Romero-Soría, Paulo C

    2011-12-01

    Using an example of vector Gaussian Schell-model beam, we demonstrate and analyze the dependence of the spatial frequency resolution in optical Fourier transforming system on the intrinsic coherence-polarization structure of illumination.

  3. Surface plasmon optical antennae in the infrared region with high resonant efficiency and frequency selectivity.

    PubMed

    Ueno, Kosei; Sun, Quan; Mino, Masahiro; Itoh, Takumi; Oshikiri, Tomoya; Misawa, Hiroaki

    2016-08-08

    Infrared light has received attention for sensor applications, including fingerprint spectroscopy, in the bioengineering and security fields. Surface plasmon physics enables the operation of a light harvesting optical antenna. Gold nanochains exhibit localized surface plasmon resonance (LSPR) in the infrared region with high frequency selectivity. However, a feasible design for optical antennae with a higher resonant efficiency and frequency selectivity as a function of structural design and periodicity is still unknown. In the present study, we investigated the relationship between the resonant efficiency and frequency selectivity as a function of the structural design of gold nanochains and explored structural periodicity for obtaining highly frequency-selective optical antennae. An optical antenna design with higher resonant efficiency is proposed on the basis of its efficient interaction with non-polarized light.

  4. Effect of noise on Frequency-Resolved Optical Gating measurements of ultrashort pulses

    SciTech Connect

    Fittinghoff, D.N.; DeLong, K.W.; Ladera, C.L.; Trebino, R.

    1995-02-01

    We study the effects of noise in Frequency-Resolved Optical Gating measurements of ultrashort pulses. We quantify the measurement accuracy in the presence of additive, muliplicative, and quantization noise, and discuss filtering and pre-processing of the data.

  5. Mid-infrared optical parametric oscillators and frequency combs for molecular spectroscopy.

    PubMed

    Vainio, M; Halonen, L

    2016-02-14

    Nonlinear optical frequency conversion is one of the most versatile methods to generate wavelength-tunable laser light in the mid-infrared region. This spectral region is particularly important for trace gas detection and other applications of molecular spectroscopy, because it accommodates the fundamental vibrational bands of several interesting molecules. In this article, we review the progress of the most significant nonlinear optics instruments for widely tunable, high-resolution mid-infrared spectroscopy: continuous-wave optical parametric oscillators and difference frequency generators. We extend our discussion to mid-infrared optical frequency combs, which are becoming increasingly important spectroscopic tools, owing to their capability of highly sensitive and selective parallel detection of several molecular species. To illustrate the potential and limitations of mid-infrared sources based on nonlinear optics, we also review typical uses of these instruments in both applied and fundamental spectroscopy.

  6. Frequency-resolved noise figure measurements of phase (in)sensitive fiber optical parametric amplifiers.

    PubMed

    Malik, R; Kumpera, A; Lorences-Riesgo, A; Andrekson, P A; Karlsson, M

    2014-11-17

    We measure the frequency-resolved noise figure of fiber optical parametric amplifiers both in phase-insensitive and phase-sensitive modes in the frequency range from 0.03 to 3 GHz. We also measure the variation in noise figure due to the degradation in pump optical signal to noise ratio and also as a function of the input signal powers. Noise figure degradation due to stimulated Brillouin scattering is observed.

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

    SciTech Connect

    Arakawa, Hiroyuki Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

    2014-04-15

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

  8. Frequency-modulated light scattering interferometry used for assessment of optical properties in turbid media

    NASA Astrophysics Data System (ADS)

    Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune

    2013-02-01

    Frequency-modulated light scattering interferometry, which employs a frequency-modulated coherent light source and examines the intensity fluctuation of the resulting scattered light using a heterodyne detection scheme, was utilized to evaluate the optical properties of liquid phantoms made of Intralipid® and Indian ink. Based on the diffusion theory, nonlinear fits to the power spectrum of the heterodyne-detected light intensity are performed and discussed in detail, and the optical properties of liquid phantoms are consequently retrieved.

  9. FBG sensor interrogation using fiber optical bistability in frequency domain

    NASA Astrophysics Data System (ADS)

    Lv, Guohui; Ou, Jinping; Ye, Hongan; Zhou, Zhi; Shang, Shaohua; Yang, Chao; Wang, Huiying

    2007-01-01

    In this paper, we propose a novel scheme of fiber Bragg grating interrogation by use of hybrid fiber optical bistable device (OBD). The OBD is realized in the fiber Bragg grating (FBG) sensing element. Light source is an electronic tuned widely swept ring fiber laser. In this experiment, FBG's are acting as optical intensity modulator and sensing elements at same time. Combined with feedback control circuit, the OBD can be used as an optic-fiber sensor working in digital type through bistable switching phenomenon. We discuss the mechanism of this bistable sensor. Scanning the bias Voltage on PZT, the bistable pulse signal can be counted by circuit that operates in the manner of a pulse-equivalent. If we use 16 bit Digital Analog Converter (DAC), the resolution will achieve 1pm level. High accuracy, high speed and high ratio of signal to noise are the advantages of this scheme.

  10. Frequency transfer via a two-way optical phase comparison on a multiplexed fiber network.

    PubMed

    Calosso, C E; Bertacco, E; Calonico, D; Clivati, C; Costanzo, G A; Frittelli, M; Levi, F; Mura, A; Godone, A

    2014-03-01

    We performed a two-way remote optical phase comparison on optical fiber. Two optical frequency signals were launched in opposite directions in an optical fiber and their phases were simultaneously measured at the other end. In this technique, the fiber noise is passively canceled, and we compared two optical frequencies at the ultimate 10(-21) stability level. The experiment was performed on a 47 km fiber that is part of the metropolitan network for Internet traffic. The technique relies on the synchronous measurement of the optical phases at the two ends of the link, which is here performed by digital electronics. This scheme offers some advantages with respect to active noise cancellation schemes, as the light travels only once in the fiber.

  11. Parallel multichannel optical correlator for frequency subband decomposition

    NASA Astrophysics Data System (ADS)

    Barbe, J.; Campos, Juan; Iemmi, Claudio C.; Nicolas, Josep

    2001-08-01

    Many applications require a complex processing, using for it a bank of filters. Different architectures have been proposed of optical processors to perform a parallel filtering. We prose a new multichannel architecture based in the translation Fourier Transform properties. These properties allowed us to design multichannels phase filters. The architecture does not need the introduction of any additional modification in the optical processor. We developed an application for texture classification in real time. We obtain excellent results in the texture classification process, 99 percent of images have been correctly classified.

  12. Mid-Range Spatial Frequency Errors in Optical Components.

    DTIC Science & Technology

    1983-01-01

    pattern. Malacara (1978, pp. 356-359) describes the diffraction intensity distri- bution on either side of the focal plane and presents a diagram of the...Leoble and Co., Ltd., Aug. 1963. Kintner, Eric C., and Richard M. Sillitto. "A New Analytic Method for Computing the Optical Transfer Function." OPTICA ...2, 1976. Malacara , Daniel (ed). Optical Shop Testing. New York: John Wiley and Sons, 1978. Reticon Corporation. Reticon G Series Data Sheet. Sunnyvale, CA: Reticon, 1976. 41 FILMED 9-85 DTIC

  13. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

    PubMed Central

    Consoli, F.; De Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Verona, C.

    2016-01-01

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation. PMID:27301704

  14. Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

    NASA Astrophysics Data System (ADS)

    Consoli, F.; de Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; di Giorgio, G.; Ingenito, F.; Verona, C.

    2016-06-01

    We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation.

  15. Flight-Like Optical Reference Cavity for GRACE Follow-On Laser Frequency Stabilization

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; deVine, G.; Klipstein, W. M.; McKenzie, K.; Spero, R.; Thompson, R.; Yu, N.; Stephens, M.; Leitch, J.; Pierce, R.; Shaddock, D.; Lam, T.

    2011-01-01

    We describe a prototype optical cavity and associated optics that has been developed to provide a stable frequency reference for a future space-based laser ranging system. This instrument is being considered for inclusion as a technology demonstration on the recently announced GRACE follow-on mission, which will monitor variations in the Earth's gravity field.

  16. Long-Distance Frequency Transfer Over an Urban Fiber Link Using Optical Phase Stabilization

    DTIC Science & Technology

    2008-12-01

    eliability, and the potential for phase noise cancellation. Microwave frequency transmission using amplitude odulation of an optical carrier has demonstrated...isolation box. About W of optical power, including 30% in the phase odulation sidebands, are typically sent onto the cavity ith a coupling

  17. Frequency dependent optical conductivity of strained graphene at T=0 from an effective quantum field theory

    NASA Astrophysics Data System (ADS)

    Zhang, Shi-Jiang; Pan, Hui; Wang, Hai-Long

    2017-04-01

    An effective quantum field theory (EQFT) graphene sheet with arbitrary one dimensional strain field is derived from a microscopic effective low energy Hamiltonian. The geometric meaning of the strain-induced complex gauge field is clarified. The optical conductivity is also investigated, and a frequency dependent optical conductivity is obtained. The actual value of interband optical conductivity along the deformed direction is C0 + C1/ω2 in spite of the particular strain fields at T=0.

  18. Frequency-resolved optical-gating measurements of ultrashort pulses using surface third-harmonic generation

    SciTech Connect

    Tsang, T.; Krumbuegel, M.A.; DeLong, K.W.; Fittinghoff, D.N.; Trebino, R.

    1996-09-01

    We demonstrate what is to our knowledge the first frequency-resolved optical gating (FROG) technique to measure ultrashort pulses from an unamplified Ti:sapphire laser oscillator without direction-of-time ambiguity. This technique utilizes surface third-harmonic generation as the nonlinear-optical effect and, surprisingly, is the most sensitive third-order FROG geometry yet. {copyright} {ital 1996 Optical Society of America.}

  19. Recent developments and proposed schemes for trapped ion frequency standards. [trapped mercury ions for microwave and optical frequency standards

    NASA Technical Reports Server (NTRS)

    Maleki, L.

    1982-01-01

    Ion traps are exciting candidates as future precision frequency sources. Recent developments demonstrate that mercury ion frequency standards are capable of a stability performance comparable to commercial cesium standards. There is, however, considerable room for improvement with regard to the signal to noise problem. The 40 GHz microwave frequency implies that a careful design should be implemented to ensure the elimination of the unwanted side bands in the microwave pump signal. A long life, high performance light source to be used in a trapped mercury ion microwave standard must be developed and the long term performance of a trapped mercury ion microwave standard must be investigated. While newly proposed two photon pumping schemes in conjuction with mercury ions promise exciting developments for both microwave and optical frequency standards, other ions that may be potential candidates should be evaluated for their usefulness.

  20. Optically based quantification of absolute cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution in rodents

    NASA Astrophysics Data System (ADS)

    Yaseen, Mohammad A.; Srinivasan, Vivek J.; Sakadžić, Sava; Vinogradov, Sergei A.; Boas, David A.

    2010-02-01

    Measuring oxygen delivery in brain tissue is important for identifying the pathophysiological changes associated with brain injury and various diseases such as cancer, stroke, and Alzheimer's disease. We have developed a multi-modal imaging system for minimally invasive measurement of cerebral oxygenation and blood flow in small animals with high spatial resolution. The system allows for simultaneous measurement of blood flow using Fourier-domain optical coherence tomography, and oxygen partial pressure (pO2) using either confocal or multiphoton phosphorescence lifetime imaging with exogenous porphyrin-based dyes sensitive to dissolved oxygen. Here we present the changes in pO2 and blood flow in superficial cortical vessels of Sprague Dawley rats in response to conditions such as hypoxia, hyperoxia, and functional stimulation. pO2 measurements display considerable heterogeneity over distances that cannot be resolved with more widely used oxygen-monitoring techniques such as BOLD-fMRI. Large increases in blood flow are observed in response to functional stimulation and hypoxia. Our system allows for quantification of cerebral metabolic rate of oxygen (CMRO2) with high spatial resolution, providing a better understanding of metabolic dynamics during functional stimulation and under various neuropathologies. Ultimately, better insight into the underlying mechanisms of neuropathologies will facilitate the development of improved therapeutic strategies to minimize damage to brain tissue.

  1. Dual frequency optical carrier technique for transmission of reference frequencies in dispersive media

    NASA Technical Reports Server (NTRS)

    Maleki, Lutfollah (Inventor)

    1993-01-01

    Two different carrier frequencies modulated by a reference frequency are transmitted to each receiver to be synchronized therewith. Each receiver responds to local phase differences between the two received signals to correct the phase of one of them so as to maintain the corrected signal as a reliable synchronization reference.

  2. Doppler-Free Two-Photon Absorption Spectroscopy of Naphthalene Assisted by AN Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Nishiyama, Akiko; Matsuba, Ayumi; Misono, Masatoshi

    2014-06-01

    Optical frequency combs are powerful tools for precise frequency measurements in various wavelength regions. The combs have been applied not only to metrology, but also to molecular spectroscopy. Recently, we studied high resolution spectroscopy of iodine molecule assisted by an optical frequency comb. In the study, the comb was used for frequency calibration of a scanning dye laser. In this study, we developed a frequency calibration scheme with a comb and an acousto-optic modulator to realize more precise frequency measurement in a wide frequency range. And the frequency calibration scheme was applied to Doppler-free two-photon absorption (DFTPA) spectroscopy of naphthalene. Naphthalene is one of the prototypical aromatic molecules, and its detailed structure and dynamics in excited states have been reported. We measured DFTPA spectra of A^1B1u(v4=1) ← X^1A_g(v=0) transition around 298 nm. A part of obtained spectra is shown in the figure. The spectral lines are rotationally resolved and the resolution is about 100 kHz. The horizontal axis was calibrated by the developed frequency calibration system employing the comb. The uncertainties of the calibrated frequencies were determined by the fluctuations of the comb modes which were stabilized to a GPS-disciplined clock. A. Nishiyama, D. Ishikawa, and M. Misono, J. Opt. Soc. Am. B 30, 2107 (2013).

  3. High resolution atomic coherent control via spectral phase manipulation of an optical frequency comb.

    PubMed

    Stowe, Matthew C; Cruz, Flavio C; Marian, Adela; Ye, Jun

    2006-04-21

    We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

  4. High Resolution Atomic Coherent Control via Spectral Phase Manipulation of an Optical Frequency Comb

    SciTech Connect

    Stowe, Matthew C.; Cruz, Flavio C.; Marian, Adela; Ye Jun

    2006-04-21

    We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

  5. High Accuracy Optical Inverse Square Law Experiment Using Inexpensive Light to Frequency Converters

    ERIC Educational Resources Information Center

    Wanser, Keith H.; Mahrley, Steve; Tanner, Joshua

    2012-01-01

    In this paper we report on the use of two different light to frequency converters, four different light sources, three of which are novel and inexpensive, and a hand held digital multimeter with a frequency counter, suitable for making accurate and rapid determination of the optical inverse square law exponent of -2 to better than [plus or…

  6. Elimination of the light shift in rubidium gas cell frequency standards using pulsed optical pumping

    NASA Technical Reports Server (NTRS)

    English, T. C.; Jechart, E.; Kwon, T. M.

    1978-01-01

    Changes in the intensity of the light source in an optically pumped, rubidium, gas cell frequency standard can produce corresponding frequency shifts, with possible adverse effects on the long-term frequency stability. A pulsed optical pumping apparatus was constructed with the intent of investigating the frequency stability in the absence of light shifts. Contrary to original expectations, a small residual frequency shift due to changes in light intensity was experimentally observed. Evidence is given which indicates that this is not a true light-shift effect. Preliminary measurements of the frequency stability of this apparatus, with this small residual pseudo light shift present, are presented. It is shown that this pseudo light shift can be eliminated by using a more homogeneous C-field. This is consistent with the idea that the pseudo light shift is due to inhomogeneity in the physics package (position-shift effect).

  7. Two-Photon Spectroscopy in Rb for an Optical Frequency Standard

    NASA Astrophysics Data System (ADS)

    Martin, Kyle; Phelps, Gretchen; Lemke, Nathan; Blakley, Daniel; Erickson, Christopher; Burke, John; Applied Technology Associates Team; Space Dynamics Laboratory Team; Air Force Research Laboratory Team

    2016-05-01

    The Air Force Research Laboratory is pursuing optical atomic clocks for navigation and timing applications. Optical clocks are of particular interest owing to their very high oscillation frequencies. We present an optical rubidium atomic frequency standard (O-RAFS), based upon a two-photon transition at 778 nm, that utilizes readily available commercial off-the-shelf components. Compared to existing GPS clocks, O-RAFS offers reduced short-term instability (7 ×10-13 /√{ τ}), improved manufacturability, and competitive size, weight, and power, making it an attractive candidate for future space operation.

  8. High Resolution Spectroscopy of Naphthalene Calibrated by AN Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Nishiyama, Akiko; Nakashima, Kazuki; Matsuba, Ayumi; Misono, Masatoshi

    2015-06-01

    In high-resolution molecular spectroscopy, the precise measure of the optical frequency is crucial to evaluate minute shifts and splittings of the energy levels. On the other hand, in such spectroscopy, thousands of spectral lines distributed over several wavenumbers have to be measured by a continuously scanning cw laser. Therefore, the continuously changing optical frequency of the scanning laser has to be determined with enough precision. To satisfy these contradictory requirements, we have been developed two types of high-resolution spectroscopic systems employing an optical frequency comb. One of the systems employs RF band-pass filters to generate equally spaced frequency markers for optical frequency calibration, and is appropriate for wide wavelength-range measurement with relatively high scanning rate.^a In the other system, the beat frequency between the optical frequency comb and the scanning laser is controlled by an acousto-optic frequency shifter. This system is suitable for more precise measurement, and enables detailed analyses of frequency characteristics of scanning laser.^b In the present study, we observe Doppler-free two-photon absorption spectra of A^1B1u (v_4 = 1) ← X^1A_g (v = 0) transition of naphthalene around 298 nm. The spectral lines are rotationally resolved and the resolution is about 100 kHz. For ^qQ transition, the rotational lines are assigned, and molecular constants in the excited state are determined. In addition, we analyze the origin of the measured linewidth and Coriolis interactions between energy levels. To determine molecular constants more precisely, we proceed to measure and analyze spectra of other transitions, such as ^sS transitions. ^a A. Nishiyama, D. Ishikawa, and M. Misono, J. Opt. Soc. Am. B 30, 2107 (2013). ^b A. Nishiyama, A. Matsuba, and M. Misono, Opt. Lett. 39, 4923 (2014).

  9. Development Of Frequency Transfer Via Optical Fiber Link at NICT

    DTIC Science & Technology

    2008-12-01

    al., 2006 “Comparison between frequency standards in Europe and the USA at the 10-15 uncertainty level,” Metrologia , 43, 109-120. [4] H. Kiuchi, T...M. Hosokawa, 2008, “Evaluation of caesium atomic fountain NICT-CsF1,” Metrologia , 45, 139-148. [12] M. Kumagai, H. Ito, G. Santarelli, C. Locke, J

  10. Noise-Induced Phase Locking and Frequency Mixing in an Optical Bistable System with Delayed Feedback

    NASA Astrophysics Data System (ADS)

    Misono, Masatoshi; Miyakawa, Kenji

    2011-11-01

    The interplay between stochastic resonance (SR) and coherence resonance (CR) is experimentally studied in an optical bistable system with a time-delayed feedback loop. We demonstrate that the phase of the noise-induced motion is locked to that of the periodic input when the ratio of their frequencies is a simple rational number. We also demonstrate that the interplay between SR and CR generates frequency-mixed modes, and that the efficiency of frequency mixing is enhanced by the optimum noise.

  11. CMOS in-pixel optical pulse frequency modulator

    NASA Astrophysics Data System (ADS)

    Nel, Nicolaas E.; du Plessis, M.; Joubert, T.-H.

    2016-02-01

    This paper covers the design of a complementary metal oxide semiconductor (CMOS) pixel readout circuit with a built-in frequency conversion feature. The pixel contains a CMOS photo sensor along with all signal-to-frequency conversion circuitry. An 8×8 array of these pixels is also designed. Current imaging arrays often use analog-to-digital conversion (ADC) and digital signal processing (DSP) techniques that are off-chip1. The frequency modulation technique investigated in this paper is preferred over other ADC techniques due to its smaller size, and the possibility of a higher dynamic range. Careful considerations are made regarding the size of the components of the pixel, as various characteristics of CMOS devices are limited by decreasing the scale of the components2. The methodology used was the CMOS design cycle for integrated circuit design. All components of the pixel were designed from first principles to meet necessary requirements of a small pixel size (30×30 μm2) and an output resolution greater than that of an 8-bit ADC. For the photodetector, an n+-p+/p-substrate diode was designed with a parasitic capacitance of 3 fF. The analog front-end stage was designed around a Schmitt trigger circuit. The photo current is integrated on an integration capacitor of 200 fF, which is reset when the Schmitt trigger output voltage exceeds a preset threshold. The circuit schematic and layout were designed using Cadence Virtuoso and the process used was the AMS CMOS 350 nm process using a power supply of 5V. The simulation results were confirmed to comply with specifications, and the layout passed all verification checks. The dynamic range achieved is 58.828 dB per pixel, with the output frequencies ranging from 12.341kHz to 10.783 MHz. It is also confirmed that the output frequency has a linear relationship to the photocurrent generated by the photodiode.

  12. Holographic Optical Elements with Ultra-High Spatial Frequencies.

    DTIC Science & Technology

    1983-01-01

    capable of solving most of these problems. Holography Wavefront reconstruction, now known as holography, was invented by Dennis Gabor in 194821. At...Zone Plate. How- ever, it was not until Gabor proposed his principle of wave- front reconstruction and Leith and Upatnieks introduced off-axis... Gabor , Nature 161, 777 (1948). 22. J. W. Goodman, Introduction to Fourier Optics, McGraw- Hill Book Company, St. Louis,MI (1968). 23. R. J. Collier, C. B

  13. High frequency optoelectronic oscillators based on the optical feedback of semiconductor mode-locked laser diodes.

    PubMed

    Haji, Mohsin; Hou, Lianping; Kelly, Anthony E; Akbar, Jehan; Marsh, John H; Arnold, John M; Ironside, Charles N

    2012-01-30

    Optical self seeding feedback techniques can be used to improve the noise characteristics of passively mode-locked laser diodes. External cavities such as fiber optic cables can increase the memory of the phase and subsequently improve the timing jitter. In this work, an improved optical feedback architecture is proposed using an optical fiber loop delay as a cavity extension of the mode-locked laser. We investigate the effect of the noise reduction as a function of the loop length and feedback power. The well known composite cavity technique is also implemented for suppressing supermode noise artifacts presented due to harmonic mode locking effects. Using this method, we achieve a record low radio frequency linewidth of 192 Hz for any high frequency (>1 GHz) passively mode-locked laser to date (to the best of the authors' knowledge), making it promising for the development of high frequency optoelectronic oscillators.

  14. Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process

    PubMed Central

    Zheng, Jian; Katsuragawa, Masayuki

    2015-01-01

    Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies. Furthermore, we show that such optical-frequency conversions can be realized by using a surprisingly simple technology where transparent plates are placed in a nonlinear optical medium and their positions and thicknesses are adjusted precisely. In a numerical simulation assuming practically applicable parameters in detail, we demonstrate a single-frequency tunable laser that covers the whole vacuum-ultraviolet spectral range of 120 to 200 nm. PMID:25748023

  15. Transportable cavity-stabilized laser system for optical carrier frequency transmission experiments.

    PubMed

    Parker, B; Marra, G; Johnson, L A M; Margolis, H S; Webster, S A; Wright, L; Lea, S N; Gill, P; Bayvel, P

    2014-12-10

    We report the design and performance of a transportable laser system at 1543 nm, together with its application as the source for a demonstration of optical carrier frequency transmission over 118 km of an installed dark fiber network. The laser system is based around an optical reference cavity featuring an elastic mounting that bonds the cavity to its support, enabling the cavity to be transported without additional clamping. The cavity exhibits passive fractional frequency insensitivity to vibration along the optical axis of 2.0×10(-11)  m(-1) s(2). With active fiber noise cancellation, the optical carrier frequency transmission achieves a fractional frequency instability, measured at the user end, of 2.6×10(-16) at 1 s, averaging down to below 3×10(-18) after 20,000 s. The fractional frequency accuracy of the transfer is better than 3×10(-18). This level of performance is sufficient for comparison of state-of-the-art optical frequency standards and is achieved in an urban fiber environment.

  16. Asymmetric corner frequency in the 1/f FM-noise PSD of optical frequency combs generated by quantum-dash mode-locked lasers

    NASA Astrophysics Data System (ADS)

    Panapakkam, V.; Anthur, A.; Vujicic, V.; Gaimard, Q.; Merghem, K.; Aubin, G.; Lelarge, F.; Viktorov, E.; Barry, L. P.; Ramdane, A.

    2016-10-01

    We experimentally investigate the corner frequency in the 1/f frequency noise of the longitudinal modes of an InAs/InP quantum-dash based single-section passive mode-locked laser. The corner frequency features a strong asymmetry across the optical frequency comb with the values ranging from 10 MHz in the low-frequency side to 180 MHz in the high-frequency side. Actively mode-locking the laser induces a reduction in the corner frequency as it changes from 3 MHz in the low-frequency side to 70 MHz in the high-frequency side and the asymmetry persists.

  17. A novel method of developing all-optical frequency encoded memory unit exploiting nonlinear switching character of semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Kumar Garai, Sisir; Mukhopadhyay, Sourangshu

    2010-10-01

    The very fast running optical memory and optical logic gates are the basic building blocks for any optical computing data processing system. Realization of a very fast memory-cell in the optical domain is very challenging. In the last two decades many methods of implementing all-optical flip-flops have been proposed. Most of these suffer from speed limitation because of low switching response of the active devices. In our present communication the authors propose a method of developing a frequency encoded memory unit based on the switching action of semiconductor optical amplifier (SOA). Nonlinear polarization rotation characters of SOA and 'SOA based Mach-Zehnder Interferometer' switch, i.e. 'SOA-MZI' switch, are exploited for the purpose of some switching action with least switching power (<-3 dB m) and high switching contrast ratio (20 dB). Here two logic states ('0' state and '1' state) of the memory is encoded by two different frequencies, which will remain unchanged throughout the data communication irrespective of loss of light energy due to reflection, refraction, attenuation, etc. Though the SOA based switch runs with the operational speed 100 Gb/s, still due to the presence of the other optical components in the memory unit, the overall speed of the proposed system will come down to 10 Gb/s.

  18. Photonic chip-based optical frequency comb using soliton Cherenkov radiation.

    PubMed

    Brasch, V; Geiselmann, M; Herr, T; Lihachev, G; Pfeiffer, M H P; Gorodetsky, M L; Kippenberg, T J

    2016-01-22

    Optical solitons are propagating pulses of light that retain their shape because nonlinearity and dispersion balance each other. In the presence of higher-order dispersion, optical solitons can emit dispersive waves via the process of soliton Cherenkov radiation. This process underlies supercontinuum generation and is of critical importance in frequency metrology. Using a continuous wave-pumped, dispersion-engineered, integrated silicon nitride microresonator, we generated continuously circulating temporal dissipative Kerr solitons. The presence of higher-order dispersion led to the emission of red-shifted soliton Cherenkov radiation. The output corresponds to a fully coherent optical frequency comb that spans two-thirds of an octave and whose phase we were able to stabilize to the sub-Hertz level. By preserving coherence over a broad spectral bandwidth, our device offers the opportunity to develop compact on-chip frequency combs for frequency metrology or spectroscopy.

  19. Multiple frequency optical mixer and demultiplexer and apparatus for remote sensing

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R. (Inventor)

    2010-01-01

    A pulsed laser system includes a modulator module configured to provide pulsed electrical signals and a plurality of solid-state seed sources coupled to the modulator module and configured to operate, responsive to the pulsed electrical signals, in a pulse mode. Each of the plurality of solid-state seed sources is tuned to a different frequency channel separated from any adjacent frequency channel by a frequency offset. The pulsed laser system also includes a combiner that combines outputs from each of the solid state seed sources into a single optical path and an optical doubler and demultiplexer coupled to the single optical path and providing each doubled seed frequency on a separate output path.

  20. Photonic chip-based optical frequency comb using soliton Cherenkov radiation

    NASA Astrophysics Data System (ADS)

    Brasch, V.; Geiselmann, M.; Herr, T.; Lihachev, G.; Pfeiffer, M. H. P.; Gorodetsky, M. L.; Kippenberg, T. J.

    2016-01-01

    Optical solitons are propagating pulses of light that retain their shape because nonlinearity and dispersion balance each other. In the presence of higher-order dispersion, optical solitons can emit dispersive waves via the process of soliton Cherenkov radiation. This process underlies supercontinuum generation and is of critical importance in frequency metrology. Using a continuous wave-pumped, dispersion-engineered, integrated silicon nitride microresonator, we generated continuously circulating temporal dissipative Kerr solitons. The presence of higher-order dispersion led to the emission of red-shifted soliton Cherenkov radiation. The output corresponds to a fully coherent optical frequency comb that spans two-thirds of an octave and whose phase we were able to stabilize to the sub-Hertz level. By preserving coherence over a broad spectral bandwidth, our device offers the opportunity to develop compact on-chip frequency combs for frequency metrology or spectroscopy.

  1. Research study of fiber-optic interferometry at very low frequencies

    NASA Astrophysics Data System (ADS)

    Edwards, R. B.

    1984-06-01

    A comprehensive review of fiber-optic interferometry shows that frequency-dependent phenomena affecting fiber-optic interferometric electromagnetic sensors at very low frequencies have been neither adequately understood nor quantitatively described. In addition to the electro-optical and magneto-strictive (or electro-strictive) factors that intrinsically limit transduction, other interactive mechanisms such as skin-depth and mechanical loading are commonly supposed to affect the detection sensitivity of the interferometric sensor. This research study of fiber-optic interferometry consists of the following: a review of fiber-optic interferometry, analyses aimed at understanding the mechanisms and quantifying where possible, their effects, and an investigation of means to reduce their impact on the performance of practical sensor implementations. Additional experimental studies have been planned in an attempt to address these interactive mechanisms, their effects and methods of mitigating them. The experimental studies have been performed on a best efforts basis due to cost and schedule constraints.

  2. Theoretical analysis and system design of two-photon based optical frequency standards

    NASA Astrophysics Data System (ADS)

    Burger, J. P.; Jivan, P.; Matthee, C.; Kritzinger, R.; Hussein, H.; Terra, O.

    2014-06-01

    The National Metrology Institute of South Africa (NMISA) is developing a new optical frequency standard based on the Rubidium two-photon transition in collaboration with the National Institute of Standards (NIS, Egypt) that will use both bulk and fiber optics in the system. This is system is called A-POD; an acronym for a portable photonic oscillator device. Rubidium two-photon standards can yield relatively simple and precise standards that are compatible with standard Ti:Sapphire optical frequency combs, as well as the need for a precise frequency standard in the optical telecommunication domain and for measurement of length with a visible beam. The robustness and transportability of the standard are important considerations for the optical frequency standard. This projects implements a framework for better two-photon standards that can be highly accurate, and possibly compete with much more complex clocks in the metrology environment, and especially so in the smaller national metrology institutes found in the developing world. This paper discusses the design constraints and the development considerations towards the optical setup. The robustness and transportability was greatly improved via the usage of optical fiber in the light source of the system, or even in atom-light interaction region. Of particular importance are the beam parameters inside the atomic interaction area. The extent of Doppler broadening and the intensity dependent line shift have to be optimized within practical extents, where both these aspects are affected by the beam shape and optical geometry. A way to fully treat the optical beam effects together with atomic movement is proposed. Furthermore a method is proposed to do real time compensation of intensity dependent light shift, which could have major applicability to frequency standards in general - the complexity is shifted from physical setups to digital signal processing, which is easily adaptable and stable.

  3. Low Frequency Error Analysis and Calibration for High-Resolution Optical Satellite's Uncontrolled Geometric Positioning

    NASA Astrophysics Data System (ADS)

    Wang, Mi; Fang, Chengcheng; Yang, Bo; Cheng, Yufeng

    2016-06-01

    The low frequency error is a key factor which has affected uncontrolled geometry processing accuracy of the high-resolution optical image. To guarantee the geometric quality of imagery, this paper presents an on-orbit calibration method for the low frequency error based on geometric calibration field. Firstly, we introduce the overall flow of low frequency error on-orbit analysis and calibration, which includes optical axis angle variation detection of star sensor, relative calibration among star sensors, multi-star sensor information fusion, low frequency error model construction and verification. Secondly, we use optical axis angle change detection method to analyze the law of low frequency error variation. Thirdly, we respectively use the method of relative calibration and information fusion among star sensors to realize the datum unity and high precision attitude output. Finally, we realize the low frequency error model construction and optimal estimation of model parameters based on DEM/DOM of geometric calibration field. To evaluate the performance of the proposed calibration method, a certain type satellite's real data is used. Test results demonstrate that the calibration model in this paper can well describe the law of the low frequency error variation. The uncontrolled geometric positioning accuracy of the high-resolution optical image in the WGS-84 Coordinate Systems is obviously improved after the step-wise calibration.

  4. A FEMTOSECOND-LEVEL FIBER-OPTICS TIMING DISTRIBUTION SYSTEM USING FREQUENCY-OFFSET INTERFEROMETRY

    SciTech Connect

    Staples, J.W.; Byrd, J.; Doolittle, L.; Huang, G.; Wilcox, R.

    2009-10-17

    An optical fiber-based frequency and timing distribution system based on the principle of heterodyne interferometry has been in development at LBNL for several years. The fiber drift corrector has evolved from an RF-based to an optical-based system, from mechanical correctors (piezo and optical trombone) to fully electronic, and the electronics from analog to fully digital, all using inexpensive off-the-shelf commodity fiber components. Short-term optical phase jitter and long-term phase drift are both in the femtosecond range over distribution paths of 2 km or more.

  5. Nonlinear modification of the laser noise power spectrum induced by frequency-shifted optical feedback

    NASA Astrophysics Data System (ADS)

    Lacot, Eric; Houchmandzadeh, Bahram; Girardeau, Vadim; Hugon, Olivier; Jacquin, Olivier

    2016-09-01

    In this article, we study the nonlinear coupling between the stationary (i.e., the beating modulation signal) and transient (i.e., the laser quantum noise) dynamics of a laser subjected to frequency-shifted optical feedback. We show how the noise power spectrum and more specifically the relaxation oscillation frequency of the laser are modified under different optical feedback conditions. Specifically we study the influence of (i) the amount of light returning to the laser cavity and (ii) the initial detuning between the frequency shift and intrinsic relaxation frequency. The present work shows how the relaxation frequency is related to the strength of the beating signal, and the shape of the noise power spectrum gives an image of the transfer modulation function (i.e., of the amplification gain) of the nonlinear-laser dynamics. The theoretical predictions, confirmed by numerical resolutions, are in good agreement with the experimental data.

  6. Building a Pulse Detector using the Frequency Resolved Optical Gating Technique

    SciTech Connect

    Vallin, J

    2004-02-05

    We show how to construct a diagnostic optical layout known as Frequency Resolved Optical Gating (FROG) for an ir mode-locked laser by using the nonlinear effect known as second harmonic generation (SHG). In this paper, we explain the principle of operation and the theory upon which this diagnostic is based. Moreover, we described the procedure used to measure the duration and frequency components of a pulse. This process consists of calibrating the scales of a two-dimensional image, time delay vs. frequency, known as FROG spectrogram or FROG trace. This calibration of the time delay scale yields the correspondence between a pixel and time delay. Similarly, the calibration of the frequency scale yields the correspondence between a pixel, and frequency.

  7. Optical frequency standard by using a 1560 nm diode laser locked to saturated absorption lines of rubidium vapor

    SciTech Connect

    Masuda, Shin; Seki, Atsushi; Niki, Shoji

    2007-07-20

    A robust, compact, highly accurate rubidium optical frequency standard module was developed to overcome the delicate performance of conventional frequency stabilized lasers. A frequency doubled1560 nm distributed feedback diode laser locked to a rubidium D2 saturated absorption line without using an optical amplifier was demonstrated, and dithering-free optical output was obtained. In addition, the sensitivity of the developed optical frequency standard to magnetic fields was investigated. We confirmed that the influence of the magnetic fields on the optical frequency standard can be almost negligible when using appropriate magnetic-shield films. As a result, the magnetic-field-insensitive optical frequency standard, which can be embedded in optical systems,exhibiting uncertainty less than at least 100 kHz, was successfully realized for the first time to the best of our knowledge.

  8. Frequency combs and platicons in optical microresonators with normal GVD.

    PubMed

    Lobanov, V E; Lihachev, G; Kippenberg, T J; Gorodetsky, M L

    2015-03-23

    We predict the existence of a novel type of the flat-top dissipative solitonic pulses, "platicons", in microresonators with normal group velocity dispersion (GVD). We propose methods to generate these platicons from cw pump. Their duration may be altered significantly by tuning the pump frequency. The transformation of a discrete energy spectrum of dark solitons of the Lugiato-Lefever equation into a quasicontinuous spectrum of platicons is demonstrated. Generation of similar structures is also possible with bi-harmonic, phase/amplitude modulated pump or via laser injection locking.

  9. High-resolution frequency domain second harmonic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Su, Jianping; Tomov, I. V.; Jiang, Yi; Chen, Zhongping

    2007-02-01

    We used continuum generated in an 8.5 cm long fiber by a femtosecond Yb fiber laser to improve threefold the axial resolution of frequency domain SH-OCT to 12μm. The acquisition time was shortened by more than two orders of magnitude compared to time domain SH-OCT. The system was applied to image biological tissue of fish scales, pig leg tendon and rabbit eye sclera. Highly organized collagen fibrils can be visualized in the recorded images. Polarization dependence on second harmonic has been used to obtain polarization resolved images.

  10. Development of a frequency-tunable optical phase lock loop (OPLL) for high resolution fiber optic distributed sensing

    NASA Astrophysics Data System (ADS)

    Kuperschmidt, Vladimir; Stolpner, Lew; Mols, Peter; Alalusi, Mazin; Mehnert, Axel; Barsan, Radu; Ansari, Farhad

    2011-04-01

    We report on the development of a precision-tunable, dual wavelength, optical light source suitable for high performance fiber optic Brillouin scattering distributed sensing. The design is based on an Optical Phase Locked Loop (OPLL) system using novel narrow linewidth, low frequency noise and high stability PLANEX external cavity semiconductor. The inherent wavelength stability of PLANEX lasers (typically an order of magnitude better that any DFB laser on the market) enable the OPLL to operate continuously over a wide ambient temperature range without degradation in wavelength locking performance. The OPLL architecture is implemented with polarization maintaining (PM) components and has a very low beat frequency jitter on the order of few kHz. The OPLL frequency tuning range is between 8 and 14 GHz, with fast tuning of sweep steps on the order of 100 μsec. Such a frequency tuning range covers practically all corresponding temperature and strain sensing applications based on the measurement of the frequency shift produced by spontaneous or stimulated Brillouin scattering, and thus is a versatile and enabling technology for both BOTDA/BOTDR distributed sensing systems.

  11. Development and test of the Ball Aerospace optical frequency comb: a versatile measurement tool for aerospace applications

    NASA Astrophysics Data System (ADS)

    Wachs, Jordan; Leitch, James; Knight, Scott; Pierce, Robert; Adkins, Michael

    2016-07-01

    The Ball Fiber Optical Comb Demo is a lab-based system which is used to develop space applications for optical frequency combs. These developments utilize the broadband optical coherence of the frequency comb to expand the capabilities of ground test and orbital systems used for optical wave-front measurement, control of adaptive optics, precision ranging, and reference frequency stabilization. The work expands upon a NIST-developed all-fiber frequency comb that exhibits high stability in a compact, enclosed package. Previously demonstrated applications for frequency combs include: Spectroscopy, distance and velocity measurement, frequency conversion, and timing transfer. Results from the Ball system show the characterization and performance of a frequency comb system with a technological path-to-space. Demonstrations in high precision metrology and long distance ranging are also presented for application in adaptive and multi-body optical systems.

  12. Frequency-based design of Adaptive Optics systems

    NASA Astrophysics Data System (ADS)

    Agapito, Guido; Battistelli, Giorgio; Mari, Daniele; Selvi, Daniela; Tesi, Alberto; Tesi, Pietro

    2013-12-01

    The problem of reducing the effects of wavefront distortion and structural vibrations inground-based telescopes is addressed within a modal-control framework. The proposed approach aimsat optimizing the parameters of a given modal stabilizing controller with respect to a performance criterionwhich reflects the residual phase variance and is defined on a sampled frequency domain. Thisframework makes it possible to account for turbulence and vibration profiles of arbitrary complexity(even empirical power spectral densities from data), while the controller order can be kept at a desiredvalue. Moreover it is possible to take into account additional requirements, as robustness in the presenceof disturbances whose intensity and frequency profile vary with time. The proposed design procedureresults in solving a minmax problem and can be converted into a linear programming problem withquadratic constraints, for which there exist several standard optimization techniques. The optimizationstarts from a given stabilizing controller which can be either a non-model-based controller (in this caseno identification effort is required), or a model-based controller synthesized by means of turbulence andvibration models of limited complexity. In this sense the approach can be viewed not only as alternative,but also as cooperative with other control design approaches. The results obtained by means of anEnd-to-End simulator are shown to emphasize the power of the proposed method.

  13. Synchronously Pumped Optical Parametric Oscillator with Intracavity Difference Frequency Mixing

    DTIC Science & Technology

    1998-06-29

    temperature given by Eq. (2.4). Thus we have, dAkQL dT dAkQL dT dAkc, dT dAk LRf(T) + dT LRf(T) + AkQLR 2TT df(T) dT df(T) ARf 2(T) dT...5.57 dL . , , dAk -1 (2.23) Using the same OPO example as earlier, this gives a rather large temperature accep- tance bandwidth of 16.6° C. As...1979. [85] D. T. Reid, Z. Penman, M. Ebrahimzadeh, W. Sibbett, H. Karlsson, and F. Lau - rell, "Broadly tunable infrared femtosecond optical

  14. Optical Reflection Measurement System Using A Swept Modulation Frequency Technique

    NASA Astrophysics Data System (ADS)

    Braun, David M.; Leyde, Kent W.

    1989-03-01

    A measurement system has been developed capable of mea-suring reflected optical power as low as 0.0025% with a spot size diam-eter of 24 Am. One application for this system is the characterization of small-area photodetectors. The operation of the measurement system is simple, allowing the operator to quickly make multiple reflection measurements, and it does not require a darkroom. The measurement system merges a microscope, for visual alignment and focusing of the laser beam, with a lightwave component analyzer using modulation vec-tor error correction. A measurement comparison between the analyzer-based system and a power-meter-based system showed that each sys-tem can measure reflections as low as 0.0025%. However, the analyzer-based system offers the advantage of identifying the location and magnitude of system reflections. The system operates at a wavelength of 1310 nm.

  15. Phase Analysis for Frequency Standards in the Microwave and Optical Domains.

    PubMed

    Kazda, Michael; Gerginov, Vladislav; Huntemann, Nils; Lipphardt, Burghard; Weyers, Stefan

    2016-07-01

    Coherent manipulation of atomic states is a key concept in high-precision spectroscopy and used in atomic fountain clocks and a number of optical frequency standards. Operation of these standards can involve a number of cyclic switching processes, which may induce cycle-synchronous phase excursions of the interrogation signal and thus lead to shifts in the output of the frequency standard. We have built a field-programmable gate array (FPGA)-based phase analyzer to investigate these effects and conducted measurements on two kinds of frequency standards. For the caesium fountains PTB-CSF1 and PTB-CSF2, we were able to exclude phase variations of the microwave source at the level of a few microradians, corresponding to relative frequency shifts of less than [Formula: see text]. In the optical domain, we investigated phase variations in PTB's Yb (+) optical frequency standard and made detailed measurements of acousto-optic modulator (AOM) chirps and their scaling with duty cycle and driving power. We ascertained that cycle-synchronous as well as long-term phase excursion do not cause frequency shifts larger than [Formula: see text].

  16. All-optical binary logic unit (BLU) using frequency encoded data

    NASA Astrophysics Data System (ADS)

    Mandal, Dhoumendra; Garai, Sisir Kumar

    2015-03-01

    In frequency division multiplexing based communication network frequency encoded data is very important. In this communication, authors propose a new approach of developing an all-optical binary logic unit (BLU) by means of which sixteen different types of binary logic operations can be performed using frequency encoded data. The authors first develop all-optical NOT, AND, OR, XOR, etc. logic gates exploiting the polarization switching character of semiconductor optical amplifier which works based on the principle of nonlinear state of polarization rotation of the probe beam. Finally these logic gates are coupled by means of polarization switches, and activated to implement different logic operations as desired using control beams of different frequencies, after being proper routing the control beams by means of 16:1 MUX and 1:16 DMUX. Frequency conversion by polarization switching character of SOA is very efficient and faster with least optical power consumption, and therefore our proposed scheme of binary logic unit with frequency encoded data offers bit error free secure different binary logic operations with faster speed of processing. Simulation result reflects the feasibility of the proposed scheme.

  17. Variable pulse repetition frequency output from an optically injected solid state laser.

    PubMed

    Kane, D M; Toomey, J P

    2011-02-28

    An optically injected solid state laser (OISSL) system is known to generate complex nonlinear dynamics within the parameter space of varying the injection strength of the master laser and the frequency detuning between the master and slave lasers. Here we show that within these complex nonlinear dynamics, a system which can be operated as a source of laser pulses with a pulse repetition frequency (prf) that can be continuously varied by a single control, is embedded. Generation of pulse repetition frequencies ranging from 200 kHz up to 4 MHz is shown to be achievable for an optically injected Nd:YVO4 solid state laser system from analysis of prior experimental and simulation results. Generalizing this to other optically injected solid state laser systems, the upper bound on the repetition frequency is of order the relaxation oscillation frequency for the lasers. The system is discussed in the context of prf versatile laser systems more generally. Proposals are made for the next generation of OISSLs that will increase understanding of the variable pulse repetition frequency operation, and determine its practical limitations. Such variable prf laser systems; both low powered, and, higher powered systems achieved using one or more optical power amplifier stages; have many potential applications from interrogating resonance behaviors in microscale structures, through sensing and diagnostics, to laser processing.

  18. Antenna-load interactions at optical frequencies: impedance matching to quantum systems

    NASA Astrophysics Data System (ADS)

    Olmon, R. L.; Raschke, M. B.

    2012-11-01

    The goal of antenna design at optical frequencies is to deliver optical electromagnetic energy to loads in the form of, e.g., atoms, molecules or nanostructures, or to enhance the radiative emission from such structures, or both. A true optical antenna would, on a qualitatively new level, control the light-matter interaction on the nanoscale for controlled optical signal transduction, radiative decay engineering, quantum coherent control, and super-resolution microscopy, and provide unprecedented sensitivity in spectroscopy. Resonant metallic structures have successfully been designed to approach these goals. They are called optical antennas in analogy to radiofrequency (RF) antennas due to their capability to collect and control electromagnetic fields at optical frequencies. However, in contrast to the RF, where exact design rules for antennas, waveguides, and antenna-load matching in terms of their impedances are well established, substantial physical differences limit the simple extension of the RF concepts into the optical regime. Key distinctions include, for one, intrinsic material resonances including quantum state excitations (metals, metal oxides, semiconductor homo- and heterostructures) and extrinsic resonances (surface plasmon/phonon polaritons) at optical frequencies. Second, in the absence of discrete inductors, capacitors, and resistors, new design strategies must be developed to impedance match the antenna to the load, ultimately in the form of a vibrational, electronic, or spin excitation on the quantum level. Third, there is as yet a lack of standard performance metrics for characterizing, comparing and quantifying optical antenna performance. Therefore, optical antenna development is currently challenged at all the levels of design, fabrication, and characterization. Here we generalize the ideal antenna-load interaction at optical frequencies, characterized by three main steps: (i) far-field reception of a propagating mode exciting an antenna

  19. Antenna-load interactions at optical frequencies: impedance matching to quantum systems.

    PubMed

    Olmon, R L; Raschke, M B

    2012-11-09

    The goal of antenna design at optical frequencies is to deliver optical electromagnetic energy to loads in the form of, e.g., atoms, molecules or nanostructures, or to enhance the radiative emission from such structures, or both. A true optical antenna would, on a qualitatively new level, control the light-matter interaction on the nanoscale for controlled optical signal transduction, radiative decay engineering, quantum coherent control, and super-resolution microscopy, and provide unprecedented sensitivity in spectroscopy. Resonant metallic structures have successfully been designed to approach these goals. They are called optical antennas in analogy to radiofrequency (RF) antennas due to their capability to collect and control electromagnetic fields at optical frequencies. However, in contrast to the RF, where exact design rules for antennas, waveguides, and antenna-load matching in terms of their impedances are well established, substantial physical differences limit the simple extension of the RF concepts into the optical regime. Key distinctions include, for one, intrinsic material resonances including quantum state excitations (metals, metal oxides, semiconductor homo- and heterostructures) and extrinsic resonances (surface plasmon/phonon polaritons) at optical frequencies. Second, in the absence of discrete inductors, capacitors, and resistors, new design strategies must be developed to impedance match the antenna to the load, ultimately in the form of a vibrational, electronic, or spin excitation on the quantum level. Third, there is as yet a lack of standard performance metrics for characterizing, comparing and quantifying optical antenna performance. Therefore, optical antenna development is currently challenged at all the levels of design, fabrication, and characterization. Here we generalize the ideal antenna-load interaction at optical frequencies, characterized by three main steps: (i) far-field reception of a propagating mode exciting an antenna

  20. Ion optics system incorporating radio frequency mass separation

    NASA Technical Reports Server (NTRS)

    Anderson, John R.; Carruth, M. R., Jr.

    1990-01-01

    Results of an experimental study are presented. They show that an RF mass discriminator, based on a Bennett mass spectrometer concept, can be used to discriminate between two species of ions with about a 2-to-1 charge-to-mass ratio. Such a device would be useful for separating monatomic and diatomic oxygen ions in a system designed to simulate the environment that spacecraft encounter in low earth orbit. The influence of changing mass discriminator parameters - such as the spacing of its grids, the amplitude and frequency of RF voltage signals applied to it and the current density of ions incident upon it - on its species discrimination capabilities is discussed. Experimental results are also compared to the results of a simple theoretical model to gain insight into the processes occurring in the discriminator. These results are shown to be in good agreement.

  1. Radio frequency phototube and optical clock: High resolution, high rate and highly stable single photon timing technique

    SciTech Connect

    Margaryan, Amur

    2011-10-01

    A new timing technique for single photons based on the radio frequency phototube and optical clock or femtosecond optical frequency comb generator is proposed. The technique has a 20 ps resolution for single photons, is capable of operating with MHz frequencies and achieving 10 fs instability level.

  2. Modeling hemoglobin at optical frequency using the unconditionally stable fundamental ADI-FDTD method.

    PubMed

    Heh, Ding Yu; Tan, Eng Leong

    2011-04-12

    This paper presents the modeling of hemoglobin at optical frequency (250 nm - 1000 nm) using the unconditionally stable fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) method. An accurate model based on complex conjugate pole-residue pairs is proposed to model the complex permittivity of hemoglobin at optical frequency. Two hemoglobin concentrations at 15 g/dL and 33 g/dL are considered. The model is then incorporated into the FADI-FDTD method for solving electromagnetic problems involving interaction of light with hemoglobin. The computation of transmission and reflection coefficients of a half space hemoglobin medium using the FADI-FDTD validates the accuracy of our model and method. The specific absorption rate (SAR) distribution of human capillary at optical frequency is also shown. While maintaining accuracy, the unconditionally stable FADI-FDTD method exhibits high efficiency in modeling hemoglobin.

  3. Optical frequency comb profilometry based on a single-pixel phase imaging

    NASA Astrophysics Data System (ADS)

    Makhtar, Nabila; Pham, Quang Duc; Mizutani, Yasuhiro; Hayasaki, Yoshio

    2016-08-01

    In this research, we introduce a new system based on the ghost imaging, for measuring the surface profile of an object using optical frequency comb laser and a single-pixel camera. The optical frequency comb laser was used to record the relative phase of the object precisely whilst the ghost imaging technique was applied to reconstruct the object's profile. The effect of using a mask on the parameters such as number of object point, number of measurements and sparse number related to the complexity of the object for reconstruction was studied by a simulation. The performance of the system strongly depends on the design of the mask. The random mask and the Hadamard mask were used to estimate the performances in the optical frequency comb profilometry.

  4. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing

    NASA Astrophysics Data System (ADS)

    Wang, Weiqiang; Chu, Sai T.; Little, Brent E.; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-06-01

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness.

  5. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing.

    PubMed

    Wang, Weiqiang; Chu, Sai T; Little, Brent E; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-06-24

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness.

  6. Modeling hemoglobin at optical frequency using the unconditionally stable fundamental ADI-FDTD method

    PubMed Central

    Heh, Ding Yu; Tan, Eng Leong

    2011-01-01

    This paper presents the modeling of hemoglobin at optical frequency (250 nm – 1000 nm) using the unconditionally stable fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) method. An accurate model based on complex conjugate pole-residue pairs is proposed to model the complex permittivity of hemoglobin at optical frequency. Two hemoglobin concentrations at 15 g/dL and 33 g/dL are considered. The model is then incorporated into the FADI-FDTD method for solving electromagnetic problems involving interaction of light with hemoglobin. The computation of transmission and reflection coefficients of a half space hemoglobin medium using the FADI-FDTD validates the accuracy of our model and method. The specific absorption rate (SAR) distribution of human capillary at optical frequency is also shown. While maintaining accuracy, the unconditionally stable FADI-FDTD method exhibits high efficiency in modeling hemoglobin. PMID:21559129

  7. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing

    PubMed Central

    Wang, Weiqiang; Chu, Sai T.; Little, Brent E.; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-01-01

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness. PMID:27338250

  8. Method of implementing frequency encoded multiplexer and demultiplexer systems using nonlinear semiconductor optical amplifiers

    NASA Astrophysics Data System (ADS)

    Garai, Sisir Kumar; Mukhopadhyay, Sourangshu

    2009-11-01

    Multiplexing and demultiplexing are the essential parts of any communication network. In case of optical multiplexing and demultiplexing the coding of the data as well as the coding of control signals are most important issues. Many encoding/decoding mechanisms have already been developed in optical communication technology. Recently frequency encoding technique has drawn some special interest to the scientific communities. The advantage of frequency encoding technique over any other techniques is that as the frequency is fundamental character of any signal so it remains unaltered in reflection, refraction, absorption, etc. during transmission of the signal and therefore the system will execute the operation with reliability. On the other hand, the switching speed of semiconductor optical amplifiers (SOA) is sufficiently high with property of best on/off contrast ratio. In our present communication we propose a method of implementing a '4-to-1' multiplexer (MUX) and a '1-to-4' demultiplexer (DEMUX) exploiting the switching character of nonlinear SOA with the use of frequency encoded control signals. To implement the '4-to-1' MUX and '1-to-4' DEMUX system, the frequency selection by multiquantum well (MQW)-grating filter-based SOA has been used for frequency routing purpose. At the same time, the polarization rotation character of SOA has also been exploited to get the desired purpose. Here the fast switching action of SOA with reliable frequency encoded control input signals, it is possible to achieve a faithful MUX/DEMUX service at tera-Hz operational speed.

  9. Performance analysis on quality of optical frequency comb generated by the recirculating frequency shifter based on linear IQ modulator

    NASA Astrophysics Data System (ADS)

    Sun, Lu; Li, Jianping; Lin, Jiachuan; Xi, Lixia; Tang, Xianfeng; Zhang, Xiaoguang

    2015-11-01

    An optical frequency comb generator using a modified single-sideband recirculating frequency shifter scheme adopting a linear IQ modulator as the kernel device (SSB-RFS-LIQM) is proposed. The optical comb lines generated by the proposed scheme possess good features such as extreme flatness and high optical signal-to-noise ratio (OSNR), compared to the quality we can obtain when we use a conventional IQ modulator in the SSB-RFS structure (called SSB-RFS-CIQM scheme). The mechanism of how the SSB-RFS-LIQM works is carefully analyzed with analytical and numerical methods. With the capability of strong suppression of high-order crosstalk and less demand of the gain of erbium-doped fiber amplifiers (and hence less amplified spontaneous noise induced) in the loop, 5.5 dB OSNR improvement can be achieved when 100 extreme flat comb lines are generated using the SSB-RFS-LIQM scheme compared to using the SSB-RFS-CIQM scheme.

  10. Colloidal superlattices for unnaturally high-index metamaterials at broadband optical frequencies.

    PubMed

    Lee, Seungwoo

    2015-11-02

    The recent advance in the assembly of metallic nanoparticles (NPs) has enabled sophisticated engineering of unprecedented light-matter interaction at the optical domain. In this work, I expand the design flexibility of NP optical metamaterial to push the upper limit of accessible refractive index to the unnaturally high regime. The precise control over the geometrical parameters of NP superlattice monolayer conferred the dramatic increase in electric resonance and related effective permittivity far beyond the naturally accessible regime. Simultaneously, effective permeability change, another key factor to achieving high refractive index, was effectively suppressed by reducing the thickness of NPs. By establishing this design rule, I have achieved unnaturally high refractive index (15.7 at the electric resonance and 7.3 at the quasi-static limit) at broadband optical frequencies (100 THz ~300 THz). I also combined this NP metamaterial with graphene to electrically control the high refractive index over the broad optical frequencies.

  11. WDM-CAP-PON integration with VLLC system based on optical frequency comb

    NASA Astrophysics Data System (ADS)

    He, Jing; Dong, Huan; Deng, Rui; Shi, Jin; Chen, Lin

    2016-09-01

    In this paper, a wavelength division multiplexing carrier-less amplitude phase modulation passive optical network (WDM-CAP-PON) integration with visible laser light communication (VLLC) system is proposed and experimentally demonstrated. To reduce the cost of WDM system, the optical frequency comb scheme using one Mach-Zehnder modulator (MZM) is utilized and five flat optical combs can be generated. Meanwhile, a blue laser diode (LD) as a VLLC optical source can provide high data rate and long transmission distance. Utilizing overlap frequency domain equalization (OFDE) and negative chirp of MZM, the system performance in both Q-factor and receiver sensitivity can be improved. After 20 km standard single mode fiber (SSMF) and 4.5 m free space transmission, the experimental results show that 10 Gb/s CAP signal can be achieved under 7% forward error correction (FEC) limit of 3 . 8 × 10-3.

  12. A wide-band fiber optic frequency distribution system employing thermally controlled phase compensation

    NASA Technical Reports Server (NTRS)

    Johnson, Dean; Calhoun, Malcolm; Sydnor, Richard; Lutes, George

    1993-01-01

    An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmental temperature changes is described. The distribution system utilizes bidirectional dual wavelength transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered differs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase variations. Two advantages of the wide-band system over earlier designs are (1) that it provides phase compensation for all transmitted frequencies, and (2) the compensation is applied after the optical interface rather than electronically ahead of it as in earlier schemes. Experimental results on the first prototype shows that the thermal stabilizer reduces phase variations and Allan deviation by a factor of forty over an equivalent uncompensated fiber optic distribution system.

  13. All-optical frequency downconversion technique utilizing a four-wave mixing effect in a single semiconductor optical amplifier for wavelength division multiplexing radio-over-fiber applications.

    PubMed

    Kim, Hyoung-Jun; Song, Jong-In

    2012-03-26

    An all-optical frequency downconversion utilizing a four-wave mixing effect in a single semiconductor optical amplifier (SOA) was experimentally demonstrated for wavelength division multiplexing (WDM) radio-over-fiber (RoF) applications. Two WDM optical radio frequency (RF) signals having 155 Mbps differential phase shift keying (DPSK) data at 28.5 GHz were simultaneously down-converted to two WDM optical intermediate frequency (IF) signals having an IF frequency of 4.5 GHz by mixing with an optical local oscillator (LO) signal having a LO frequency of 24 GHz in the SOA. The bit-error-rate (BER) performance of the RoF up-links with different optical fiber lengths employing all-optical frequency downconversion was investigated. The receiver sensitivity of the RoF up-link with a 6 km single mode fiber and an optical IF signal in an optical double-sideband format was approximately -8.5 dBm and the power penalty for simultaneous frequency downconversion was approximately 0.63 dB. The BER performance showed a strong dependence on the fiber length due to the fiber dispersion. The receiver sensitivity of the RoF up-link with the optical IF signal in the optical single-sideband format was reduced to approximately -17.4 dBm and showed negligible dependence on the fiber length.

  14. Gated frequency-resolved optical imaging with an optical parametric amplifier

    DOEpatents

    Cameron, Stewart M.; Bliss, David E.; Kimmel, Mark W.; Neal, Daniel R.

    1999-01-01

    A system for detecting objects in a turbid media utilizes an optical parametric amplifier as an amplifying gate for received light from the media. An optical gating pulse from a second parametric amplifier permits the system to respond to and amplify only ballistic photons from the object in the media.

  15. Gated frequency-resolved optical imaging with an optical parametric amplifier

    DOEpatents

    Cameron, S.M.; Bliss, D.E.; Kimmel, M.W.; Neal, D.R.

    1999-08-10

    A system for detecting objects in a turbid media utilizes an optical parametric amplifier as an amplifying gate for received light from the media. An optical gating pulse from a second parametric amplifier permits the system to respond to and amplify only ballistic photons from the object in the media. 13 figs.

  16. An investigation of optical feedback to extend the frequency response of solid-state detector systems

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.

    1972-01-01

    A primary limitation of many solid-state photodetectors used in electro-optical systems such as the facsimile camera is their slow response in converting light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without significantly degrading their signal-to-noise performance. This technique is analyzed to predict improvement, implemented, and evaluated to verify analytical results.

  17. Frequency-resolved optical gating for characterization of VUV pulses using ultrafast plasma mirror switching.

    PubMed

    Itakura, Ryuji; Kumada, Takayuki; Nakano, Motoyoshi; Akagi, Hiroshi

    2015-05-04

    We propose and experimentally demonstrate a method for characterizing vacuum ultraviolet (VUV) pulses based on time-resolved reflection spectroscopy of fused silica pumped by an intense laser pulse. Plasma mirror reflection is used as an ultrafast optical switch, which enables us to measure frequency-resolved optical gating (FROG) traces. The VUV temporal waveform can be retrieved from the measured FROG trace using principal component generalized projections algorithm with modification. The temporal profile of the plasma mirror reflectivity is also extracted simultaneously.

  18. Synthesis of virtual Brillouin frequency shift profiles in BOTDA sensors using optical source dithering

    NASA Astrophysics Data System (ADS)

    Urricelqui, Javier; Sagues, Mikel; Loayssa, Alayn

    2014-05-01

    We demonstrate a novel concept for Brillouin optical time domain analysis sensors that is based on synthesizing a virtual Brillouin frequency shift profile along the sensing fiber. The technique is based on modulating the wavelength of the optical source with a periodic waveform that is synchronized to the pump pulse. Application of this new tool to the compensation of non-local effects and Brillouin-induced noise in distributed sensors is experimentally demonstrated.

  19. Acousto-optical modulation of light at a doubled sound frequency

    SciTech Connect

    Kotov, V M; Averin, S V; Shkerdin, G N

    2016-02-28

    A method of acousto-optical (AO) Bragg diffraction is proposed that provides the amplitude modulation of optical radiation at a doubled acoustic frequency. The method is based on the double transmission of the light through the AO modulator made of a gyrotropic crystal and is experimentally tested by the example of the modulation of light with a wavelength of 0.63 μm, controlled by the paratellurite AO cell. (acoustooptics)

  20. Circuit elements at optical frequencies from first principles: A synthesis of electronic structure and circuit theories

    NASA Astrophysics Data System (ADS)

    Ramprasad, R.; Tang, C.

    2006-08-01

    A first principles electronic structure based method is presented to determine the equivalent circuit representations of nanostructured physical systems at optical frequencies, via a mapping of the effective permittivity calculated for a lattice of physical nano-elements using density functional theory to that calculated for a lattice of impedances using circuit theory. Specifically, it is shown that silicon nanowires and carbon nanotubes can be represented as series combinations of inductance, capacitance and resistance. It is anticipated that the generality of this approach will allow for an alternate description of physical systems at optical frequencies, and in the realization of novel opto- and nanoelectronic devices, including negative refractive index materials.

  1. Optical properties assessment for liquid phantoms using fiber based frequency-modulated light scattering interferometry

    NASA Astrophysics Data System (ADS)

    Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune

    2014-03-01

    Fiber based frequency-modulated light scattering interferometry (FMLSI) is developed for optical properties studies of liquid phantoms, made of Intralipid®. By employing optical frequency modulation on a tunable diode laser, the power spectrum of the heterodyne-detected intensity fluctuations through the dynamic turbid medium is a combination of the time-of-flight distribution and the Doppler power spectrum due to the movement of the scattering particles. The reduced scattering coefficient, absorption coefficient and Brownian diffusion constant are retrieved by employing nonlinear fitting to the power spectrum based on diffusion theory.

  2. Improving the scale factor for rotation sensing in a frequency sensitive integrated optical gyroscope

    NASA Astrophysics Data System (ADS)

    Zhao, Long; Li, Wenxiu; Zhang, Hao; Yang, Yang; Huang, Anping; Xiao, Zhisong

    2016-01-01

    We theoretically analyze the characteristics of scale factor in frequency sensitive integrated optical gyroscope consisting of a ring resonator coupled with double ring resonators. The impact of through coupling coefficients is investigated to decide the optimal parameters located at 0s-1 for improving the scale factor. It demonstrates that the scale factor enhancement in this frequency sensitive optical gyroscope, without increasing the overall footprint, can be improved compared with conventional single ring resonator gyroscope and presents the characteristic of better performance within low-rate range. It implies a broad prospect in highly integrated on-chip applications, especially in aeronautic and astronautic area.

  3. Frequency stabilization for space-based missions using optical fiber interferometry.

    PubMed

    McRae, Terry G; Ngo, Silvie; Shaddock, Daniel A; Hsu, Magnus T L; Gray, Malcolm B

    2013-02-01

    We present measurement results for a laser frequency reference, implemented with an all-optical fiber Michelson interferometer, down to frequencies as low as 1 mHz. Optical fiber is attractive for space-based operations as it is physically robust, small and lightweight. The small free spectral range of fiber interferometers also provides the possibility to prestabilize two lasers on two distant spacecraft and ensures that the beatnote remains within the detector bandwidth. We demonstrate that these fiber interferometers are viable candidates for future laser-based gravity recovery and climate experiment missions requiring a stability of 30 Hz/√Hz over a 10 mHz-1 Hz bandwidth.

  4. Multidie LED combined with homogenizing optics to improve frequency response and intensity for FLIM applications.

    PubMed

    Liu, H-T; Lin, W-L; Feng, Y-L; Lin, Y; Chen, Y-C

    2017-03-15

    Application of light-emitting diodes (LEDs) in frequency-domain fluorescence lifetime imaging microscopy (FLIM) has been limited by the trade-off between modulation frequency and illumination intensity of LEDs, which affects the signal-to-noise ratio in fluorescence lifetime measurements. To increase modulation frequency without sacrificing output power of LEDs, we propose to use LEDs with multiple dice connected in series. The LED capacitance was reduced with series connection; therefore, the frequency response of multidie LED was significantly increased. LEDs in visible light, including blue, green, amber and red, were all applicable in FLIM. We also present a homogenizing optics design, so that multidie LEDs produced uniform illumination on the same focal spot. When the homogenizing optics was combined with multicolour emitters, it provides multiple colour selection in a compact and convenient design.

  5. Frequency dependent optical and dielectric properties of zinc sulfide in Terahertz regime

    NASA Astrophysics Data System (ADS)

    Ganti, Satya R.; Sundaram, S. K.; McCloy, John S.

    2014-07-01

    Frequency dependent optical and dielectric properties for several grades of chemical vapor deposited (CVD) zinc sulfide (standard, elemental, and multi-spectral) was performed using a terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.15 THz to 2.5 THz. Zinc sulfide exhibits low frequency vibrational modes characterized by the THz-TDS. Two low-frequency phonon resonance lines were revealed at 0.78 THz and 2.20 THz. These samples were also characterized in the GHz range using a backward wave oscillator (BWO) source quasi-optical spectrometer, and the data obtained by both approaches were compared. Experimental data were also compared with an undamped harmonic oscillator model. These results compare well with the literature values obtained using other methods.

  6. Scanning-free BOTDA based on ultra-fine digital optical frequency comb.

    PubMed

    Jin, Chao; Guo, Nan; Feng, Yuanhua; Wang, Liang; Liang, Hao; Li, Jianping; Li, Zhaohui; Yu, Changyuan; Lu, Chao

    2015-02-23

    We realize a scanning-free Brillouin optical time domain analyzer (BOTDA) based on an ultra-fine digital optical frequency comb (DOFC) with 1.95MHz frequency spacing and 2GHz bandwidth. The DOFC can be used to reconstruct the Brillouin gain spectrum (BGS) and locate the Brillouin frequency shift (BFS) without frequency scanning and thus can improve the measurement speed about 100 times compared with the conventional BOTDA. This scanning-free BOTDA scheme has also been demonstrated experimentally with 51.2m spatial resolution over 10km standard single mode fiber (SSMF) and with resolution of 1.5°C for temperature and 43.3με for strain measurement respectively.

  7. Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

    PubMed Central

    Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon

    2017-01-01

    Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources. PMID:28102352

  8. Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

    NASA Astrophysics Data System (ADS)

    Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon

    2017-01-01

    Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10‑9 fs2/Hz (equivalent to ‑174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources.

  9. Multicast contention resolution based on time-frequency joint scheduling in elastic optical switching networks

    NASA Astrophysics Data System (ADS)

    Liu, Huanlin; Li, Yuan; Peng, Han; Huang, Jun; Kong, Deqian

    2017-01-01

    Resolving the optical multicast contention in optical switch node is an effective approach to improve the performance of elastic optical multicast switch. An optical node architecture integrating with output shared all-optical Orthogonal Frequency Division Multiplexing (OFDM) network coding technology and shared feedback fiber delay lines (FDLs) buffer is designed. And a time-frequency joint scheduling strategy (TFJSS) is proposed. In TFJSS, the maximal weighted independent set algorithm is used to select the output packets with no overlapping spectrum among the contending multicast packets. The remaining contention packets are compressed by OFDM network coding with all-optical XOR operation. Hence, the contention is avoided in spectrum domain by encoding the contending unicast/multicast packets and changing the carrier frequency of encoded packets. If the network coding cannot successfully resolve the contending packets, the shared feedback FDLs are called to address the contention in time domain. Compared with the existing node architecture and scheduling algorithm, the simulation results show that the proposed architecture and the TFJSS can reduce the packet loss probability with low delay largely.

  10. Simple laser velocimeter that uses photoconductive semiconductors to measure optical frequency differences.

    PubMed

    Wang, C C; Davidson, F; Trivedi, S

    1995-10-01

    The dc photocurrents generated by steady-state moving space-charge fields inside photoconductive semiconductors containing deep level donors and traps can be used to determine the relative frequency differences between the two interfering optical fields that establish the space-charge fields. A simple laser velocimeter that uses a semi-insulating GaAs:Cr sample to detect the Doppler frequency shift between two laser beams is demonstrated.

  11. Single-mode waveguide optical isolator based on direction-dependent cutoff frequency.

    PubMed

    Tang, Lingling; Drezdzon, Samuel M; Yoshie, Tomoyuki

    2008-09-29

    A single-mode-waveguide optical isolator based on propagation direction dependent cut-off frequency is proposed. The isolation bandwidth is the difference between the cut-off frequencies of the lowest forward and backward propagating modes. Perturbation theory is used for analyzing the correlation between the material distribution and the bandwidth. The mode profile determines an appropriate distribution of non-reciprocal materials.

  12. Frequency tuning of the optical delay in cesium D{sub 2} line including hyperfine structure

    SciTech Connect

    Anderson, Monte D.; Perram, Glen P.

    2010-03-15

    The frequency dependence of optical delays in both the wings and core of the cesium 6 {sup 2}S{sub 1/2}-6 {sup 2}P{sub 3/2} transition have been observed and modeled with a Voigt line shape convolved with the six hyperfine components. Tunable delays of 0-37 ns are achieved by tuning the laser frequency through resonance at various vapor pressures of 0.15-5.28 mTorr.

  13. A novel elastic optical path network that utilizes bitrate-specific anchored frequency slot arrangement.

    PubMed

    Shen, Zhi-shu; Hasegawa, Hiroshi; Sato, Ken-ichi; Tanaka, Takafumi; Hirano, Akira

    2014-02-10

    We propose a novel elastic optical path network where each specific bitrate signal uses its own dedicated fixed grid and one edge of its frequency grid is anchored at a specific frequency. Numerical evaluations using various bitrate signal patterns and network topologies show that the network proposal can almost match the performance of conventional flexible grid networks, while greatly mitigating the hardware requirements: it allows the use of the tunable filters for the fixed grid systems.

  14. Frequency estimation for optical coherent M-QAM system without removing modulated data phase

    NASA Astrophysics Data System (ADS)

    Yu, Song; Cao, Yinwen; Leng, Haijun; Wu, Guohua; Gu, Wanyi

    2012-08-01

    For optical coherent M-ary quadrature amplitude modulation (M-QAM) system, the frequency offset can be extracted directly by applying Fast Fourier Transform (FFT) to the signal's argument, without removing the modulated data phase. By categorizing the constellation points and rotating some constellation points by π/4, this algorithm is robust to extract the frequency offset against the noise. Numerical simulations of 16-QAM and 256-QAM coherent systems are presented to demonstrate this algorithm.

  15. Towards spatial frequency domain optical imaging of neurovascular coupling in a mouse model of Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Lin, Alexander J.; Konecky, Soren D.; Rice, Tyler B.; Green, Kim N.; Choi, Bernard; Durkin, Anthony J.; Tromberg, Bruce J.

    2012-02-01

    Early neurovascular coupling (NVC) changes in Alzheimer's disease can potentially provide imaging biomarkers to assist with diagnosis and treatment. Previous efforts to quantify NVC with intrinsic signal imaging have required assumptions of baseline optical pathlength to calculate changes in oxy- and deoxy-hemoglobin concentrations during evoked stimuli. In this work, we present an economical spatial frequency domain imaging (SFDI) platform utilizing a commercially available LED projector, camera, and off-the-shelf optical components suitable for imaging dynamic optical properties. The fast acquisition platform described in this work is validated on silicone phantoms and demonstrated in neuroimaging of a mouse model.

  16. Multipixel system for gigahertz frequency-domain optical imaging of finger joints

    NASA Astrophysics Data System (ADS)

    Netz, Uwe J.; Beuthan, Jürgen; Hielscher, Andreas H.

    2008-03-01

    Frequency-domain optical imaging systems have shown great promise for characterizing blood oxygenation, hemodynamics, and other physiological parameters in human and animal tissues. However, most of the frequency domain systems presented so far operate with source modulation frequencies below 150MHz. At these low frequencies, their ability to provide accurate data for small tissue geometries such as encountered in imaging of finger joints or rodents is limited. Here, we present a new system that can provide data up to 1GHz using an intensity modulated charged coupled device camera. After data processing, the images show the two-dimensional distribution of amplitude and phase of the light modulation on the finger surface. The system performance was investigated and test measurements on optical tissue phantoms were taken to investigate whether higher frequencies yield better signal-to-noise ratios (SNRs). It could be shown that local changes in optical tissue properties, as they appear in the initial stages of rheumatoid arthritis in a finger joint, are detectable by simple image evaluation, with the range of modulation frequency around 500MHz proving to yield the highest SNR.

  17. Multipixel system for gigahertz frequency-domain optical imaging of finger joints.

    PubMed

    Netz, Uwe J; Beuthan, Jürgen; Hielscher, Andreas H

    2008-03-01

    Frequency-domain optical imaging systems have shown great promise for characterizing blood oxygenation, hemodynamics, and other physiological parameters in human and animal tissues. However, most of the frequency domain systems presented so far operate with source modulation frequencies below 150 MHz. At these low frequencies, their ability to provide accurate data for small tissue geometries such as encountered in imaging of finger joints or rodents is limited. Here, we present a new system that can provide data up to 1 GHz using an intensity modulated charged coupled device camera. After data processing, the images show the two-dimensional distribution of amplitude and phase of the light modulation on the finger surface. The system performance was investigated and test measurements on optical tissue phantoms were taken to investigate whether higher frequencies yield better signal-to-noise ratios (SNRs). It could be shown that local changes in optical tissue properties, as they appear in the initial stages of rheumatoid arthritis in a finger joint, are detectable by simple image evaluation, with the range of modulation frequency around 500 MHz proving to yield the highest SNR.

  18. Brain connectivity study of joint attention using frequency-domain optical imaging technique

    NASA Astrophysics Data System (ADS)

    Chaudhary, Ujwal; Zhu, Banghe; Godavarty, Anuradha

    2010-02-01

    Autism is a socio-communication brain development disorder. It is marked by degeneration in the ability to respond to joint attention skill task, from as early as 12 to 18 months of age. This trait is used to distinguish autistic from nonautistic populations. In this study, diffuse optical imaging is being used to study brain connectivity for the first time in response to joint attention experience in normal adults. The prefrontal region of the brain was non-invasively imaged using a frequency-domain based optical imager. The imaging studies were performed on 11 normal right-handed adults and optical measurements were acquired in response to joint-attention based video clips. While the intensity-based optical data provides information about the hemodynamic response of the underlying neural process, the time-dependent phase-based optical data has the potential to explicate the directional information on the activation of the brain. Thus brain connectivity studies are performed by computing covariance/correlations between spatial units using this frequency-domain based optical measurements. The preliminary results indicate that the extent of synchrony and directional variation in the pattern of activation varies in the left and right frontal cortex. The results have significant implication for research in neural pathways associated with autism that can be mapped using diffuse optical imaging tools in the future.

  19. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  20. Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region

    NASA Astrophysics Data System (ADS)

    Tripathi, Saroj R.; Miyata, Eisuke; Ishai, Paul Ben; Kawase, Kodo

    2015-03-01

    It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 +/- 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings.

  1. Morphology of human sweat ducts observed by optical coherence tomography and their frequency of resonance in the terahertz frequency region

    PubMed Central

    Tripathi, Saroj R.; Miyata, Eisuke; Ishai, Paul Ben; Kawase, Kodo

    2015-01-01

    It is crucial to understand the various biological effects induced by terahertz (THz) electromagnetic waves with the rapid development of electronic and photonic devices operating in the THz frequency region. The presence of sweat glands plays an important role in THz wave interactions with human skin. We investigated the morphological features of sweat ducts using optical coherence tomography (OCT) to further understand such phenomena. We observed remarkable features of the ducts, such as their clear helical structure. The intersubject and intrasubject variations in the diameter of sweat ducts were considerably smaller than the variations in other structural parameters, such as length and number of turns. Based on the sweat duct dimensions and THz dielectric properties of skin measured using terahertz time-domain spectroscopy (THz-TDS), we calculated the resonating frequency of the sweat duct under the assumption of it functioning as a helical antenna. Here, we show that the resonance frequency in the axial mode of operation lies in the THz wave region with a centre frequency of 0.44 ± 0.07 THz. We expect that these findings will further our understanding of the various health consequences of the interaction of THz waves with human beings. PMID:25766116

  2. Optical whispering-gallery mode resonators for applications in optical communication and frequency control

    NASA Astrophysics Data System (ADS)

    Grutter, Karen Esther

    High quality factor (Q) optical whispering gallery mode resonators are a key component in many on-chip optical systems, such as delay lines, modulators, and add-drop filters. They are also a convenient, compact structure for studying optomechanical interactions on-chip. In all these applications, optical Q is an important factor for high performance. For optomechanical reference oscillators in particular, high mechanical Q is also necessary. Previously, optical microresonators have been made in a wide variety of materials, but it has proven challenging to demonstrate high optical Q and high mechanical Q in a single, integrated device. This work demonstrates a new technique for achieving high optical Q on chip, a fully-integrated tunable filter with ultra-narrow minimum bandwidth, and the effect of material choice and device design on optical Q, mechanical Q and phase noise in microring optomechanical oscillators. To achieve a high optical Q, phosphosilicate glass (PSG) is studied as a resonator material. The low melting point of PSG enables wafer-scale reflow, which reduces sidewall roughness without significantly changing lithographically-defined dimensions. With this process, optical Qs up to 1.5 x 10. 7 are achieved, overten times higher than typical silicon optical resonators. These high-Q PSG resonators are then integrated with MEMS-actuated waveguides in a tunable-bandwidth filter. Due to the high Q of the PSG resonator, this device has a best-to-date minimum bandwidth of 0.8 GHz, with a tuning range of 0.8 to 8.5GHz. Finally, microring optomechanical oscillators (OMOs) in PSG, stoichiometric silicon nitride, and silicon are fabricated, and their performance is compared after characterization via a tapered optical fiber in vacuum. The silicon nitride device has the best performance, with a mechanical Q of more than 1 x 10. 4and record-breaking OMO phase noise of -102 dBc/Hz at a 1 kHz offset from a 72 MHz carrier.

  3. Full-range swept source optical coherence tomography based on carrier frequency by transmissive dispersive optical delay line.

    PubMed

    Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui

    2011-12-01

    A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.

  4. Full-range swept source optical coherence tomography based on carrier frequency by transmissive dispersive optical delay line

    NASA Astrophysics Data System (ADS)

    Wu, Tong; Ding, Zhihua; Wang, Chuan; Chen, Minghui

    2011-12-01

    A high speed swept source optical coherence tomography (SS-OCT) system capable of full-range imaging is presented. Wave-number carrier frequency is introduced into the spectral interference signal by a transmissive dispersive optical delay line (TDODL). High carrier frequency in the spectral interference signal corresponding to an equivalent distance-shift is exploited to obtain full-range OCT imaging. Theoretical development is conducted with the instantaneous coherence function introduced for a complete description of a spectral interference signal. Performance advantage of the TDODL-based method over the conventional approach where only one side (positive or negative path length difference) is used for imaging to avoid overlaying mirror artifacts is confirmed by the measured envelopes of spectral interference signal. Feasibility of the proposed method for full-range imaging is validated in a custom-built SS-OCT system by in vivo imaging of a biological sample.

  5. Development of high precision digital driver of acoustic-optical frequency shifter for ROG

    NASA Astrophysics Data System (ADS)

    Zhang, Rong; Kong, Mei; Xu, Yameng

    2016-10-01

    We develop a high precision digital driver of the acoustic-optical frequency shifter (AOFS) based on the parallel direct digital synthesizer (DDS) technology. We use an atomic clock as the phase-locked loop (PLL) reference clock, and the PLL is realized by a dual digital phase-locked loop. A DDS sampling clock up to 320 MHz with a frequency stability as low as 10-12 Hz is obtained. By constructing the RF signal measurement system, it is measured that the frequency output range of the AOFS-driver is 52-58 MHz, the center frequency of the band-pass filter is 55 MHz, the ripple in the band is less than 1 dB@3MHz, the single channel output power is up to 0.3 W, the frequency stability is 1 ppb (1 hour duration), and the frequency-shift precision is 0.1 Hz. The obtained frequency stability has two orders of improvement compared to that of the analog AOFS-drivers. For the designed binary frequency shift keying (2-FSK) and binary phase shift keying (2-PSK) modulation system, the demodulating frequency of the input TTL synchronous level signal is up to 10 kHz. The designed digital-bus coding/decoding system is compatible with many conventional digital bus protocols. It can interface with the ROG signal detecting software through the integrated drive electronics (IDE) and exchange data with the two DDS frequency-shift channels through the signal detecting software.

  6. Determining optical path difference with a frequency-modulated continuous-wave method.

    PubMed

    Song, Ningfang; Lu, Xiangxiang; Li, Wei; Li, Yang; Wang, Yingying; Liu, Jixun; Xu, Xiaobin; Pan, Xiong

    2015-08-01

    A technique for determining the optical path difference (OPD) between two Raman beams using a frequency-modulated continuous-wave method is investigated. This approach greatly facilitates the measurement and adjustment of the OPD when tuning the OPD is essential to minimize the effects of the diode laser's phase noise on Raman lasers. As a demonstration, the frequencies of the beat note with different OPDs are characterized and analyzed. When the measured beat frequency is 0.367 Hz, the OPD between Raman beams is zero. The phase noise of the Raman laser system after implementation of zeroing of the OPD is also measured.

  7. Simultaneous broadband microwave downconversion and programmable complex filtering by optical frequency comb shaping.

    PubMed

    Torres-Company, Victor; Leaird, Daniel E; Weiner, Andrew M

    2012-10-01

    High-repetition-rate optical frequency combs can act as broadband photonic mixers and downconvert a microwave signal to an intermediate frequency (IF) band so that it becomes accessible with high-speed electronics. In this Letter, we show that with line-by-line pulse shaping and dispersive propagation, the photonic mixer can simultaneously perform programmable multitap complex-coefficient-filtering within the IF band. This solution opens new possibilities for microwave signal processing by combining the flexibility of optoelectronic frequency comb technology with high-speed analog-to-digital converters.

  8. Extracting infrared absolute reflectance from relative reflectance measurements.

    PubMed

    Berets, Susan L; Milosevic, Milan

    2012-06-01

    Absolute reflectance measurements are valuable to the optics industry for development of new materials and optical coatings. Yet, absolute reflectance measurements are notoriously difficult to make. In this paper, we investigate the feasibility of extracting the absolute reflectance from a relative reflectance measurement using a reference material with known refractive index.

  9. Three-dimensional pointwise comparison of human retinal optical property at 845 and 1060 nm using optical frequency domain imaging.

    PubMed

    Chen, Yueli; Burnes, Daina L; de Bruin, Martijn; Mujat, Mircea; de Boer, Johannes F

    2009-01-01

    To compare the optical properties of the human retina, 3-D volumetric images of the same eye are acquired with two nearly identical optical coherence tomography (OCT) systems at center wavelengths of 845 and 1060 nm using optical frequency domain imaging (OFDI). To characterize the contrast of individual tissue layers in the retina at these two wavelengths, the 3-D volumetric data sets are carefully spatially matched. The relative scattering intensities from different layers such as the nerve fiber, photoreceptor, pigment epithelium, and choroid are measured and a quantitative comparison is presented. OCT retinal imaging at 1060 nm is found to have a significantly better depth penetration but a reduced contrast between the retinal nerve fiber, the ganglion cell, and the inner plexiform layers compared to the OCT retinal imaging at 845 nm.

  10. High-resolution differential mode delay measurement for a multimode optical fiber using a modified optical frequency domain reflectometer.

    PubMed

    Ahn, T-J; Kim, D

    2005-10-03

    A novel differential mode delay (DMD) measurement technique for a multimode optical fiber based on optical frequency domain reflectometry (OFDR) has been proposed. We have obtained a high-resolution DMD value of 0.054 ps/m for a commercial multimode optical fiber with length of 50 m by using a modified OFDR in a Mach-Zehnder interferometer structure with a tunable external cavity laser and a Mach-Zehnder interferometer instead of Michelson interferometer. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method. DMD resolution with our proposed OFDR technique is more than an order of magnitude better than a result obtainable with a conventional time-domain method.

  11. Three-dimensional pointwise comparison of human retinal optical property at 845 and 1060 nm using optical frequency domain imaging

    NASA Astrophysics Data System (ADS)

    Chen, Yueli; Burnes, Daina L.; de Bruin, Martijn; Mujat, Mircea; de Boer, Johannes F.

    2009-03-01

    To compare the optical properties of the human retina, 3-D volumetric images of the same eye are acquired with two nearly identical optical coherence tomography (OCT) systems at center wavelengths of 845 and 1060 nm using optical frequency domain imaging (OFDI). To characterize the contrast of individual tissue layers in the retina at these two wavelengths, the 3-D volumetric data sets are carefully spatially matched. The relative scattering intensities from different layers such as the nerve fiber, photoreceptor, pigment epithelium, and choroid are measured and a quantitative comparison is presented. OCT retinal imaging at 1060 nm is found to have a significantly better depth penetration but a reduced contrast between the retinal nerve fiber, the ganglion cell, and the inner plexiform layers compared to the OCT retinal imaging at 845 nm.

  12. Simultaneously improving the sensitivity and absolute accuracy of CPT magnetometer.

    PubMed

    Liang, Shang-Qing; Yang, Guo-Qing; Xu, Yun-Fei; Lin, Qiang; Liu, Zhi-Heng; Chen, Zheng-Xiang

    2014-03-24

    A new method to improve the sensitivity and absolute accuracy simultaneously for coherent population trapping (CPT) magnetometer based on the differential detection method is presented. Two modulated optical beams with orthogonal circular polarizations are applied, in one of which two magnetic resonances are excited simultaneously by modulating a 3.4GHz microwave with Larmor frequency. When a microwave frequency shift is introduced, the difference in the power transmitted through the cell in each beam shows a low noise resonance. The sensitivity of 2pT/Hz @ 10Hz is achieved. Meanwhile, the absolute accuracy of ± 0.5nT within the magnetic field ranging from 20000nT to 100000nT is realized.

  13. New optical and radio frequency angular tropospheric refraction models for deep space applications

    NASA Technical Reports Server (NTRS)

    Berman, A. L.; Rockwell, S. T.

    1976-01-01

    The development of angular tropospheric refraction models for optical and radio frequency usage is presented. The models are compact analytic functions, finite over the entire domain of elevation angle, and accurate over large ranges of pressure, temperature, and relative humidity. Additionally, FORTRAN subroutines for each of the models are included.

  14. Space and frequency-multiplexed optical linear algebra processor - Fabrication and initial tests

    NASA Technical Reports Server (NTRS)

    Casasent, D.; Jackson, J.

    1986-01-01

    A new optical linear algebra processor architecture is described. Space and frequency-multiplexing are used to accommodate bipolar and complex-valued data. A fabricated laboratory version of this processor is described, the electronic support system used is discussed, and initial test data obtained on it are presented.

  15. Observation of fundamental thermal noise in optical fibers down to infrasonic frequencies

    NASA Astrophysics Data System (ADS)

    Dong, Jing; Huang, Junchao; Li, Tang; Liu, Liang

    2016-01-01

    The intrinsic thermal noise in optical fibers represents the ultimate limit for fiber-based systems. However, at infrasonic frequencies, the spectral behavior of the intrinsic thermal noise is still unclear. In this letter, we present measurements of the fundamental thermal noise in optical fibers that are obtained using a balanced fiber Michelson interferometer. When an ultra-stable laser is used as the laser source and other noise sources are carefully controlled, the 1/f spectral density of the thermal noise is observed down to infrasonic frequencies, and the measured magnitude is consistent with the results of theoretical predictions at frequencies over the range from 0.2 Hz to 20 kHz. Moreover, as observed experimentally, the level of the 1/f thermal noise can be reduced by changing the coatings of the optical fibers. This therefore indicates one possible way to reduce thermal noise in optical fibers at low Fourier frequencies. Finally, the inconsistency between the experimental data and the existing theory for thermomechanical noise is discussed.

  16. Pump wavelength tuning of optical parametric oscillations and frequency mixing in KTiOAsO4

    NASA Technical Reports Server (NTRS)

    Jani, Mahendra G.; Murray, James T.; Petrin, Roger R.; Powell, Richard C.; Loiacono, D. N.; Loiacono, G. M.

    1992-01-01

    The properties of alexandrite laser-pumped optical parametric oscillators are reported for potassium titanyl arsenate. Near-infrared tuning curves and slope efficiencies were measured as functions of pump wavelength and pump power. In addition, sum frequency mixing of red and infrared wavelengths to produce green emission is also reported.

  17. Electro-optic modulation of a laser at microwave frequencies for interferometric purposes

    NASA Astrophysics Data System (ADS)

    Specht, Paul E.; Jilek, Brook A.

    2017-02-01

    A multi-point microwave interferometer (MPMI) concept was previously proposed by the authors for spatially-resolved, non-invasive tracking of a shock, reaction, or detonation front in energetic media [P. Specht et al., AIP Conf. Proc. 1793, 160010 (2017).]. The advantage of the MPMI concept over current microwave interferometry techniques is its detection of Doppler shifted microwave signals through electro-optic (EO) modulation of a laser. Since EO modulation preserves spatial variations in the Doppler shift, collecting the EO modulated laser light into a fiber array for recording with an optical heterodyne interferometer yields spatially-resolved velocity information. This work demonstrates the underlying physical principle of the MPMI diagnostic: the monitoring of a microwave signal with nanosecond temporal resolution using an optical heterodyne interferometer. For this purpose, the MPMI concept was simplified to a single-point construction using two tunable 1550 nm lasers and a 35.2 GHz microwave source. A (110) ZnTe crystal imparted the microwave frequency onto a laser, which was combined with a reference laser for determination of the microwave frequency in an optical heterodyne interferometer. A single, characteristic frequency associated with the microwave source was identified in all experiments, providing a means to monitor a microwave signal on nanosecond time scales. Lastly, areas for improving the frequency resolution of this technique are discussed, focusing on increasing the phase-modulated signal strength.

  18. Gated frequency-resolved optical imaging with an optical parametric amplifier for medical applications

    SciTech Connect

    Cameron, S.M.; Bliss, D.E.

    1997-02-01

    Implementation of optical imagery in a diffuse inhomogeneous medium such as biological tissue requires an understanding of photon migration and multiple scattering processes which act to randomize pathlength and degrade image quality. The nature of transmitted light from soft tissue ranges from the quasi-coherent properties of the minimally scattered component to the random incoherent light of the diffuse component. Recent experimental approaches have emphasized dynamic path-sensitive imaging measurements with either ultrashort laser pulses (ballistic photons) or amplitude modulated laser light launched into tissue (photon density waves) to increase image resolution and transmissive penetration depth. Ballistic imaging seeks to compensate for these {open_quotes}fog-like{close_quotes} effects by temporally isolating the weak early-arriving image-bearing component from the diffusely scattered background using a subpicosecond optical gate superimposed on the transmitted photon time-of-flight distribution. The authors have developed a broadly wavelength tunable (470 nm -2.4 {mu}m), ultrashort amplifying optical gate for transillumination spectral imaging based on optical parametric amplification in a nonlinear crystal. The time-gated image amplification process exhibits low noise and high sensitivity, with gains greater than 104 achievable for low light levels. We report preliminary benchmark experiments in which this system was used to reconstruct, spectrally upcovert, and enhance near-infrared two-dimensional images with feature sizes of 65 {mu}m/mm{sup 2} in background optical attenuations exceeding 10{sup 12}. Phase images of test objects exhibiting both absorptive contrast and diffuse scatter were acquired using a self-referencing Shack-Hartmann wavefront sensor in combination with short-pulse quasi-ballistic gating. The sensor employed a lenslet array based on binary optics technology and was sensitive to optical path distortions approaching {lambda}/100.

  19. Comparative Study of Optical and Radio-Frequency Communication Systems for a Deep-Space Mission

    NASA Technical Reports Server (NTRS)

    Hemmati, H.; Wilson, K.; Sue, M. K.; Harcke, L. J.; Wilhelm, M.; Chen, C.-C.; Lesh, J.; Feria, Y.; Rascoe, D.; Lansing, F.

    1997-01-01

    We have performed a study on telecommunication systems for a hypothetical mission to Mars. The objective of the study was to evaluate and compare the benefits that microwave-X-band (8.4 GHz) and Ka-band (32 GHz) - and optical communications technologies a afford to future missions. The telecommunication systems were required to return data after launch and in orbit at 2.7 AU with daily data volumes of 0.1, 1.0, or 10.0 Gbits (Gb). Spacecraft terminals capable of delivering each of the three data volumes were proposed and characterized in terms of mass, power consumption, size, and cost. The estimated parameters for X-band, Ka-band, and optical frequencies are compared and presented here. For all cases, the optical light terminal exhibits about 60 percent of the mass of the corresponding radio frequency (RF) subsystem. Power consumption is comparable for all three technologies at a 0.1 Gb/day data volume, but the power required at either Ka-band or optical is less than half of the X-band requirement at 10 Gb/day. These benefits can be obtained only with a suitable investment in reception facilities for Ka-band or optical frequencies.

  20. Full-field time-encoded frequency-domain optical coherence tomography.

    PubMed

    Povazay, Boris; Unterhuber, Angelika; Hermann, Boris; Sattmann, Harald; Arthaber, Holger; Drexler, Wolfgang

    2006-08-21

    Ultrahigh axial resolution surface profiling as well as volumetric optical imaging based on time encoded optical coherence tomography in the frequency domain without any mechanical scanning element is presented. A frequency tuned broad bandwidth titanium sapphire laser is interfaced to an optical microscope (Axioskop 2 MAT, Carl Zeiss Meditec) that is enhanced with an interferometric imaging head. The system is equipped with a 640 x 480 pixel CMOS camera, optimized for the 800 nm wavelength tuning range for transmission and reflection measurements of a microscopic sample. Sample volume information over 1.3 x 1 x 0.2 mm(3) with ~3 mum axial and ~4 mum transverse resolution in tissue is acquired by a single wavelength scan over more than 100 nm optical bandwidth from <760 to >860 nm with 128-2048 equidistant optical frequency steps with an acquisition time of 1 to 50 ms per step. Topography and tomography with a signal to noise ratio of 83 dB is demonstrated on test surfaces and biological specimen respectively. This novel OCT technique promises to enable high speed, three dimensional imaging by employing high frame rate cameras and state of the art tunable lasers in a mechanically stable environment, due to lack of moving components while reducing the intensity on the sample.

  1. Extending the effective imaging depth in spectral domain optical coherence tomography by dual spatial frequency encoding

    NASA Astrophysics Data System (ADS)

    Wu, Tong; Wang, Qingqing; Liu, Youwen; Wang, Jiming

    2016-03-01

    We present a spatial frequency domain multiplexing method for extending the imaging depth range of a SDOCT system without any expensive device. This method uses two reference arms with different round-trip optical delay to probe different depth regions within the sample. Two galvo scanners with different pivot-offset distances in the reference arms are used for spatial frequency modulation and multiplexing. While simultaneously driving the galvo scanners in the reference arms and the sample arm, the spatial spectrum of the acquired two-dimensional OCT spectral interferogram corresponding to the shallow and deep depth of the sample will be shifted to the different frequency bands in the spatial frequency domain. After data filtering, image reconstruction and fusion the spatial frequency multiplexing SDOCT system can provide an approximately 1.9 fold increase in the effective ranging depth compared with that of a conventional single-reference-arm full-range SDOCT system.

  2. Laser Frequency Stabilization and Control through Offset Sideband Locking to Optical Cavities

    NASA Technical Reports Server (NTRS)

    Thorpe, James I.; Livas, J.; Numata, K.

    2008-01-01

    We describe a class of techniques whereby a laser frequency can be stabilized to a fixed optical cavity resonance with an adjustable offset, providing a wide tuning range for the central frequency. These techniques require only minor modifications to the standard Pound-Drever-Hall locking techniques and have the advantage of not altering the intrinsic stability of the frequency reference. In a laboratory investigation the sideband techniques were found to perform equally well as the standard, non-tunable Pound-Drever-Hall technique, each providing more than four decades of frequency noise suppression over the free-running noise. An application of a tunable system as a pre-stabilization stage in a phase-lock loop is also presented with the combined system achieving a frequency noise suppression of nearly twelve orders of magnitude.

  3. Comparison of DSP schemes with frequency domain equalization for passive optical networks

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Ye, Jia; Liu, Yanhe; Yan, Lianshan

    2015-08-01

    In recent years, digital signal processing (DSP) has been widely investigated for the applications in future next generation passive optical networks (PONs). In this paper, we compare four transmission technologies based on DSP with frequency domain equalization (FDE) for PON transmission with double-side band (DSB) intensity modulation and direct detection. These schemes include orthogonal frequency division multiplexing (OFDM), single-carrier frequency domain equalization (SCFDE), discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) and interleaved frequency division multiplexing (IFDM). We analyze their computational complexity and flexibility in PON applications, and compare their transmission performance by experiments. Based on above work, we propose and experimentally demonstrate a hybrid DSP-enhanced PON architecture with downstream OFDM modulation and upstream SCFDE modulation.

  4. Frequency-agile kilohertz repetition-rate optical parametric oscillator based on periodically poled lithium niobate

    SciTech Connect

    Yang, S.T.; Velsko, S.P.

    1999-02-01

    We report kilohertz repetition-rate pulse-to-pulse wavelength tuning from 3.22 to 3.7 {mu}m in a periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO). Rapid tuning over 400thinspcm{sup {minus}1} with random wavelength accessibility is achieved by rotation of the pump beam angle by no more than 24thinspthinspmrad in the PPLN crystal by use of an acousto-optic beam deflector. Over the entire tuning range, a near-transform-limited OPO bandwidth can be obtained by means of injection seeding with a single-frequency 1.5-{mu}m laser diode. The frequency agility, high repetition rate, and narrow bandwidth of this mid-IR PPLN OPO make it well suited as a lidar transmitter source. {copyright} {ital 1999} {ital Optical Society of America}

  5. Frequency-modulated light scattering interferometry employed for optical properties and dynamics studies of turbid media

    PubMed Central

    Mei, Liang; Somesfalean, Gabriel; Svanberg, Sune

    2014-01-01

    In the present work, fiber-based frequency-modulated light scattering interferometry (FMLSI) is developed and employed for studies of optical properties and dynamics in liquid phantoms made from Intralipid®. The fiber-based FMLSI system retrieves the optical properties by examining the intensity fluctuations through the turbid medium in a heterodyne detection scheme using a continuous-wave frequency-modulated coherent light source. A time resolution of 21 ps is obtained, and the experimental results for the diluted Intralipid phantoms show good agreement with the predicted results based on published data. The present system shows great potential for assessment of optical properties as well as dynamic studies in liquid phantoms, dairy products, and human tissues. PMID:25136504

  6. High-resolution optical frequency dissemination on a telecommunications network with data traffic.

    PubMed

    Kéfélian, Fabien; Lopez, Olivier; Jiang, Haifeng; Chardonnet, Christian; Amy-Klein, Anne; Santarelli, Giorgio

    2009-05-15

    We transferred the frequency of an ultrastable laser over a 108-km-long urban fiber link comprising 22 km of an optical communications network fiber simultaneously carrying Internet data traffic. The metrological signal and the digital data signal were transferred over two different frequency channels in a dense wavelength-division multiplexing scheme. The metrological signal was inserted in and extracted from the communication network using bidirectional off-the-shelf optical add-drop multiplexers. The link-induced phase noise was measured and canceled with a round-trip technique using an all-fiber-based interferometer. The compensated link showed an Allan deviation of a few 10(-16) at 1 s and below 10(-19) at 10,000 s. This work paves the way to a wide dissemination of ultrastable optical clock signals between distant laboratories via the Internet.

  7. Lightning detection from Space Science and Applications Team review. [optical and radio frequency sensors

    NASA Technical Reports Server (NTRS)

    Few, A. A., Jr.

    1981-01-01

    The various needs for lightning data that exist among potential users of satellite lightning data were identified and systems were defined which utilize the optical and radio frequency radiations from lightning to serve as the satellite based lightning mapper. Three teams worked interactively with NASA to develop a system concept. An assessment of the results may be summarized as follows: (1) a small sensor system can be easily designed to operate on a geostationary satellite that can provide the bulk of the real time user requirements; (2) radio frequency systems in space may be feasible but would be much larger and more costly; RF technology for this problem lags the optical technology by years; and (3) a hybrid approach (optical in space and RF on the ground) would provide the most complete information but is probably unreasonably complex and costly at this time.

  8. Enhanced hybrid asymmetrically clipped orthogonal frequency division multiplexing for optical wireless communications

    NASA Astrophysics Data System (ADS)

    Guan, Rui; Huang, Nuo; Wang, Jin-Yuan; Wang, Houyu; Chen, Ming

    2016-05-01

    This paper presents an enhanced hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (EHACO-OFDM) scheme, which benefits from the simultaneous transmission of ACO-OFDM, pulse-amplitude-modulated discrete multitone modulation, and direct-current-biased optical orthogonal frequency division multiplexing (DCO-OFDM). Since the entire available bandwidth is utilized for data modulation, this scheme can achieve higher spectral efficiency than HACO-OFDM and ACO-OFDM. Moreover, as a smaller DC bias is introduced in our scheme, it is more power efficient than asymmetrically clipped DC-biased optical OFDM (ADO-OFDM) and DCO-OFDM. A modified receiver is also designed for this system, taking advantage of an iterative algorithm and a pairwise averaging. It has been shown by simulation that our three-path simultaneous transmission scheme can surpass the existing mixed OFDM-based schemes at high data rates. In addition, compared with the noniterative receiver, the modified receiver exhibits significant gains.

  9. Method for determiantion of the frequency-contrast characteristics of electronic-optic systems

    NASA Astrophysics Data System (ADS)

    Mardirossian, Garo; Zhekov, Zhivko

    The frequency-contrast characteristics is an important criterion to judge the quality of electronic-optic systems, which boast an increasing application in space research, astronomy, martial art etc. The paper provides a brief description of the methods for determining the frequency-contrast characteristics of optic systems, developed at the Space Research Institute of the Bulgarian Academy of Science. The suggested methods have been used to develop a couple of electronic-optic systems participated in the designed ground-based and aerospace scientific-research equipment. Based on the obtained practical results, the conclusion was made that the methods provide to obtain sufficiently precise data, which coincide well with the results, obtained when using other methods.

  10. Characterization of Ultrafast Laser Pulses using a Low-dispersion Frequency Resolved Optical Grating Spectrometer

    NASA Astrophysics Data System (ADS)

    Whitelock, Hope; Bishop, Michael; Khosravi, Soroush; Obaid, Razib; Berrah, Nora

    2016-05-01

    A low dispersion frequency-resolved optical gating (FROG) spectrometer was designed to characterize ultrashort (<50 femtosecond) laser pulses from a commercial regenerative amplifier, optical parametric amplifier, and a home-built non-colinear optical parametric amplifier. This instrument splits a laser pulse into two replicas with a 90:10 intensity ratio using a thin pellicle beam-splitter and then recombines the pulses in a birefringent medium. The instrument detects a wavelength-sensitive change in polarization of the weak probe pulse in the presence of the stronger pump pulse inside the birefringent medium. Scanning the time delay between the two pulses and acquiring spectra allows for characterization of the frequency and time content of ultrafast laser pulses, that is needed for interpretation of experimental results obtained from these ultrafast laser systems. Funded by the DoE-BES, Grant No. DE-SC0012376.

  11. All-optical central-frequency-programmable and bandwidth-tailorable radar

    PubMed Central

    Zou, Weiwen; Zhang, Hao; Long, Xin; Zhang, Siteng; Cui, Yuanjun; Chen, Jianping

    2016-01-01

    Radar has been widely used for military, security, and rescue purposes, and modern radar should be reconfigurable at multi-bands and have programmable central frequencies and considerable bandwidth agility. Microwave photonics or photonics-assisted radio-frequency technology is a unique solution to providing such capabilities. Here, we demonstrate an all-optical central-frequency-programmable and bandwidth-tailorable radar architecture that provides a coherent system and utilizes one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates a wideband linearly chirped radar signal. The working bands can be flexibly tailored with the desired bandwidth at a user-preferred carrier frequency. Radar echoes are first modulated onto the pre-chirped optical pulse, which is also used for signal generation, and then stretched in time or compressed in frequency several fold based on the time-stretch principle. Thus, digitization is facilitated without loss of detection ability. We believe that our results demonstrate an innovative radar architecture with an ultra-high-range resolution. PMID:26795596

  12. Development of compact and ultra-high-resolution spectrograph with multi-GHz optical frequency comb

    NASA Astrophysics Data System (ADS)

    Endo, Mamoru; Sukegawa, Takashi; Silva, Alissa; Kobayashi, Yohei

    2014-08-01

    In recent years, a calibration method for an astronomical spectrograph using an optical frequency comb (OFC) with a repetition rate of more than ten GHz has been developed successfully [1-5]. But controlling filtering cavities that are used for thinning out longitudinal modes precludes long term stability. The super-mode noise coming from the fundamental repetition rate is an additional problem. We developed a laser-diode pumped Yb:Y2O3 ceramic oscillator, which enabled the generation of 4-GHz (maximum repetition rate of 6.7 GHz) pulse trains directly with a spectrum width of 7 nm (full-width half-maximum, FWHM), and controlled its optical frequency within a MHz level of accuracy using a beat note between the 4-GHz laser and a 246-MHz Yb-fiber OFC. The optical frequency of the Yb-fiber OFC was phase locked to a Rb clock frequency standard. Furthermore we also built a table-top multi-pass spectrograph with a maximum frequency resolution of 600 MHz and a bandwidth of 1 nm using a large-size high-efficiency transmission grating. The resolution could be changed by selecting the number of passes through the grating. This spectrograph could resolve each longitudinal mode of our 4-GHz OFC clearly, and more than 10% throughput was obtained when the resolution was set to 600 MHz. We believe that small and middle scale astronomical observatories could easily implement such an OFC-calibrated spectrograph.

  13. All-optical central-frequency-programmable and bandwidth-tailorable radar

    NASA Astrophysics Data System (ADS)

    Zou, Weiwen; Zhang, Hao; Long, Xin; Zhang, Siteng; Cui, Yuanjun; Chen, Jianping

    2016-01-01

    Radar has been widely used for military, security, and rescue purposes, and modern radar should be reconfigurable at multi-bands and have programmable central frequencies and considerable bandwidth agility. Microwave photonics or photonics-assisted radio-frequency technology is a unique solution to providing such capabilities. Here, we demonstrate an all-optical central-frequency-programmable and bandwidth-tailorable radar architecture that provides a coherent system and utilizes one mode-locked laser for both signal generation and reception. Heterodyning of two individually filtered optical pulses that are pre-chirped via wavelength-to-time mapping generates a wideband linearly chirped radar signal. The working bands can be flexibly tailored with the desired bandwidth at a user-preferred carrier frequency. Radar echoes are first modulated onto the pre-chirped optical pulse, which is also used for signal generation, and then stretched in time or compressed in frequency several fold based on the time-stretch principle. Thus, digitization is facilitated without loss of detection ability. We believe that our results demonstrate an innovative radar architecture with an ultra-high-range resolution.

  14. Measurement of absolute displacement by a double-modulation technique based on a Michelson interferometer.

    PubMed

    Chang, L W; Chien, P Y; Lee, C T

    1999-05-01

    A novel method is presented for of measuring absolute displacement with a synthesized wavelength interferometer. The optical phase of the interferometer is simultaneously modulated with a frequency-modulated laser diode and optical path-length difference. The error signal originating from the intensity modulation of the source is eliminated by a signal processing circuit. In addition, a lock-in technique is used to demodulate the envelope of the interferometric signal. The displacement signal is derived by the self-mixing technique.

  15. Ultralow-phase-noise millimetre-wave signal generator assisted with an electro-optics-modulator-based optical frequency comb

    PubMed Central

    Ishizawa, A.; Nishikawa, T.; Goto, T.; Hitachi, K.; Sogawa, T.; Gotoh, H.

    2016-01-01

    Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. However, the phase noise of widely used conventional signal generators (SGs) will increase as the millimetre-wave frequency increases. Our goal has been to improve commercially available SGs so that they provide a low-phase-noise millimetre-wave signal with assistance from an electro-optics-modulator-based optical frequency comb (EOM-OFC). Here, we show that the phase noise can be greatly reduced by bridging the vast frequency difference between the gigahertz and terahertz ranges with an EOM-OFC. The EOM-OFC serves as a liaison that magnifies the phase noise of the SG. With the EOM-OFC used as a phase noise “booster” for a millimetre-wave signal, the phase noise of widely used SGs can be reduced at an arbitrary frequency f (6 ≦ f ≦ 72 GHz). PMID:27185040

  16. Ultralow-phase-noise millimetre-wave signal generator assisted with an electro-optics-modulator-based optical frequency comb.

    PubMed

    Ishizawa, A; Nishikawa, T; Goto, T; Hitachi, K; Sogawa, T; Gotoh, H

    2016-05-17

    Low-noise millimetre-wave signals are valuable for digital sampling systems, arbitrary waveform generation for ultra-wideband communications, and coherent radar systems. However, the phase noise of widely used conventional signal generators (SGs) will increase as the millimetre-wave frequency increases. Our goal has been to improve commercially available SGs so that they provide a low-phase-noise millimetre-wave signal with assistance from an electro-optics-modulator-based optical frequency comb (EOM-OFC). Here, we show that the phase noise can be greatly reduced by bridging the vast frequency difference between the gigahertz and terahertz ranges with an EOM-OFC. The EOM-OFC serves as a liaison that magnifies the phase noise of the SG. With the EOM-OFC used as a phase noise "booster" for a millimetre-wave signal, the phase noise of widely used SGs can be reduced at an arbitrary frequency f (6 ≦ f ≦ 72 GHz).

  17. Ultrabroadband phased-array radio frequency (RF) receivers based on optical techniques

    NASA Astrophysics Data System (ADS)

    Overmiller, Brock M.; Schuetz, Christopher A.; Schneider, Garrett; Murakowski, Janusz; Prather, Dennis W.

    2014-03-01

    Military operations require the ability to locate and identify electronic emissions in the battlefield environment. However, recent developments in radio detection and ranging (RADAR) and communications technology are making it harder to effectively identify such emissions. Phased array systems aid in discriminating emitters in the scene by virtue of their relatively high-gain beam steering and nulling capabilities. For the purpose of locating emitters, we present an approach realize a broadband receiver based on optical processing techniques applied to the response of detectors in conformal antenna arrays. This approach utilizes photonic techniques that enable us to capture, route, and process the incoming signals. Optical modulators convert the incoming signals up to and exceeding 110 GHz with appreciable conversion efficiency and route these signals via fiber optics to a central processing location. This central processor consists of a closed loop phase control system which compensates for phase fluctuations induced on the fibers due to thermal or acoustic vibrations as well as an optical heterodyne approach for signal conversion down to baseband. Our optical heterodyne approach uses injection-locked paired optical sources to perform heterodyne downconversion/frequency identification of the detected emission. Preliminary geolocation and frequency identification testing of electronic emissions has been performed demonstrating the capabilities of our RF receiver.

  18. High-frequency chaotic dynamics enabled by optical phase-conjugation

    PubMed Central

    Mercier, Émeric; Wolfersberger, Delphine; Sciamanna, Marc

    2016-01-01

    Wideband chaos is of interest for applications such as random number generation or encrypted communications, which typically use optical feedback in a semiconductor laser. Here, we show that replacing conventional optical feedback with phase-conjugate feedback improves the chaos bandwidth. In the range of achievable phase-conjugate mirror reflectivities, the bandwidth increase reaches 27% when compared with feedback from a conventional mirror. Experimental measurements of the time-resolved frequency dynamics on nanosecond time-scales show that the bandwidth enhancement is related to the onset of self-pulsing solutions at harmonics of the external-cavity frequency. In the observed regime, the system follows a chaotic itinerancy among these destabilized high-frequency external-cavity modes. The recorded features are unique to phase-conjugate feedback and distinguish it from the long-standing problem of time-delayed feedback dynamics. PMID:26739806

  19. Frequency Comparison of Two High-Accuracy Al{sup +} Optical Clocks

    SciTech Connect

    Chou, C. W.; Hume, D. B.; Koelemeij, J. C. J.; Wineland, D. J.; Rosenband, T.

    2010-02-19

    We have constructed an optical clock with a fractional frequency inaccuracy of 8.6x10{sup -18}, based on quantum logic spectroscopy of an Al{sup +} ion. A simultaneously trapped Mg{sup +} ion serves to sympathetically laser cool the Al{sup +} ion and detect its quantum state. The frequency of the {sup 1}S{sub 0}reversible{sup 3}P{sub 0} clock transition is compared to that of a previously constructed Al{sup +} optical clock with a statistical measurement uncertainty of 7.0x10{sup -18}. The two clocks exhibit a relative stability of 2.8x10{sup -15}tau{sup -1/2}, and a fractional frequency difference of -1.8x10{sup -17}, consistent with the accuracy limit of the older clock.

  20. Wired/wireless access integrated RoF-PON with scalable generation of multi-frequency MMWs enabled by tunable optical frequency comb.

    PubMed

    Xiang, Yu; Jiang, Ning; Chen, Chen; Zhang, Chongfu; Qiu, Kun

    2013-08-26

    In this paper, a novel wired/wireless access integrated radio-over-fiber passive optical network (RoF-PON) system that utilizes scalable multiple-frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC) is proposed. The TOFC is performed by cascading a phase modulator (PM) and two intensity modulators (IMs), and with proper selection of the peak-to-peak voltage of the PM, a flat and effective optical comb with tens of frequency lines is achieved. The MF-MMWs are generated by beating the optical comb line pairs with an interval about 60 GHz. The feasibility and scalability of the proposed wired/wireless access integrated RoF-PON scheme are confirmed by the simulations of simultaneous distribution of wired and wireless data with the proposed multiple frequency MMW generation technology.

  1. Bi-directional conversion between microwave and optical frequencies in a piezoelectric optomechanical device

    NASA Astrophysics Data System (ADS)

    Vainsencher, Amit; Satzinger, K. J.; Peairs, G. A.; Cleland, A. N.

    2016-07-01

    We describe the principles of design, fabrication, and operation of a piezoelectric optomechanical crystal with which we demonstrate bi-directional conversion of energy between microwave and optical frequencies. The optomechanical crystal has an optical mode at 1523 nm co-located with a mechanical breathing mode at 3.8 GHz, with a measured optomechanical coupling strength gom/2π of 115 kHz. The breathing mode is driven and detected by curved interdigitated transducers that couple to a Lamb mode in suspended membranes on either end of the optomechanical crystal, allowing the external piezoelectric modulation of the optical signal as well as the converse, the detection of microwave electrical signals generated by a modulated optical signal. We compare measurements to theory where appropriate.

  2. Database applicaton for absolute spectrophotometry

    NASA Astrophysics Data System (ADS)

    Bochkov, Valery V.; Shumko, Sergiy

    2002-12-01

    32-bit database application with multidocument interface for Windows has been developed to calculate absolute energy distributions of observed spectra. The original database contains wavelength calibrated observed spectra which had been already passed through apparatus reductions such as flatfielding, background and apparatus noise subtracting. Absolute energy distributions of observed spectra are defined in unique scale by means of registering them simultaneously with artificial intensity standard. Observations of sequence of spectrophotometric standards are used to define absolute energy of the artificial standard. Observations of spectrophotometric standards are used to define optical extinction in selected moments. FFT algorithm implemented in the application allows performing convolution (deconvolution) spectra with user-defined PSF. The object-oriented interface has been created using facilities of C++ libraries. Client/server model with Windows Socket functionality based on TCP/IP protocol is used to develop the application. It supports Dynamic Data Exchange conversation in server mode and uses Microsoft Exchange communication facilities.

  3. Demonstration of space optical transmitter development for multiple high-frequency bands

    NASA Astrophysics Data System (ADS)

    Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

    2013-05-01

    As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

  4. Demonstration of Space Optical Transmitter Development for Multiple High Frequency Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Hung; Simons, Rainee; Wintucky, Edwin; Freeman, Jon

    2013-01-01

    As the demand for multiple radio frequency carrier bands continues to grow in space communication systems, the design of a cost-effective compact optical transmitter that is capable of transmitting selective multiple RF bands is of great interest, particularly for NASA Space Communications Network Programs. This paper presents experimental results that demonstrate the feasibility of a concept based on an optical wavelength division multiplexing (WDM) technique that enables multiple microwave bands with different modulation formats and bandwidths to be combined and transmitted all in one unit, resulting in many benefits to space communication systems including reduced size, weight and complexity with corresponding savings in cost. Experimental results will be presented including the individual received RF signal power spectra for the L, C, X, Ku, Ka, and Q frequency bands, and measurements of the phase noise associated with each RF frequency. Also to be presented is a swept RF frequency power spectrum showing simultaneous multiple RF frequency bands transmission. The RF frequency bands in this experiment are among those most commonly used in NASA space environment communications.

  5. Multi-carrier transmission for hybrid radio frequency with optical wireless communications

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Chen, Genshe; Shen, Dan; Pham, Khanh; Blasch, Erik; Nguyen, Tien M.

    2015-05-01

    Radio frequency (RF) wireless communication is reaching its capacity to support large data rate transmissions due to hardware constraints (e.g., silicon processes), software strategies (e.g., information theory), and consumer desire for timely large file exchanges (e.g., big data and mobile cloud computing). A high transmission rate performance must keep pace with the generated huge volumes of data for real-time processing. Integrated RF and optical wireless communications (RF/OWC) could be the next generation transmission technology to satisfy both the increased data rate exchange and the communications constraints. However, with the promising benefits of RF/OWC, challenges remain to fully develop hybrid RF with wireless optical communications such as uniform waveform design for information transmission and detection. In this paper, an orthogonal frequency division multiplexing (OFDM) transmission scheme, which widely employed in RF communications, is developed for optical communications. The traditional high peak-to-average power ratio (PAPR) in OFDM is reduced to improve system performance. The proposed multi-carrier waveform is evaluated with a frequency-selective fading channel. The results demonstrate that bit error rate (BER) performance of our proposed optical OFDM transmission technique outperforms the traditional OWC on-off keying (OOK) transmission scheme.

  6. Short-term stability improvements of an optical frequency standard based on free Ca atoms

    NASA Astrophysics Data System (ADS)

    Sherman, Jeff; Oates, Chris

    2010-03-01

    Compared to optical frequency standards featuring trapped ions or atoms in optical lattices, the strength of a standard using freely expanding neutral calcium atoms is not ultimate accuracy but rather short-term stability and experimental simplicity. Recently, a fractional frequency instability of 4 x10-15 at 1 second was demonstrated for the Ca standard at 657 nm [1]. The short cycle time (˜2 ms) combined with only a moderate interrogation duty cycle (˜15 %) is thought to introduce excess, and potentially critically limiting technical noise due to the Dick effect---high-frequency noise on the laser oscillator is not averaged away but is instead down-sampled by aliasing. We will present results of two strategies employed to minimize this effect: the reduction of clock laser noise by filtering the master clock oscillator through a high-finesse optical cavity [2], and an optimization of the interrogation cycle to match our laser's noise spectrum.[4pt] [1] Oates et al., Optics Letters, 25(21), 1603--5 (2000)[0pt] [2] Nazarova et al., J. Opt. Soc. Am. B, 5(10), 1632--8 (2008)

  7. Observation of a different birefringence order at optical and THz frequencies in LBO crystal

    NASA Astrophysics Data System (ADS)

    Andreev, Yu. M.; Kokh, A. E.; Kokh, K. A.; Lanskii, G. V.; Litvinenko, K.; Mamrashev, A. A.; Molloy, J. F.; Murdin, B.; Naftaly, M.; Nikolaev, N. A.; Svetlichnyi, V. A.

    2017-04-01

    THz optical properties of lithium borate (LBO) crystals were measured using time-domain spectroscopy (TDS). The LBO crystal samples were of high optical quality and were cut and polished along the <100>, <010> and <001> axes. Two independent measurements were performed in order to confirm the reproducibility and consistency of results. The contradictions in the previously published data on the THz optical properties of LBO were clarified. It was shown that the birefringence order at THz frequencies is nz optical frequencies it is known to be nx frequencies up to 0.5 THz for a wave polarized parallel to the Z-axis. A set of new dispersion equations was designed for the entire transparency range.

  8. Direct Spectroscopy in Hollow Optical with Fiber-Based Optical Frequency Combs

    DTIC Science & Technology

    2015-07-09

    filled frequency reference in a 10 m length. Since optimal single-modedness is expected at longer lengths (~10-30 m), a gas such as ammonia , with weaker...Conference on(2010), pp. 16-17. 41. A. M. Cubillas, J. Hald, and J. C. Petersen, "High resolution spectroscopy of ammonia in a hollow-core fiber," Opt

  9. Scanning micro-resonator direct-comb absolute spectroscopy

    NASA Astrophysics Data System (ADS)

    Gambetta, Alessio; Cassinerio, Marco; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-10-01

    Direct optical Frequency Comb Spectroscopy (DFCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DFCS approach based on a scanning Fabry-Pérot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from UV to THz. We present an application to high-precision spectroscopy of acetylene at 1.54 μm, demonstrating performances comparable or even better than current state-of-the-art DFCS systems in terms of sensitivity, optical bandwidth and frequency-resolution.

  10. Scanning micro-resonator direct-comb absolute spectroscopy

    PubMed Central

    Gambetta, Alessio; Cassinerio, Marco; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-01-01

    Direct optical Frequency Comb Spectroscopy (DFCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DFCS approach based on a scanning Fabry-Pérot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from UV to THz. We present an application to high-precision spectroscopy of acetylene at 1.54 μm, demonstrating performances comparable or even better than current state-of-the-art DFCS systems in terms of sensitivity, optical bandwidth and frequency-resolution. PMID:27752132

  11. Feasibility of spatial frequency domain imaging (SFDI) for optically characterizing a preclinical oncology model

    PubMed Central

    Tabassum, Syeda; Zhao, Yanyu; Istfan, Raeef; Wu, Junjie; Waxman, David J.; Roblyer, Darren

    2016-01-01

    Determination of chemotherapy efficacy early during treatment would provide more opportunities for physicians to alter and adapt treatment plans. Diffuse optical technologies may be ideally suited to track early biological events following chemotherapy administration due to low cost and high information content. We evaluated the use of spatial frequency domain imaging (SFDI) to characterize a small animal tumor model in order to move towards the goal of endogenous optical monitoring of cancer therapy in a controlled preclinical setting. The effects of key measurement parameters including the choice of imaging spatial frequency and the repeatability of measurements were evaluated. The precision of SFDI optical property extractions over repeat mouse measurements was determined to be within 3.52% for move and replace experiments. Baseline optical properties and chromophore values as well as intratumor heterogeneity were evaluated over 25 tumors. Additionally, tumor growth and chemotherapy response were monitored over a 45 day longitudinal study in a small number of mice to demonstrate the ability of SFDI to track treatment effects. Optical scattering and oxygen saturation increased as much as 70% and 25% respectively in treated tumors, suggesting SFDI may be useful for preclinical tracking of cancer therapies. PMID:27867722

  12. Hollow-core photonic-crystal-fiber-based optical frequency references

    NASA Astrophysics Data System (ADS)

    Holá, Miroslava; Hrabina, Jan; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

    2016-12-01

    This research deals with preparation of an optical frequency references based on hollow-core photonic crystal fibers (HC-PCF). This fiber-based type of absorption cells represents a effiecient way how to replace classic bulky and fragile glass made tubes references with low-weight and low-volume optical fibers. This approach allows not only to increase possible interaction length between incident light and absorption media but it also carries a possibility of manufacturing of easy-operable reference which is set up just by plugging-in of optical connectors into the optical setup. We present the results of preparation, manufacturing and filling of a set of fiber-based cells intended for lasers frequency stabilization. The work deals with setting and optimalization of HC-PCF splicing processes, minimalization of optical losses between HC-PCF and SMF fiber transitions and finishing of HC-PCF spliced ends with special care for optimal closing of hollow-core structure needed for avoiding of absorption media leakage.

  13. A compact laser head with high-frequency stability for Rb atomic clocks and optical instrumentation

    SciTech Connect

    Affolderbach, Christoph; Mileti, Gaetano

    2005-07-15

    We present a compact and frequency-stabilized laser head based on an extended-cavity diode laser. The laser head occupies a volume of 200 cm{sup 3} and includes frequency stabilization to Doppler-free saturated absorption resonances on the hyperfine components of the {sup 87}Rb D{sub 2} lines at 780 nm, obtained from a simple and compact spectroscopic setup using a 2 cm{sup 3} vapor cell. The measured frequency stability is {<=}2x10{sup -12} over integration times from 1 s to 1 day and shows the potential to reach 2x10{sup -13} over 10{sup 2}-10{sup 5} s. Compact laser sources with these performances are of great interest for applications in gas-cell atomic frequency standards, atomic magnetometers, interferometers and other instruments requiring stable and narrow-band optical sources.

  14. Magic radio-frequency dressing of nuclear spins in high-accuracy optical clocks.

    PubMed

    Zanon-Willette, Thomas; de Clercq, Emeric; Arimondo, Ennio

    2012-11-30

    A Zeeman-insensitive optical clock atomic transition is engineered when nuclear spins are dressed by a nonresonant radio-frequency field. For fermionic species as (87)Sr, (171)Yb, and (199)Hg, particular ratios between the radio-frequency driving amplitude and frequency lead to "magic" magnetic values where a net cancelation of the Zeeman clock shift and a complete reduction of first-order magnetic variations are produced within a relative uncertainty below the 10(-18) level. An Autler-Townes continued fraction describing a semiclassical radio-frequency dressed spin is numerically computed and compared to an analytical quantum description including higher-order magnetic field corrections to the dressed energies.

  15. Coherent optical time domain reflectometry by logarithmic detection and timed random frequency hopping

    NASA Astrophysics Data System (ADS)

    Lu, Lidong; Sun, Xiaoyan; Bu, Xiande; Li, Binglin

    2017-02-01

    A scheme using timed random frequency hopping and signal logarithmic mean method is proposed and experimentally demonstrated in a coherent optical time domain reflectometry (OTDR) system to reduce the fading noise of the OTDR trace and simplify the signal processing procedure. The timed random frequency hopping is realized by randomly changing the driving current of the laser at certain time points. By this method, the fading noise of OTDR trace can be reduced to be 1/5 of that without using it. Also, a radio frequency power detector (RFPD), whose output voltage has linear relationship with the input logarithmic RF power, is used to extract the power of the RF signals from the balanced photodetector. Then, a data acquisition card directly captures and adds the digital voltage signals from the RFPD to reduce the fading noise and improve the measurement dynamic range. Compared with synchronous and asynchronous frequency hopping scheme, the proposed method is of high efficiency.

  16. Prospect of optical frequency standard based on a {sup 43}Ca{sup +} ion

    SciTech Connect

    Kajita, Masatoshi; Li Ying; Matsubara, Kensuke; Hayasaka, Kazuhiro; Hosokawa, Mizuhiko

    2005-10-15

    An optical frequency standard based on the S-D transition of trapped {sup 43}Ca{sup +} is possible by using just laser diodes for cooling and probing. We discuss two open problems related to the feasibility of this frequency standard, the attainable frequency uncertainty and the method of initial-state preparation. The uncertainty of the clock transition frequency can be so small as 1x10{sup -15}. Using a laser system consisting of three lasers at different detunings and polarizations, the ion can be cooled down to the Lamb-Dicke regime and then prepared in the m=0 state within a period much shorter than the cooling period without being heated. The details of our numerical simulation are described.

  17. Some aspects of optical feedback with cadmium sulfide and related photoconductors. [for extended frequency response

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.

    1974-01-01

    A primary limitation of many solid state photoconductors used in electro-optical systems is their slow response in converting varying light intensities into electrical signals. An optical feedback technique is presented which can extend the frequency response of systems that use these detectors by orders of magnitude without adversely affecting overall signal-to-noise ratio performance. The technique is analyzed to predict the improvement possible and a system is implemented using cadmium sulfide to demonstrate the effectiveness of the technique and the validity of the analysis.

  18. Radio frequency spectral characterization and model parameters extraction of high Q optical resonators

    PubMed Central

    Abdallah, Zeina; Boucher, Yann G.; Fernandez, Arnaud; Balac, Stéphane; Llopis, Olivier

    2016-01-01

    A microwave domain characterization approach is proposed to determine the properties of high quality factor optical resonators. This approach features a very high precision in frequency and aims to acquire a full knowledge of the complex transfer function (amplitude and phase) characterizing an optical resonator using a microwave vector network analyzer. It is able to discriminate between the different coupling regimes, from the under-coupling to the selective amplification, and it is used together with a model from which the main resonator parameters are extracted, i.e. coupling factor, intrinsic losses, phase slope, intrinsic and external quality factor. PMID:27251460

  19. Experimental Realization of Multipartite Entanglement of 60 Modes of a Quantum Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier

    2014-03-01

    We report the experimental realization and characterization of one 60-mode copy and of two 30-mode copies of a dual-rail quantum-wire cluster state in the quantum optical frequency comb of a bimodally pumped optical parametric oscillator. This is the largest entangled system ever created whose subsystems are all available simultaneously. The entanglement proceeds from the coherent concatenation of a multitude of Einstein, Podolsky, and Rosen pairs by a single beam splitter, a procedure which is also a building block for the realization of hypercubic-lattice cluster states for universal quantum computing.

  20. Convergence test for inversion of frequency-resolved optical gating spectrograms

    SciTech Connect

    Kane, Daniel J.; Omenetto, Fiorenzo G.; Taylor, Antoinette J.

    2000-08-15

    We describe a new and simple method to aid in the analysis of retrieved pulses from inverted frequency-resolved optical gating (FROG) traces. The analysis can separate noise from distortion and shows that distortion is more deleterious to the retrieved pulse than is pure noise. The analysis relies on the fact that FROG traces can be constructed from a single outer product of two vectors, whereas distortion and noise require the sum of a series of outer products. (c) 2000 Optical Society of America.