Sample records for atomic frequency comb

  1. Difference-frequency combs in cold atom physics

    CERN Document Server

    Kliese, Russell; Puppe, Thomas; Rohde, Felix; Sell, Alexander; Zach, Armin; Leisching, Patrick; Kaenders, Wilhelm; Keegan, Niamh C; Bounds, Alistair D; Bridge, Elizabeth M; Leonard, Jack; Adams, Charles S; Cornish, Simon L; Jones, Matthew P A


    Optical frequency combs provide the clockwork to relate optical frequencies to radio frequencies. Hence, combs allow to measure optical frequencies with respect to a radio frequency where the accuracy is limited only by the reference signal. In order to provide a stable link between the radio and optical frequencies, the two parameters of the frequency comb must be fixed: the carrier envelope offset frequency $f_{\\rm ceo}$ and the pulse repetition-rate $f_{\\rm rep}$. We have developed the first optical frequency comb based on difference frequency generation (DFG) that eliminates $f_{\\rm ceo}$ by design - specifically tailored for applications in cold atom physics. An $f_{\\rm ceo}$-free spectrum at 1550 nm is generated from a super continuum spanning more than an optical octave. Established amplification and frequency conversion techniques based on reliable telecom fiber technology allow generation of multiple wavelength outputs. In this paper we discuss the frequency comb design, characterization, and optical...

  2. Optical Frequency Comb Spectroscopy of Rare Earth Atoms (United States)

    Swiatlowski, Jerlyn; Palm, Christopher; Joshi, Trinity; Montcrieffe, Caitlin; Jackson Kimball, Derek


    We discuss progress in our experimental program to employ optical-frequency-comb-based spectroscopy to understand the complex spectra of rare-earth atoms. We plan to carry out systematic measurements of atomic transitions in rare-earth atoms to elucidate the energy level structure and term assignment and determine presently unknown atomic state parameters. This spectroscopic information is important in view of the increasing interest in rare-earth atoms for atomic frequency standards, in astrophysical investigations of chemically peculiar stars, and in tests of fundamental physics (tests of parity and time-reversal invariance, searches for time variation of fundamental constants, etc.). We are presently studying the use of hollow cathode lamps as atomic sources for two-photon frequency comb spectroscopy. Supported by the National Science Foundation under grant PHY-0958749.

  3. Modeling Frequency Comb Sources

    Directory of Open Access Journals (Sweden)

    Li Feng


    Full Text Available Frequency comb sources have revolutionized metrology and spectroscopy and found applications in many fields. Stable, low-cost, high-quality frequency comb sources are important to these applications. Modeling of the frequency comb sources will help the understanding of the operation mechanism and optimization of the design of such sources. In this paper,we review the theoretical models used and recent progress of the modeling of frequency comb sources.

  4. On Frequency Combs in Monolithic Resonators

    Directory of Open Access Journals (Sweden)

    Savchenkov A. A.


    Full Text Available Optical frequency combs have become indispensable in astronomical measurements, biological fingerprinting, optical metrology, and radio frequency photonic signal generation. Recently demonstrated microring resonator-based Kerr frequency combs point the way towards chip scale optical frequency comb generator retaining major properties of the lab scale devices. This technique is promising for integrated miniature radiofrequency and microwave sources, atomic clocks, optical references and femtosecond pulse generators. Here we present Kerr frequency comb development in a historical perspective emphasizing its similarities and differences with other physical phenomena. We elucidate fundamental principles and describe practical implementations of Kerr comb oscillators, highlighting associated solved and unsolved problems.

  5. Spin and motion entanglement of neutral atoms with optical frequency combs (United States)

    Quraishi, Qudsia; Malinovsky, Vladimir; Alexander, Jason; Prieto, Violeta; Rowlett, Chris; Lee, Patricia


    Optical frequency combs, emitted by ultrafast modelocked pulsed lasers, are excellent tools to perform quantum coherent control. The spectral purity, large bandwidth and high pulse powers makes these sources attractive for precision control of multi-level atoms. We envisage using pairs of OFC modes to drive stimulated Raman transitions between the two hyperfine clock states of ^87Rb confined on an atom chip. The Raman transitions will be driven using an all optical, four photon technique, whereby the first photon pair drives off-resonantly to the intermediate state ^2S1/2 |F=2, mf=0> and then a second photon pair resonantly drives to ^2S1/2 |F=2, mf=+1>. Co-propagating Raman fields impart only a spin flip whereas non-copropagating fields transfer two photon recoil momentum to the atoms, thus entangling the internal spin with the external motion of the atoms. For site dependent control, we plan to use the high AC Stark shifts produced by the high intensity pulses.

  6. Frequency comb swept lasers. (United States)

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G


    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  7. Widely tunable extreme ultraviolet frequency comb generation

    NARCIS (Netherlands)

    Pinkert, T. J.; Kandula, D. Z.; Gohle, Ch; Morgenweg, J.; Barmes, I.; Ubachs, W.; Eikema, K. S E


    Frequency comb lasers [1] have led to great advances in fields such as precision spectroscopy, optical atomic clocks, and attosecond science. We transfer the remarkable precision of frequency combs to extreme ultraviolet (XUV) wavelengths by parametric amplification and high-harmonic generation

  8. Spectrally resolved frequency comb interferometry (United States)

    van den Berg, S.


    In this contribution a novel method for interferometric distance measurement is presented, that is based on unraveling the spectrum of a femtosecond frequency comb. The light of a frequency comb is sent into a Michelson interferometer. The output of the interferometer is analyzed by a high-resolution spectrometer, resolving the individual comb modes. The path-length difference between the two arms is determined on the level of tens of nm, by utilizing the wealth of information present in the unraveled spectrum, showing homodyne interference for each individual frequency comb mode. The measurement method allows for high-accuracy measurements in combination with a large range of non-ambiguity.

  9. Microresonator Frequency Comb Optical Clock (United States)


    and T. J. Kippenberg , “Optical frequency comb generation from a monolithic microresonator,” Nature 450, 1214–1217 (2007). 2. T. J. Kippenberg , R...Mon. Not. R. Astron. Soc. 380, 839–847 (2007). 8. P. Del’Haye, O. Arcizet, A. Schliesser, R. Holzwarth, and T. J. Kippenberg , “Full stabilization of a...Lett. 112, 043905 (2014). 18. T. Herr, V. Brasch, J. D. Jost, C. Y. Wang, N. M. Kondratiev, M. L. Gorodetsky, and T. J. Kippenberg , “Temporal solitons

  10. A stable frequency comb directly referenced to rubidium electromagnetically induced transparency and two-photon transitions

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Dong; Wu, Jiutao; Zhang, Shuangyou; Ren, Quansheng; Zhang, Zhigang; Zhao, Jianye, E-mail: [Department of Electronics, Peking University, Beijing, 100871 (China)


    We demonstrate an approach to create a stable erbium-fiber-based frequency comb at communication band by directly locking the combs to two rubidium atomic transitions resonances (electromagnetically induced transparency absorption and two-photon absorption), respectively. This approach directly transfers the precision and stability of the atomic transitions to the comb. With its distinguishing feature of compactness by removing the conventional octave-spanning spectrum and f-to-2f beating facilities and the ability to directly control the comb's frequency at the atomic transition frequency, this stable optical comb can be widely used in optical communication, frequency standard, and optical spectroscopy and microscopy.

  11. Frequency Comb Spectroscopy - From IR to XUV (United States)


    parts-per-billion (ppb); in the presence of 2.8% of water the detection limit is 130 ppb. Spectra of acetylene, methane and nitrous oxide at...development of XUV frequency comb in the Ye group has demonstrated that spectral resolution at the MHz-level can be obtained . In 2013, we demonstrated that...XUV frequency combs for a direct heterodyne beat measurement. We identified various noise contributions to the obtainable comb linewidth in the XUV

  12. Active laser ranging with frequency transfer using frequency comb

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hongyuan; Wei, Haoyun; Yang, Honglei; Li, Yan, E-mail: [State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China)


    A comb-based active laser ranging scheme is proposed for enhanced distance resolution and a common time standard for the entire system. Three frequency combs with different repetition rates are used as light sources at the two ends where the distance is measured. Pulse positions are determined through asynchronous optical sampling and type II second harmonic generation. Results show that the system achieves a maximum residual of 379.6 nm and a standard deviation of 92.9 nm with 2000 averages over 23.6 m. Moreover, as for the frequency transfer, an atom clock and an adjustable signal generator, synchronized to the atom clock, are used as time standards for the two ends to appraise the frequency deviation introduced by the proposed system. The system achieves a residual fractional deviation of 1.3 × 10{sup −16} for 1 s, allowing precise frequency transfer between the two clocks at the two ends.

  13. Nanomaterial-enhanced frequency combs (Conference Presentation) (United States)

    Armani, Andrea M.; Castro-Beltran, Rigoberto; Diep, Vinh; Gungor, Eda; Shen, Xiaoqin; Soltani, Soheil


    Optical cavities are able to confine and store specific wavelengths of light, acting as optical amplifiers at those wavelengths. Because the amount of amplification is directly related to the cavity quality factor (Q) (or the cavity finesse), frequency comb research has focused on high-Q and ultra-high Q microcavities fabricated from a range of materials using a variety of methods. In all cases, the comb generation relies on a nonlinear process known as parametric frequency conversion which is based on a third order nonlinear interaction and which results in four wave mixing (FWM). Clearly, this approach requires significant optical power, which was the original motivation for using ultra-high-Q cavities. In fact, the majority of research to date has focused on pursuing increasingly high Q factors. However, another strategy is to improve the nonlinearity of the resonator through intelligently designing materials for this application. In the present work, a suite of nanomaterials (organic and inorganic) have been intelligently designed with the explicit purpose to enhance the nonlinearity of the resonator and reducing the threshold for frequency comb generation in the near-IR. The nanomaterials do not change the structure of the comb and only act to reduce the comb threshold. The silica microcavity is used as a testbed for initial demonstration and verification purposes. However, the fundamental strategy is translatable to other whispering gallery mode cavities.

  14. Octave spanning tunable frequency comb from a microresonator. (United States)

    Del'Haye, P; Herr, T; Gavartin, E; Gorodetsky, M L; Holzwarth, R; Kippenberg, T J


    We report the generation of an octave-spanning optical frequency comb in a continuous wave laser pumped microresonator. The generated comb spectrum covers the wavelength range from 990 to 2170 nm without relying on additional external broadening. Continuous tunability of the generated frequency comb over more than an entire free spectral range is demonstrated. Moreover, the linewidth of individual optical comb components and its relation to the pump laser phase noise is studied. The ability to derive octave-spanning spectra from microresonator comb generators represents a key step towards f-2f self-referencing of microresonator-based optical frequency combs.

  15. Precision Spectroscopy of Hydrogen and Femtosecond Laser Frequency Combs (United States)

    Udem, Thomas


    A femtosecond frequency comb is a simple and compact tool that allows the phase coherent connection of the radio frequency domain (below 100 GHz) with the optical domain (above 200 THz). It greatly simplified high precision optical frequency measurements and provides the long awaited clockwork mechanism for an all-optical atomic clock. We have used such a frequency comb to measure the absolute frequency of the 1S-2S two-photon transition in atomic hydrogen, i.e. comparing it with the Cs ground state hyperfine splitting. By comparing data taken in 2003 with earlier measurements in 1999 we can set an upper limit on the variation of the 1S-2S transition frequency of (-29 ±57) Hz within 44 months. To derive limits on the drift rates of fundamental constant such as the fine structure constant, we combine these measurements with other optical frequency measurements in Hg^+ and in Yb^+ performed at NIST, Boulder/USA and at PTB, Braunschweig/Germany respectively. This combined method gives precise and separate restrictions for the fractional time variation of the fine structure constant and the Cs nuclear magnetic moment measured in Bohr magnetons. The latter is a measure of the drift rate of the strong interaction. We also report on efforts to convert the frequency comb technology to much shorter wavelength. Based on intra cavity high harmonic generation an XUV (up to 60 nm) frequency comb is generated with a repetition rate of more than 100 MHz useful for high resolution laser spectroscopy in this region.

  16. Analysis on characteristic and application of THz frequency comb and THz sub-comb

    Energy Technology Data Exchange (ETDEWEB)

    Liu Pengxiang; Xu Degang; Yao Jianquan, E-mail: [Institute of Laser and Optoelectronics, College of Precision Instruments and Opto-electronic Engineering, Tianjin University, Tianjin, 300072 (China); Key Laboratory of Opto-electronic Information Science and Technology, Ministry of Education, Tianjin, 300072 (China)


    In this paper, we proposed a method for THz sub-comb generation based on spectral interference. The result of our calculation indicated that the THz pulse train, generated by surface-emitted optical rectification of femtosecond (fs) laser pulse in periodically poled lithium niobate (PPLN), has a comb-like spectrum. The characteristic of this THz sub-comb was analyzed both in frequency and time domain. Compared with the THz frequency comb emitted by a photoconductive antenna (PCA), THz sub-comb has a lower spectral resolution and wider free spectral range. Thus it could be an ideal source for wavelength division multiplexing (WDM) in THz wireless communication system.

  17. Phononic frequency comb via three-mode parametric resonance (United States)

    Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin


    This paper is motivated by the recent demonstration of a phononic frequency comb. While previous experiments have shown the existence of a three-wave mixing pathway in a system of two-coupled phonon modes, this work demonstrates a similar pathway in a system of three-coupled phonon modes. This paper also presents a number of interesting experimental facts concomitant to the three-mode parametric resonance based frequency comb observed in a specific micromechanical device. The experimental validation of frequency combs via three-mode parametric resonance along with the previous demonstration of two-mode frequency combs points to the ultimate possibility of multimode frequency combs.

  18. Frequency combs for cavity cascades: OPO combs and graphene-coupled cavities (United States)

    Lee, Kevin F.; Kowzan, Grzegorz; Lee, C.-C.; Mohr, C.; Jiang, Jie; Schunemann, Peter G.; Schibli, T. R.; Maslowski, Piotr; Fermann, M. E.


    Frequency combs can be used directly, for example as a highly precise spectroscopic light source. They can also be used indirectly, as a bridge between devices whose high precision requirements would normally make them incompatible. Here, we demonstrate two ways that a frequency comb enables new technologies by matching optical cavities. One cavity is the laser oscillator. A second cavity is a low-threshold doubly-resonant optical parametric oscillator (OPO). Extending optical referencing to the doubly-resonant OPO turns the otherwise unstable device into an extremely precise midinfrared frequency comb. Another cavity is an optical enhancement cavity for amplifying spectral absorption in a gas. With the high speed of a graphene-modulated frequency comb, we can couple a frequency comb directly into a high-finesse cavity for trace gas detection.

  19. Multispectral Kerr frequency comb initiated by Faraday ripples

    CERN Document Server

    Huang, Shu-Wei


    In a uniform microresonator, the generation of a broadband Kerr frequency comb is triggered by Turing patterns. Here, we study a distinctly different route to initiate the Kerr frequency comb by Faraday ripples. Momentum conservation is ensured by azimuthal modulation of the cavity dispersion. With a good agreement with the theoretical analysis, we demonstrate a multispectral Kerr frequency comb covering telecommunication O, C, L, and 2 {\\mu}m bands. Comb coherence and absence of a subcomb offset are confirmed by cw heterodyne beat note and amplitude noise spectra measurements. The device can be used for achieving broadband optical frequency synthesizer and high-capacity coherent telecommunication.

  20. Arbitrary optical frequency synthesis traced to an optical frequency comb (United States)

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


    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.

  1. Frequency comb laser spectroscopy in the vacuum-ultraviolet region

    NARCIS (Netherlands)

    Zinkstok, R.T.; Witte, S.; Ubachs, W.M.G.; Hogervorst, W.; Eikema, K.S.E.


    We demonstrate that the output of a frequency comb laser can be amplified and upconverted to the vacuum ultraviolet (vuv) in a gaseous medium while its phase coherence is maintained to a high degree (< 1 30 of a vuv cycle). The produced vuv pulses are well suited to perform frequency comb

  2. Optical-frequency-comb based ultrasound sensor (United States)

    Minamikawa, Takeo; Ogura, Takashi; Masuoka, Takashi; Hase, Eiji; Nakajima, Yoshiaki; Yamaoka, Yoshihisa; Minoshima, Kaoru; Yasui, Takeshi


    Photo-acoustic imaging is a promising modality for deep tissue imaging with high spatial resolution in the field of biology and medicine. High penetration depth and spatial resolution of the photo-acoustic imaging is achieved by means of the advantages of optical and ultrasound imaging, i.e. tightly focused beam confines ultrasound-generated region within micrometer scale and the ultrasound can propagate through tissues without significant energy loss. To enhance the detection sensitivity and penetration depth of the photo-acoustic imaging, highly sensitive ultrasound detector is greatly desired. In this study, we proposed a novel ultrasound detector employing optical frequency comb (OFC) cavity. Ultrasound generated by the excitation of tightly focused laser beam onto a sample was sensed with a part of an OFC cavity, being encoded into OFC. The spectrally encoded OFC was converted to radio-frequency by the frequency link nature of OFC. The ultrasound-encoded radio-frequency can therefore be directly measured with a high-speed photodetector. We constructed an OFC cavity for ultrasound sensing with a ring-cavity erbium-doped fiber laser. We provided a proof-of-principle demonstration of the detection of ultrasound that was generated by a transducer operating at 10 MHz. Our proposed approach will serve as a unique and powerful tool for detecting ultrasounds for photo-acoustic imaging in the future.

  3. Dynamics of microresonator frequency comb generation: models and stability

    Directory of Open Access Journals (Sweden)

    Hansson Tobias


    Full Text Available Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  4. High spectral purity Kerr frequency comb radio frequency photonic oscillator. (United States)

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L


    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  5. Broadband degenerate OPO for mid-infrared frequency comb generation

    National Research Council Canada - National Science Library

    Leindecker, Nick; Marandi, Alireza; Byer, Robert L; Vodopyanov, Konstantin L


    .... Our source is based on a degenerate optical parametric oscillator (OPO) which rigorously both down-converts and augments the spectrum of a pump frequency comb provided by a commercial mode-locked near-IR laser...

  6. Asymmetric micro-Doppler frequency comb generation via magnetoelectric coupling (United States)

    Filonov, Dmitry; Steinberg, Ben Z.; Ginzburg, Pavel


    Electromagnetic scattering from moving bodies, being an inherently time-dependent phenomenon, gives rise to a generation of new frequencies, which can be used to characterize the motion. Whereas an ordinary motion along a linear path produces a constant Doppler shift, an accelerated scatterer can generate a micro-Doppler frequency comb. The spectra produced by rotating objects were studied and observed in a bistatic lock-in detection scheme. The internal geometry of a scatterer was shown to determine the spectrum, and the degree of structural asymmetry was suggested to be identified via signatures in the micro-Doppler comb. In particular, hybrid magnetoelectric particles, showing an ultimate degree of asymmetry in forward and backward scattering directions, were investigated. It was shown that the comb in the backward direction has signatures at the fundamental rotation frequency and its odd harmonics, whereas the comb of the forward scattered field has a prevailing peak at the doubled frequency and its multiples. Additional features of the comb were shown to be affected by the dimensions of the particle and by the strength of the magnetoelectric coupling. Experimental verification was performed with a printed circuit board antenna based on a wire and a split ring, while the structure was illuminated at a 2 GHz carrier frequency. Detailed analysis of micro-Doppler combs enables remote detection of asymmetric features of distant objects and could find use in a span of applications, including stellar radiometry and radio identification.

  7. High-Resolution Dual-Comb Spectroscopy with Ultra-Low Noise Frequency Combs (United States)

    Hänsel, Wolfgang; Giunta, Michele; Beha, Katja; Perry, Adam J.; Holzwarth, R.


    Dual-comb spectroscopy is a powerful tool for fast broad-band spectroscopy due to the parallel interrogation of thousands of spectral lines. Here we report on the spectroscopic analysis of acetylene vapor in a pressurized gas cell using two ultra-low noise frequency combs with a repetition rate around 250 MHz. Optical referencing to a high-finesse cavity yields a sub-Hertz stability of all individual comb lines (including the virtual comb lines between 0 Hz and the carrier) and permits one to pick a small difference of repetition rate for the two frequency combs on the order of 300 Hz, thus representing an optical spectrum of 100 THz (˜3300 \\wn) within half the free spectral range (125 MHz). The transmission signal is derived straight from a photodetector and recorded with a high-resolution spectrum analyzer or digitized with a computer-controlled AD converter. The figure to the right shows a schematic of the experimental setup which is all fiber-coupled with polarization-maintaining fiber except for the spectroscopic cell. The graph on the lower right reveals a portion of the recorded radio-frequency spectrum which has been scaled to the optical domain. The location of the measured absorption coincides well with data taken from the HITRAN data base. Due to the intrinsic linewidth of all contributing comb lines, each sampling point in the transmission graph corresponds to the probing at an optical frequency with sub-Hertz resolution. This resolution is maintained in coherent wavelength conversion processes such as difference-frequency generation (DFG), sum-frequency generation (SFG) or non-linear broadening (self-phase modulation), and is therefore easily transferred to a wide spectral range from the mid infrared up to the visible spectrum.

  8. Frequency combs enable rapid and high-resolution multidimensional coherent spectroscopy (United States)

    Lomsadze, Bachana; Cundiff, Steven T.


    Dual laser frequency combs can rapidly measure high-resolution linear absorption spectra. However, one-dimensional linear techniques cannot distinguish the sources of resonances in a mixture of different analytes, nor can they separate inhomogeneous and homogeneous broadening. Here, we overcame these limitations by acquiring high-resolution multidimensional nonlinear coherent spectra with frequency combs. We experimentally differentiated and assigned the Doppler-broadened features of two naturally occurring isotopes of rubidium atoms (87Rb and 85Rb) according to the placement of their hyperfine energy states in a two-dimensional spectrum.

  9. A quantitative mode-resolved frequency comb spectrometer. (United States)

    Hébert, Nicolas Bourbeau; Scholten, Sarah K; White, Richard T; Genest, Jérôme; Luiten, Andre N; Anstie, James D


    We have developed a frequency-comb spectrometer that records 35-nm (4 THz) spectra with 2-pm (250 MHz) spectral sampling and an absolute frequency accuracy of 2 kHz. We achieve a signal-to-noise ratio of ~400 in a measurement time of 8.2 s. The spectrometer is based on a commercial frequency comb decimated by a variable-length, low-finesse Fabry Pérot filter cavity to fully resolve the comb modes as imaged by a virtually imaged phased array (VIPA), diffraction grating and near-IR camera. By tuning the cavity length, spectra derived from all unique decimated combs are acquired and then interleaved to achieve frequency sampling at the comb repetition rate of 250 MHz. We have validated the performance of the spectrometer by comparison with a previous high-precision absorption measurement of H13C14N near 1543 nm. We find excellent agreement, with deviations from the expected line centers and widths of, at most, 1 pm (125 MHz) and 3 pm (360 MHz), respectively.

  10. Femtosecond Optical Frequency Comb Technology Principle, Operation and Application

    CERN Document Server

    Ye, Jun


    Over the last few years, there has been a remarkable convergence among the fields of ultrafast optics, optical frequency metrology, and precision laser spectroscopy. This convergence has enabled unprecedented advances in control of the electric field of the pulses produced by femtosecond mode-locked lasers. The resulting spectrum consists of a comb of sharp spectral lines with well-defined frequencies. These new techniques and capabilities are generally known as "femtosecond comb technology." They have had dramatic impact on the diverse fields of precision measurement and extreme nonlinear optical physics. This book provides an introductory description of mode-locked lasers, the connection between time and frequency descriptions of their output and the physical origins of the electric field dynamics, together with an overview of applications of femtosecond comb technology. Individual chapters go into more detail on mode-locked laser development, spectral broadening in microstructure fiber, optical parametric ...

  11. Broadband degenerate OPO for mid-infrared frequency comb generation. (United States)

    Leindecker, Nick; Marandi, Alireza; Byer, Robert L; Vodopyanov, Konstantin L


    We present a new technique suitable for generating broadband phase- and frequency-locked frequency combs in the mid-infrared. Our source is based on a degenerate optical parametric oscillator (OPO) which rigorously both down-converts and augments the spectrum of a pump frequency comb provided by a commercial mode-locked near-IR laser. Low intracavity dispersion, combined with extensive cross-mixing of comb components, results in extremely broad instantaneous mid-IR bandwidths. We achieve an output power of 60 mW and 20 dB bandwidth extending from 2500 to 3800 nm. Among other applications, such a source is well-suited for coherent Fourier-transform spectroscopy in the absorption-rich mid-IR 'molecular fingerprint' region.

  12. Monolithic device for modelocking and stabilization of frequency combs. (United States)

    Lee, C-C; Hayashi, Y; Silverman, K L; Feldman, A; Harvey, T; Mirin, R P; Schibli, T R


    We demonstrate a device that integrates a III-V semiconductor saturable absorber mirror with a graphene electro-optic modulator, which provides a monolithic solution to modelocking and noise suppression in a frequency comb. The device offers a pure loss modulation bandwidth exceeding 5 MHz and only requires a low voltage driver. This hybrid device provides not only compactness and simplicity in laser cavity design, but also small insertion loss, compared to the previous metallic-mirror-based modulators. We believe this work paves the way to portable and fieldable phase-coherent frequency combs.

  13. Intensity autocorrelation measurements of frequency combs in the terahertz range (United States)

    Benea-Chelmus, Ileana-Cristina; Rösch, Markus; Scalari, Giacomo; Beck, Mattias; Faist, Jérôme


    We report on direct measurements of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. Our implementation is based on fast electro-optic sampling, with a detection spectral bandwidth matching the emission bandwidth of the comb laser, around 2.5 THz. We find the output of these frequency combs to be continuous even in the locked regime, but accompanied by a strong intensity modulation. Moreover, with our record temporal resolution of only few hundreds of femtoseconds, we can resolve correlated intensity modulation occurring on time scales as short as the gain recovery time, about 4 ps. By direct comparison with pulsed terahertz light originating from a photoconductive emitter, we demonstrate the peculiar emission pattern of these lasers. The measurement technique is self-referenced and ultrafast, and requires no reconstruction. It will be of significant importance in future measurements of ultrashort pulses from quantum cascade lasers.

  14. The Physics of Ultrabroadband Frequency Comb Generation and Optimized Combs for Measurements in Fundamental Physics (United States)


    order phase-matched cascaded frequency gene, high harmonic generation, fine structure constant measurements, -envelope phase stabilization, ultra fast...partially) coherent seed. Figure 1: Experimental Setup used Our experiments showed control of both the spectral and noise properties of optical fibre...specifically linked to the studies funded by the grant are: D. M. Nguyen, T. Godin, S. Toenger, Y. Combes, B. Wetzel, T. Sylvestre, et al

  15. Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy. (United States)

    Yi, X; Vahala, K; Li, J; Diddams, S; Ycas, G; Plavchan, P; Leifer, S; Sandhu, J; Vasisht, G; Chen, P; Gao, P; Gagne, J; Furlan, E; Bottom, M; Martin, E C; Fitzgerald, M P; Doppmann, G; Beichman, C


    An important technique for discovering and characterizing planets beyond our solar system relies upon measurement of weak Doppler shifts in the spectra of host stars induced by the influence of orbiting planets. A recent advance has been the introduction of optical frequency combs as frequency references. Frequency combs produce a series of equally spaced reference frequencies and they offer extreme accuracy and spectral grasp that can potentially revolutionize exoplanet detection. Here we demonstrate a laser frequency comb using an alternate comb generation method based on electro-optical modulation, with the comb centre wavelength stabilized to a molecular or atomic reference. In contrast to mode-locked combs, the line spacing is readily resolvable using typical astronomical grating spectrographs. Built using commercial off-the-shelf components, the instrument is relatively simple and reliable. Proof of concept experiments operated at near-infrared wavelengths were carried out at the NASA Infrared Telescope Facility and the Keck-II telescope.

  16. Practical system for the generation of pulsed quantum frequency combs. (United States)

    Roztocki, Piotr; Kues, Michael; Reimer, Christian; Wetzel, Benjamin; Sciara, Stefania; Zhang, Yanbing; Cino, Alfonso; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto


    The on-chip generation of large and complex optical quantum states will enable low-cost and accessible advances for quantum technologies, such as secure communications and quantum computation. Integrated frequency combs are on-chip light sources with a broad spectrum of evenly-spaced frequency modes, commonly generated by four-wave mixing in optically-excited nonlinear micro-cavities, whose recent use for quantum state generation has provided a solution for scalable and multi-mode quantum light sources. Pulsed quantum frequency combs are of particular interest, since they allow the generation of single-frequency-mode photons, required for scaling state complexity towards, e.g., multi-photon states, and for quantum information applications. However, generation schemes for such pulsed combs have, to date, relied on micro-cavity excitation via lasers external to the sources, being neither versatile nor power-efficient, and impractical for scalable realizations of quantum technologies. Here, we introduce an actively-modulated, nested-cavity configuration that exploits the resonance pass-band characteristic of the micro-cavity to enable a mode-locked and energy-efficient excitation. We demonstrate that the scheme allows the generation of high-purity photons at large coincidence-to-accidental ratios (CAR). Furthermore, by increasing the repetition rate of the excitation field via harmonic mode-locking (i.e. driving the cavity modulation at harmonics of the fundamental repetition rate), we managed to increase the pair production rates (i.e. source efficiency), while maintaining a high CAR and photon purity. Our approach represents a significant step towards the realization of fully on-chip, stable, and versatile sources of pulsed quantum frequency combs, crucial for the development of accessible quantum technologies.

  17. One-way quantum computing in the optical frequency comb. (United States)

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


    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.

  18. Short-pulse properties of optical frequency comb generators. (United States)

    Kovacich, R P; Sterr, U; Telle, H R


    An optical frequency comb generator, based on a simple electro-optic modulator in an optical resonator, can produce high-repetition-rate picosecond pulses. Unlike conventional picosecond lasers, the properties of these pulses are greatly affected by detuning the optical cavity and by dispersion caused by the electro-optic crystal. Picosecond pulses were studied in a physical device by numerical simulation and intensity autocorrelation measurements. The pulse width and pulse-to-pulse spacing were greatly affected by detuning the input laser frequency and the resonance of the optical resonator, and the numerical simulations showed that dispersion causes temporal ripples that are antisymmetric between pulse pairs.

  19. Linear and nonlinear frequency- and time-domain spectroscopy with multiple frequency combs (United States)

    Bennett, Kochise; Rouxel, Jeremy R.; Mukamel, Shaul


    Two techniques that employ equally spaced trains of optical pulses to map an optical high frequency into a low frequency modulation of the signal that can be detected in real time are compared. The development of phase-stable optical frequency combs has opened up new avenues to metrology and spectroscopy. The ability to generate a series of frequency spikes with precisely controlled separation permits a fast, highly accurate sampling of the material response. Recently, pairs of frequency combs with slightly different repetition rates have been utilized to down-convert material susceptibilities from the optical to microwave regime where they can be recorded in real time. We show how this one-dimensional dual comb technique can be extended to multiple dimensions by using several combs. We demonstrate how nonlinear susceptibilities can be quickly acquired using this technique. In a second class of techniques, sequences of ultrafast mode locked laser pulses are used to recover pathways of interactions contributing to nonlinear susceptibilities by using a photo-acoustic modulation varying along the sequences. We show that these techniques can be viewed as a time-domain analog of the multiple frequency comb scheme.

  20. Symmetry Breaking of Frequency Comb in Varying Normal Dispersion Fiber Ring Cavity

    CERN Document Server

    Afzal, Muhammad Imran; Lee, Yong Tak


    We build on a previously reported frequency comb of mode spacing 0.136 nm in a fiber ring cavity of varying normal dispersion [1], to generate, for the first time, a frequency comb of mode spacing 0.144 nm centered at 978.544 nm to demonstrate the symmetry-breaking. By controlling the birefringence of the optical cavity through fiber stretching and polarization control, the spacing of the comb lines increases from 0.136 nm to 0.144 nm, and this small change in mode spacing generates very different spectral symmetry-breaking in the frequency comb relative to the frequency comb of mode spacing 0.136 nm. Interestingly, non-uniform depletion of primary modes is also observed. The experimental results are an important contribution in the continuing effort of understanding the dynamics of frequency combs involving large number of modes, nontrivial nonlinear waves and deterministic chaos.

  1. Very Flat Optical Frequency Comb Generation based on Polarization Modulator and Recirculation Frequency Shifter (United States)

    Li, Ruxing; Wu, Shibao; Ye, Shujian; Cui, Yaling


    We propose and experimentally demonstrate a novel scheme to generate a flat and stable optical frequency comb by using recirculation frequency shifter (RFS) loop and polarization-modulator based single-side-band modulator (PSSBM). An ultra-flat 5-carriers generated by a polarization modulator is set as the seed light source of the recirculating loop, and the recirculation times is greatly reduced compared with the regular scheme based on RFS. Through theoretical analysis and experiment simulations, it is shown that the optical frequency comb of high quality with 50 spectral lines and the flatness fluctuation of less than 1 dB can be achieved.

  2. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.


    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers...

  3. Frequency-comb-referenced multi-channel fiber laser for DWDM communication. (United States)

    Chun, Byung Jae; Hyun, Sangwon; Kim, Seungman; Kim, Seung-Woo; Kim, Young-Jin


    We propose an all-fiber-based multi-channel optical scheme that enables simultaneous generation of multiple continuous-wave laser wavelengths with stabilization to the frequency comb of a femtosecond laser. The intention is to produce highly stable, accurate wavelength channels with immunity to environmental disturbance so as to enhance the transmission capacity of dense wavelength division multiplexing (DWDM) communications. Generated wavelengths lie over a wide spectral range of 5 THz about 1550 nm, each yielding a narrow linewidth of less than 24 kHz with an absolute position uncertainty of ~2.24 × 10¹² (10 s averaging) traceable directly to the atomic Rb clock.

  4. Dynamics of dual-polarization VCSEL-based optical frequency combs under optical injection locking. (United States)

    Prior, E; de Dios, C; Criado, R; Ortsiefer, M; Meissner, P; Acedo, P


    The present experimental work studies the dynamics of dual-polarization optical frequency combs (OFCs) based on gain switching (GS) vertical-cavity surface-emitting laser (VCSEL) diodes under optical injection locking (OIL). This study presents two main results. First, we have obtained an overall comb formed by two orthogonally polarized sub-combs with comparable span and power. The overall comb shows enhanced optical span and flatness and high coherence between its modes. The second result is that we have been able to control the polarization state of the overall comb by tuning the polarization state of the injected light by locking the same single teeth of the comb. This produces an overall comb with single polarization that is parallel or orthogonal. These are novel findings that provide for the development of efficient and compact OFCs based on GS VCSEL sources with versatile polarization dynamics.

  5. Dual-etalon, cavity-ring-down, frequency comb spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Strecker, Kevin E.; Chandler, David W.


    The 'dual etalon frequency comb spectrometer' is a novel low cost spectometer with limited moving parts. A broad band light source (pulsed laser, LED, lamp ...) is split into two beam paths. One travels through an etalon and a sample gas, while the second arm is just an etalon cavity, and the two beams are recombined onto a single detector. If the free spectral ranges (FSR) of the two cavities are not identical, the intensity pattern at the detector with consist of a series of heterodyne frequencies. Each mode out of the sample arm etalon with have a unique frequency in RF (radio-frequency) range, where modern electronics can easily record the signals. By monitoring these RF beat frequencies we can then determine when an optical frequencies is absorbed. The resolution is set by the FSR of the cavity, typically 10 MHz, with a bandwidth up to 100s of cm{sup -1}. In this report, the new spectrometer is described in detail and demonstration experiments on Iodine absorption are carried out. Further we discuss powerful potential next generation steps to developing this into a point sensor for monitoring combustion by-products, environmental pollutants, and warfare agents.

  6. Quantum state generation via integrated frequency combs (Conference Presentation) (United States)

    Roztocki, Piotr; Kues, Michael; Reimer, Christian; Wetzel, Benjamin; Grazioso, Fabio; Little, Brent E.; Chu, Sai T.; Johnston, Tudor W.; Bromberg, Yaron; Caspani, Lucia; Moss, David J.; Morandotti, Roberto


    The on-chip generation of optical quantum states will enable accessible advances for quantum technologies. We demonstrate that integrated quantum frequency combs (based on high-Q microring resonators made from a CMOS-compatible, high refractive-index doped-glass platform) can enable the generation of pure heralded single photons, cross-polarized photon pairs, as well as bi- and multi-photon entangled qubit states over a broad frequency comb covering the S, C, L telecommunications band, with photon frequencies corresponding to standard telecommunication channels spaced by 200 GHz. Exploiting a self-locked, intra-cavity excitation configuration, a highly-stable source of multiplexed heralded single photons is demonstrated, operating continuously for several weeks with less than 5% fluctuations. The photon bandwidth of 110 MHz is compatible with quantum memories, and high photon purity was confirmed through single-photon auto-correlation measurements. In turn, by simultaneously exciting two orthogonal polarization mode resonances, we demonstrate the first realization of type-II spontaneous FWM (in analogy to type-II spontaneous parametric down-conversion), allowing the direct generation of orthogonally-polarized photon pairs on a chip. By using a double-pulse excitation, we demonstrate the generation of time-bin entangled photon pairs. We measure qubit entanglement with visibilities above 90%, enabling the implementation of quantum information processing protocols. Finally, the excitation field and the generated photons are intrinsically bandwidth-matched due to the resonant characteristics of the ring cavity, enabling the multiplication of Bell states and the generation of a four-photon time-bin entangled state. We confirm the generation of this four-photon entangled state through four-photon quantum interference.

  7. Optical fiber strain sensor using fiber resonator based on frequency comb Vernier spectroscopy

    DEFF Research Database (Denmark)

    Zhang, Liang; Lu, Ping; Chen, Li


    A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber...

  8. Microresonator-Based Optical Frequency Combs: A Time Domain Perspective (United States)


    modes in these multimode waveguides. Further data demonstrate such interactions play a major role in the generation of combs, especially for normal...offers promise to replace traditional mode -locked laser combs and to substantially shrink the size of comb sources to the chip-level for applications...spatial modes in the few- moded waveguides from which the microresonators are fabricated. Time domain measurements show for the first time that under

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

    Energy Technology Data Exchange (ETDEWEB)

    Galindo-Santos, J.; Velasco, A. V.; Corredera, P. [Instituto de Óptica IO-CSIC, C/Serrano 121, 28006 Madrid (Spain)


    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.

  10. Fully stabilized mid-infrared frequency comb for high-precision molecular spectroscopy. (United States)

    Vainio, Markku; Karhu, Juho


    A fully stabilized mid-infrared optical frequency comb spanning from 2.9 to 3.4 µm is described in this article. The comb is based on half-harmonic generation in a femtosecond optical parametric oscillator, which transfers the high phase coherence of a fully stabilized near-infrared Er-doped fiber laser comb to the mid-infrared region. The method is simple, as no phase-locked loops or reference lasers are needed. Precise locking of optical frequencies of the mid-infrared comb to the pump comb is experimentally verified at sub-20 mHz level, which corresponds to a fractional statistical uncertainty of 2 × 10-16 at the center frequency of the mid-infrared comb. The fully stabilized mid-infrared comb is an ideal tool for high-precision molecular spectroscopy, as well as for optical frequency metrology in the mid-infrared region, which is difficult to access with other stabilized frequency comb techniques.

  11. Spectral linewidth preservation in parametric frequency combs seeded by dual pumps. (United States)

    Tong, Zhi; Wiberg, Andreas O J; Myslivets, Evgeny; Kuo, Bill P P; Alic, Nikola; Radic, Stojan


    We demonstrate new technique for generation of programmable-pitch, wideband frequency combs with low phase noise. The comb generation was achieved using cavity-less, multistage mixer driven by two tunable continuous-wave pump seeds. The approach relies on phase-correlated continuous-wave pumps in order to cancel spectral linewidth broadening inherent to parametric comb generation. Parametric combs with over 200-nm bandwidth were obtained and characterized with respect to phase noise scaling to demonstrate linewidth preservation over 100 generated tones.

  12. Frequency-comb spectroscopy of the hydrogen 1S-3S and 1S-3D transitions

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Elisabeth; Haensch, Theodor W. [Max-Planck-Institut fuer Quantenoptik, Garching (Germany); Ludwig-Maximilians-Universitaet, Muenchen (Germany); Yost, Dylan C.; Matveev, Arthur; Udem, Thomas [Max-Planck-Institut fuer Quantenoptik, Garching (Germany)


    An observation of the 1S-3S and 1S-3D two-photon transitions in an atomic hydrogen beam using direct frequency-comb spectroscopy in a Doppler-free arrangement is reported. The measurements of these transition frequencies may be used for an improved determination of the Rydberg constant and the 1S Lamb shift and could shed light on the current discrepancy in the determination of the proton charge radius. Concurrently, a frequency comb well-suited for high-precision, Doppler-free spectroscopy in the deep ultraviolet (DUV) wavelength region is demonstrated. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Efficient frequency comb generation in AlGaAs-on-insulator

    DEFF Research Database (Denmark)

    Pu, Minhao; Ottaviano, Luisa; Semenova, Elizaveta


    The combination of nonlinear and integrated photonics enables Kerr frequency comb generation in stable chip-based microresonators. Such a comb system will revolutionize applications, including multi-wavelength lasers, metrology, and spectroscopy. Aluminum gallium arsenide (AlGaAs) exhibits very...... high material nonlinearity and low nonlinear loss. However, difficulties in device processing and low device effective nonlinearity made Kerr frequency comb generation elusive. Here, we demonstrate AlGaAs-on-insulator as a nonlinear platform at telecom wavelengths with an ultra-high device nonlinearity...

  14. Quantum-fluctuation-initiated coherence in multioctave Raman optical frequency combs. (United States)

    Wang, Y Y; Wu, Chunbai; Couny, F; Raymer, M G; Benabid, F


    We show experimentally and theoretically that the spectral components of a multioctave frequency comb spontaneously created by stimulated Raman scattering in a hydrogen-filled hollow-core photonic crystal fiber exhibit strong self-coherence and mutual coherence within each 12 ns driving laser pulse. This coherence arises in spite of the field's initiation being from quantum zero-point fluctuations, which causes each spectral component to show large phase and energy fluctuations. This points to the possibility of an optical frequency comb with nonclassical correlations between all comb lines.

  15. DWDM Fiber-Wireless Access System with Centralized Optical Frequency Comb-based RF Carrier Generation

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Beltrán, Marta; Sánchez, José


    We propose and experimentally demonstrate an optical wireless DWDM system at 60 GHz with optical incoherent heterodyne up-conversion using an optical frequency comb. Multiple users with wireline and wireless services are simultaneously supported.......We propose and experimentally demonstrate an optical wireless DWDM system at 60 GHz with optical incoherent heterodyne up-conversion using an optical frequency comb. Multiple users with wireline and wireless services are simultaneously supported....

  16. Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs (United States)

    Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon


    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.

  17. Modeling of octave-spanning Kerr frequency combs using a generalized mean-field Lugiato-Lefever model. (United States)

    Coen, Stéphane; Randle, Hamish G; Sylvestre, Thibaut; Erkintalo, Miro


    A generalized Lugiato-Lefever equation is numerically solved with a Newton-Raphson method to model Kerr frequency combs. We obtain excellent agreement with past experiments, even for an octave-spanning comb. Simulations are much faster than with any other technique despite including more modes than ever before. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of Kerr-comb formation.

  18. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide. (United States)

    Kuyken, Bart; Ideguchi, Takuro; Holzner, Simon; Yan, Ming; Hänsch, Theodor W; Van Campenhout, Joris; Verheyen, Peter; Coen, Stéphane; Leo, Francois; Baets, Roel; Roelkens, Gunther; Picqué, Nathalie


    Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500-3,300 nm) spectra with a coupled input pulse energy as low as 16 pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip.

  19. Radio-frequency clock delivery via free-space frequency comb transmission. (United States)

    Alatawi, Ayshah; Gollapalli, Ravi P; Duan, Lingze


    We characterize the instability of an rf clock signal caused by free-space transmission of a frequency comb (FC) under typical laboratory conditions. The phase-noise spectra show the involvement of multiple random processes. For a 10 m transmission, the rms timing jitter integrated over 1-10(5) Hz is 95 fs, and the root Allan variance over 1 s is 4x10(-13). The measured Allan variance has a tau(-1) behavior and an excellent agreement with the phase noise measurement. These results indicate the feasibility of FC-based free-space rf clock distribution over short distances.

  20. Frequency-comb-based BOTDA sensors for high-spatial-resolution/long-distance sensing. (United States)

    Jia, Xin-Hong; Chang, Han-Qing; Lin, Kai; Xu, Cong; Wu, Jia-Gui


    Frequency-comb-based Brillouin optical time-domain analysis (BOTDA) sensors were developed to achieve acquisition-time reduction and high-spatial-resolution/long-distance sensing simultaneously. We found that, for the standard frequency-comb-based BOTDA, the use of a double-sideband (DSB) pulse generates a series of pulse pairs that simultaneously propagate along the sensing fiber, leading to a nonlinear interaction between the two sidebands of each frequency comb pulse, and a significant splitting of the Brillouin gain spectrum (BGS). This problem prevents its application in high-spatial-resolution sensing due to the higher pulse power requirement. Thus, one of the sidebands of DSB pulse was proposed for greatly suppressing the BGS distortion. In combination with the phonon pre-excitation technique based on phase-shifted pulse, a sensor with a spatial-resolution approximately 60 cm along a fiber approximately 592 m in length was demonstrated. Furthermore, we explored the detailed performance of long-distance sensing by frequency- comb-based BOTDA. The use of a frequency comb for the probe wave can suppress the pulse distortion and non-local effect, which is helpful for extending the sensing distance. A spatial resolution of approximately 6 m along a sensing fiber approximately 74.2 km in length was successfully demonstrated.

  1. Generation of a coherent near-infrared Kerr frequency comb in a monolithic microresonator with normal GVD

    CERN Document Server

    Liang, Wei; Ilchenko, Vladimir S; Eliyahu, Danny; Seidel, David; Matsko, Andrey B; Maleki, Lute


    We demonstrate experimentally, and explain theoretically, generation of a wide, fundamentally phase locked Kerr frequency comb in a nonlinear resonator with a normal group velocity dispersion. A magnesium fluoride whispering gallery resonator characterized with 10 GHz free spectral range and pumped either at 780 nm or 795 nm is used in the experiment. The envelope of the observed frequency comb differs significantly from the Kerr frequency comb spectra reported previously. We show via numerical simulation that, while the frequency comb does not correspond to generation of short optical pulses, the relative phases of the generated harmonics are fixed.

  2. Frequency comb vernier spectroscopy for broadband, high-resolution, high-sensitivity absorption and dispersion spectra

    NARCIS (Netherlands)

    Gohle, C.; Stein, B.; Schliesser, A.; Udem, T.; Hansch, T.W.


    A femtosecond frequency comb provides a vast number of equidistantly spaced narrow band laser modes that can be simultaneously tuned and frequency calibrated with 15 digit accuracy. Our Vernier spectrometer utilizes all of theses modes in a massively parallel manner to rapidly record both absorption

  3. 1-GHz repetition rate femtosecond OPO with stabilized offset between signal and idler frequency combs. (United States)

    Gebs, R; Dekorsy, T; Diddams, S A; Bartels, A


    We report an optical parametric oscillator (OPO) based on periodically poled lithium niobate (PPLN) that is synchronously pumped by a femtosecond Ti:sapphire laser at 1 GHz repetition rate. The signal output has a center wavelength of 1558 nm and its spectral bandwidth amounts to 40 nm. The OPO operates in a regime where the signal- and idler frequency combs exhibit a partial overlap around 1600 nm. In this near-degeneracy region, a beat at the offset between the signal and idler frequency combs is detected. Phase-locking this beat to an external reference stabilizes the spectral envelopes of the signal- and idler output. At the same time, the underlying frequency combs are stabilized relative to each other with an instability of 1.5x10(-17) at 1 s gate time.

  4. On the generation of octave-spanning optical frequency combs using monolithic whispering-gallery-mode microresonators. (United States)

    Chembo, Yanne K; Yu, Nan


    Octave-spanning optical frequency combs are especially interesting in optical metrology owing to the ability of self-referencing. We report a theoretical study on the generation of octave-spanning combs in the whispering gallery modes of a microresonator. Through a modal expansion model simulation in a calcium fluoride microcavity, we show that a combination of suitable pump power, Kerr nonlinearity, and dispersion profile can lead to stable and robust octave-spanning optical frequency combs.

  5. Signal line shapes of Fourier transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs

    CERN Document Server

    Johansson, Alexandra C; Khodabakhsh, Amir; Foltynowicz, Aleksandra


    We present a thorough analysis of the signal line shapes of Fourier transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f${_m}$, to the molecular line width, {\\Gamma}. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f${_m}$/{\\Gamma} ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting NICE-OFCS spectra of CO${_2}$ at 1575 nm using a system based on an Er:fiber femtosecond laser and a cavity with a finesse of ~11000.

  6. Low threshold frequency comb generation in AlGaAs-on-insulator microresonator in the normal dispersion regime

    DEFF Research Database (Denmark)

    Kamel, Ayman Nassar; Pu, Minhao; Yvind, Kresten


    We present milli-Watt threshold frequency comb generation in AlGaAs-on-insulator integrated microresonators exhibiting normal GVD by employing the effects of mode interaction.......We present milli-Watt threshold frequency comb generation in AlGaAs-on-insulator integrated microresonators exhibiting normal GVD by employing the effects of mode interaction....

  7. A decade of astrocombs: recent advances in frequency combs for astronomy. (United States)

    McCracken, Richard A; Charsley, Jake M; Reid, Derryck T


    A new regime of precision radial-velocity measurements in the search for Earth-like exoplanets is being facilitated by high-resolution spectrographs calibrated by laser frequency combs. Here we review recent advances in the development of astrocomb technology, and discuss the state of the field going forward.

  8. High-resolution terahertz spectroscopy with a single tunable frequency comb. (United States)

    Skryl, A S; Pavelyev, D G; Tretyakov, M Y; Bakunov, M I


    We report an improvement of three orders of magnitude in the spectral resolution of a recently proposed single-comb terahertz spectroscopy [Opt. Lett.39, 5669 (2014)]. The improvement is achieved by using a femtosecond optical pulse train with a tunable repetition rate. Terahertz comb with tunable spectral line spacing generated by the train is detected via nonlinear mixing with a harmonic of a CW signal from a microwave frequency synthesizer. By applying this technique to the low-pressure gas spectroscopy, we achieved a 100 kHz spectral resolution in measuring separate absorption lines of the rotational manifold of fluoroform (CF3H).

  9. Frequency-comb-referenced singly-resonant OPO for sub-Doppler spectroscopy. (United States)

    Ricciardi, I; De Tommasi, E; Maddaloni, P; Mosca, S; Rocco, A; Zondy, J-J; De Rosa, M; De Natale, P


    We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W between 2.7 and 4.2 μm, which is phase locked to a self-referenced frequency comb. Both pump and signal frequencies are directly phase-locked to the frequency comb of a NIR-emitting fs mode-locked fibre laser, linked, in turn, to the caesium primary standard. We estimate for the idler frequency a fractional Allan deviation of ∼ 3 × 10⁻¹²τ⁻½ between 1 and 200 s. To test the spectroscopic performance of the OPO, we carried out saturation spectroscopy of several transitions belonging to the ν1 rovibrational band of CH₃I, resolving their electronic quadrupole hyperfine structure, estimating a linewidth better than 200 kHz FWHM for the idler, and determining the absolute frequency of the hyperfine components with a 50-kHz-uncertainty.

  10. Surpassing the Path-Limited Resolution of a Fourier Transform Spectrometer with Frequency Combs

    CERN Document Server

    Maslowski, Piotr; Johansson, Alexandra C; Khodabakhsh, Amir; Kowzan, Grzegorz; Rutkowski, Lucile; Mills, Andrew A; Mohr, Christian; Jiang, Jie; Fermann, Martin E; Foltynowicz, Aleksandra


    Fourier transform spectroscopy based on incoherent light sources is a well-established tool in research fields from molecular spectroscopy and atmospheric monitoring to material science and biophysics. It provides broadband molecular spectra and information about the molecular structure and composition of absorptive media. However, the spectral resolution is fundamentally limited by the maximum delay range ({\\Delta}$_{max}$) of the interferometer, so acquisition of high-resolution spectra implies long measurement times and large instrument size. We overcome this limit by combining the Fourier transform spectrometer with an optical frequency comb and measuring the intensities of individual comb lines by precisely matching the {\\Delta}$_{max}$ to the comb line spacing. This allows measurements of absorption lines narrower than the nominal (optical path-limited) resolution without ringing effects from the instrumental lineshape and reduces the acquisition time and interferometer length by orders of magnitude.

  11. Frequency-agile vector signal generation based on optical frequency comb and pre-coding (United States)

    Qu, Kun; Zhao, ShangHong; Tan, QingGui; Liang, DanYa


    In this paper, we experimentally demonstrate the generation of frequency-agile vector signals based on an optical frequency comb (OFC) and unbalanced pre-coding technology by employing a dual-driven Mach-Zehnder Modulator (DD-MZM) and an intensity modulator (IM). The OFC is generated by the DD-MZM and sent to the IM as a carrier. The IM is driven by a 5 GHz 2 Gbaud quadrature phase-shift keying (QPSK) vector signal with unbalanced pre-coding. The -1st order sideband of one OFC line and the +1st order sideband of another OFC line are selected by a programmable pulse shaper (PPS), after square-low photodiode detection, the frequency-agile vector signal can be obtained. The results show that the 2 Gbaud QPSK vector signals at 30 GHz, 50 GHz, 70 GHz and 90 GHz can be generated by only pre-coding once. It is possible to achieve a bit-error-rate (BER) below 1e-3 for wireless transmissions over 0.5 m using this method.

  12. Raman induced soliton self-frequency shift in microresonator Kerr frequency combs

    CERN Document Server

    Karpov, Maxim; Kordts, Arne; Brasch, Victor; Pfeiffer, Martin; Zervas, Michail; Geiselmann, Michael; Kippenberg, Tobias J


    The formation of temporal dissipative solitons in continuous wave laser driven microresonators enables the generation of coherent, broadband and spectrally smooth optical frequency combs as well as femtosecond pulses with compact form factor. Here we report for the first time on the observation of a Raman-induced soliton self-frequency shift for a microresonator soliton. The Raman effect manifests itself in amorphous SiN microresonator based single soliton states by a spectrum that is hyperbolic secant in shape, but whose center is spectrally red-shifted (i.e. offset) from the continuous wave pump laser. The Raman induced spectral red-shift is found to be tunable via the pump laser detuning and grows linearly with peak power. The shift is theoretically described by the first order shock term of the material's Raman response, and we infer a Raman shock time of 20 fs for amorphous SiN. Moreover, we observe that the Raman induced frequency shift can lead to a cancellation or overcompensation of the soliton recoi...

  13. Generation of green frequency comb from chirped χ{sup (2)} nonlinear photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lai, C.-M. [Department of Electronic Engineering, Ming Chuan University, Taoyuan, Taiwan (China); Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Peng, L.-H. [Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan (China); Yu, N. E. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Boudrioua, A. [LPL, CNRS - UMR 7538, Université Paris 13, Sorbone Paris Cité (France); Kung, A. H. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan (China); Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan (China)


    Spectrally broad frequency comb generation over 510–555 nm range was reported on chirped quasi-phase-matching (QPM) χ{sup (2)} nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 μm to 7.1 μm. When pumped with nanosecond infrared (IR) frequency comb derived from a QPM optical parametric oscillator (OPO) and spanned over 1040 nm to 1090 nm wavelength range, the 520 nm to 545 nm up-converted green spectra were shown to consist of contributions from (a) second-harmonic generation among the signal or the idler modes, and (b) sum-frequency generation (SFG) from the neighboring pairs of the signal or the idler modes. These mechanisms led the up-converted green frequency comb to have the same mode spacing of 450 GHz as that in the IR-OPO pump comb. As the pump was further detuned from the aforementioned near-degeneracy point and moved toward the signal (1020–1040 nm) and the idler (1090–1110 nm) spectral range, the above QPM parametric processes were preserved in the chirped QPM devices to support up-converted green generation in the 510–520 nm and the 545–555 nm spectral regime. Additional 530–535 nm green spectral generation was also observed due to concurrence of multi-wavelength SFG processes between the (signal, idler) mode pairs. These mechanisms facilitate the chirped QPM device to support a single-pass up-conversion efficiency ∼10% when subject to an IR-OPO pump comb with 200 mW average power operated near- or off- the degeneracy point.

  14. Reconfigurable broadband microwave photonic intensity differentiator based on an integrated optical frequency comb source

    Directory of Open Access Journals (Sweden)

    Xingyuan Xu


    Full Text Available We propose and experimentally demonstrate a microwave photonic intensity differentiator based on a Kerr optical comb generated by a compact integrated micro-ring resonator (MRR. The on-chip Kerr optical comb, containing a large number of comb lines, serves as a high-performance multi-wavelength source for implementing a transversal filter, which will greatly reduce the cost, size, and complexity of the system. Moreover, owing to the compactness of the integrated MRR, frequency spacings of up to 200-GHz can be achieved, enabling a potential operation bandwidth of over 100 GHz. By programming and shaping individual comb lines according to calculated tap weights, a reconfigurable intensity differentiator with variable differentiation orders can be realized. The operation principle is theoretically analyzed, and experimental demonstrations of the first-, second-, and third-order differentiation functions based on this principle are presented. The radio frequency amplitude and phase responses of multi-order intensity differentiations are characterized, and system demonstrations of real-time differentiations for a Gaussian input signal are also performed. The experimental results show good agreement with theory, confirming the effectiveness of our approach.

  15. Reconfigurable broadband microwave photonic intensity differentiator based on an integrated optical frequency comb source (United States)

    Xu, Xingyuan; Wu, Jiayang; Shoeiby, Mehrdad; Nguyen, Thach G.; Chu, Sai T.; Little, Brent E.; Morandotti, Roberto; Mitchell, Arnan; Moss, David J.


    We propose and experimentally demonstrate a microwave photonic intensity differentiator based on a Kerr optical comb generated by a compact integrated micro-ring resonator (MRR). The on-chip Kerr optical comb, containing a large number of comb lines, serves as a high-performance multi-wavelength source for implementing a transversal filter, which will greatly reduce the cost, size, and complexity of the system. Moreover, owing to the compactness of the integrated MRR, frequency spacings of up to 200-GHz can be achieved, enabling a potential operation bandwidth of over 100 GHz. By programming and shaping individual comb lines according to calculated tap weights, a reconfigurable intensity differentiator with variable differentiation orders can be realized. The operation principle is theoretically analyzed, and experimental demonstrations of the first-, second-, and third-order differentiation functions based on this principle are presented. The radio frequency amplitude and phase responses of multi-order intensity differentiations are characterized, and system demonstrations of real-time differentiations for a Gaussian input signal are also performed. The experimental results show good agreement with theory, confirming the effectiveness of our approach.

  16. Frequency locking of an extended-cavity quantum cascade laser to a frequency comb for precision mid infrared spectroscopy

    KAUST Repository

    Alsaif, Bidoor


    Extended-cavity quantum cascade lasers (EC-QCLs) enable mode-hope-free frequency sweeps in the mid-infrared region over ranges in excess of 100 cm−1, at speeds up to 1 THz/s and with a 100-mW optical power level. This makes them ideally suited for broadband absorption spectroscopy and for the simultaneous detection of multiple gases. On the other hand, their use for precision spectroscopy has been hampered so far by a large amount of frequency noise, resulting in an optical linewidth of about 30 MHz over 50 ms [1]. This is one of the reasons why neither their frequency nor their phase have been so far locked to a frequency comb. Their use in combination with frequency combs has been performed in an open loop regime only [2], which has the merit of preserving the inherently fast modulation speed of these lasers, yet not to afford high spectral resolution and accuracy.

  17. Quantum Theory of Conditional Phonon States in a Dual-Pumped Raman Optical Frequency Comb (United States)

    Mondloch, Erin

    In this work, we theoretically and numerically investigate nonclassical phonon states created in the collective vibration of a Raman medium by the generation of a dual-pumped Raman optical frequency comb in an optical cavity. This frequency comb is generated by cascaded Raman scattering driven by two phase-locked pump lasers that are separated in frequency by three times the Raman phonon frequency. We characterize the variety of conditioned phonon states that are created when the number of photons in all optical frequency modes except the pump modes are measured. Almost all of these conditioned phonon states are extremely well approximated as three-phonon-squeezed states or Schrodinger-cat states, depending on the outcomes of the photon number measurements. We show how the combinations of first-, second-, and third-order Raman scattering that correspond to each set of measured photon numbers determine the fidelity of the conditioned phonon state with model three-phonon-squeezed states and Schrodinger-cat states. All of the conditioned phonon states demonstrate preferential growth of the phonon mode along three directions in phase space. That is, there are three preferred phase values that the phonon state takes on as a result of Raman scattering. We show that the combination of Raman processes that produces a given set of measured photon numbers always produces phonons in multiples of three. In the quantum number-state representation, these multiples of three are responsible for the threefold phase-space symmetry seen in the conditioned phonon states. With a semiclassical model, we show how this three-phase preference can also be understood in light of phase correlations that are known to spontaneously arise in single-pumped Raman frequency combs. Additionally, our semiclassical model predicts that the optical modes also grow preferentially along three phases, suggesting that the dual-pumped Raman optical frequency comb is partially phase-stabilized.

  18. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing (United States)

    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


    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

  19. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering. (United States)

    Morville, Jérôme; Rutkowski, Lucile; Dobrev, Georgi; Crozet, Patrick


    We present a new approach to Cavity Enhanced - Direct Frequency Comb Spectroscopy where the full emission bandwidth of a Titanium:Sapphire laser is exploited at GHz resolution. The technique is based on a low-resolution Vernier filtering obtained with an appreciable -actively stabilized- mismatch between the cavity Free Spectral Range and the laser repetition rate, using a diffraction grating and a split-photodiode. This particular approach provides an immunity to frequency-amplitude noise conversion, reaching an absorption baseline noise in the 10-9 cm-1 range with a cavity finesse of only 3000. Spectra covering 1800 cm-1 (˜ 55 THz) are acquired in recording times of about 1 second, providing an absorption figure of merit of a few 10-11 cm-1/√{Hz}. Initially tested with ambient air, we report progress in using the Vernier frequency comb method with a discharge source of small radicals. Rutkowski et al, Opt. Lett., 39(23)2014

  20. Near infrared frequency comb vernier spectrometer for broadband trace gas detection. (United States)

    Zhu, Feng; Bounds, James; Bicer, Aysenur; Strohaber, James; Kolomenskii, Alexandre A; Gohle, Christoph; Amani, Mahmood; Schuessler, Hans A


    We present a femtosecond frequency comb vernier spectrometer in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such a spectrometer provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8 × 10(-8) cm(-1)Hz(-1/2), corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. Such measurements have broad applications for sensing greenhouse gases in this fingerprint near infrared region with a simple apparatus.

  1. Simple optical frequency comb generation using a passively mode-locked quantum dot laser (United States)

    Liu, Li; Zhang, Xiupu; Xu, Tiefeng; Dai, Zhenxiang; Liu, Taijun


    A simple and quasi-tunable optical frequency comb (OFC) generator is proposed and experimentally demonstrated using a C-band passively Fabry-Pérot quantum dot mode-locked laser and a dual-driven LiNbO3 Mach-Zehnder modulator. A 16-nm bandwidth OFC with 81, 58 and 30 comb lines at frequency interval of 23.3 GHz, 35 GHz and 70 GHz respectively is obtained experimentally. Measured average optical signal to noise ratio of 10-dB bandwidth OFCs is 36.3 dB, 38.5 dB and 40.8 dB at frequency interval of 23.3 GHz, 35 GHz and 70 GHz, respectively. Besides, single-sideband phase noise of the 23.3 GHz and 35 GHz frequency comb is -110 dBc/Hz and -102 dBc/Hz at an offset of 1 kHz, respectively. RF linewidth of the 23.3 GHz and 35 GHz OFC is about from 275 Hz to 289 Hz. This is considered a very simple OFC generator with a broadband and seamless spectrum.

  2. Direct Spectroscopy in Hollow Optical with Fiber-Based Optical Frequency Combs (United States)


    S. K. T. M. Fortier, F. Quinlan, J. Taylor, J. C. Bergquist, T. Rosenband, N. Lemke, A. Ludlow, Y. Jiang, C. W. Oates and S. A. Diddams, "Generation...34 in CLEO: 2014, OSA Technical Digest (online) (Optical Society of America, 2014), paper SM3N.7. frequency comb," in CLEO: 2014, OSA Technical Digest (online) (Optical Society of America, 2014), paper SW1O.7.

  3. A near infrared laser frequency comb for high precision Doppler planet surveys

    Directory of Open Access Journals (Sweden)

    Bally J.


    Full Text Available Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV measurements, with the most stable visible light spectrographs reporting RV results the order of 1 m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

  4. Repetition rate multiplication of frequency comb using all-pass fiber resonator. (United States)

    Yang, Lijun; Yang, Honglei; Zhang, Hongyuan; Wei, Haoyun; Li, Yan


    We propose a stable method for repetition rate multiplication of a 250-MHz Er-fiber frequency comb by a phase-locked all-pass fiber ring resonator, whose phase-locking configuration is simple. The optical path length of the fiber ring resonator is automatically controlled to be accurately an odd multiple of half of the original cavity length using an electronical phase-locking unit with an optical delay line. As for shorter cavity length of the comb, high-order odd multiple is preferable. Because the power loss depends only on the net-attenuation of the fiber ring resonator, the energetic efficiency of the proposed method is high. The input and output optical spectrums show that the spectral width of the frequency comb is clearly preserved. Besides, experimental results show less pulse intensity fluctuation and 35 dB suppression ratio of side-modes while providing a good long-term and short-term frequency stability. Higher-order repetition rate multiplication to several GHz can be obtained by using several fiber ring resonators in cascade configuration.

  5. Optical frequency synthesizer for precision spectroscopy of Rydberg states of Rb atoms (United States)

    Watanabe, Naoto; Tamura, Hikaru; Musha, Mitsuru; Nakagawa, Ken'ichi


    We have developed an optical frequency synthesizer for the precision spectroscopy of highly excited Rydberg states of Rb atoms. This synthesizer can generate a widely tunable 480 nm laser light with an optical power of 150 mW and an absolute frequency uncertainty of less than 100 kHz using a high-repetition-rate (325 MHz) Er fiber-based optical frequency comb and a tunable frequency-doubled diode laser at 960 nm. We demonstrate the precision two-photon spectroscopy of the Rydberg states of 87Rb atoms by observing the electromagnetically induced transparency in a vapor cell, and measure the absolute transition frequencies of 87Rb to nD (n = 53-92) and nS (n = 60-90) Rydberg states with an uncertainty of less than 250 kHz. It is the first direct frequency measurements of these transitions using an optical frequency comb.

  6. Interrogation system with auto-calibration for fiber Bragg grating sensors using VCSEL based optical frequency comb generators (United States)

    Poiana, D. A.; Garcia-Souto, J. A.; Posada-Román, J. E.; Acedo, P.


    A new instrumentation system for FBG interrogation is proposed. It combines the use of a VCSEL as a tunable laser and an optical frequency comb generator as a selective broadband source. Features such as auto-calibration and wave-length tracking are provided with this interrogation system. First a fast sweep searches for the FBG spectral position, its reflection profile and finds the best set of operating points for the optical comb. Then, the VCSEL is tuned with the FBG through a feedback loop to withstand large-range slow changes (strain and temperature) and, at the same time, the faster phenomena (vibrations and ultrasounds) are measured by the optical frequency comb generator. In practice, a dual comb is proposed to interrogate actively the FBG reflection in order to obtain radio frequency signals that contain the FBG dynamic-strain due to applied vibrations.

  7. Stably accessing octave-spanning microresonator frequency combs in the soliton regime. (United States)

    Li, Qing; Briles, Travis C; Westly, Daron A; Drake, Tara E; Stone, Jordan R; Ilic, B Robert; Diddams, Scott A; Papp, Scott B; Srinivasan, Kartik


    Microresonator frequency combs can be an enabling technology for optical frequency synthesis and timekeeping in low size, weight, and power architectures. Such systems require comb operation in low-noise, phase-coherent states such as solitons, with broad spectral bandwidths (e.g., octave-spanning) for self-referencing to detect the carrier-envelope offset frequency. However, accessing such states is complicated by thermo-optic dispersion. For example, in the Si3N4 platform, precisely dispersion-engineered structures can support broadband operation, but microsecond thermal time constants often require fast pump power or frequency control to stabilize the solitons. In contrast, here we consider how broadband soliton states can be accessed with simple pump laser frequency tuning, at a rate much slower than the thermal dynamics. We demonstrate octave-spanning soliton frequency combs in Si3N4 microresonators, including the generation of a multi-soliton state with a pump power near 40 mW and a single-soliton state with a pump power near 120 mW. We also develop a simplified two-step analysis to explain how these states are accessed without fast control of the pump laser, and outline the required thermal properties for such operation. Our model agrees with experimental results as well as numerical simulations based on a Lugiato-Lefever equation that incorporates thermo-optic dispersion. Moreover, it also explains an experimental observation that a member of an adjacent mode family on the red-detuned side of the pump mode can mitigate the thermal requirements for accessing soliton states.

  8. Centralized optical-frequency-comb-based RF carrier generator for DWDM fiber-wireless access systems

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Beltran, Marta; Sanchez, Jose


    In this paper, we report on a gigabit capacity fiber-wireless system that enables smooth integration between high-speed wireless networks and dense wavelength-division-multiplexing (DWDM) access networks. By employing a centralized optical frequency comb, both the wireline and the wireless services...... for each DWDM user can be simultaneously supported. Besides, each baseband channel can be transparently upconverted tomultiple radio-frequency (RF) bands for different wireless standards, which can be flexibly filtered at the end user to select the on-demand RF band, depending on the wireless applications...

  9. Weaving quantum optical frequency combs into continuous-variable hypercubic cluster states (United States)

    Wang, Pei; Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier


    Cluster states with higher-dimensional lattices that cannot be physically embedded in three-dimensional space have important theoretical interest in quantum computation and quantum simulation of topologically ordered condensed-matter systems. We present a simple, scalable, top-down method of entangling the quantum optical frequency comb into hypercubic-lattice continuous-variable cluster states of a size of about 104 quantum field modes, using existing technology. A hypercubic lattice of dimension D (linear, square, cubic, hypercubic, etc.) requires but D optical parametric oscillators with bichromatic pumps whose frequency splittings alone determine the lattice dimensionality and the number of copies of the state.

  10. Fast, precise, and widely tunable frequency control of an optical parametric oscillator referenced to a frequency comb (United States)

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


    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.

  11. Generation of two-cycle pulses and octave-spanning frequency combs in a dispersion-flattened micro-resonator. (United States)

    Zhang, Lin; Bao, Chengying; Singh, Vivek; Mu, Jianwei; Yang, Changxi; Agarwal, Anuradha M; Kimerling, Lionel C; Michel, Jurgen


    We show that octave-spanning Kerr frequency combs with improved spectral flatness of comb lines can be generated in dispersion-flattened microring resonators. The resonator is formed by a strip/slot hybrid waveguide, exhibiting a flat and low anomalous dispersion between two zero-dispersion wavelengths that are separated by one octave from near-infrared to mid-infrared. Such flattened dispersion profiles allow for the generation of mode-locked frequency combs, using relatively low pump power to obtain two-cycle cavity solitons on a chip, associated with the octave-spanning comb bandwidth. The wavelength dependence of the optical loss and of the coupling coefficient and thus wavelength dependent Q-factor are also considered.

  12. Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator

    CERN Document Server

    Yang, Yong; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan; Yang, Lan; Chormaic, Síle Nic


    Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \\textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

  13. Characterization of coherent quantum frequency combs using electro-optic phase modulation (United States)

    Imany, Poolad; Odele, Ogaga D.; Jaramillo-Villegas, Jose A.; Leaird, Daniel E.; Weiner, Andrew M.


    We demonstrate a two-photon interference experiment for phase coherent biphoton frequency combs (BFCs), created through spectral amplitude filtering of biphotons with a continuous broadband spectrum. By using an electro-optic phase modulator, we project the BFC lines into sidebands that overlap in frequency. The resulting high-visibility interference patterns provide an approach to verify frequency-bin entanglement even with slow single-photon detectors; we show interference patterns with visibilities that surpass the classical threshold for qubit and qutrit states. Additionally, we show that with entangled qutrits, two-photon interference occurs even with projections onto different final frequency states. Finally, we show the versatility of this scheme for weak-light measurements by performing a series of two-dimensional experiments at different signal-idler frequency offsets to measure the dispersion of a single-mode fiber.

  14. Self-referenceable frequency comb from an ultrafast thin disk laser. (United States)

    Saraceno, Clara J; Pekarek, Selina; Heckl, Oliver H; Baer, Cyrill R E; Schriber, Cinia; Golling, Matthias; Beil, Kolja; Kränkel, Christian; Huber, Günter; Keller, Ursula; Südmeyer, Thomas


    We present the first measurement of the carrier envelope offset (CEO) frequency of an ultrafast thin disk laser (TDL). The TDL used for this proof-of-principle experiment was based on the gain material Yb:Lu(2)O(3) and delivered 7 W of average power in 142-fs pulses, which is more than two times shorter than previously realized with this material. Using only 65 mW of the output of the laser, we generated a coherent octave-spanning supercontinuum (SC) in a highly nonlinear photonic crystal fiber (PCF). We detected the CEO beat signal using a standard f-to-2f interferometer, achieving a signal-to-noise ratio of >25 dB (3 kHz resolution bandwidth). The CEO frequency was tunable with the pump current with a slope of 33 kHz/mA. This result opens the door towards high-power frequency combs from unamplified oscillators. Furthermore, it confirms the suitability of these sources for future intralaser extreme nonlinear optics experiments such as high harmonic generation and VUV frequency comb generation from compact sources. © 2012 Optical Society of America

  15. Frequency Comb Driven Raman Transitions in the THz Range: High Precision Isotope Shift Measurements in Ca+

    DEFF Research Database (Denmark)

    Meyer, Steffen


    to picoseconds in the previous experiments. For the broad spectrum, the additional effect of group delay dispersion (GDD) has to be taken into account, since the Raman process relies on the coherent interaction of all frequency components of the spectrum, with GDD influencing the relative phase which leads......This thesis presents for the first time the experimental implementation of coherent Raman oscillations with a femtosecond frequency comb for transition frequencies in the THz range. The technique has been successfully demonstrated before to drive Raman transitions between hyperfine structure states...... to destructive interference. Therefore, GDD is compensated using a prism compressor and it is shown quantitatively that the measured GDD matches the theoretically predicted effect on the total Raman Rabi frequency. For the measurements and compensation of GDD, the techniques of interferometric autocorrelation...

  16. Frequency comb-based time transfer over a 159 km long installed fiber network (United States)

    Lessing, M.; Margolis, H. S.; Brown, C. T. A.; Marra, G.


    We demonstrate a frequency comb-based time transfer technique on a 159 km long installed fiber link. Timing information is superimposed onto the optical pulse train of an ITU-channel-filtered mode-locked laser using an intensity modulation scheme. The environmentally induced optical path length fluctuations are compensated using a round-trip phase noise cancellation technique. When the fiber link is stabilized, a time deviation of 300 fs at 5 s and an accuracy at the 100 ps level are achieved.

  17. Multitap microwave photonic filters with programmable phase response via optical frequency comb shaping. (United States)

    Song, Minhyup; Torres-Company, Victor; Metcalf, Andrew J; Weiner, Andrew M


    We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration. © 2012 Optical Society of America

  18. Offset-Free Gigahertz Midinfrared Frequency Comb Based on Optical Parametric Amplification in a Periodically Poled Lithium Niobate Waveguide (United States)

    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.


    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.

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

    Directory of Open Access Journals (Sweden)

    Julio E. Posada-Roman


    Full Text Available 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.

  20. Frequency stability measurement of a transfer-cavity-stabilized diode laser by using an optical frequency comb (United States)

    Uetake, S.; Matsubara, K.; Ito, H.; Hayasaka, K.; Hosokawa, M.


    We report results of frequency stability measurements of an extended cavity diode laser (ECDL) whose frequency is stabilized by a non-evacuated scanning transfer cavity. The transfer cavity is locked to a commercial frequency stabilized helium-neon laser. Frequency stability is measured by use of an optical frequency comb. The environmental perturbations (variations of temperature, air pressure, and humidity) are also simultaneously measured. The observed frequency drift of the ECDL is well explained by environmental perturbations. An atmospheric pressure variation, which is difficult to control with a non-evacuated cavity, is mainly affected to the frequency stability. Thus we put the cavity into a simple O-ring sealed (non-evacuated) tube. With this simple O-ring sealed tube, the frequency drift is reduced by a factor of 3, and the Allan variance reaches a value of 2.4×10-10, corresponds to the frequency stability of 83 kHz, at the average time of 3000 s. Since the actual frequency drift is well estimated by simultaneous measurement of the ambient temperature, pressure, and humidity, a feed-forward compensation of frequency drifts is also feasible in order to achieve a higher frequency stability with a simple non-evacuated transfer cavity.

  1. Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking (United States)

    Navarrete-Benlloch, Carlos; Patera, Giuseppe; de Valcárcel, Germán J.


    Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities driven by mode-locked lasers, and containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. SPOPOs have received a lot of attention lately because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging and interesting regime where spontaneous symmetry breaking confers strong nonclassical properties to the emitted light, which has eluded experimental observation so far. Apart from opening the possibility of studying experimentally this elusive regime of dissipative phase transitions, our predictions will have a practical impact, since we show that spontaneous symmetry breaking provides a specific spatiotemporal mode with large quadrature squeezing for any value of the system parameters, turning SPOPOs into robust sources of highly nonclassical light above threshold.

  2. Optimal periodic frequency combs for high-efficiency optical quantum memory based on rare-earth ion crystals (United States)

    Arslanov, N. M.; Moiseev, S. A.


    The possibility of enhancing the quantum efficiency of photon echo broadband quantum memory in rare-earth-ion-doped crystals with a frequency comb structure of optical transition inhomogeneous broadening is studied. We have found the optimal parameters of the frequency combs for implementing the preassigned quantum efficiency in the chosen spectral range of the optical transitions of rare-earth ions with real parameters. The obtained results allow the conditions to be formulated for increasing the efficiency of broadband quantum memory. The possibilities of experimental implementation of such memory are also discussed.

  3. Increasing the density of modes in an optical frequency comb by cascaded four-wave mixing in a nonlinear optical fiber (United States)

    Karki, Khadga J.


    Here, it is shown that when two optical frequency combs with identical mode spacing but different offset frequencies copropagate through a nonlinear optical fiber, four-wave mixing between them generates new modes. Although the spacings between the new modes depend on the difference of the offset frequencies, they appear irregular because of the large number of possible four-wave-mixing processes. However, when the difference in the offset frequencies is an integer fraction of the mode spacing of the original combs, the cascaded four-wave mixing generates a new comb with a fixed mode spacing given by the difference in the offset frequencies. This process can be used to substantially increase the mode density of a frequency comb. The method can be used in conjunction with new sources of frequency combs, such as quantum cascade lasers and microresonators, which have large mode spacing of tens of GHz. Decreasing the mode spacing of such sources is likely to increase their applicability.

  4. Broadband Enhancement of Optical Frequency Comb Using Cascaded Four-Wave Mixing in Photonic Crystal Fiber

    Directory of Open Access Journals (Sweden)

    Tawfig Eltaif


    Full Text Available A cascaded intensity modulator (IM and phase modulator (PM are used to modulate a continuous-wave (CW laser and generate an optical frequency comb (OFC. Thus, the generated comb is utilized as an initial seed and combined with another CW-laser to generate four-wave mixing (FWM in photonic crystal fiber (PCF. Results show that an initial flat 30 GHz OFC of 29, 55 lines within power fluctuation of 0.8 dB and 2 dB, respectively, can be achieved by setting the ratio of the DC bias to amplitude of sinusoidal signal at 0.1 and setting the modulation indices of both IM and PM at 10. Moreover, the 1st order of FWM created through 14 m of PCF has over 68 and 94 lines with fluctuation of 0.8 dB and 2 dB, respectively. Hence, the generated wavelengths of 1st left and right order of FWM can be tuned in a range from ~1500 nm to ~1525 nm and ~1590 nm to ~1604 nm, respectively.

  5. Coherence properties of a 2.6-7.5  μm frequency comb produced as a subharmonic of a Tm-fiber laser. (United States)

    Smolski, V O; Yang, H; Gorelov, S D; Schunemann, P G; Vodopyanov, K L


    We study the temporal coherence of an ultrabroadband frequency comb produced in a degenerate GaAs optical parametric oscillator (OPO) pumped by a stabilized Tm-fiber comb, by observing multiheterodyne beats in the RF domain. We infer that in such a regime the OPO automatically produces a stable frequency comb that is phase and frequency locked to the pump. By varying intracavity dispersion, we achieve a comb spanning 2.6-7.5 μm at a -20  dB level. Low pump threshold (down to 7 mW), high average power (up to 73 mW), broad spectral coverage, flat spectrum, and high coherence make this comb a source suitable for various applications, foremost dual-comb molecular spectroscopy.

  6. Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators (United States)

    Nagarjun, K. P.; Selvaraja, Shankar Kumar; Supradeepa, V. R.


    High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

  7. Development of compact and ultra-high-resolution spectrograph with multi-GHz optical frequency comb (United States)

    Endo, Mamoru; Sukegawa, Takashi; Silva, Alissa; Kobayashi, Yohei


    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.

  8. Wired/wireless access integrated RoF-PON with scalable generation of multi-frequency MMWs enabled by tunable optical frequency comb. (United States)

    Xiang, Yu; Jiang, Ning; Chen, Chen; Zhang, Chongfu; Qiu, Kun


    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.

  9. Spectroscopic near-field microscopy using frequency combs in the mid-infrared. (United States)

    Brehm, Markus; Schliesser, Albert; Keilmann, Fritz


    We introduce a new concept of spectroscopic near-field optical microscopy that records broad infrared spectra at each pixel during scanning. Two coherent beams with harmonic frequency-comb spectra are employed, one for illuminating the scanning tip, the other as reference for multi-heterodyne detection of the scattered light. Our implementation yields 200 cm(-1) wide amplitude and phase spectra centered at 950 cm(-1) (this band can be tuned between 700 and 1400 cm(-1)). We introduce a new technique of background suppression enabled by the short, 10 mus "snapshot" acquisition of infrared spectra which allows time-resolving the tapping motion. Thus we demonstrate broad-band mid-infrared near-field imaging that is essentially free of background artefacts.

  10. Broadband cavity-enhanced molecular spectra from Vernier filtering of a complete frequency comb. (United States)

    Rutkowski, Lucile; Morville, Jérôme


    We present a new approach to cavity enhanced-direct frequency comb spectroscopy where the full emission bandwidth of a titanium:sapphire laser is exploited, currently at gigahertz resolution. The technique is based on low-resolution Vernier filtering obtained with an appreciable actively stabilized mismatch between the cavity-free spectral range and the laser repetition rate, using a diffraction grating and a split-photodiode. Spectra covering 1300  cm⁻¹ (40 THz) are acquired in less than 100 ms, and a baseline noise of 1.7×10⁻⁸ cm⁻¹ is reached with a cavity finesse of only 300, providing an absorption figure of merit M=6×10⁻¹¹ cm⁻¹·Hz(-1/2).

  11. 42 nm wide coherent frequency comb generated by a QW based integrated passively mode-locked laser

    NARCIS (Netherlands)

    Moskalenko, Valentina; Williams, Kevin; Koelemeij, Jeroen; Bente, Erwin


    An experimental study of an InP extended cavity passively mode-locked ring laser which shows extra wide frequency comb generation is presented. An increase of the bandwidth to over 40nm at-20dB level is observed. Confirmation of the coherence and measurements of the relative time delay across the

  12. High-power, hybrid Er:fiber/Tm:fiber frequency comb source in the 2 {\\mu}m wavelength region


    Adler, Florian; Diddams, Scott A.


    We present a 2-\\mum frequency comb based on a reliable mode-locked Er:fiber laser with 100 MHz repetition rate. After shifting the spectrum of the amplified Er:fiber comb to longer wavelengths, a single-clad Tm/Ho:fiber is used as a self-pumped pre-amplifier to generate a coherent and broadband spectrum centered at 1.93 \\mum. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 \\mum. After compression in a compact grating compressor, ...

  13. High-power, hybrid Er:fiber/Tm:fiber frequency comb source in the 2 μm wavelength region. (United States)

    Adler, Florian; Diddams, Scott A


    We present a 2 μm frequency comb based on a reliable mode-locked Er:fiber laser with 100 MHz repetition rate. After shifting the spectrum of the amplified Er:fiber comb to longer wavelengths, a single-clad Tm/Ho:fiber is used as a self-pumped pre-amplifier to generate a coherent and broadband spectrum centered at 1.93 μm. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 μm. After compression in a compact grating compressor, our amplified Er:fiber/Tm:fiber hybrid system delivers as much as 2.9 W with a pulse duration of 141 fs. The system's comb properties are examined via heterodyne measurement.

  14. Frequency-comb-assisted precision laser spectroscopy of CHF{sub 3} around 8.6 μm

    Energy Technology Data Exchange (ETDEWEB)

    Gambetta, Alessio; Coluccelli, Nicola; Cassinerio, Marco; Fernandez, Toney Teddy; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca, E-mail: [Dipartimento di Fisica - Politecnico di Milano and Istituto di Fotonica e Nanotecnologie - CNR, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Castrillo, Antonio; Fasci, Eugenio; Gianfrani, Livio [Dipartimento di Matematica e Fisica - Seconda Università di Napoli, Viale Lincoln 5, 81100 Caserta (Italy); Ceausu-Velcescu, Adina [Laboratoire de Mathématiques et Physique, Université de Perpignan, Via Domitia EA 4217, F-66860 Perpignan (France); Santamaria, Luigi; Di Sarno, Valentina [CNR-INO, Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, NA (Italy); Maddaloni, Pasquale [CNR-INO, Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, NA (Italy); INFN, Istituto Nazionale di Fisica Nucleare, Sez. Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, FI (Italy); De Natale, Paolo [INFN, Istituto Nazionale di Fisica Nucleare, Sez. Firenze, Via G. Sansone 1, 50019 Sesto Fiorentino, FI (Italy); CNR-INO, Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze (Italy)


    We report a high-precision spectroscopic study of room-temperature trifluoromethane around 8.6 μm, using a CW quantum cascade laser phase-locked to a mid-infrared optical frequency comb. This latter is generated by a nonlinear down-conversion process starting from a dual-branch Er:fiber laser and is stabilized against a GPS-disciplined rubidium clock. By tuning the comb repetition frequency, several transitions falling in the υ{sub 5} vibrational band are recorded with a frequency resolution of 20 kHz. Due to the very dense spectra, a special multiple-line fitting code, involving a Voigt profile, is developed for data analysis. The combination of the adopted experimental approach and survey procedure leads to fractional accuracy levels in the determination of line center frequencies, down to 2 × 10{sup −10}. Line intensity factors, pressure broadening, and shifting parameters are also provided.

  15. Generation and Photonic Guidance of Multi-Octave Optical-Frequency Combs

    DEFF Research Database (Denmark)

    Couny, F.; Benabid, F.; Roberts, John


    Ultrabroad coherent comb-like optical spectra spanning several octaves are a chief ingredient in the emerging field of attoscience. We demonstrate generation and guidance of a three-octave spectral comb, spanning wavelengths from 325 to 2300 nanometers, in a hydrogen-filled hollow-core photonic c...

  16. Analysis of the feed-forward method for the referencing of a CW laser to a frequency comb. (United States)

    Gatti, D; Sala, T; Gambetta, A; Coluccelli, N; Conti, G Nunzi; Galzerano, G; Laporta, P; Marangoni, M


    We report on a comprehensive theoretical and experimental analysis of the feed-forward method for external frequency stabilization of a continuous wave laser against a frequency comb. Application of the method to a distributed feedback diode laser at 1.55 μm allows line narrowing from 800 to 10 kHz, with frequency noise reduction by more than 2 decades up to a Fourier frequency of 100 kHz and a maximum control bandwidth of 0.8 MHz. The results are consistent with a relative phase fluctuation of 1.4 rad rms, as limited by uncompensated high-frequency noise of the slave laser.

  17. Comparison of astrophysical laser frequency combs with respect to the requirements of HIRES (United States)

    Charsley, Jake M.; McCracken, Richard A.; Reid, Derryck T.; Kowzan, Grzegorz; Maslowski, Piotr; Reiners, Ansgar; Huke, Philipp


    Precise astronomical spectroscopy with the forthcoming E-ELT and its high resolution spectrograph HIRES will address a number of important science cases,1 e.g. detection of atmospheres of exoplanets. Challenging technical requirements have been identified to achieve these cases, principal among which is the goal to achieve a radial velocity precision on the order of 10 cms-1. HIRES will experience systematic errors like intrapixel variations and random variations like fiber noise, caused by the non-uniform illumination of the coupling fibers, with these and other systematic errors affecting the performance of the spectrograph. Here, we describe the requirements for the calibration sources which may be used for mitigating such systematic errors in HIRES. Precise wavelength calibration with wide-mode-spacing laser frequency combs (LFCs), so called astrocombs, has been demonstrated with different astronomical spectrographs. Here we present a comparison of currently used astrocombs and outline a possible solution to meet the requirements of HIRES with a single broadband astrocomb.

  18. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy (United States)

    Rutkowski, Lucile; Morville, Jérôme


    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique which allows us to record broadband spectra at high sensitivity and GHz resolution (Rutkowski and Morville, 2014) [1]. We discuss here the effect of Vernier filtering on the observed lineshapes in the 3 ν + δ band of water vapor and the entire A-band of oxygen around 800 nm in ambient air. We derive expressions for the absorption profiles resulting from the continuous Vernier filtering method, testing them on spectra covering more than 2000 cm-1 around 12,500 cm-1. With 31,300 independent spectral elements acquired at the second time scale, an absorption baseline noise of 2 ×10-8cm-1 is obtained, providing a figure of merit of 1.1×10-10 cm-1/√{ Hz } per spectral element with a cavity finesse of 3000 and a cavity round-trip length around 3.3 m.

  19. 18-THz-wide optical frequency comb emitted from monolithic passively mode-locked semiconductor quantum-well laser (United States)

    Lo, Mu-Chieh; Guzmán, Robinson; Ali, Muhsin; Santos, Rui; Augustin, Luc; Carpintero, Guillermo


    We report on an optical frequency comb with 14nm (~1.8 THz) spectral bandwidth at -3 dB level that is generated using a passively mode-locked quantum-well (QW) laser in photonic integrated circuits (PICs) fabricated through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by on-chip reflectors incorporating intracavity phase modulators followed by an extra-cavity SOA as booster amplifier. A 1.8-THz-wide optical comb spectrum is presented with ultrafast pulse that is 0.35-ps-wide. The radio frequency beat note has a 3-dB linewidth of 450 kHz and 35-dB SNR.

  20. Coupled Lugiato-Lefever equation for nonlinear frequency comb generation at an avoided crossing of a microresonator (United States)

    D'Aguanno, Giuseppe; Menyuk, Curtis R.


    Guided-mode coupling in a microresonator generally manifests itself through avoided crossings of the corresponding resonances. This coupling can strongly modify the resonator local effective dispersion by creating two branches that have dispersions of opposite sign in spectral regions that would otherwise be characterized by either positive (normal) or negative (anomalous) dispersion. In this paper, we study, both analytically and computationally, the general properties of nonlinear frequency comb generation at an avoided crossing using the coupled Lugiato-Lefever equation. In particular, we find that bright solitons and broadband frequency combs can be excited when both branches are pumped for a suitable choice of the pump powers and the detuning parameters. A deterministic path for soliton generation is found. Contribution to the Topical Issue "Theory and applications of the Lugiato-Lefever Equation", edited by Yanne K. Chembo, Damia Gomila, Mustapha Tlidi, Curtis R. Menyuk.

  1. Soliton breathing induced by stimulated Raman scattering and self-steepening in octave-spanning Kerr frequency comb generation. (United States)

    Bao, Chengying; Zhang, Lin; Kimerling, Lionel C; Michel, Jurgen; Yang, Changxi


    We investigate the impact of stimulated Raman scattering (SRS) and self-steepening (SS) on breather soliton dynamics in octave-spanning Kerr frequency comb generation. SRS and SS can transform chaotic fluctuations in cavity solitons into periodic breathing. Furthermore, with SRS and SS considered, bandwidth of the soliton breathes more than two times stronger. The simultaneous presence of SRS and SS also make the soliton breathe slower and degrades the coherence of the soliton.

  2. Grism-based pulse shaper for line-by-line control of more than 600 optical frequency comb lines. (United States)

    Kirchner, M S; Diddams, S A


    We construct a line-by-line pulse shaper using a grism (grating plus prism) dispersive element, which provides constant angular dispersion over 13.4 THz centered at ~311 THz (965 nm). When combined with a dual-mask liquid crystal modulator, this grism-based shaper is capable of line-by-line amplitude and phase control of over 600 modes of a 21 GHz stabilized optical frequency comb.

  3. Theoretical study of collinear optical frequency comb generation under multi-wave, transient stimulated Raman scattering in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Smetanin, S N [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)


    Using mathematical modelling we have studied the conditions of low-threshold collinear optical frequency comb generation under transient (picosecond) stimulated Raman scattering (SRS) and parametric four-wave coupling of SRS components in crystals. It is shown that Raman-parametric generation of an octave-spanning optical frequency comb occurs most effectively under intermediate, transient SRS at a pump pulse duration exceeding the dephasing time by five-to-twenty times. We have found the optimal values of not only the laser pump pulse duration, but also of the Raman crystal lengths corresponding to highly efficient generation of an optical frequency comb from the second anti-Stokes to the fourth Stokes Raman components. For the KGd(WO{sub 4}){sub 2} (high dispersion) and Ba(NO{sub 3}){sub 2} (low dispersion) crystals pumped at a wavelength of 1.064 μm and a pulse duration five or more times greater than the dephasing time, the optimum length of the crystal was 0.3 and 0.6 cm, respectively, which is consistent with the condition of the most effective Stokes – anti-Stokes coupling ΔkL ≈ 15, where Δk is the wave detuning from phase matching of Stokes – anti-Stokes coupling, determined by the refractive index dispersion of the SRS medium. (nonlinear optical phenomena)

  4. Nuclear charge radii of light isotopes based on frequency comb measurements

    Energy Technology Data Exchange (ETDEWEB)

    Zakova, Monika


    Optical frequency comb technology has been used in this work for the first time to investigate the nuclear structure of light radioactive isotopes. Therefore, three laser systems were stabilized with different techniques to accurately known optical frequencies and used in two specialized experiments. Absolute transition frequency measurements of lithium and beryllium isotopes were performed with accuracy on the order of 10{sup -10}. Such a high accuracy is required for the light elements since the nuclear volume effect has only a 10{sup -9} contribution to the total transition frequency. For beryllium, the isotope shift was determined with an accuracy that is sufficient to extract information about the proton distribution inside the nucleus. A Doppler-free two-photon spectroscopy on the stable lithium isotopes {sup 6,7}Li was performed in order to determine the absolute frequency of the 2S {yields} 3S transition. The achieved relative accuracy of 2 x 10{sup -10} is improved by one order of magnitude compared to previous measurements. The results provide an opportunity to determine the nuclear charge radius of the stable and short-lived isotopes in a pure optical way but this requires an improvement of the theoretical calculations by two orders of magnitude. The second experiment presented here was performed at ISOLDE/CERN, where the absolute transition frequencies of the D{sub 1} and D{sub 2} lines in beryllium ions for the isotopes {sup 7,9,10,11}Be were measured with an accuracy of about 1 MHz. Therefore, an advanced collinear laser spectroscopy technique involving two counter-propagating frequency-stabilized laser beams with a known absolute frequency was developed. The extracted isotope shifts were combined with recent accurate mass shift calculations and the root-mean square nuclear charge radii of {sup 7,10}Be and the one-neutron halo nucleus {sup 11}Be were determined. Obtained charge radii are decreasing from {sup 7}Be to {sup 10}Be and increasing again for

  5. Atomic frequency standard relativistic Doppler shift experiment (United States)

    Peters, H. E.; Reinhardt, V. S.


    An experiment has been performed to measure possible space anisotropy as it would effect the frequency of a cesium atomic beam standard clock in a laboratory on earth due to motion relative to external coordinate frames. The cesium frequency was measured as a function of orientation with respect to an atomic hydrogen maser standard. Over a period of 34 days 101 measurements were made. The results are consistent with a conclusion that no general orientation dependance attributable to spacial anisotropy was observed. It is shown that both the airplane clock results, and the null results for the atomic beam clock, are consistent with Einstein general or special relativity, or with the Lorentz transformations alone.

  6. Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-modelocked 1.5-µm solid-state laser. (United States)

    Schilt, Stephane; Bucalovic, Nikola; Dolgovskiy, Vladimir; Schori, Christian; Stumpf, Max C; Di Domenico, Gianni; Pekarek, Selina; Oehler, Andreas E H; Südmeyer, Thomas; Keller, Ursula; Thomann, Pierre


    We report the first full stabilization of an optical frequency comb generated from a femtosecond diode-pumped solid-state laser (DPSSL) operating in the 1.5-μm spectral region. The stability of the comb is characterized in free-running and in phase-locked operation by measuring the noise properties of the carrier-envelope offset (CEO) beat, of the repetition rate, and of a comb line at 1558 nm. The high Q-factor of the semiconductor saturable absorber mirror (SESAM)-modelocked 1.5-µm DPSSL results in a low-noise CEO-beat, for which a tight phase lock can be much more easily realized than for a fiber comb. Using a moderate feedback bandwidth of only 5.5 kHz, we achieved a residual integrated phase noise of 0.72 rad rms for the locked CEO, which is one of the smallest values reported for a frequency comb system operating in this spectral region. The fractional frequency stability of the CEO-beat is 20‑fold better than measured in a standard self-referenced commercial fiber comb system and contributes only 10(-15) to the optical carrier frequency instability at 1 s averaging time. © 2011 Optical Society of America

  7. Optical frequency comb generator based on a monolithically integrated passive mode-locked ring laser with a Mach-Zehnder interferometer. (United States)

    Corral, V; Guzmán, R; Gordón, C; Leijtens, X J M; Carpintero, G


    We report the demonstration of an optical-frequency comb generator based on a monolithically integrated ring laser fabricated in a multiproject wafer run in an active/passive integration process in a generic foundry using standardized building blocks. The device is based on a passive mode-locked ring laser architecture, which includes a Mach-Zehnder interferometer to flatten the spectral shape of the comb output. This structure allows monolithic integration with other optical components, such as optical filters for wavelength selection, or dual wavelength lasers for their stabilization. The results show a -10  dB span of the optical comb of 8.7 nm (1.08 THz), with comb spacing of 10.16 GHz. We also obtain a flatness of 44 lines within a 1.8 dB power variation.

  8. Optical frequency comb generation for DWDM transmission over 25- to 50-km standard single-mode fiber (United States)

    Ullah, Rahat; Bo, Liu; Yaya, Mao; Ullah, Sibghat; Khan, Muhammad Saad; Tian, Feng; Ali, Amjad; Ahmad, Ibrar; Xiangjun, Xin


    Dense wavelength division multiplexed (DWDM) transmission equal to 1.2 Tbps over 25 to 50 km across standard single-mode fiber (SSMF) in the C band is performed based on an optical frequency comb generator. Sixty-one flattened optical frequency tones were realized with 30-GHz frequency spacing, high side-mode suppression ratio over 35 dB, and minimum amplitude difference was realized using amplitude modulator for first time in cascade mode with two Mach-Zehnder modulators (MZMs) where all the modulators were tailored by RF signals. 20×61 Gbps DWDM-based differential quadrature phase shift keying modulated signals were successfully transmitted over SSMF and analyze its transmission capability for range of 25 to 50 km with acceptable power penalties and bit error rates.

  9. Quasi-supercontinuum source in the extreme ultraviolet using multiple frequency combs from high-harmonic generation. (United States)

    Wünsche, Martin; Fuchs, Silvio; Aull, Stefan; Nathanael, Jan; Möller, Max; Rödel, Christian; Paulus, Gerhard G


    A quasi-supercontinuum source in the extreme ultraviolet (XUV) is demonstrated using a table-top femtosecond laser and a tunable optical parametric amplifier (OPA) as a driver for high-harmonic generation (HHG). The harmonic radiation, which is usually a comb of odd multiples of the fundamental frequency, is generated by near-infrared (NIR) laser pulses from the OPA. A quasi-continuous XUV spectrum in the range of 30 to 100 eV is realized by averaging over multiple harmonic comb spectra with slightly different fundamental frequencies and thus different spectral spacing between the individual harmonics. The driving laser wavelength is swept automatically during an averaging time period. With a total photon flux of 4×109 photons/s in the range of 30 eV to 100 eV and 1×107photons/s in the range of 100 eV to 200 eV, the resulting quasi-supercontinuum XUV source is suited for applications such as XUV coherence tomography (XCT) or near-edge absorption fine structure spectroscopy (NEXAFS).

  10. Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

    Directory of Open Access Journals (Sweden)

    Martin Čížek


    Full Text Available A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. A stabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more with the relative stability better than 1.6 × 10−11.

  11. Single-Source AlGaAs Frequency Comb Transmitter for 661 Tbit/s Data Transmission in a 30-core Fiber

    DEFF Research Database (Denmark)

    Hu, Hao; Da Ros, Francesco; Ye, Feihong


    We demonstrate an AlGaAs-on-insulator nano-waveguide-based frequency comb with high OSNR enabling a single-source to fully load a 9.6-km heterogeneous 30-core fibre with 661 Tbit/s data achieved by 30xcores, 80xWDM, 40 Gbaud, and PDM-16QAM......We demonstrate an AlGaAs-on-insulator nano-waveguide-based frequency comb with high OSNR enabling a single-source to fully load a 9.6-km heterogeneous 30-core fibre with 661 Tbit/s data achieved by 30xcores, 80xWDM, 40 Gbaud, and PDM-16QAM...

  12. 10 GHz frequency comb spectral broadening in AlGaAs-on-Insulator nano-waveguide with ultra-low pump power

    DEFF Research Database (Denmark)

    Hu, Hao; Pu, Minhao; Yvind, Kresten


    We experimentally demonstrated 10 GHz frequency comb spectral broadening with a 30-dB bandwidth of 238 nm in an 11-mm long AlGaAsOI nano-waveguide. The 10-GHz 230-fs pump pulse has an average power of only 12 mW.......We experimentally demonstrated 10 GHz frequency comb spectral broadening with a 30-dB bandwidth of 238 nm in an 11-mm long AlGaAsOI nano-waveguide. The 10-GHz 230-fs pump pulse has an average power of only 12 mW....

  13. Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-5.4  μm. (United States)

    Khodabakhsh, Amir; Ramaiah-Badarla, Venkata; Rutkowski, Lucile; Johansson, Alexandra C; Lee, Kevin F; Jiang, Jie; Mohr, Christian; Fermann, Martin E; Foltynowicz, Aleksandra


    We present a versatile mid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 μm range and two detection methods: a Fourier transform spectrometer (FTS) and a continuous-filtering Vernier spectrometer (CF-VS). Using the FTS with a multipass cell, we measure high precision broadband absorption spectra of CH4 at 3.3 μm and NO at 5.25 μm, the latter for the first time with comb spectroscopy, and we detect atmospheric species (CH4, CO, CO2, and H2O) in air in the signal and idler ranges. Multiline fitting yields minimum detectable concentrations of 10-20  ppb Hz-1/2 for CH4, NO, and CO. For the first time in the mid-infrared, we perform CF-VS using an enhancement cavity, a grating, and a single detector, and we measure the absorption spectrum of CH4 and H2O in ambient air at ∼3.3  μm, reaching a 40 ppb concentration detection limit for CH4 in 2 ms.

  14. Application of Optical Frequency Comb in High-Capacity Long Distance Optical Communication for China-Pakistan Economic Corridor (United States)

    Latif, Zahid; Jianqiu, Zeng; Ullah, Rahat; Pathan, Zulfiqar Hussain; Latif, Shahid


    The current study examines the fiber optic connectivity from Chinese boundary to Rawalpindi and proposes a novel technique for carrying large capacity triple play services across China Pakistan economic corridor (CPEC). With the help of this technique, various wavelength data services can be extended to Pakistan, which can decrease the low bandwidth, poor connectivity and low speed problems of data transfer in Pakistan. This study contributes toward the existing literature in a way that this novel technique of data transmission not only relaxes the laying of fiber optic cable but also reduces the total cost of the project. The proposed technique proposes the deployment of optical frequency comb technique for 820 km CPEC route which could support 4 Tbps data. From the perspective of time energy consumption, the assessment suggests that the laying of fiber optic cable in CPEC is feasible with the existing route at the lowest cost between the two sovereign countries.

  15. Sub-picosecond pulse and terahertz optical frequency comb generation by monolithically integrated linear mode-locked laser (United States)

    Lo, Mu-Chieh; Guzmán, Robinson; Ali, Muhsin; Santos, Rui; Augustin, Luc; Carpintero, Guillermo


    We report on a record broad 3-dB bandwidth of 14 nm ( 1.8 THz around 1532 nm) optical frequency comb generated from a passively mode-locked quantum-well (QW) laser in the form of photonic integrated circuits through an InP generic photonic integration technology platform. This 21.5-GHz colliding-pulse mode-locked laser cavity is defined by two on-chip reflectors incorporating intracavity phase modulators followed by an out-of-cavity SOA as booster. Under certain operating conditions, an ultra-wide spectral bandwidth is achieved along with an autocorrelation trace confirming the mode locking nature exhibiting a pulse width of 0.35 ps. The beat note RF spectrum has a linewidth of sub-MHz and 35-dB SNR.

  16. Measurement of frequency sweep nonlinearity using atomic absorption spectroscopy (United States)

    Song, Ningfang; Lu, Xiangxiang; Xu, Xiaobin; Pan, Xiong; Li, Wei; Hu, Di; Liu, Jixun


    A novel scheme to determine frequency sweep nonlinearity using atomic saturated absorption spectroscopy is proposed and demonstrated. The frequency modulation rate is determined by directly measuring the interference fringe number and the frequency gap between two atomic transition peaks of rubidium atom. An experimental setup is established, and test results show that the frequency sweep nonlinearity is ∼10%, with an average frequency modulation rate of ∼1.12 THz/s. Moreover, the absolute optical frequency and optical path difference between two laser beams are simultaneously determined with this method. This low-cost technique can be used for optical frequency sweep nonlinearity correction and real-time frequency monitor.

  17. Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs (United States)

    Caspani, Lucia; Reimer, Christian; Kues, Michael; Roztocki, Piotr; Clerici, Matteo; Wetzel, Benjamin; Jestin, Yoann; Ferrera, Marcello; Peccianti, Marco; Pasquazi, Alessia; Razzari, Luca; Little, Brent E.; Chu, Sai T.; Moss, David J.; Morandotti, Roberto


    Recent developments in quantum photonics have initiated the process of bringing photonic-quantumbased systems out-of-the-lab and into real-world applications. As an example, devices to enable the exchange of a cryptographic key secured by the laws of quantum mechanics are already commercially available. In order to further boost this process, the next step is to transfer the results achieved by means of bulky and expensive setups into miniaturized and affordable devices. Integrated quantum photonics is exactly addressing this issue. In this paper, we briefly review the most recent advancements in the generation of quantum states of light on-chip. In particular, we focus on optical microcavities, as they can offer a solution to the problem of low efficiency that is characteristic of the materials typically used in integrated platforms. In addition, we show that specifically designed microcavities can also offer further advantages, such as compatibility with telecom standards (for exploiting existing fibre networks) and quantum memories (necessary to extend the communication distance), as well as giving a longitudinal multimode character for larger information transfer and processing. This last property (i.e., the increased dimensionality of the photon quantum state) is achieved through the ability to generate multiple photon pairs on a frequency comb, corresponding to the microcavity resonances. Further achievements include the possibility of fully exploiting the polarization degree of freedom, even for integrated devices. These results pave the way for the generation of integrated quantum frequency combs that, in turn, may find important applications toward the realization of a compact quantum-computing platform.

  18. Comparison of Monolithic Optical Frequency Comb Generators Based on Passively Mode-Locked Lasers for Continuous Wave mm-Wave and Sub-THz Generation

    DEFF Research Database (Denmark)

    Criado, A. R.; de Dios, C.; Acedo, P.


    In this paper, two different Passive Mode-Locked Laser Diodes (PMLLD) structures, a Fabry–Perot cavity and a ring cavity laser are characterized and evaluated as monolithic Optical Frequency Comb Generators (OFCG) for CW sub-THz generation. An extensive characterization of the devices under study...

  19. On the dispersion management of fluorite whispering-gallery mode resonators for Kerr optical frequency comb generation in the telecom and mid-infrared range. (United States)

    Lin, Guoping; Chembo, Yanne K


    Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above 109. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion (GVD). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the GVD of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar GVD, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to push the zero-dispersion wavelength of fluorite crystals towards the mid-infrared (mid-IR) range, thereby allowing for efficient Kerr comb generation in that spectral range. We show that barium fluoride is the most interesting crystal in this regard, due to its zero dispersion wavelength (ZDW) at 1.93 μm and an optimal dispersion profile in the mid-IR regime. We expect our results to facilitate the design of different platforms for Kerr frequency comb generations in both telecommunication and mid-IR spectral ranges.

  20. Frequency-comb based collinear laser spectroscopy of Be for nuclear structure investigations and many-body QED tests

    CERN Document Server

    Krieger, A; Geppert, Ch; Blaum, K; Bissell, M L; Frömmgen, N; Hammen, M; Kreim, K; Kowalska, M; Krämer, J; Neugart, R; Neyens, G; Sánchez, R; Tiedemann, D; Yordanov, D T; Zakova, M


    Absolute transition frequencies of the $2s\\,^2{\\rm{S}}_{1/2}$ $\\rightarrow$ $2p\\,^2{\\rm{P}}_{1/2,3/2}$ transitions in Be$^+$ were measured with a frequency comb in stable and short-lived isotopes at ISOLDE (CERN) using collinear laser spectroscopy. Quasi-simultaneous measurements in copropagating and counterpropagating geometry were performed to become independent from acceleration voltage determinations for Doppler-shift corrections of the fast ion beam. Isotope shifts and fine structure splittings were obtained from the absolute transition frequencies with accuracies better than 1\\,MHz and led to a precise determination of the nuclear charge radii of $^{7,10-12}$Be relative to the stable isotope $^9$Be. Moreover, an accurate determination of the $2p$ fine structure splitting allowed a test of high-precision bound-state QED calculations in the three-electron system. Here, we describe the laser spectroscopic method in detail, including several tests that were carried out to determine or estimate systematic un...

  1. Phase locking of a mode-locked titanium-sapphire laser-based optical frequency comb to a reference laser using a fast piezoelectric actuator. (United States)

    Hatanaka, Shuhei; Sugiyama, Kazuhiko; Mitaki, Masatoshi; Misono, Masatoshi; Slyusarev, Sergey N; Kitano, Masao


    We phase lock an octave-spanning optical frequency comb, generated using a mode-locked titanium-sapphire laser and a photonic-crystal fiber, to a continuous-wave laser line-narrowed to a reference cavity. To phase lock the pulse-repetition frequency, the cavity length of the mode-locked laser is controlled by using a fast piezoelectric-actuated mirror of a servo bandwidth up to 80 kHz. The residual phase noise is 0.35 rad, and 89% of the power is concentrated to the carrier. To apply the system to optical frequency-ratio measurements and to evaluate the phase locking, a simultaneous frequency measurement of the beat between the other mode of the comb and another laser line-narrowed to a different resonance of the common reference cavity is demonstrated.

  2. Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers (United States)

    Waxman, Eleanor M.; Cossel, Kevin C.; Truong, Gar-Wing; Giorgetta, Fabrizio R.; Swann, William C.; Coburn, Sean; Wright, Robert J.; Rieker, Gregory B.; Coddington, Ian; Newbury, Nathan R.


    We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm-1 (1568 to 1660 nm), corresponding to a 355 cm-1 bandwidth, at 0.0067 cm-1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10-4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO2), methane (CH4), water (H2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO2, 0.35 % (7 ppb) for CH4, and 0.40 % (36 ppm) for H2O at ˜ 30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down point sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4.

  3. Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

    Directory of Open Access Journals (Sweden)

    E. M. Waxman


    Full Text Available We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm−1 (1568 to 1660 nm, corresponding to a 355 cm−1 bandwidth, at 0.0067 cm−1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10−4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO2, methane (CH4, water (H2O, and deuterated water (HDO. The retrieved dry mole fractions agree to 0.14 % (0.57 ppm for CO2, 0.35 % (7 ppb for CH4, and 0.40 % (36 ppm for H2O at  ∼  30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO-calibrated cavity ring-down point sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4.

  4. Ultra-low phase-noise microwave generation using a diode-pumped solid-state laser based frequency comb and a polarization-maintaining pulse interleaver

    CERN Document Server

    Portuondo-Campa, Erwin; Kundermann, Stefan; Balet, Laurent; Lecomte, Steve


    We report ultra-low phase-noise microwave generation at a 9.6 GHz carrier frequency from optical frequency combs based on diode-pumped solid-state lasers emitting at telecom wavelength and referenced to a common cavity-stabilized continuous-wave laser. Using a novel fibered polarization-maintaining pulse interleaver, a single-oscillator phase-noise floor of -171 dBc/Hz has been measured with commercial PIN InGaAs photodiodes, constituting a record for this type of detector. Also, a direct optical measurement of the stabilized frequency combs timing jitter was performed using a balanced optical cross correlator, allowing for an identification of the origin of the current phase-noise limitations in the system.

  5. Edward A. Bouchet Award Talk: Ultrafast Coherent Optical Signal Processing using Stabilized Optical Frequency Combs from Mode-locked Semiconductor Diode Lasers (United States)

    Delfyett, Peter


    The development of high speed communications, interconnects and signal processing are critical for an information based economy. Lightwave technologies offer the promise of high bandwidth connectivity from component development that is manufacturable, cost effective, and electrically efficient. The concept of optical frequency/wavelength division multiplexing has revolutionized methods of optical communications, however the development of optical systems using 100's of wavelengths present challenges for network planners. The development of compact, efficient optical sources capable of generating a multiplicity of optical frequencies/wavelength channels from a single device could potentially simplify the operation and management of high capacity optical interconnects and links. Over the years, we have been developing mode-locked semiconductor lasers to emit ultrashort optical pulses at high pulse repetition frequencies for a wide variety of applications, but geared toward optical communications using time division multiplexed optical links. The periodic nature of optical pulse generation from mode-locked semiconductor diode lasers also make these devices ideal candidates for the generation of high quality optical frequency combs, or multiple wavelengths, in addition to the temporally stable, high peak intensity optical pulses that one is accustomed to. The optical frequency combs enables a variety of optical communication and signal processing applications that can exploit the large bandwidth and speed that femtosecond pulse generation implies, however the aggregate speed and bandwidth can be achieved by spectrally channelizing the bandwidth, and utilize lower speed electronics for control of the individual spectral components of the mode-locked laser. This presentation will highlight our recent results in the generation of stabilized frequency combs, and in developing approaches for filtering, modulating and detecting individual comb components. We then show how

  6. Ultracold atoms in multiple radio-frequency dressed adiabatic potentials (United States)

    Harte, T. L.; Bentine, E.; Luksch, K.; Barker, A. J.; Trypogeorgos, D.; Yuen, B.; Foot, C. J.


    We present the first experimental demonstration of a multiple radio-frequency dressed potential for the configurable magnetic confinement of ultracold atoms. We load cold 87Rb atoms into a double-well potential with an adjustable barrier height, formed by three radio-frequencies applied to atoms in a static quadrupole magnetic field. Our multiple radio-frequency approach gives precise control over the double-well characteristics, including the depth of individual wells and the height of the barrier, and enables reliable transfer of atoms between the available trapping geometries. We characterize the multiple radio-frequency dressed system using radio-frequency spectroscopy, finding good agreement with the eigenvalues numerically calculated using Floquet theory. This method creates trapping potentials that can be reconfigured by changing the amplitudes, polarizations, and frequencies of the applied dressing fields and easily extended with additional dressing frequencies.

  7. Local Perturbations in the (10110) and (10101) Levels of C_2H_2 from Frequency Comb-Referenced Spectroscopy (United States)

    Sears, Trevor; Twagirayezu, Sylvestre; Forthomme, Damien; Hall, Gregory; Cich, Matthew


    In work reported by Twagirayezu et al. at this meeting, the rest frequencies of more than 100 lines in the ν_4 and ν_5 hot bands in the ν_1 + ν_3 combination band of acetylene have been measured by saturation dip spectroscopy using an extended cavity diode laser locked to a frequency comb. This work was orginally directed towards providing a set of accurate frequencies for the hot band line positions to aid in modeling the lineshapes of the main lines in the band. In analyzing the results, we find that many of the upper levels in the hot band transitions suffer small, and in some cases not so small, local perturbations. These arise because of J-dependent near degeneracies between the title levels and background levels of the same symmetry, mostly derived from zero order states involving multiple quanta of bending excitation. The vibration-rotation levels at the energies in question have previously been modeled using a polyad-based Hamiltonian and the present data can be interpreted on the basis of this model, but they also provide information which can be used to refine the model, and point to terms that may have previously been neglected. The most important result is that the high precision of the measurements gives the opportunity to calibrate the effects of background levels associated with high bending quantum numbers and angular momentun states that are otherwise very difficult to access. Acknowledgments: We are most grateful to D. S Perry (U. Akron) and M. Herman (U. Libre de Bruxelles) for helpful discussions. Work at Brookhaven National Laboratory is funded by the Division of Chemical Sciences, Geosciences and Biosciences within the Offices of Basic Energy Sciences, Office of Sciences, U.S. Department of Energy under Contract Nos. DE-AC02-98CH10886 and DE-SC0012704. M. Herman and D. S. Perry, Phys. Chem. Chem. Phys., 15, 9970-9993 (2013)

  8. Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-54 μm (United States)

    Khodabakhsh, Amir; Ramaiah-Badarla, Venkata; Rutkowski, Lucile; Johansson, Alexandra C.; Lee, Kevin F.; Jiang, Jie; Mohr, Christian; Fermann, Martin E.; Foltynowicz, Aleksandra


    We present a versatile mid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 {\\mu}m range and two detection methods, a Fourier transform spectrometer (FTS) and a Vernier spectrometer. Using the FTS with a multipass cell we measure high-precision broadband absorption spectra of CH$_4$ and NO at ~3.3 {\\mu}m and ~5.2 {\\mu}m, respectively, and of atmospheric species (CH$_4$, CO, CO$_2$ and H$_2$O) in air in the signal and idler wavelength range. The figure of merit of the system is on the order of 10$^{-8}$ cm$^{-1}$ Hz$^{-1/2}$ per spectral element, and multiline fitting yields minimum detectable concentrations of 10-20 ppb Hz$^{-1/2}$ for CH$_4$, NO and CO. For the first time in the mid-infrared, we perform continuous-filtering Vernier spectroscopy using a low finesse enhancement cavity, a grating and a single detector, and measure the absorption spectrum of CH$_4$ and H$_2$O in ambient air at ~3.3 {\\mu}m.

  9. On the dispersion management of fluorite whispering-gallery mode resonators for Kerr optical frequency comb generation in the telecom and mid-infrared range

    CERN Document Server

    Lin, Guoping


    Optical whispering gallery mode (WGM) resonators have been very attracting platforms for versatile Kerr frequency comb generations. We report a systematic study on the material dispersion of various optical materials that are capable of supporting quality factors above $10^9$. Using an analytical approximation of WGM resonant frequencies in disk resonators, we investigate the effect of the geometry and transverse mode order on the total group-velocity dispersion ($GVD$). We demonstrate that the major radii and the radial mode indices play an important role in tailoring the $GVD$ of WGM resonators. In particular, our study shows that in WGM disk-resonators, the polar families of modes have very similar $GVD$, while the radial families of modes feature dispersion values that can differ by up to several orders of magnitude. The effect of these giant dispersion shifts are experimentally evidenced in Kerr comb generation with magnesium fluoride. From a more general perspective, this critical feature enables to pus...

  10. High-precision molecular interrogation by direct referencing of a quantum-cascade-laser to a near-infrared frequency comb. (United States)

    Gatti, D; Gambetta, A; Castrillo, A; Galzerano, G; Laporta, P; Gianfrani, L; Marangoni, M


    This work presents a very simple yet effective way to obtain direct referencing of a quantum-cascade-laser at 4.3 μm to a near-IR frequency-comb. Precise tuning of the comb repetition-rate allows the quantum-cascade-laser to be scanned across absorption lines of a CO2 gaseous sample and line profiles to be acquired with extreme reproducibility and accuracy. By averaging over 50 acquisitions, line-centre frequencies are retrieved with an uncertainty of 30 kHz in a linear interaction regime. The extension of this methodology to other lines and molecules, by the use of widely tunable extended-cavity quantum-cascade-lasers, paves the way to a wide availability of high-quality and traceable spectroscopic data in the most crucial region for molecular detection and interrogation.

  11. Coherent Generation of Broadband Pulsed Light in the SWIR and Mwir Using AN all Polarization-Maintaining Fiber Frequency Comb Source (United States)

    Hoogland, H.; Engelbrecht, M.; McRaven, C.; Holzwarth, R.; Thai, A.; Sánchez, D.; Cousin, S. L.; Hemmer, M.; Baudisch, M.; Zawilski, K.; Schunemann, P. G.; Biegert, J.


    We report on an all polarization-maintaining, modelocked, fiber laser system which generates coherent broadband pulses centered at 2.03 μm with a spectral FWHM bandwidth of 60 nm and 360 mW. Using this frequency comb source, we generate phase-coherent, ultra-broadband pulses centered at 6.5 μm and spanning 5.5 μm to 8 μm with DFG in CdSiP_2.

  12. Intracavity trace molecular detection with a broadband mid-IR frequency comb source

    CERN Document Server

    Haakestad, Magnus W; Leindecker, Nick; Marandi, Alireza; Vodopyanov, Konstantin L


    Ultrasensitive detection of methane, isotopic carbon dioxide, carbon monoxide, formaldehyde, acetylene and ethylene is performed in the spectral range 2.5 - 5 \\mu m using intracavity spectroscopy in broadband optical parametric oscillators (OPOs). The OPOs were operated near degeneracy and synchronously pumped either by a mode-locked erbium (1560 nm) or thulium (2050 nm) fiber laser. A large instantaneous bandwidth of up to 800 cm$^{-1}$ allows for simultaneous detection of several gases. We observe an effective path length enhancement due to coherent interaction inside the OPO cavity and achieve part-per-billion sensitivity levels. The measured spectral shapes are in good agreement with a model that takes into account group delay dispersion across the broad OPO frequency band.

  13. An atom in a multi-frequency laser emission field

    Energy Technology Data Exchange (ETDEWEB)

    Delone, N.B.; Kovarskii, V.A.; Masalov, A.V.; Perelman, N.F.


    An analysis of the features of the interaction between a nonmonochromatic multi-frequency laser emission field and an isolated atom is given. The multi-photon excitation and non-linear ionization of the atom during the excitation of the atomic levels by the laser emission field are examined. Specific cases of the interaction between the atom and the field are examined in detail: the case of a broad laser emission laser spectrum (rapid field fluctuations) and the case of a narrow spectrum (slow fluctuation). The available experimental data relating to these problems are analyzed.

  14. High-frequency multimodal atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Adrian P. Nievergelt


    Full Text Available Multifrequency atomic force microscopy imaging has been recently demonstrated as a powerful technique for quickly obtaining information about the mechanical properties of a sample. Combining this development with recent gains in imaging speed through small cantilevers holds the promise of a convenient, high-speed method for obtaining nanoscale topography as well as mechanical properties. Nevertheless, instrument bandwidth limitations on cantilever excitation and readout have restricted the ability of multifrequency techniques to fully benefit from small cantilevers. We present an approach for cantilever excitation and deflection readout with a bandwidth of 20 MHz, enabling multifrequency techniques extended beyond 2 MHz for obtaining materials contrast in liquid and air, as well as soft imaging of delicate biological samples.

  15. Resonant difference-frequency atomic force ultrasonic microscope (United States)

    Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)


    A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

  16. High-resolution quantization based on soliton self-frequency shift and spectral compression in a bi-directional comb-fiber architecture (United States)

    Zhang, Xuyan; Zhang, Zhiyao; Wang, Shubing; Liang, Dong; Li, Heping; Liu, Yong


    We propose and demonstrate an approach that can achieve high-resolution quantization by employing soliton self-frequency shift and spectral compression. Our approach is based on a bi-directional comb-fiber architecture which is composed of a Sagnac-loop-based mirror and a comb-like combination of N sections of interleaved single-mode fibers and high nonlinear fibers. The Sagnac-loop-based mirror placed at the terminal of a bus line reflects the optical pulses back to the bus line to achieve additional N-stage spectral compression, thus single-stage soliton self-frequency shift (SSFS) and (2 N - 1)-stage spectral compression are realized in the bi-directional scheme. The fiber length in the architecture is numerically optimized, and the proposed quantization scheme is evaluated by both simulation and experiment in the case of N = 2. In the experiment, a quantization resolution of 6.2 bits is obtained, which is 1.2-bit higher than that of its uni-directional counterpart.

  17. Generation of a vacuum ultraviolet to visible Raman frequency comb in H2-filled kagomé photonic crystal fiber. (United States)

    Mridha, M K; Novoa, D; Bauerschmidt, S T; Abdolvand, A; St J Russell, P


    We report on the generation of a purely vibrational Raman comb, extending from the vacuum ultraviolet (184 nm) to the visible (478 nm), in hydrogen-filled kagomé-style photonic crystal fiber pumped at 266 nm. Stimulated Raman scattering and molecular modulation processes are enhanced by higher Raman gain in the ultraviolet. Owing to the pressure-tunable normal dispersion landscape of the "fiber + gas" system in the ultraviolet, higher-order anti-Stokes bands are generated preferentially in higher-order fiber modes. The results pave the way toward tunable fiber-based sources of deep and vacuum ultraviolet light for applications in, e.g., spectroscopy and biomedicine.

  18. A bidirectional dual-comb ring laser for simple and robust dual-comb spectroscopy

    CERN Document Server

    Ideguchi, Takuro; Kobayashi, Yohei; Goda, Keisuke


    Fourier-transform spectroscopy is an indispensable tool for analyzing chemical samples in scientific research as well as chemical and pharmaceutical industries. Recently, its measurement speed, sensitivity, and precision have been shown to be significantly enhanced by using dual frequency combs. However, wide acceptance of this technique is hindered by its requirement for two frequency combs and active stabilization of the combs. Here we overcome this predicament with a Kerr-lens mode-locked bidirectional ring laser that generates two frequency combs with slightly different pulse repetition rates and a tunable yet highly stable rate difference. This peculiar lasing principle builds on a slight difference in optical cavity length between two counter-propagating lasing modes due to Kerr lensing. Since these combs are produced by the one and same laser cavity, their relative coherence stays passively stable without the need for active stabilization. To show its utility, we demonstrate broadband dual-comb spectro...

  19. Frequency-comb referenced spectroscopy of v4- and v5-excited hot bands in the 1.5 μm spectrum of C2H2 (United States)

    Twagirayezu, Sylvestre; Cich, Matthew J.; Sears, Trevor J.; McRaven, Christopher P.; Hall, Gregory E.


    Doppler-free transition frequencies for v4- and v5-excited hot bands have been measured in the v1 + v3 band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v1 + v3 band itself, is between 3 and 22 kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infrared absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100-7600 cm-1 energy region.

  20. Narrow line width frequency comb source based on an injection-locked III-V-on-silicon mode-locked laser. (United States)

    Uvin, Sarah; Keyvaninia, Shahram; Lelarge, Francois; Duan, Guang-Hua; Kuyken, Bart; Roelkens, Gunther


    In this paper, we report the optical injection locking of an L-band (∼1580 nm) 4.7 GHz III-V-on-silicon mode-locked laser with a narrow line width continuous wave (CW) source. This technique allows us to reduce the MHz optical line width of the mode-locked laser longitudinal modes down to the line width of the source used for injection locking, 50 kHz. We show that more than 50 laser lines generated by the mode-locked laser are coherent with the narrow line width CW source. Two locking techniques are explored. In a first approach a hybrid mode-locked laser is injection-locked with a CW source. In a second approach, light from a modulated CW source is injected in a passively mode-locked laser cavity. The realization of such a frequency comb on a chip enables transceivers for high spectral efficiency optical communication.

  1. Broadband mid-IR frequency comb with CdSiP2 and AgGaS2 from an Er,Tm:Ho fiber laser. (United States)

    Sánchez, D; Hemmer, M; Baudisch, M; Zawilski, K; Schunemann, P; Hoogland, H; Holzwarth, R; Biegert, J


    We report on the generation of a 2500 nm bandwidth frequency comb at 6.5 μm central wavelength based on critically phase-matched parametric down-conversion in the nonlinear crystal CdSiP(2) (CSP), driven by a compact Er,Tm:Ho fiber laser. The generated ultra-broadband pulses show a transform-limited duration of 2.3 optical cycles and carry up to 150 pJ of energy at a 100 MHz pulse repetition rate. For comparison, the spectrum generated in AgGaS(2) (AGS) spans from 6.2 to 7.4 μm at full-width at half-maximum (FWHM) with a pulse energy of 3 pJ. A full 3D nonlinear wave propagation code is used for optimization of the noncollinear angle, propagation direction, and crystal thickness.

  2. A compact echelle spectrograph for characterization of astro-combs (United States)

    Probst, Rafael A.; Steinmetz, Tilo; Wu, Yuanjie; Grupp, Frank; Udem, Thomas; Holzwarth, Ronald


    We present an echelle spectrograph that is optimized for characterization of frequency combs for astronomical applications (astro-combs). In spite of its very compact and cost-efficient design, it allows viewing the spectrum of a frequency comb in nearly the same way as a full-sized high-resolution echelle spectrograph as used at astronomical observatories. This is of great value for testing and characterizing astro-combs during their assembly phase. The spectrograph can further be utilized to effectfully demonstrate the remarkable capabilities of astro-combs.

  3. Comparing the flight activities of workers from two stocks of honey bees (Apis mellifera) raised in gamma-irradiated combs using radio-frequency identification (RFID) technology (United States)

    Gamma irradiation has been shown to inactivate pathogens (virus, American foulbrood and Nosema) that are harmful to honey bees. Preliminary data suggest that queens raised in mating nucleus colonies having gamma-irradiated combs outperformed queens from nucleus colonies not having irradiated combs. ...

  4. Frequency-Adaptive Modified Comb-Filter-Based Phase-Locked Loop for a Doubly-Fed Adjustable-Speed Pumped-Storage Hydropower Plant under Distorted Grid Conditions

    Directory of Open Access Journals (Sweden)

    Wei Luo


    Full Text Available The control system of a doubly-fed adjustable-speed pumped-storage hydropower plant needs phase-locked loops (PLLs to obtain the phase angle of grid voltage. The main drawback of a comb-filter-based phase-locked loop (CF-PLL is the slow dynamic response. This paper presents a modified comb-filter-based phase-locked loop (MCF-PLL by improving the pole-zero pattern of the comb filter, and gives the parameters’ setting method of the controller, based on the discrete model of MCF-PLL. In order to improve the disturbance resistibility of MCF-PLL when the power grid’s frequency changes, this paper proposes a frequency-adaptive modified, comb-filter-based, phase-locked loop (FAMCF-PLL and its digital implementation scheme. Experimental results show that FAMCF-PLL has good steady-state and dynamic performance under distorted grid conditions. Furthermore, FAMCF-PLL can determine the phase angle of the grid voltage, which is locked when it is applied to a doubly-fed adjustable-speed pumped-storage hydropower experimental platform.

  5. The Brazilian time and frequency atomic standards program

    Directory of Open Access Journals (Sweden)

    Mushtaq Ahmed


    Full Text Available Cesium atomic beam clocks have been the workhorse for many demanding applications in science and technology for the past four decades. Tests of the fundamental laws of physics and the search for minute changes in fundamental constants, the synchronization of telecommunication networks, and realization of the satellite-based global positioning system would not be possible without atomic clocks. The adoption of optical cooling and trapping techniques, has produced a major advance in atomic clock precision. Cold-atom fountain and compact cold-atom clocks have also been developed. Measurement precision of a few parts in 10(15 has been demonstrated for a cold-atom fountain clock. We present here an overview of the time and frequency metrology program based on cesium atoms under development at USP São Carlos. This activity consists of construction and characterization of atomic-beam, and several variations of cold-atom clocks. We discuss the basic working principles, construction, evaluation, and important applications of atomic clocks in the Brazilian program.Relógios atômicos de feixe de Césio têm sido a base para diversas aplicações em ciência e tecnologia nas últimas quatro décadas. Testes de leis fundamentais de física, buscas por mínimas variações em constantes fundamentais, sincronização de redes de telecomunicações e o funcionamento do sistema de posicionamento global, baseado em satélites de navegação, não seriam possíveis sem os relógios atômicos. A adoção de técnicas de aprisionamento e resfriamento ópticos tem permitido um grande avanço na precisão dos relógios atômicos. Chafarizes de átomos frios e relógios compactos de átomos frios também têm sido desenvolvidos. Precisões de medida de algumas partes em 1015 foram demonstradas para relógios do tipo chafariz de átomos frios. Apresentamos uma visão geral do programa de metrologia de tempo e freqüência baseado em átomos de césio, em

  6. Multispectral Fitting Validation of the Speed Dependent Voigt Profile at up to 1300K in Water Vapor with a Dual Frequency Comb Spectrometer (United States)

    Schroeder, Paul James; Cich, Matthew J.; Yang, Jinyu; Drouin, Brian; Rieker, Greg B.


    Using broadband, high resolution dual frequency comb spectroscopy, we test the power law temperature scaling relationship with Voigt, Rautian, and quadratic speed dependent Voigt profiles over a temperature range of 296-1300K for pure water vapor. The instrument covers the spectral range from 6800 cm^{-1} to 7200 cm^{-1} and samples the (101)-(000), (200)-(000), (021)-(000), (111)-(010), (210)-(010), and (031)-(010) vibrational bands of water. The data is sampled with a point spacing of 0.0033 cm^{-1} and absolute frequency accuracy of gas temperature within coal gasifiers and other high temperature systems. In order to extract water concentration and temperature, an extended range of lineshape parameters are needed. Lineshape parameters for pure and argon broadened water are obtained for 278 transitions using the multispectral fitting program Labfit, including self-broadening coefficients, power law temperature scaling exponents, and speed dependence coefficients. The extended temperature range of the data provides valuable insight into the application of the speed-dependence corrections of the line profiles, which are shown to have more reasonable line broadening temperature dependencies.

  7. Autopilot for frequency-modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri, E-mail: [Department of Physics and the Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa 32000 (Israel)


    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  8. Autopilot for frequency-modulation atomic force microscopy (United States)

    Kuchuk, Kfir; Schlesinger, Itai; Sivan, Uri


    One of the most challenging aspects of operating an atomic force microscope (AFM) is finding optimal feedback parameters. This statement applies particularly to frequency-modulation AFM (FM-AFM), which utilizes three feedback loops to control the cantilever excitation amplitude, cantilever excitation frequency, and z-piezo extension. These loops are regulated by a set of feedback parameters, tuned by the user to optimize stability, sensitivity, and noise in the imaging process. Optimization of these parameters is difficult due to the coupling between the frequency and z-piezo feedback loops by the non-linear tip-sample interaction. Four proportional-integral (PI) parameters and two lock-in parameters regulating these loops require simultaneous optimization in the presence of a varying unknown tip-sample coupling. Presently, this optimization is done manually in a tedious process of trial and error. Here, we report on the development and implementation of an algorithm that computes the control parameters automatically. The algorithm reads the unperturbed cantilever resonance frequency, its quality factor, and the z-piezo driving signal power spectral density. It analyzes the poles and zeros of the total closed loop transfer function, extracts the unknown tip-sample transfer function, and finds four PI parameters and two lock-in parameters for the frequency and z-piezo control loops that optimize the bandwidth and step response of the total system. Implementation of the algorithm in a home-built AFM shows that the calculated parameters are consistently excellent and rarely require further tweaking by the user. The new algorithm saves the precious time of experienced users, facilitates utilization of FM-AFM by casual users, and removes the main hurdle on the way to fully automated FM-AFM.

  9. Mercury Atomic Frequency Standards for Space Based Navigation and Timekeeping (United States)

    Tjoelker, R. L.; Burt, E. A.; Chung, S.; Hamell, R. L.; Prestage, J. D.; Tucker, B.; Cash, P.; Lutwak, R.


    A low power Mercury Atomic Frequency Standard (MAFS) has been developed and demonstrated on the path towards future space clock applications. A self contained mercury ion breadboard clock: emulating flight clock interfaces, steering a USO local oscillator, and consuming approx 40 Watts has been operating at JPL for more than a year. This complete, modular ion clock instrument demonstrates that key GNSS size, weight, and power (SWaP) requirements can be achieved while still maintaining short and long term performance demonstrated in previous ground ion clocks. The MAFS breadboard serves as a flexible platform for optimizing further space clock development and guides engineering model design trades towards fabrication of an ion clock for space flight.

  10. Intelligent Systems for Stabilizing Mode-Locked Lasers and Frequency Combs: Machine Learning and Equation-Free Control Paradigms for Self-Tuning Optics

    Directory of Open Access Journals (Sweden)

    Kutz J. Nathan


    Full Text Available We demonstrate that a software architecture using innovations in machine learning and adaptive control provides an ideal integration platform for self-tuning optics. For mode-locked lasers, commercially available optical telecom components can be integrated with servocontrollers to enact a training and execution software module capable of self-tuning the laser cavity even in the presence of mechanical and/or environmental perturbations, thus potentially stabilizing a frequency comb. The algorithm training stage uses an exhaustive search of parameter space to discover best regions of performance for one or more objective functions of interest. The execution stage first uses a sparse sensing procedure to recognize the parameter space before quickly moving to the near optimal solution and maintaining it using the extremum seeking control protocol. The method is robust and equationfree, thus requiring no detailed or quantitatively accurate model of the physics. It can also be executed on a broad range of problems provided only that suitable objective functions can be found and experimentally measured.

  11. Broad expansion of optical frequency combs by self-Raman scattering in coupled-cavity self-mode-locked monolithic lasers. (United States)

    Chang, M T; Huang, T L; Liang, H C; Su, K W; Chen, Y F


    Broad expansion of optical frequency comb (OFC) by the self-Raman scattering is numerically analyzed and experimentally accomplished in a coupled-cavity self-mode-locked (SML) monolithic Yb:KGW laser. The gain medium is coated to achieve the monolithic SML operation and a partially reflective mirror is further exploited to form the coupled cavity and to multiply the repetition rate up to 128.9 GHz. With a coupled reflectivity of 95%, it is experimentally found that not only the first-order but also second-order stimulated Raman scattering (SRS) can be efficiently generated. The mode-locked OFC can be consequently expanded to reach approximately 8.4 THz, leading the pulse width to be as narrow as 53 fs. At the pump power of 8.7 W, the total output power for the fundamental and the first- and second-Stokes waves can be maintained at 1.6 W. The present exploration provides a promising way to generate the ultrahigh-repetition-rate broadband OFC via the simultaneous SML and SRS processes.

  12. Few-second-long correlation times in a quantum dot nuclear spin bath probed by frequency-comb nuclear magnetic resonance spectroscopy (United States)

    Waeber, A. M.; Hopkinson, M.; Farrer, I.; Ritchie, D. A.; Nilsson, J.; Stevenson, R. M.; Bennett, A. J.; Shields, A. J.; Burkard, G.; Tartakovskii, A. I.; Skolnick, M. S.; Chekhovich, E. A.


    One of the key challenges in spectroscopy is the inhomogeneous broadening that masks the homogeneous spectral lineshape and the underlying coherent dynamics. Techniques such as four-wave mixing and spectral hole-burning are used in optical spectroscopy, and spin-echo in nuclear magnetic resonance (NMR). However, the high-power pulses used in spin-echo and other sequences often create spurious dynamics obscuring the subtle spin correlations important for quantum technologies. Here we develop NMR techniques to probe the correlation times of the fluctuations in a nuclear spin bath of individual quantum dots, using frequency-comb excitation, allowing for the homogeneous NMR lineshapes to be measured without high-power pulses. We find nuclear spin correlation times exceeding one second in self-assembled InGaAs quantum dots--four orders of magnitude longer than in strain-free III-V semiconductors. This observed freezing of the nuclear spin fluctuations suggests ways of designing quantum dot spin qubits with a well-understood, highly stable nuclear spin bath.

  13. Reduced pulse energy for frequency comb offset stabilization with a dual-pitch periodically poled lithium niobate ridge waveguide (United States)

    Hitachi, K.; Hara, K.; Tadanaga, O.; Ishizawa, A.; Nishikawa, T.; Gotoh, H.


    The pulse energy for stabilizing the carrier-envelop offset frequency of an Er-doped fiber laser was reduced by a dual-pitch (DP-) periodically poled lithium niobate (PPLN) ridge waveguide implemented in a 2f-to-3f self-referencing interferometer (SRI). The pulse energy requirement was less than half that for a single-pitch PPLN ridge waveguide implemented in an f-to-2f SRI. We also found that environmental noise could be reduced by adjusting the pulse energy for frequency stabilization with the DP-PPLN ridge waveguide, as estimated from the phase noise of an out-of-loop interferometer.

  14. Rydberg atoms in low-frequency fields : fundamental aspects and applications

    NARCIS (Netherlands)

    Gürtler, Andreas Stefan


    In this thesis we investigate highly excited atoms, so-called Rydberg atoms, in oscillating fields with frequencies from the megahertz to the terahertz domain. The strong interaction of Rydberg atoms with external fields is used to establish a connection between the ionization of Rydberg atoms by

  15. Visible wavelength astro-comb. (United States)

    Benedick, Andrew J; Chang, Guoqing; Birge, Jonathan R; Chen, Li-Jin; Glenday, Alexander G; Li, Chih-Hao; Phillips, David F; Szentgyorgyi, Andrew; Korzennik, Sylvain; Furesz, Gabor; Walsworth, Ronald L; Kärtner, Franz X


    We demonstrate a tunable laser frequency comb operating near 420 nm with mode spacing of 20-50 GHz, usable bandwidth of 15 nm and output power per line of ~20 nW. Using the TRES spectrograph at the Fred Lawrence Whipple Observatory, we characterize this system to an accuracy below 1m/s, suitable for calibrating high-resolution astrophysical spectrographs used, e.g., in exoplanet studies.

  16. Spin-exchange frequency shift in a cesium atomic fountain

    NARCIS (Netherlands)

    Tiesinga, E.; Verhaar, B.J.; Stoof, H.T.C.; Bragt, D. van


    In connection with experiments aiming at the improvement of the cesium atomic beam clock by means of a fountain of laser-cooled cesium atoms, we present expressions for the line shift and line broadening due to collisions between cesium atoms. The coherent collision cross sections occurring in these

  17. Very high frequency plasma reactant for atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Il-Kwon; Yoo, Gilsang; Yoon, Chang Mo [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Tae Hyung; Yeom, Geun Young [Department of Advanced Materials Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Kangsik; Lee, Zonghoon [School Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919 (Korea, Republic of); Jung, Hanearl; Lee, Chang Wan [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kim, Hyungjun, E-mail: [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Lee, Han-Bo-Ram, E-mail: [Department of Materials Science and Engineering, Incheon National University, 406-840 Incheon (Korea, Republic of)


    Highlights: • Fundamental research plasma process for thin film deposition is presented. • VHF plasma source for PE-ALD Al{sub 2}O{sub 3} was employed to reduce plasma damage. • The use of VHF plasma improved all of the film qualities and growth characteristics. - Abstract: Although plasma-enhanced atomic layer deposition (PE-ALD) results in several benefits in the formation of high-k dielectrics, including a low processing temperature and improved film properties compared to conventional thermal ALD, energetic radicals and ions in the plasma cause damage to layer stacks, leading to the deterioration of electrical properties. In this study, the growth characteristics and film properties of PE-ALD Al{sub 2}O{sub 3} were investigated using a very-high-frequency (VHF) plasma reactant. Because VHF plasma features a lower electron temperature and higher plasma density than conventional radio frequency (RF) plasma, it has a larger number of less energetic reaction species, such as radicals and ions. VHF PE-ALD Al{sub 2}O{sub 3} shows superior physical and electrical properties over RF PE-ALD Al{sub 2}O{sub 3}, including high growth per cycle, excellent conformality, low roughness, high dielectric constant, low leakage current, and low interface trap density. In addition, interlayer-free Al{sub 2}O{sub 3} on Si was achieved in VHF PE-ALD via a significant reduction in plasma damage. VHF PE-ALD will be an essential process to realize nanoscale devices that require precise control of interfaces and electrical properties.

  18. Tunable dual-frequency laser source for coherent population trapping cesium atomic clocks (United States)

    Camargo, F. A.; Georges, P.; Lucas-Leclin, G.; Baili, G.; Morvan, L.; Dolfi, D.; Holleville, D.; Guerandel, S.; Sagnes, I.


    Coherent population trapping (CPT) has been demonstrated as an interesting technique for miniature atomic frequency references [1,2] and quantum information. It is based on the coupling of the two hyperfine ground states of an alkali atom - namely cesium (133Cs) for atomic clocks - through excitation to a common atomic level by two phase-coherent laser fields nearly resonant with the atomic transitions. The frequency difference between the two laser fields is tuned at the atomic frequency splitting in the microwave range, equal to 9.192 GHz for 133Cs atoms. Outputs powers in the mW range and narrow-linewidth emission (<500 kHz) are required for the two laser beams.

  19. ACADEMIC TRAINING: Probing nature with high precision; particle traps, laser spectroscopy and optical combs

    CERN Multimedia

    Françoise Benz


    17, 18, 19 June LECTURE SERIES from 11.00 to 12.00 hrs - Auditorium, bldg. 500 Probing nature with high precision; particle traps, laser spectroscopy and optical combs by G. GABRIELSE / Harvard University, USA Experiments with atomic energy scales probe nature and its symmetries with exquisite precision. Particle traps allow the manipulation of single charged particles for months at a time, allow the most accurate comparison of theory and experiment, and promise to allow better measurement of fundamental quantities like the fine structure constant. Ions and atoms can be probed with lasers that are phase locked to microwave frequency standards via optical combs, thus calibrating optical sources in terms of the official cesium second. A series of three lectures will illustrate what can be measured and discuss key techniques.  ACADEMIC TRAINING Françoise Benz Tel. 73127

  20. Atoms in the counter-propagating frequency-modulated waves: splitting, cooling, confinement (United States)

    Romanenko, Victor I.; Kornilovska, Nataliya V.


    We show that the counter-propagating frequency-modulated (FM) waves of the same intensity can split an orthogonal atomic beam into two beams. We calculate the temperature of the atomic ensemble for the case when the atoms are grouped around zero velocity in the direction of the waves propagation. The high-intensity laser radiation with a properly chosen carrier frequency can form a one-dimensional trap for atoms. We carry out the numerical simulation of the atomic motion (two-level model of the atom-field interaction) using parameters appropriate for sodium atoms and show that sub-Doppler cooling can be reached. We suppose that such a cooling is partly based on the cooling without spontaneous emission in polychromatic waves [H. Metcalf, Phys. Rev. A 77, 061401 (2008)]. We calculate the state of the atom in the field by the Monte Carlo wave-function method and describe its mechanical motion by the classical mechanics.

  1. Modern atomic physics

    CERN Document Server

    Natarajan, Vasant


    Much of our understanding of physics in the last 30-plus years has come from research on atoms, photons, and their interactions. Collecting information previously scattered throughout the literature, Modern Atomic Physics provides students with one unified guide to contemporary developments in the field. After reviewing metrology and preliminary material, the text explains core areas of atomic physics. Important topics discussed include the spontaneous emission of radiation, stimulated transitions and the properties of gas, the physics and applications of resonance fluorescence, coherence, cooling and trapping of charged and neutral particles, and atomic beam magnetic resonance experiments. Covering standards, a different way of looking at a photon, stimulated radiation, and frequency combs, the appendices avoid jargon and use historical notes and personal anecdotes to make the topics accessible to non-atomic physics students. Written by a leader in atomic and optical physics, this text gives a state-of-the...

  2. Neutral Atom Lithography With Multi-Frequency Laser Fields

    National Research Council Canada - National Science Library

    Elliott, Daniel S; Janes, David B


    In this final report we describe our efforts in exposing self-assembled molecular monolayers to a beam of neutral sodium atoms and chemically etching the resulting substrate and characterization of the resulting surface...

  3. Optimization of filtering schemes for broadband astro-combs. (United States)

    Chang, Guoqing; Li, Chih-Hao; Phillips, David F; Szentgyorgyi, Andrew; Walsworth, Ronald L; Kärtner, Franz X


    To realize a broadband, large-line-spacing astro-comb, suitable for wavelength calibration of astrophysical spectrographs, from a narrowband, femtosecond laser frequency comb ("source-comb"), one must integrate the source-comb with three additional components: (1) one or more filter cavities to multiply the source-comb's repetition rate and thus line spacing; (2) power amplifiers to boost the power of pulses from the filtered comb; and (3) highly nonlinear optical fiber to spectrally broaden the filtered and amplified narrowband frequency comb. In this paper we analyze the interplay of Fabry-Perot (FP) filter cavities with power amplifiers and nonlinear broadening fiber in the design of astro-combs optimized for radial-velocity (RV) calibration accuracy. We present analytic and numeric models and use them to evaluate a variety of FP filtering schemes (labeled as identical, co-prime, fraction-prime, and conjugate cavities), coupled to chirped-pulse amplification (CPA). We find that even a small nonlinear phase can reduce suppression of filtered comb lines, and increase RV error for spectrograph calibration. In general, filtering with two cavities prior to the CPA fiber amplifier outperforms an amplifier placed between the two cavities. In particular, filtering with conjugate cavities is able to provide 300 nm wavelength coverage. Such superior performance will facilitate the search for and characterization of Earth-like exoplanets, which requires <10 cm/s RV calibration error.

  4. Multiband left handed biaxial meta atom at microwave frequency (United States)

    Mehedi Hasan, Md; Faruque, Mohammad Rashed Iqbal; Tariqul Islam, Mohammad


    Left handed meta atoms are special class materials that characterized by the negative refractive index. In this paper, a left handed biaxial meta-atom is reported that has 5.81 GHz wide bandwidth and applicable for C-, X- and Ku-band applications. The meta atom is developed by an outer and the inner split ring resonator with inverse E-shape metal strips of copper, which are connected with the outer ring resonator that look like a mirror-shape structure. A finite integration technique based CST Microwave Studio is utilized to design, simulation and analysis purposes, where the Agilent N5227A vector network analyzer is utilized for measurement purpose. Measurements show that, the measured and simulated results are well complied together and negative index bandwidth from 3.27 to 6.55 GHz (bandwidth of 3.28 GHz) and 7 to 12.81 GHz (bandwidth of 5.81 GHz) along the z-axis wave propagation. The total dimensions of the designed structure are 0.2λ  ×  0.2λ  ×  0.035λ and the effective medium ratio 5, makes the proposed biaxial meta-atom is suitable for practical applications.

  5. Rydberg-atom based radio-frequency electrometry using frequency modulation spectroscopy in room temperature vapor cells. (United States)

    Kumar, Santosh; Fan, Haoquan; Kübler, Harald; Jahangiri, Akbar J; Shaffer, James P


    Rydberg atom-based electrometry enables traceable electric field measurements with high sensitivity over a large frequency range, from gigahertz to terahertz. Such measurements are particularly useful for the calibration of radio frequency and terahertz devices, as well as other applications like near field imaging of electric fields. We utilize frequency modulated spectroscopy with active control of residual amplitude modulation to improve the signal to noise ratio of the optical readout of Rydberg atom-based radio frequency electrometry. Matched filtering of the signal is also implemented. Although we have reached similarly, high sensitivity with other read-out methods, frequency modulated spectroscopy is advantageous because it is well-suited for building a compact, portable sensor. In the current experiment, ∼3 µV cm-1 Hz-1/2 sensitivity is achieved and is found to be photon shot noise limited.

  6. Ultracold atoms in radio-frequency dressed potentials beyond the rotating-wave approximation

    DEFF Research Database (Denmark)

    Hofferberth, S.; Fischer, B.; Schumm, Thorsten


    We study dressed Bose-Einstein condensates in an atom chip radio-frequency trap. We show that in this system sufficiently strong dressing can be achieved to cause the widely used rotating-wave approximation (RWA) to break down. We present a full calculation of the atom-field coupling which shows...

  7. An experimental study of intermodulation effects in an atomic fountain frequency standard


    Guéna, Jocelyne; Dudle, Gregor; Thomann, Pierre


    International audience; The short-term stability of passive atomic frequency standards, especially in pulsed operation, is often limited by local oscillator noise via intermodulation effects. We present an experimental demonstration of the intermodulation effect on the frequency stability of a continuous atomic fountain clock where, under normal operating conditions, it is usually too small to observe. To achieve this, we deliberately degrade the phase stability of the microwave field interro...

  8. Electro-optic dual-comb interferometry over 40-nm bandwidth

    CERN Document Server

    Duran, Vicente; Torres-Company, Victor


    Dual-comb interferometry is a measurement technique that uses two laser frequency combs to retrieve complex spectra in a line-by-line basis. This technique can be implemented with electro-optic frequency combs, offering intrinsic mutual coherence, high acquisition speed and flexible repetition-rate operation. A challenge with the operation of this kind of frequency comb in dual-comb interferometry is its limited optical bandwidth. Here, we use coherent spectral broadening and demonstrate electro-optic dual-comb interferometry over the entire telecommunications C band (200 lines covering ~ 40 nm, measured within 10 microseconds at 100 signal-to-noise ratio per spectral line). These results offer new prospects for electro-optic dual-comb interferometry as a suitable technology for high-speed broadband metrology, for example in optical coherence tomography or coherent Raman microscopy.

  9. A high stability optical frequency reference based on thermal calcium atoms (United States)


    simple, compact optical frequency standard based upon thennal calcium atoms. Using a Ramsey- Borde specu·ometer we excite features with linewidths < 5kHz...Optical Frequency (kHz) Figure 2: Ramsey- Borde fringes , shown here with both recoil components. Fringe width is < 5kHz (FWHM). tlli.s theoretical value...send ~ 2 m W of the light to a fom-beam Ramsey- Borde spectrometer that excites the atoms in a thermal beam [3]. Atoms emerge from an aperture in theCa

  10. Atomic fountain clock with very high frequency stability employing a pulse-tube-cryocooled sapphire oscillator. (United States)

    Takamizawa, Akifumi; Yanagimachi, Shinya; Tanabe, Takehiko; Hagimoto, Ken; Hirano, Iku; Watabe, Ken-ichi; Ikegami, Takeshi; Hartnett, John G


    The frequency stability of an atomic fountain clock was significantly improved by employing an ultra-stable local oscillator and increasing the number of atoms detected after the Ramsey interrogation, resulting in a measured Allan deviation of 8.3 × 10(-14)τ(-1/2)). A cryogenic sapphire oscillator using an ultra-low-vibration pulse-tube cryocooler and cryostat, without the need for refilling with liquid helium, was applied as a local oscillator and a frequency reference. High atom number was achieved by the high power of the cooling laser beams and optical pumping to the Zeeman sublevel m(F) = 0 employed for a frequency measurement, although vapor-loaded optical molasses with the simple (001) configuration was used for the atomic fountain clock. The resulting stability is not limited by the Dick effect as it is when a BVA quartz oscillator is used as the local oscillator. The stability reached the quantum projection noise limit to within 11%. Using a combination of a cryocooled sapphire oscillator and techniques to enhance the atom number, the frequency stability of any atomic fountain clock, already established as primary frequency standard, may be improved without opening its vacuum chamber.

  11. On the generation of waveforms having comb-shaped spectra (United States)

    Black, Bruce A.


    Two techniques, direct sequence and spread spectrum and frequency hopping are widely used to provide an antijam capability for communications systems. To test the effectiveness of such systems, suitable jammers must be devised. A frequency hopping system can be jammed by wideband noise, by a following frequency hopped carrier (if the hopper is slow enough), or by a multitone jamming signal. Multitone jamming signals are considered advantageous in that jamming power is not wasted on frequencies never visited by the frequency hopper, as is the case when wideband noise is used. This report considers several classes of waveforms having power spectra that are approximately comb-shaped. The report relates the properties of the comb spectrum to the time-domain properties of the waveforms. These are the repeated pseudorandom sequence, used to modulate a carrier, and the frequency-swept sinusoid. A good quality comb spectrum should have uniformly strong teeth over its passband, and the spectrum should fall away rapidly at the band edges. To minimize the distortion caused by saturating power amplifiers, it is helpful is the time-domain function has a constant envelope. It is shown that a pseudorandom sequence that is low-pass filtered prior to modulation can produce a very uniform comb with sharp band edges, provided that the required width of the comb is not excessive. A swept-frequency sinusoid can produce a comb of very wide bandwidth, also with sharp band edges.

  12. Frequency Function in Atomic Force Microscopy Applied to a Liquid Environment

    Directory of Open Access Journals (Sweden)

    Po-Jen Shih


    Full Text Available Scanning specimens in liquids using commercial atomic force microscopy (AFM is very time-consuming due to the necessary try-and-error iteration for determining appropriate triggering frequencies and probes. In addition, the iteration easily contaminates the AFM tip and damages the samples, which consumes probes. One reason for this could be inaccuracy in the resonant frequency in the feedback system setup. This paper proposes a frequency function which varies with the tip-sample separation, and it helps to improve the frequency shift in the current feedback system of commercial AFMs. The frequency function is a closed-form equation, which allows for easy calculation, as confirmed by experimental data. It comprises three physical effects: the quasi-static equilibrium condition, the atomic forces gradient effect, and hydrodynamic load effect. While each of these has previously been developed in separate studies, this is the first time their combination has been used to represent the complete frequency phenomenon. To avoid “jump to contact” issues, experiments often use probes with relatively stiffer cantilevers, which inevitably reduce the force sensitivity in sensing low atomic forces. The proposed frequency function can also predict jump to contact behavior and, thus, the probe sensitivity could be increased and soft probes could be widely used. Additionally, various tip height behaviors coupling with the atomic forces gradient and hydrodynamic effects are discussed in the context of carbon nanotube probes.

  13. Self-oscillating mode for frequency modulation noncontact atomic force microscopy


    Giessibl, Franz J.; Tortonese, Marco


    Frequency modulation atomic force microscopy (FM-AFM) has made imaging of surfaces in ultrahigh vacuum with atomic resolution possible. Here, we demonstrate a new approach which simplifies the implementation of FM-AFM considerably and enhances force sensitivity by directly exciting the cantilever with the thermal effects involved in the deflection measurement process. This approach reduces the mechanically oscillating mass by 6 to 8 orders of magnitude as compared to conventional FM-AFM, beca...

  14. A Circuit to Improve Power Amplitude Stability in Miniature Rubidium Atomic Frequency Standard

    Directory of Open Access Journals (Sweden)

    LUO Qi


    Full Text Available The radiofrequency circuit of traditional miniature rubidium atomic frequency standard (RAFS uses saturated output, which can stabilize the amplitude, but not the waveform, of the radiofrequency signal. This would lead to insufficient microwave power stability. In this study, an improved circuit for stabilizing power amplitude in miniature rubidium atomic frequency standard was described. The circuit took the bias voltage of step recovery diode (SRD as a reference to achieve automatic gain control (AGC through controlling the gain of the variable gain amplifier (VGA. This scheme controlled both the amplitude and the waveform of the radiofrequency signal. The results showed that this scheme can effectively improve power stability of the microwave signal in miniature rubidium atomic frequency standard.

  15. Optical Measurements of Strong Radio-Frequency Fields Using Rydberg Atoms (United States)

    Miller, Stephanie Anne

    There has recently been an initiative toward establishing atomic measurement standards for field quantities, including radio-frequency, millimeter-wave, and micro-wave electric fields. Current measurement standards are obtained using dipole antennas, which are fundamentally limited in frequency bandwidth (set by the physical size of the antenna) and accuracy (due to the metal perturbing the field during the measurement). Establishing an atomic standard rectifies these problems. My thesis work contributes to an ongoing effort towards establishing the viability of using Rydberg electromagnetically induced transparency (EIT) to perform atom-based measurements of radio-frequency (RF) fields over a wide range of frequencies and field strengths, focusing on strong-field measurements. Rydberg atoms are atoms with an electron excited to a high principal quantum number, resulting in a high sensitivity to an applied field. A model based on Floquet theory is implemented to accurately describe the observed atomic energy level shifts from which information about the field is extracted. Additionally, the effects due to the different electric field domains within the measurement volume are accurately modeled. Absolute atomic measurements of fields up to 296 V/m within a +/-0.35% relative uncertainty are demonstrated. This is the strongest field measured at the time of data publication. Moreover, the uncertainty is over an order of magnitude better than that of current standards. A vacuum chamber setup that I implemented during my graduate studies is presented and its unique components are detailed. In this chamber, cold-atom samples are generated and Rydberg atoms are optically excited within the ground-state sample. The Rydberg ion detection and imaging procedure are discussed, particularly the high magnification that the system provides. By analyzing the position of the ions, the spatial correlation g(2) (r) of Rydberg-atom distributions can be extracted. Aside from ion

  16. Limits on gravitational Einstein Equivalence Principle violation from monitoring atomic clock frequencies during a year

    CERN Document Server

    Dzuba, V A


    Sun's gravitation potential at earth varies during a year due to varying Earth-Sun distance. Comparing the results of very accurate measurements of atomic clock transitions performed at different time in the year allows us to study the dependence of the atomic frequencies on the gravitational potential. We examine the measurement data for the ratio of the frequencies in Hg$^+$ and Al$^+$ clock transitions and absolute frequency measurements (with respect to caesium frequency standard) for Dy, Sr, H, hyperfine transitions in Rb and H, and obtain significantly improved limits on the values of the gravity related parameter of the Einstein Equivalence Principle violating term in the Standard Model Extension Hamiltonian $c_{00} = (3.0 \\pm 5.7) \\times 10^{-7}$ and the parameter for the gravity-related variation of the fine structure constant $\\kappa_{\\alpha} = (-5.3 \\pm 10) \\times 10^{-8}$.

  17. Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies. (United States)

    Tettamanzi, Giuseppe Carlo; Hile, Samuel James; House, Matthew Gregory; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y


    The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

  18. Improvement of the frequency stability below the Dick limit with a continuous atomic fountain clock. (United States)

    Devenoges, Laurent; Stefanov, André; Joyet, Alain; Thomann, Pierre; Di Domenico, Gianni


    The frequency instability of a shot-noise limited atomic fountain clock is inversely proportional to its signal-tonoise ratio. Therefore, increasing the atomic flux is a direct way to improve the stability. Nevertheless, in pulsed operation, the local oscillator noise limits the performance via the Dick effect. We experimentally demonstrate here that a continuous atomic fountain allows one to overcome this limitation. In this work, we take advantage of two-laser optical pumping on a cold cesium beam to increase the useful fountain flux and, thus, to reduce the frequency instability below the Dick limit. A stability of 6 × 10(-14)τ(-1/2) has been measured with the continuous cesium fountain FOCS-2.

  19. Manipulation of ultracold atoms in dressed adiabatic radio-frequency potentials

    DEFF Research Database (Denmark)

    Lesanovsky, Igor; Hofferberth, S.; Schmiedmayer, Jörg


    We explore properties of atoms whose magnetic hyperfine sublevels are coupled by an external magnetic radio frequency (rf) field. We perform a thorough theoretical analysis of this driven system and present a number of systematic approximations which eventually give rise to dressed adiabatic radio...... frequency potentials. The predictions of this analytical investigation are compared to numerically exact results obtained by a wave packet propagation. We outline the versatility and flexibility of this class of potentials and demonstrate their potential use to build atom optical elements such as double...... wells, interferometers, and ringtraps. Moreover, we perform simulations of interference experiments carried out in rf induced double-well potentials. We discuss how the nature of the atom-field coupling mechanism gives rise to a decrease of the interference contrast....

  20. Noise conversion in Kerr comb RF photonic oscillators

    CERN Document Server

    Matsko, Andrey B


    Transfer of amplitude and phase noise from a continuous wave optical pump to the repetition rate of a Kerr frequency comb is studied theoretically, with focus on generation of spectrally pure radio frequency (RF) signals via demodulation of the frequency comb on a fast photodiode. It is shown that both the high order chromatic dispersion of the resonator spectrum and frequency-dependent quality factor of the resonator modes facilitate the optical-to-RF noise conversion that limits spectral purity of the RF signal.

  1. An atomic magnetometer with autonomous frequency stabilization and large dynamic range

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, S., E-mail:, E-mail:; Poornima,; Dasgupta, K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India); Homi Bhabha National Institute, Department of Atomic Energy, Mumbai 85 (India); Mishra, S.; Behera, R. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 85 (India)


    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  2. Frequency-tunable microwave field detection in an atomic vapor cell (United States)

    Horsley, Andrew; Treutlein, Philipp


    We use an atomic vapor cell as a frequency tunable microwave field detector operating at frequencies from GHz to tens of GHz. We detect microwave magnetic fields from 2.3 GHz to 26.4 GHz, and measure the amplitude of the σ+ component of an 18 GHz microwave field. Our proof-of-principle demonstration represents a four orders of magnitude extension of the frequency tunable range of atomic magnetometers from their previous dc to several MHz range. When integrated with a high-resolution microwave imaging system [Horsley et al., New J. Phys. 17, 112002 (2015)], this will allow for the complete reconstruction of the vector components of a microwave magnetic field and the relative phase between them. Potential applications include near-field characterisation of microwave circuitry and devices, and medical microwave sensing and imaging.

  3. Temporal interference with frequency-controllable long photons from independent cold atomic sources (United States)

    Qian, Peng; Gu, Zhenjie; Wen, Rong; Zhang, Weiping; Chen, J. F.


    The interference of single photons from independent sources is an essential tool in quantum information processing. However, the interfering of photons with long temporal states in a time-resolved manner has rarely been studied. This is because without transmitting spectral filters or coupling to a cavity mode single photons generated in traditional nonlinear crystals suffer from a short temporal profile below 1 ns. With spectral correlation maintained in the biphotons generated from spontaneous four-wave mixing process in cold atom clouds, here we demonstrate the temporal interference of two frequency-tunable long photons from two independent cold atomic sources. We observe and analyze the interference of frequency-mismatched photons, where the phenomenon of the quantum beat at megahertz separation is displayed. Our paper provides more details for the quantum beat of two independent narrow-band single photons, which may find potential application in frequency-encoded photonic qubits in quantum information processing.

  4. Supercontinuum comb sources for broadband communications based on AlGaAs-on-insulator

    DEFF Research Database (Denmark)

    Hu, Hao; Pu, Minhao; Da Ros, Francesco


    We experimentally demonstrated 10 GHz frequency comb spectral broadening in an AlGaAsOI nano-waveguide with the peak power of only several watts. The spectral broadened 10 GHz frequency comb has high optical signal to noise ratio (OSNR) at the output of the nano-waveguide. As far as we know, it i...

  5. Phase locking of a semiconductor double-quantum-dot single-atom maser (United States)

    Liu, Y.-Y.; Hartke, T. R.; Stehlik, J.; Petta, J. R.


    We experimentally study the phase stabilization of a semiconductor double-quantum-dot (DQD) single-atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output field demonstrate that the maser can be phase locked to an external cavity drive, with a resulting phase noise L =-99 dBc/Hz at a frequency offset of 1.3 MHz. The injection locking range, and the phase of the maser output relative to the injection locking input tone are in good agreement with Adler's theory. Furthermore, the electrically tunable DQD energy level structure allows us to rapidly switch the gain medium on and off, resulting in an emission spectrum that resembles a frequency comb. The free running frequency comb linewidth is ≈8 kHz and can be improved to less than 1 Hz by operating the comb in the injection locked regime.

  6. Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber. (United States)

    Wu, Shun; Wang, Chenchen; Fourcade-Dutin, Coralie; Washburn, Brian R; Benabid, Fetah; Corwin, Kristan L


    We have isolated a single tooth from a fiber laser-based optical frequency comb for nonlinear spectroscopy and thereby directly referenced the comb. An 89 MHz erbium fiber laser frequency comb is directly stabilized to the P(23) (1539.43 nm) overtone transition of (12)C(2)H(2) inside a hollow-core photonic crystal fiber. To do this, a single comb tooth is isolated and amplified from 20 nW to 40 mW with sufficient fidelity to perform saturated absorption spectroscopy. The fractional stability of the comb, ~7 nm away from the stabilized tooth, is shown to be 6 × 10(-12) at 100 ms gate time, which is over an order of magnitude better than that of a comb referenced to a GPS-disciplined Rb oscillator.

  7. Tunable frequency-stabilization of UV laser using a Hallow-Cathode Lamp of atomic thallium

    CERN Document Server

    Chen, Tzu-Ling; Shy, Jow-Tsong; Liu, Yi-Wei


    A frequency-stabilized ultraviolet laser system, locked to the thallium resonant transition of 377.5 nm, was demonstrated using a novel bichromatic spectroscopy technique for tuning the zero-crossing laser-lock point. The atomic thallium system is a promising candidate in atomic parity violation and permanent electric dipole moment experiments, and its 377.5 nm 6P1/2->7S1/2 transition is important for thallium laser cooling and trapping experiment. The pressure shift, owing to the high pressure bu?er gas of the hollow-cathode lamp, was observed using an atomic beam resonance as reference. Such a shift was corrected by adjusting the peak ratio of the two Doppler-free saturation pro?les resulted from two pumping beams with a 130 MHz frequency di?erence. The resulted frequency stability of the ultraviolet laser is ?0.5 MHz at 0.1 sec integration time. This scheme is compact and versatile for stabilizing UV laser systems, which acquire a sub-MHz stability and frequency tunability.

  8. Radio frequency superconducting quantum interference device meta-atoms and metamaterials: Experiment, theory and analysis (United States)

    Zhang, Daimeng

    Metamaterials are 1D, 2D or 3D arrays of artificial atoms. The artificial atoms, called "meta-atoms", can be any component with tailorable electromagnetic properties, such as resonators, LC circuits, nano particles, and so on. By designing the properties of individual meta-atoms and the interaction created by putting them in a lattice, one can create a metamaterial with intriguing properties not found in nature. My Ph. D. work examines the meta-atoms based on radio frequency superconducting quantum interference devices (rf-SQUIDs); their tunability with dc magnetic field, rf magnetic field, and temperature are studied. The rf-SQUIDs are superconducting split ring resonators in which the usual capacitance is supplemented with a Josephson junction, which introduces strong nonlinearity in the rf properties. At relatively low rf magnetic field, a magnetic field tunability of the resonant frequency of up to 80 THz/Gauss by dc magnetic field is observed, and a total frequency tunability of 100% is achieved. The macroscopic quantum superconducting metamaterial also shows manipulative self-induced broadband transparency due to a qualitatively novel nonlinear mechanism that is different from conventional electromagnetically induced transparency (EIT) or its classical analogs. A near complete disappearance of resonant absorption under a range of applied rf flux is observed experimentally and explained theoretically. The transparency comes from the intrinsic bi-stability and can be tuned on/ off easily by altering rf and dc magnetic fields, temperature and history. Hysteretic in situ 100% tunability of transparency paves the way for auto-cloaking metamaterials, intensity dependent filters, and fast-tunable power limiters. An rf-SQUID metamaterial is shown to have qualitatively the same behavior as a single rf-SQUID with regards to dc flux, rf flux and temperature tuning. The two-tone response of self-resonant rf-SQUID meta-atoms and metamaterials is then studied here via

  9. Adiabatic perturbation theory for atoms and molecules in the low-frequency regime (United States)

    Martiskainen, Hanna; Moiseyev, Nimrod


    There is an increasing interest in the photoinduced dynamics in the low frequency, ω, regime. The multiphoton absorptions by molecules in strong laser fields depend on the polarization of the laser and on the molecular structure. The unique properties of the interaction of atoms and molecules with lasers in the low-frequency regime imply new concepts and directions in strong-field light-matter interactions. Here we represent a perturbational approach for the calculations of the quasi-energy spectrum in the low-frequency regime, which avoids the construction of the Floquet operator with extremely large number of Floquet channels. The zero-order Hamiltonian in our perturbational approach is the adiabatic Hamiltonian where the atoms/molecules are exposed to a dc electric field rather than to ac-field. This is in the spirit of the first step in the Corkum three-step model. The second-order perturbation correction terms are obtained when i ℏ ω ∂/∂ τ serves as a perturbation and τ is a dimensionless variable. The second-order adiabatic perturbation scheme is found to be an excellent approach for calculating the ac-field Floquet solutions in our test case studies of a simple one-dimensional time-periodic model Hamiltonian. It is straightforward to implement the perturbation approach presented here for calculating atomic and molecular energy shifts (positions) due to the interaction with low-frequency ac-fields using high-level electronic structure methods. This is enabled since standard quantum chemistry packages allow the calculations of atomic and molecular energy shifts due to the interaction with dc-fields. In addition to the shift of the energy positions, the energy widths (inverse lifetimes) can be obtained at the same level of theory. These energy shifts are functions of the laser parameters (low frequency, intensity, and polarization).

  10. Biological and Biomimetic Comb Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Aristeidis Papagiannopoulos


    Full Text Available Some new phenomena involved in the physical properties of comb polyelectrolyte solutions are reviewed. Special emphasis is given to synthetic biomimetic materials, and the structures formed by these molecules are compared with those of naturally occurring glycoprotein and proteoglycan solutions. Developments in the determination of the structure and dynamics (viscoelasticity of comb polymers in solution are also covered. Specifically the appearance of multi-globular structures, helical instabilities, liquid crystalline phases, and the self-assembly of the materials to produce hierarchical comb morphologies is examined. Comb polyelectrolytes are surface active and a short review is made of some recent experiments in this area that relate to their morphology when suspended in solution. We hope to emphasize the wide variety of phenomena demonstrated by the vast range of naturally occurring comb polyelectrolytes and the challenges presented to synthetic chemists designing biomimetic materials.

  11. Frequency signal acquisition of scalar atomic magnetometer based on using TDC and FPGA (United States)

    Ge, Y. H.; Chen, Q. Y.; Zhang, Y. F.; Xia, M. Y.


    An improved equal precision frequency measurement method is presented for acquisition of frequency signal output from high sensitivity scalar atomic magnetometers. The frequency range to be measured is from 75 kHz to 350 kHz with a resolution better than 0.01 Hz, and the sampling rate should be at least 10 Hz. To meet the requirements on dynamic range, measurement accuracy and speed, at least eight significant digits must be kept. The TDC and FPGA are used to improve the traditional equal precision method. The FPGA acts as the controlling and computing centre, while the TDC measures the time deviation to eliminate the counting error of ±1 reference signal. A prototype frequency detector is fabricated and tested. The measured data show that the design is viable and further improvement is possible.

  12. Hyperfine frequency shift of atomic hydrogen in the presence of helium buffer gas

    Energy Technology Data Exchange (ETDEWEB)

    Jochemsen, R.; Berlinsky, A.J. (British Columbia Univ., Vancouver (Canada). Dept. of Physics)


    A quantum mechanical thermal average is performed to obtain the temperature dependence of the hyperfine frequency shift (HFS) of hydrogen atoms in the presence of He buffer gas. The calculations are based on existing ab initio calculations of the hyperfine frequency shift as a function of internuclear separation and of the interatomic potential. We find that the HFS changes sign at fairly low temperature and has a small negative value at T = 1 K in agreement with recent measurements. The overall temperature dependence is shown to be quite sensitive to the interatomic potential.

  13. Atomic-Scale Time and Space Resolution of Terahertz Frequency Acoustic Waves (United States)

    Reed, Evan J.; Armstrong, Michael R.; Kim, Ki-Yong; Glownia, James H.


    Using molecular dynamics simulations and analytics, we find that strain waves of terahertz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering AlN/GaN heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time dependence of the strain wave with potentially subpicosecond, nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude terahertz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals.

  14. Phase-locking transition in Raman combs generated with whispering gallery mode resonators. (United States)

    Lin, Guoping; Chembo, Yanne K


    We investigate the mechanisms leading to phase locking in Raman optical frequency combs generated with ultrahigh Q crystalline whispering gallery mode disk resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single-frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs, which feature high coherence and wide spectral spans, are obtained with pump powers in the range of a few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase locking.

  15. Atomic-resolution imaging in liquid by frequency modulation atomic force microscopy using small cantilevers with megahertz-order resonance frequencies. (United States)

    Fukuma, T; Onishi, K; Kobayashi, N; Matsuki, A; Asakawa, H


    In this study, we have investigated the performance of liquid-environment FM-AFM with various cantilevers having different dimensions from theoretical and experimental aspects. The results show that reduction of the cantilever dimensions provides improvement in the minimum detectable force as long as the tip height is sufficiently long compared with the width of the cantilever. However, we also found two important issues to be overcome to achieve this theoretically expected performance. The stable photothermal excitation of a small cantilever requires much higher pointing stability of the exciting laser beam than that for a long cantilever. We present a way to satisfy this stringent requirement using a temperature controlled laser diode module and a polarization-maintaining optical fiber. Another issue is associated with the tip. While a small carbon tip formed by electron beam deposition (EBD) is desirable for small cantilevers, we found that an EBD tip is not suitable for atomic-scale applications due to the weak tip-sample interaction. Here we show that the tip-sample interaction can be greatly enhanced by coating the tip with Si. With these improvements, we demonstrate atomic-resolution imaging of mica in liquid using a small cantilever with a megahertz-order resonance frequency. In addition, we experimentally demonstrate the improvement in the minimum detectable force obtained by the small cantilever in measurements of oscillatory hydration forces.

  16. Heterogeneous terahertz quantum cascade lasers exceeding 1.9 THz spectral bandwidth and featuring dual comb operation (United States)

    Rösch, Markus; Beck, Mattias; Süess, Martin J.; Bachmann, Dominic; Unterrainer, Karl; Faist, Jérôme; Scalari, Giacomo


    We report on a heterogeneous active region design for terahertz quantum cascade laser based frequency combs. Dynamic range, spectral bandwidth and output power have been significantly improved with respect to previous designs. When individually operating the lasers, narrow and stable intermode beatnote indicate frequency comb operation up to a spectral bandwidth of 1.1 THz, while in a dispersion-dominated regime a bandwidth up to 1.94 THz at a center frequency of 3 THz can be reached. A self-detected dual-comb setup has been used to verify the frequency comb nature of the lasers.

  17. Heterogeneous terahertz quantum cascade lasers exceeding 1.9 THz spectral bandwidth and featuring dual comb operation

    Directory of Open Access Journals (Sweden)

    Rösch Markus


    Full Text Available We report on a heterogeneous active region design for terahertz quantum cascade laser based frequency combs. Dynamic range, spectral bandwidth and output power have been significantly improved with respect to previous designs. When individually operating the lasers, narrow and stable intermode beatnote indicate frequency comb operation up to a spectral bandwidth of 1.1 THz, while in a dispersion-dominated regime a bandwidth up to 1.94 THz at a center frequency of 3 THz can be reached. A self-detected dual-comb setup has been used to verify the frequency comb nature of the lasers.

  18. Atomization off thin water films generated by high-frequency substrate wave vibrations (United States)

    Collins, David J.; Manor, Ofer; Winkler, Andreas; Schmidt, Hagen; Friend, James R.; Yeo, Leslie Y.


    Generating aerosol droplets via the atomization of thin aqueous films with high frequency surface acoustic waves (SAWs) offers several advantages over existing nebulization methods, particularly for pulmonary drug delivery, offering droplet sizes in the 1-5-μm range ideal for effective pulmonary therapy. Nevertheless, the physics underlying SAW atomization is not well understood, especially in the context of thin liquid film formation and spreading and how this affects the aerosol production. Here, we demonstrate that the film geometry, governed primarily by the applied power and frequency of the SAW, indeed plays a crucial role in the atomization process and, in particular, the size of the atomized droplets. In contrast to the continuous spreading of low surface energy liquids atop similar platforms, high surface energy liquids such as water, in the present case, are found to undergo transient spreading due to the SAW to form a quasisteady film whose height is determined by self-selection of the energy minimum state associated with the acoustic resonance in the film and whose length arises from a competition between acoustic streaming and capillary effects. This is elucidated from a fundamental model for the thin film spreading behavior under SAW excitation, from which we show good agreement between the experimentally measured and theoretically predicted droplet dimension, both of which consistently indicate a linear relationship between the droplet diameter and the mechanical power coupled into the liquid by the SAW (the latter captured by an acoustic Weber number to the two thirds power, and the reciprocal of the SAW frequency).

  19. Analysis of force-deconvolution methods in frequency-modulation atomic force microscopy. (United States)

    Welker, Joachim; Illek, Esther; Giessibl, Franz J


    In frequency-modulation atomic force microscopy the direct observable is the frequency shift of an oscillating cantilever in a force field. This frequency shift is not a direct measure of the actual force, and thus, to obtain the force, deconvolution methods are necessary. Two prominent methods proposed by Sader and Jarvis (Sader-Jarvis method) and Giessibl (matrix method) are investigated with respect to the deconvolution quality. Both methods show a nontrivial dependence of the deconvolution quality on the oscillation amplitude. The matrix method exhibits spikelike features originating from a numerical artifact. By interpolation of the data, the spikelike features can be circumvented. The Sader-Jarvis method has a continuous amplitude dependence showing two minima and one maximum, which is an inherent property of the deconvolution algorithm. The optimal deconvolution depends on the ratio of the amplitude and the characteristic decay length of the force for the Sader-Jarvis method. However, the matrix method generally provides the higher deconvolution quality.

  20. Microwave-to-optical frequency conversion using a cesium atom coupled to a superconducting resonator (United States)

    Gard, Bryan T.; Jacobs, Kurt; McDermott, R.; Saffman, M.


    A candidate for converting quantum information from microwave to optical frequencies is the use of a single atom that interacts with a superconducting microwave resonator on one hand and an optical cavity on the other. The large electric dipole moments and microwave transition frequencies possessed by Rydberg states allow them to couple strongly to superconducting devices. Lasers can then be used to connect a Rydberg transition to an optical transition to realize the conversion. Since the fundamental source of noise in this process is spontaneous emission from the atomic levels, the resulting control problem involves choosing the pulse shapes of the driving lasers so as to maximize the transfer rate while minimizing this loss. Here we consider the concrete example of a cesium atom, along with two specific choices for the levels to be used in the conversion cycle. Under the assumption that spontaneous emission is the only significant source of errors, we use numerical optimization to determine the likely rates for reliable quantum communication that could be achieved with this device. These rates are on the order of a few megaqubits per second.

  1. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments


    Labuda, A.; Kobayashi, K; D. Kiracofe; Suzuki, K; P. H. Grütter; Yamada, H


    In attempting to perform frequency modulation atomic force microscopy (FM-AFM) in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM) which lies in between phase modulation atomic force microscopy (PM-AFM) and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard F...

  2. Frequency Standards and Metrology (United States)

    Maleki, Lute


    Preface / Lute Maleki -- Symposium history / Jacques Vanier -- Symposium photos -- pt. I. Fundamental physics. Variation of fundamental constants from the big bang to atomic clocks: theory and observations (Invited) / V. V. Flambaum and J. C. Berengut. Alpha-dot or not: comparison of two single atom optical clocks (Invited) / T. Rosenband ... [et al.]. Variation of the fine-structure constant and laser cooling of atomic dysprosium (Invited) / N. A. Leefer ... [et al.]. Measurement of short range forces using cold atoms (Invited) / F. Pereira Dos Santos ... [et al.]. Atom interferometry experiments in fundamental physics (Invited) / S. W. Chiow ... [et al.]. Space science applications of frequency standards and metrology (Invited) / M. Tinto -- pt. II. Frequency & metrology. Quantum metrology with lattice-confined ultracold Sr atoms (Invited) / A. D. Ludlow ... [et al.]. LNE-SYRTE clock ensemble: new [symbol]Rb hyperfine frequency measurement - spectroscopy of [symbol]Hg optical clock transition (Invited) / M. Petersen ... [et al.]. Precise measurements of S-wave scattering phase shifts with a juggling atomic clock (Invited) / S. Gensemer ... [et al.]. Absolute frequency measurement of the [symbol] clock transition (Invited) / M. Chwalla ... [et al.]. The semiclassical stochastic-field/atom interaction problem (Invited) / J. Camparo. Phase and frequency noise metrology (Invited) / E. Rubiola ... [et al.]. Optical spectroscopy of atomic hydrogen for an improved determination of the Rydberg constant / J. L. Flowers ... [et al.] -- pt. III. Clock applications in space. Recent progress on the ACES mission (Invited) / L. Cacciapuoti and C. Salomon. The SAGAS mission (Invited) / P. Wolf. Small mercury microwave ion clock for navigation and radioScience (Invited) / J. D. Prestage ... [et al.]. Astro-comb: revolutionizing precision spectroscopy in astrophysics (Invited) / C. E. Kramer ... [et al.]. High frequency very long baseline interferometry: frequency standards and

  3. Frequency-doubled telecom fiber laser for a cold atom interferometer using optical lattices (United States)

    Theron, Fabien; Bidel, Yannick; Dieu, Emily; Zahzam, Nassim; Cadoret, Malo; Bresson, Alexandre


    A compact and robust frequency-doubled telecom laser system at 780 nm is presented for a rubidium cold atom interferometer using optical lattices. Adopting an optical switch at 1.5 μm and a dual-wavelength second harmonic generation system, only one laser amplifier is required for the laser system. Our system delivers a 900 mW laser beam with a detuning of 110 GHz for the optical lattice and a 650 mW laser beam with an adjustable detuning between 0 and -1 GHz for the laser cooling, the detection and the Raman transitions.

  4. Frequency, amplitude, and phase measurements in contact resonance atomic force microscopies

    Directory of Open Access Journals (Sweden)

    Gheorghe Stan


    Full Text Available The resonance frequency, amplitude, and phase response of the first two eigenmodes of two contact-resonance atomic force microscopy (CR-AFM configurations, which differ in the method used to excite the system (cantilever base vs sample excitation, are analyzed in this work. Similarities and differences in the observables of the cantilever dynamics, as well as the different effect of the tip–sample contact properties on those observables in each configuration are discussed. Finally, the expected accuracy of CR-AFM using phase-locked loop detection is investigated and quantification of the typical errors incurred during measurements is provided.

  5. Frequency doubled telecom fiber laser for a cold atom interferometer using optical lattices

    CERN Document Server

    Theron, Fabien; Dieu, Emily; Zahzam, Nassim; Cadoret, Malo; Zahzam, Nassim; Bresson, Alexandre


    A compact and robust laser system, based on a frequency-doubled telecom laser, providing all the lasers needed for a rubidium cold atom interferometer using optical lattices is presented. Thanks to an optical switch at 1.5 \\mu m and a dual-wavelength second harmonic generation system, only one laser amplifier is needed for all the laser system. Our system delivers at 780 nm a power of 900 mW with a detuning of 110 GHz for the optical lattice and a power of 650 mW with an adjustable detuning between 0 and -1 GHz for the laser cooling, the detection and the Raman transitions.

  6. Localization of cesium on montmorillonite surface investigated by frequency modulation atomic force microscopy (United States)

    Araki, Yuki; Satoh, Hisao; Okumura, Masahiko; Onishi, Hiroshi


    Cation exchange of clay mineral is typically analyzed without microscopic study of the clay surfaces. In order to reveal the distribution of exchangeable cations at the clay surface, we performed in situ atomic-scale observations of the surface changes in Na-rich montmorillonite due to exchange with Cs cations using frequency modulation atomic force microscopy (FM-AFM). Lines of protrusion were observed on the surface in aqueous CsCl solution. The amount of Cs of the montmorillonite particles analyzed by energy dispersive X-ray spectrometry was consistent with the ratio of the number of linear protrusions to all protrusions in the FM-AFM images. The results showed that the protrusions represent adsorbed Cs cations. The images indicated that Cs cations at the surface were immobile, and their occupancy remained constant at 10% of the cation sites at the surface with different immersion times in the CsCl solution. This suggests that the mobility and the number of Cs cations at the surface are controlled by the permanent charge of montmorillonite; however, the Cs distribution at the surface is independent of the charge distribution of the inner silicate layer. Our atomic-scale observations demonstrate that surface cations are distributed in different ways in montmorillonite and mica.

  7. Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers. (United States)

    Consolino, L; Taschin, A; Bartolini, P; Bartalini, S; Cancio, P; Tredicucci, A; Beere, H E; Ritchie, D A; Torre, R; Vitiello, M S; De Natale, P


    Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications.

  8. Photonic-Chip Supercontinuum with Tailored Spectra for Counting Optical Frequencies (United States)

    Carlson, David R.; Hickstein, Daniel D.; Lind, Alex; Olson, Judith B.; Fox, Richard W.; Brown, Roger C.; Ludlow, Andrew D.; Li, Qing; Westly, Daron; Leopardi, Holly; Fortier, Tara M.; Srinivasan, Kartik; Diddams, Scott A.; Papp, Scott B.


    We explore a photonic-integrated-circuit platform that implements optical-frequency measurements and timekeeping with a perspective towards next-generation portable and spaceborne frequency references and optical-clock networks. The stoichiometric-silicon-nitride waveguides we create provide an efficient and low-noise medium for nonlinear spectral broadening and supercontinuum generation with fiber-based optical-frequency combs. In particular, we demonstrate detailed control over supercontinuum emission to target specific atomic-transition wavelengths and perform an optical-clock comparison using on-chip supercontinuum sources. We report a clock-limited relative frequency instability of 3.8 ×10-15 at τ =2 s between a 1550-nm cavity-stabilized reference laser and NIST's calcium atomic-clock laser at 657 nm using a two-octave waveguide-supercontinuum frequency comb.

  9. Analysis of force-deconvolution methods in frequency-modulation atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Joachim Welker


    Full Text Available In frequency-modulation atomic force microscopy the direct observable is the frequency shift of an oscillating cantilever in a force field. This frequency shift is not a direct measure of the actual force, and thus, to obtain the force, deconvolution methods are necessary. Two prominent methods proposed by Sader and Jarvis (Sader–Jarvis method and Giessibl (matrix method are investigated with respect to the deconvolution quality. Both methods show a nontrivial dependence of the deconvolution quality on the oscillation amplitude. The matrix method exhibits spikelike features originating from a numerical artifact. By interpolation of the data, the spikelike features can be circumvented. The Sader–Jarvis method has a continuous amplitude dependence showing two minima and one maximum, which is an inherent property of the deconvolution algorithm. The optimal deconvolution depends on the ratio of the amplitude and the characteristic decay length of the force for the Sader–Jarvis method. However, the matrix method generally provides the higher deconvolution quality.

  10. Silicon-Chip-Based Optical Frequency Combs (United States)


    deposition of high quality nitride films, which in turn limited the magnitude of the anomalous GVD that could be reached. However, recent advances in...fabrication techniques have allowed for deposition of thick, high quality films [24], enabling higher anomalous GVD values and access to a wider...with the 680-nm components of the supercontinuum. After passing through a bandpass filter, the beat signals are detected using a gigahertz avalanche

  11. High power laser source for atom cooling based on reliable telecoms technology with all fibre frequency stabilisation (United States)

    Legg, Thomas; Farries, Mark


    Cold atom interferometers are emerging as important tools for metrology. Designed into gravimeters they can measure extremely small changes in the local gravitational field strength and be used for underground surveying to detect buried utilities, mineshafts and sinkholes prior to civil works. To create a cold atom interferometer narrow linewidth, frequency stabilised lasers are required to cool the atoms and to setup and measure the atom interferometer. These lasers are commonly either GaAs diodes, Ti Sapphire lasers or frequency doubled InGaAsP diodes and fibre lasers. The InGaAsP DFB lasers are attractive because they are very reliable, mass-produced, frequency controlled by injection current and simply amplified to high powers with fibre amplifiers. In this paper a laser system suitable for Rb atom cooling, based on a 1560nm DFB laser and erbium doped fibre amplifier, is described. The laser output is frequency doubled with fibre coupled periodically poled LiNbO3 to a wavelength of 780nm. The output power exceeds 1 W at 780nm. The laser is stabilised at 1560nm against a fibre Bragg resonator that is passively temperature compensated. Frequency tuning over a range of 1 GHz is achieved by locking the laser to sidebands of the resonator that are generated by a phase modulator. This laser design is attractive for field deployable rugged systems because it uses all fibre coupled components with long term proven reliability.

  12. Low frequency Raman spectroscopy of few-atomic-layer thick hBN crystals (United States)

    Stenger, I.; Schué, L.; Boukhicha, M.; Berini, B.; Plaçais, B.; Loiseau, A.; Barjon, J.


    Hexagonal boron nitride (hBN) has recently gained a strong interest as a strategic component in engineering van der Waals heterostructures built with 2D crystals such as graphene. This work reports micro-Raman measurements on hBN flakes made of a few atomic layers, prepared by mechanical exfoliation. The temperature dependence of the Raman scattering in hBN is investigated first such as to define appropriate measurements conditions suitable for thin layers avoiding undesirable heating induced effects. We further focus on the low frequency Raman mode corresponding to the rigid shearing oscillation between adjacent layers, found to be equal to 52.5 cm-1 in bulk hBN. For hBN sheets with thicknesses below typically 4 nm, the frequency of this mode presents discrete values, which are found to decrease down to 46.0(5) cm-1 for a three-layer hBN, in good agreement with the linear-chain model. This makes Raman spectroscopy a relevant tool to quantitatively determine in a non destructive way the number of layers in ultra thin hBN sheets, below 8 L, prior to their integration in van der Waals heterostructures.

  13. Role of geometry on the frequency spectra of U-shaped atomic force microscope probes (United States)

    Rezaei, E.; Turner, J. A.


    Contact resonance atomic force microscopy (CR-AFM) is a specific technique that is used to determine elastic or viscoelastic properties of materials. The success of this technique is highly dependent on the accuracy of frequency spectra that must be measured for both noncontact and the case in which the tip is in contact with the sample of interest. Thus, choosing the right probe is crucial for accurate experiments. U-shaped probes also offer new opportunities for CR-AFM measurements because of certain specific modes that have tip motion parallel to the sample surface such that these resonances can access in-plane sample properties. However, analysis of the spectra from U-shaped probes is much more challenging due to these modes. The geometry of these probes is the main driver for the spectral response. Here, this influence on the resonance frequencies of the commercially fabricated U-shaped probe AN2-300 is evaluated with respect to geometry in terms of leg width, crossbeam width, and crossbeam length. Both noncontact and contact cases are examined with respect to variations of the nominal geometry. An energy distribution approach is also presented to assist with the identification of modes that have close resonances. Finally, this analysis allows recommendations to be made in order to minimize the convergence of multiple resonances for a specific range of measurement parameters.

  14. Resolving structure and mechanical properties at the nanoscale of viruses with frequency modulation atomic force microscopy.

    Directory of Open Access Journals (Sweden)

    David Martinez-Martin

    Full Text Available Structural Biology (SB techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM fulfills these requirements providing images of individual virus particles under physiological conditions, along with the characterization of a variety of properties including local adhesion and elasticity. Using conventional AFM modes is easy to obtain molecular resolved images on flat samples, such as the purple membrane, or large viruses as the Giant Mimivirus. On the contrary, small virus particles (25-50 nm cannot be easily imaged. In this work we present Frequency Modulation atomic force microscopy (FM-AFM working in physiological conditions as an accurate and powerful technique to study virus particles. Our interpretation of the so called "dissipation channel" in terms of mechanical properties allows us to provide maps where the local stiffness of the virus particles are resolved with nanometer resolution. FM-AFM can be considered as a non invasive technique since, as we demonstrate in our experiments, we are able to sense forces down to 20 pN. The methodology reported here is of general interest since it can be applied to a large number of biological samples. In particular, the importance of mechanical interactions is a hot topic in different aspects of biotechnology ranging from protein folding to stem cells differentiation where conventional AFM modes are already being used.

  15. Resolving structure and mechanical properties at the nanoscale of viruses with frequency modulation atomic force microscopy. (United States)

    Martinez-Martin, David; Carrasco, Carolina; Hernando-Perez, Mercedes; de Pablo, Pedro J; Gomez-Herrero, Julio; Perez, Rebeca; Mateu, Mauricio G; Carrascosa, Jose L; Kiracofe, Daniel; Melcher, John; Raman, Arvind


    Structural Biology (SB) techniques are particularly successful in solving virus structures. Taking advantage of the symmetries, a heavy averaging on the data of a large number of specimens, results in an accurate determination of the structure of the sample. However, these techniques do not provide true single molecule information of viruses in physiological conditions. To answer many fundamental questions about the quickly expanding physical virology it is important to develop techniques with the capability to reach nanometer scale resolution on both structure and physical properties of individual molecules in physiological conditions. Atomic force microscopy (AFM) fulfills these requirements providing images of individual virus particles under physiological conditions, along with the characterization of a variety of properties including local adhesion and elasticity. Using conventional AFM modes is easy to obtain molecular resolved images on flat samples, such as the purple membrane, or large viruses as the Giant Mimivirus. On the contrary, small virus particles (25-50 nm) cannot be easily imaged. In this work we present Frequency Modulation atomic force microscopy (FM-AFM) working in physiological conditions as an accurate and powerful technique to study virus particles. Our interpretation of the so called "dissipation channel" in terms of mechanical properties allows us to provide maps where the local stiffness of the virus particles are resolved with nanometer resolution. FM-AFM can be considered as a non invasive technique since, as we demonstrate in our experiments, we are able to sense forces down to 20 pN. The methodology reported here is of general interest since it can be applied to a large number of biological samples. In particular, the importance of mechanical interactions is a hot topic in different aspects of biotechnology ranging from protein folding to stem cells differentiation where conventional AFM modes are already being used.

  16. Mapping power-law rheology of living cells using multi-frequency force modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Ryosuke; Okajima, Takaharu, E-mail: [Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814 (Japan)


    We present multi-frequency force modulation atomic force microscopy (AFM) for mapping the complex shear modulus G* of living cells as a function of frequency over the range of 50–500 Hz in the same measurement time as the single-frequency force modulation measurement. The AFM technique enables us to reconstruct image maps of rheological parameters, which exhibit a frequency-dependent power-law behavior with respect to G{sup *}. These quantitative rheological measurements reveal a large spatial variation in G* in this frequency range for single cells. Moreover, we find that the reconstructed images of the power-law rheological parameters are much different from those obtained in force-curve or single-frequency force modulation measurements. This indicates that the former provide information about intracellular mechanical structures of the cells that are usually not resolved with the conventional force measurement methods.

  17. Measuring the spin polarization of alkali-metal atoms using nuclear magnetic resonance frequency shifts of noble gases

    Directory of Open Access Journals (Sweden)

    X. H. Liu


    Full Text Available We report a novel method of measuring the spin polarization of alkali-metal atoms by detecting the NMR frequency shifts of noble gases. We calculated the profile of 87Rb D1 line absorption cross sections. We then measured the absorption profile of the sample cell, from which we calculated the 87Rb number densities at different temperatures. Then we measured the frequency shifts resulted from the spin polarization of the 87Rb atoms and calculated its polarization degrees at different temperatures. The behavior of frequency shifts versus temperature in experiment was consistent with theoretical calculation, which may be used as compensative signal for the NMRG closed-loop control system.

  18. Dispersion engineered high-Q silicon Nitride Ring-Resonators via Atomic Layer Deposition

    CERN Document Server

    Riemensberger, Johann; Herr, Tobias; Brasch, Victor; Holzwarth, Ronald; Kippenberg, Tobias J


    We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition (ALD). Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. All results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.

  19. Ultra-broadband Photonic Harmonic Mixer Based on Optical Comb Generation

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei


    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... without using costly ultra-broadband photodiode. It is theoretically shown that the down-conversion efficiency and the bandwidth of the mixer is highly dependent on the optical modulation indices and the fundamental frequency of comb lines. Down-conversion of a W-band (75-110GHz) fiberwireless signal...

  20. Erratum to “Ultra-Broadband Photonic Harmonic Mixer Based on Optical Comb Generation”

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei


    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented ...

  1. Atomic physics precise measurements and ultracold matter

    CERN Document Server

    Inguscio, Massimo


    Atomic Physics provides an expert guide to two spectacular new landscapes in physics: precision measurements, which have been revolutionized by the advent of the optical frequency comb, and atomic physics, which has been revolutionized by laser cooling. These advances are not incremental but transformative: they have generated a consilience between atomic and many-body physics, precipitated an explosion of scientific and technological applications, opened new areas of research, and attracted a brilliant generation of younger scientists. The research is advancing so rapidly, the barrage of applications is so dazzling, that students can be bewildered. For both students and experienced scientists, this book provides an invaluable description of basic principles, experimental methods, and scientific applications.

  2. Neutral Atom Frequency Reference in the Deep Ultraviolet with FractionalUncertainty=5.7×10-15 (United States)

    McFerran, J. J.; Yi, L.; Mejri, S.; Di Manno, S.; Zhang, W.; Guéna, J.; Le Coq, Y.; Bize, S.


    We present an assessment of the (6s2) S01↔(6s6p)P03 clock transition frequency in Hg199 with an uncertainty reduction of nearly 3 orders of magnitude and demonstrate an atomic quality factor Q of ˜1014. The Hg199 atoms are confined in a vertical lattice trap with light at the newly determined magic wavelength of 362.5697±0.0011nm and at a lattice depth of 20ER. The atoms are loaded from a single-stage magneto-optical trap with cooling light at 253.7 nm. The high Q factor is obtained with an 80 ms Rabi pulse at 265.6 nm. We find the frequency of the clock transition to be 1128575290808162.0±6.4(syst)±0.3(stat)Hz (i.e., with fractionaluncertainty=5.7×10-15). Neither an atom number nor second order Zeeman dependence has yet been detected. Only three laser wavelengths are used for the cooling, lattice trapping, probing, and detection.

  3. Neutral atom frequency reference in the deep ultraviolet with fractional uncertainty = 5.7×10(-15). (United States)

    McFerran, J J; Yi, L; Mejri, S; Di Manno, S; Zhang, W; Guéna, J; Le Coq, Y; Bize, S


    We present an assessment of the (6s2) (1)S0 ↔ (6s6p)(3)P0 clock transition frequency in 199Hg with an uncertainty reduction of nearly 3 orders of magnitude and demonstrate an atomic quality factor Q of ∼10(14). The 199Hg atoms are confined in a vertical lattice trap with light at the newly determined magic wavelength of 362.5697±0.0011  nm and at a lattice depth of 20E(R). The atoms are loaded from a single-stage magneto-optical trap with cooling light at 253.7 nm. The high Q factor is obtained with an 80 ms Rabi pulse at 265.6 nm. We find the frequency of the clock transition to be 1,128,575,290,808,162.0±6.4(syst)±0.3(stat)  Hz (i.e., with fractional uncertainty=5.7×10(-15)). Neither an atom number nor second order Zeeman dependence has yet been detected. Only three laser wavelengths are used for the cooling, lattice trapping, probing, and detection.

  4. Towards a robust green astro-comb for Earth-like exoplanet searches (United States)

    Ravi, Aakash; Martin, Leopoldo; Phillips, David; Langellier, Nicholas; Milbourne, Timothy; Dolliff, Christian; Walsworth, Ronald


    The detection of exoplanets using the radial velocity (RV) method has become a very exciting and active area of research. Detecting Earth-like planets, however, is still very challenging as it requires extremely precise calibration of the spectrographs used in such measurements. To address this challenge, we employ a visible wavelength frequency comb - referenced to the global positioning system - as a calibration source. Our comb calibrator is realized by spectrally broadening and shifting the output of a 1 GHz repetition rate modelocked Ti:sapphire laser using a photonic crystal fiber and then filtering the comb lines to create a 16 GHz-spacing comb. This system has been implemented at the TNG telescope on La Palma to calibrate the HARPS-N spectrograph. However, the complexity of the system has thus far prevented its routine use as it requires frequency comb specialists to be on site during measurements. Here, we propose some automation strategies and present preliminary results from our efforts. We also discuss ongoing comb-calibrated astrophysical observations, including measurements of the Sun. The solar measurements are part of an effort to understand stellar noise sources in the RV data and demonstrate the sensitivity of the instrument to detect terrestrial exoplanets.

  5. Dual-Colored DNA Comb Polymers for Single Molecule Rheology (United States)

    Mai, Danielle; Marciel, Amanda; Schroeder, Charles


    We report the synthesis and characterization of branched biopolymers for single molecule rheology. In our work, we utilize a hybrid enzymatic-synthetic approach to graft ``short'' DNA branches to ``long'' DNA backbones, thereby producing macromolecular DNA comb polymers. The branches and backbones are synthesized via polymerase chain reaction with chemically modified deoxyribonucleotides (dNTPs): ``short'' branches consist of Cy5-labeled dNTPs and a terminal azide group, and ``long'' backbones contain dibenzylcyclooctyne-modified (DBCO) dNTPs. In this way, we utilize strain-promoted, copper-free cycloaddition ``click'' reactions for facile grafting of azide-terminated branches at DBCO sites along backbones. Copper-free click reactions are bio-orthogonal and nearly quantitative when carried out under mild conditions. Moreover, comb polymers can be labeled with an intercalating dye (e.g., YOYO) for dual-color fluorescence imaging. We characterized these materials using gel electrophoresis, HPLC, and optical microscopy, with atomic force microscopy in progress. Overall, DNA combs are suitable for single molecule dynamics, and in this way, our work holds the potential to improve our understanding of topologically complex polymer melts and solutions.

  6. Comparison of photothermal and piezoacoustic excitation methods for frequency and phase modulation atomic force microscopy in liquid environments

    Directory of Open Access Journals (Sweden)

    A. Labuda


    Full Text Available In attempting to perform frequency modulation atomic force microscopy (FM-AFM in liquids, a non-flat phase transfer function in the self-excitation system prevents proper tracking of the cantilever natural frequency. This results in frequency-and-phase modulation atomic force microscopy (FPM-AFM which lies in between phase modulation atomic force microscopy (PM-AFM and FM-AFM. We derive the theory necessary to recover the conservative force and damping in such a situation, where standard FM-AFM theory no longer applies. Although our recovery procedure applies to all cantilever excitation methods in principle, its practical implementation may be difficult, or even impossible, if the cantilever is driven piezoacoustically. Specifically, we contrast the piezoacoustic excitation method to the photothermal method in the context of force spectroscopy of hydration structures at the mica-water interface. The results clearly demonstrate that photothermal excitation is superior to piezoacoustic excitation, as it allows for accurate quantitative interpretation of the acquired data.

  7. High order SSB modulation and its application for advanced optical comb generation based on RFS (United States)

    Sun, Lin; Du, Jiangbing; Li, Lu; He, Zuyuan


    In this work, a method for high-order single sideband (SSB) modulation is demonstrated. Extended frequency shifting can be obtained based on the high-order SSB modulator. The design of the 2nd and 3rd order SSB modulators are presented and investigated based on simulations. The demonstrated high-order SSB modulators can be used for advanced optical comb generation when they are configured in recirculating frequency shifter (RFS). Optical comb with significantly enlarged carrier-to-carrier spacing can be obtained and thus applications including wavelength division multiplexing (WDM) communication, optical frequency domain reflectometry (OFDR) and so on can be benefited.

  8. High-Q Bandpass Comb Filter for Mains Interference Extraction

    Directory of Open Access Journals (Sweden)

    Neycheva T.


    Full Text Available This paper presents a simple digital high-Q bandpass comb filter for power-line (PL or other periodical interference extraction. The filter concept relies on a correlated signal average resulting in alternating constructive and destructive spectrum interference i.e. the so-called comb frequency response. The presented filter is evaluated by Matlab simulations with real ECG signal contaminated with low amplitude PL interference. The made simulations show that this filter accurately extract the PL interference. It has high-Q notches only at PL odd harmonics and is appropriate for extraction of any kind of odd harmonic interference including rectangular shape. The filter is suitable for real-time operation with popular low-cost microcontrollers.

  9. Comb-like thermoresponsive polymeric materials : Synthesis and effect of macromolecular structure on solution properties

    NARCIS (Netherlands)

    Wever, D. A. Z.; Riemsma, E.; Picchioni, F.; Broekhuis, A. A.


    A series of comb-like block and random copolymers based on acrylamide (AM) and N-isopropylacrylamide (NIPAM) have been prepared by atom transfer radical polymerization (ATRP). The number of side-arms, the length of the AM and NIPAM blocks as well as the distribution of the two monomers (block or

  10. Application of the Molecular Combing Technique to Starch Granules

    Directory of Open Access Journals (Sweden)

    Zhong-Dong Liu


    Full Text Available The molecular combing technique was used to dissociate the nanostructural units of starch granules from the starch fragments after a gelatinization process. With the help of atomic force microscopy (AFM, we observed that some nanostructural chains were just flowing out of the granules. It proves that there are substantive nanostructural units in the starch granules, a phenomenon not previously observed, so these nanostructural units were defined as suspected intermediates. Furthermore, we conclude that blocklets of starch granules are formed through twisting or distortion of nanochains.

  11. Calculated vibrational frequencies for FeMo-co, the active site of nitrogenase, bearing hydrogen atoms and carbon monoxide. (United States)

    Dance, Ian


    The intramolecular hydrogenation paradigm for the reducing actions of the enzyme nitrogenase postulates that the iron-molybdenum cofactor (FeMo-co, Fe(7)MoS(9)N(homocitrate)) as active site contains H atoms bound to Fe and S during the catalytic cycle, and that these H atoms are the reducing agents. The reduction of N(2) and of all other non-physiological substrates is strongly inhibited by carbon monoxide, except for the formation of H(2) from protons. It has been recently reported that vanadium nitrogenase and modified molybdenum nitrogenase reduce CO to hydrocarbons. Therefore many questions now arise about relationships between CO and H on the nitrogenase cofactors. In order to assist the interpretation of kinetic infrared spectral data, vibrational frequencies and modes have been calculated for a variety of possible structures in which FeMo-co bears H atoms, or CO ligands, or both. Fe-H stretching frequencies occur in the same spectral window as the C-O stretching frequencies, with lesser intensity, and both stretches are strongly coupled in some structures. Symmetrical bridging of CO between two Fe atoms of FeMo-co is destabilised by the presence of other ligands on Fe, and the reason for this is evident. Two results for bound formyl, HCO, are reported. These calculations of reference structures allow some interpretation of existing experimental spectra, but, more significantly, they suggest further kinetic infrared experiments to elucidate the chemical mechanism of catalysis by nitrogenase under normal turnover conditions. This journal is © The Royal Society of Chemistry 2011

  12. Correlations between the mechanical loss and atomic structure of amorphous TiO2-doped Ta2O5 coatings


    Bassiri, R.; Evans, K.; Borisenko, K. B.; Fejer, M. M.; Hough, J.; MacLaren, I.; Martin, I. W.; Route, R.K.; Rowan, S


    Highly reflective dielectric mirror coatings are critical components in a range of precision optics applications including frequency combs, optical atomic clocks, precision interferometry and ring laser gyroscopes. A key limitation to the performance in these applications is thermal noise, arising from the mechanical loss of the coatings. The origins of the mechanical loss from these coatings is not well understood.\\ud \\ud Recent work suggests that the mechanical loss of amorphous Ta2O5 coati...

  13. Coherent Frequency Shifter, Optical Isolator, Lasers on an Integrated Platform for Cold Atom Microsystems (United States)


    Thomas R. Caudill, Acting Chief Program Manager, AFRL/RVBYE AFRL Battlespace Environment Division This report is published in the interest of...power operation of optical frequency shifter; (7) a new design and theoretical analysis of frequency shifter with larger electro-optical coefficients...integrated laser. 15. SUBJECT TERMS coherent frequency shifter, optical isolation, integrated photonics, 780nm laser design and fabrication 16

  14. Controlled production of atomic oxygen and nitrogen in a pulsed radio-frequency atmospheric-pressure plasma (United States)

    Dedrick, J.; Schröter, S.; Niemi, K.; Wijaikhum, A.; Wagenaars, E.; de Oliveira, N.; Nahon, L.; Booth, J. P.; O’Connell, D.; Gans, T.


    Radio-frequency driven atmospheric pressure plasmas are efficient sources for the production of reactive species at ambient pressure and close to room temperature. Pulsing the radio-frequency power input provides additional control over species production and gas temperature. Here, we demonstrate the controlled production of highly reactive atomic oxygen and nitrogen in a pulsed radio-frequency (13.56 MHz) atmospheric-pressure plasma, operated with a small 0.1 % air-like admixture (N2 /O2 at 4:1 ) through variations in the duty cycle. Absolute densities of atomic oxygen and nitrogen are determined through vacuum-ultraviolet absorption spectroscopy using the DESIRS beamline at the SOLEIL synchrotron coupled with a high resolution Fourier-transform spectrometer. The neutral-gas temperature is measured using nitrogen molecular optical emission spectroscopy. For a fixed applied-voltage amplitude (234 V), varying the pulse duty cycle from 10% to 100% at a fixed 10 kHz pulse frequency enables us to regulate the densities of atomic oxygen and nitrogen over the ranges of (0.18+/-0.03) –(3.7+/-0.1)× 1020 m-3 and (0.2+/-0.06) –(4.4+/-0.8) × 1019 m-3 , respectively. The corresponding 11 K increase in the neutral-gas temperature with increased duty cycle, up to a maximum of (314+/-4) K, is relatively small. This additional degree of control, achieved through regulation of the pulse duty cycle and time-averaged power, could be of particular interest for prospective biomedical applications.

  15. Kerr comb generation from the perspective of spatial dissipative structures (United States)

    Coillet, Aurélien; Balakireva, Irina; Saleh, Khaldoun; Henriet, Rémi; Larger, Laurent; Chembo, Yanne K.


    The theoretical understanding of Kerr combs has been the object of extensive efforts worldwide in the last ten years. Several insights have been provided since then into this problem and have enabled significant progress for the optimization and tailoring of these combs. Here, we investigate the formation of dissipative structures in crystalline whispering-gallery mode disk resonators that are pumped in different dispersion regimes. In the Fourier domain, these dissipative structures correspond to specific types of mode-locked Kerr optical frequency combs. Depending on the sign of the second-order chromatic dispersion and on the pumping conditions, we show that either bright or dark cavity solitons can emerge, and we show these two regimes are associated with characteristic spectral signatures that can be discriminated experimentally. We use the Lugiato-Lefever spatiotemporal formalism to investigate the temporal dynamics leading to the formation of these azimuthal solitons, as well as the emergence of Turing patterns. The theoretical results are in excellent agreement with experimental measurements that are obtained using calcium and magnesium fluoride disk resonators pumped near 1550 nm.

  16. Design of a Low Phase Noise VCO for Rubidium Atomic Frequency Standard

    Directory of Open Access Journals (Sweden)

    Ju Qingyun


    Full Text Available Compared to the size and the power consumption of the traditional atomic clocks, the ones based on coherent population trapping (CPT can provide improvement by two orders of magnitude in both aspects above, making them needed urgently in many fields. Among different CPT atomic clocks, the one made with the rubidium atom are used widely, and their operating performance largely depends on its internal voltage-controlled oscillator (VCO which is used to provide a proper microwave signal. Based on this, a small size and low phase noise 3.035GHz VCO is designed with a modified Clapp circuit topology using low-cost surface-mount components, including a coaxial resonant (COAX with high quality factor. The designed VCO is simulated and optimized with the combined use of the negative resistance analysis method and the transmission analysis with a virtual-ground. In order to obtain the desired results, different values of key capacitor elements are tried according to their concrete influences on the VCO during the process of the circuit tuning. The test results show that the phase noises of the VCO are -60.49dBc/Hz@300Hz, -73.08dBc/Hz@1KHz and -97.48dBc/Hz@10KHz, the output power is -1.13dBm and the voltage-controlled tuning sensitivity is about 12MHz/V.

  17. Investigation of Atomic Physics and Frequency Stability with a Croygenic Hydrogen Laser

    National Research Council Canada - National Science Library

    Walsworth, Ronald


    .... The cryogenic hydrogen maser (CHM) operates at low temperatures, and may provide frequency stability that is one to three orders of magnitude better than a room temperature hydrogen maser because of greatly reduced thermal noise and larger signal power...

  18. Mach-zehnder based optical marker/comb generator for streak camera calibration (United States)

    Miller, Edward Kirk


    This disclosure is directed to a method and apparatus for generating marker and comb indicia in an optical environment using a Mach-Zehnder (M-Z) modulator. High speed recording devices are configured to record image or other data defining a high speed event. To calibrate and establish time reference, the markers or combs are indicia which serve as timing pulses (markers) or a constant-frequency train of optical pulses (comb) to be imaged on a streak camera for accurate time based calibration and time reference. The system includes a camera, an optic signal generator which provides an optic signal to an M-Z modulator and biasing and modulation signal generators configured to provide input to the M-Z modulator. An optical reference signal is provided to the M-Z modulator. The M-Z modulator modulates the reference signal to a higher frequency optical signal which is output through a fiber coupled link to the streak camera.

  19. Analysis of HARPS Astro-Comb Data (United States)

    Milakovic, Dinko; Pasquini, L.; Lo Curto, G.; Avila, G.; Manescau, A.; Canto Martins, B. N.; Leão, I. C.; De Medeiros, J. R.; Esposito, M.; González Hernández, J. I.; Rebolo, R.; Probst, R.; Steinmetz, T.; Hänsch, T. W.; Udem, Th.; Holzwarth, R.


    "The HARPS astro-comb was repaired in October 2016, and it is under unsupervised operations since. In this poster we show the analysis of the comb data, in particular the presence of a wavelength dependent background continuum. We are able to characterise this background with respect to wavelength and time. We show that its proper evaluation is essential to optimize the performances of the system."

  20. Tailoring the pulse shape to efficiently populate atomic electron metastable states in a relativistically intense high-frequency laser field (United States)

    Emelin, M. Yu.; Smirnov, L. A.; Ryabikin, M. Yu.


    The results of both quantum-mechanical numerical calculations beyond the electric dipole approximation and relativistic classical Monte Carlo simulations are presented for a ground-state hydrogen atom exposed to a high-frequency circularly polarized laser field in a wide intensity range. The persistence of the light-induced metastable bound states well into the relativistic regime of laser-atom interaction is demonstrated. The feasibility of high-efficiency electron trapping into these metastable states is examined in the frame of a simple two-stage scenario for a laser field turning on. The optimal parameters of the laser pulse front are found, which provide an optimal balance between the needs to achieve as quickly as possible the higher intensities, for which the decay rate of the metastable states is lower, and to ensure sufficient adiabaticity of the field turning on to avoid the unwanted "shake-off" processes. As a result, more than 60% probability of electron trapping into the metastable states in a relativistically intense high-frequency laser field is demonstrated.

  1. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications (United States)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert


    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  2. Rapidly Tunable Dual-Comb RF Photonic Filter for Ultrabroadband RF Spread Spectrum Applications


    Kim, Hyoung-Jun; Leaird, Daniel E.; Weiner, Andrew M.


    IEEE Transactions on Microwave Theory and Techniques The article of record as published may be found at We demonstrate a rapidly frequency-tunable radio frequency (RF) filter using microwave photonics technology for ultrawideband RF spread spectrum applications. A pair of electro-optic frequency combs is arranged as a dispersive tapped delay line in a differential detection configuration to implement a programmable finite impulse response RF f...

  3. True atomic-scale imaging of a spinel Li{sub 4}Ti{sub 5}O{sub 12}(111) surface in aqueous solution by frequency-modulation atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kitta, Mitsunori, E-mail:; Kohyama, Masanori [Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial Science and Technology, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan); Onishi, Hiroshi [Department of Chemistry, Graduate School of Science, Kobe University 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)


    Spinel-type lithium titanium oxide (LTO; Li{sub 4}Ti{sub 5}O{sub 12}) is a negative electrode material for lithium-ion batteries. Revealing the atomic-scale surface structure of LTO in liquid is highly necessary to investigate its surface properties in practical environments. Here, we reveal an atomic-scale image of the LTO(111) surface in LiCl aqueous solution using frequency-modulation atomic force microscopy. Atomically flat terraces and single steps having heights of multiples of 0.5 nm were observed in the aqueous solution. Hexagonal bright spots separated by 0.6 nm were also observed on the flat terrace part, corresponding to the atomistic contrast observed in the ultrahigh vacuum condition, which suggests that the basic atomic structure of the LTO(111) surface is retained without dramatic reconstruction even in the aqueous solution.

  4. An unshielded radio-frequency atomic magnetometer with sub-femtoTesla sensitivity

    Directory of Open Access Journals (Sweden)

    David A. Keder


    Full Text Available We demonstrate a radio-frequency potassium-vapor magnetometer operating with sensitivities of 0.3 fT/ Hz at 0.5 MHz and 0.9 fT/ Hz at 1.31 MHz in the absence of radio-frequency and mu-metal or magnetic shielding. The use of spatially separated magnetometers, two voxels within the same cell, permits for the subtraction of common mode noise and the retention of a gradient signal, as from a local source. At 0.5 MHz the common mode noise was white and measured to be 3.4 fT/ Hz ; upon subtraction the noise returned to the values observed when the magnetometer was shielded. At 1.31 MHz, the common mode noise was from a nearby radio station and was reduced by a factor of 33 upon subtraction, limited only by the radio signal picked up by receiver electronics. Potential applications include in-the-field low-field magnetic resonance, such as the use of nuclear quadrupole resonance for the detection of explosives.

  5. Frequency chain to measure the 2S-8S/8D transitions in atomic hydrogen: measurement of the Rydberg constant in frequency unit; Chaine de frequence optique pour mesurer les transitions 2S-8S/8D dans l'atome d'hydrogene: mesure de la constante de Rydberg en unite de frequence

    Energy Technology Data Exchange (ETDEWEB)

    Nez, F


    The aim of this thesis is to make a pure measurement of the frequency of the 2S-8S/8D two-photon transition in atomic hydrogen. In that purpose we have built a frequency chain in which hydrogen frequencies are compared with the difference of two optical standards, the methane stabilized He-Ne laser (3.39 {mu}m) and the iodine stabilized He-Ne laser (633 nm). The radiation from a home made Ti-sapphire laser (TS2) at 778 nm is mixed, in a LiIO{sub 3} crystal, with the one of a auxiliary He-Ne laser at 3.39 {mu}m to produce a synthesized radiation at 633 nm. The frequency of the Ti-sapphire (TS1) laser used for the two photon excitation is 89 GHz away from the one of TS2. To compare these two lasers, we have used a Schottky diode. The two lasers and a microwave radiation at 89 GHz, produced by a Gunn diode, are focused on the Schottky diode. The Gunn diode is phase locked on an ultra-stable quartz oscillator. In this way, we have linked an optical frequency of atomic hydrogen to the cesium clock without interferometry. From our measurements, we have deduced a new value of the Rydberg constant: R{sub {infinity}} equals 109737.3156834 (24) cm{sup -1} with an uncertainty of 2.2 10{sup -11}. Our uncertainty is near the one of the Q.E.D calculations giving the theoretical values of the energy levels. This value, which is currently the most precise available, is in good agreement with the recent result obtained from the 1S-2S and 2S-4D transitions. (author)

  6. Electrostatic comb drive for vertical actuation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, A. P., LLNL


    The electrostatic comb finger drive has become an integral design for microsensor and microactuator applications. This paper reports on utilizing the levitation effect of comb fingers to design vertical-to-the-substrate actuation for interferometric applications. For typical polysilicon comb drives with 2 {micro}m gaps between the stationary and moving fingers, as well as between the microstructures and the substrate, the equilibrium position is nominally 1-2 {micro}m above the stationary comb fingers. This distance is ideal for many phase shifting interferometric applications. Theoretical calculations of the vertical actuation characteristics are compared with the experimental results, and a general design guideline is derived from these results. The suspension flexure stiffnesses, gravity forces, squeeze film damping, and comb finger thicknesses are parameters investigated which affect the displacement curve of the vertical microactuator. By designing a parallel plate capacitor between the suspended mass and the substrate, in situ position sensing can be used to control the vertical movement, providing a total feedback-controlled system. Fundamentals of various capacitive position sensing techniques are discussed. Experimental verification is carried out by a Zygo distance measurement interferometer.

  7. Noncontact Viscoelastic Imaging of Living Cells Using a Long-Needle Atomic Force Microscope with Dual-Frequency Modulation (United States)

    Guan, Dongshi; Charlaix, Elisabeth; Qi, Robert Z.; Tong, Penger


    Imaging of surface topography and elasticity of living cells can provide insight into the roles played by the cells' volumetric and mechanical properties and their response to external forces in regulating the essential cellular events and functions. Here, we report a unique technique of noncontact viscoelastic imaging of live cells using atomic force microscopy (AFM) with a long-needle glass probe. Because only the probe tip is placed in a liquid medium near the cell surface, the AFM cantilever in air functions well under dual-frequency modulation, retaining its high-quality resonant modes. The probe tip interacts with the cell surface through a minute hydrodynamic flow in the nanometer-thin gap region between them without physical contact. Quantitative measurements of the cell height, volume, and Young's modulus are conducted simultaneously. The experiment demonstrates that the long-needle AFM has a wide range of applications in the study of cell mechanics.

  8. The limit of time resolution in frequency modulation atomic force microscopy by a pump-probe approach (United States)

    Schumacher, Zeno; Spielhofer, Andreas; Miyahara, Yoichi; Grutter, Peter


    Atomic force microscopy (AFM) routinely achieves structural information in the sub-nm length scale. Measuring time resolved properties on this length scale to understand kinetics at the nm scale remains an elusive goal. We present a general analysis of the lower limit for time resolution in AFM. Our finding suggests that the time resolution in AFM is ultimately limited by the well-known thermal limit of AFM and not as often proposed by the mechanical response time of the force sensing cantilever. We demonstrate a general pump-probe approach using the cantilever as a detector responding to the averaged signal. This method can be applied to any excitation signal such as electrical, thermal, magnetic or optical. Experimental implementation of this method allows us to measure a photocarrier decay time of ˜1 ps in low temperature grown GaAs using a cantilever with a resonant frequency of 280 kHz.

  9. Limits on violations of Lorentz symmetry and the Einstein equivalence principle using radio-frequency spectroscopy of atomic dysprosium. (United States)

    Hohensee, M A; Leefer, N; Budker, D; Harabati, C; Dzuba, V A; Flambaum, V V


    We report a joint test of local Lorentz invariance and the Einstein equivalence principle for electrons, using long-term measurements of the transition frequency between two nearly degenerate states of atomic dysprosium. We present many-body calculations which demonstrate that the energy splitting of these states is particularly sensitive to violations of both special and general relativity. We limit Lorentz violation for electrons at the level of 10(-17), matching or improving the best laboratory and astrophysical limits by up to a factor of 10, and improve bounds on gravitational redshift anomalies for electrons by 2 orders of magnitude, to 10(-8). With some enhancements, our experiment may be sensitive to Lorentz violation at the level of 9 × 10(-20).

  10. A Fine-Tooth Comb to Measure the Accelerating Universe (United States)


    Astronomical instruments needed to answer crucial questions, such as the search for Earth-like planets or the way the Universe expands, have come a step closer with the first demonstration at the telescope of a new calibration system for precise spectrographs. The method uses a Nobel Prize-winning technology called a 'laser frequency comb', and is published in this week's issue of Science. Uncovering the disc ESO PR Photo 26a/08 A Laser Comb for Astronomy "It looks as if we are on the way to fulfil one of astronomers' dreams," says team member Theodor Hänsch, director at the Max Planck Institute for Quantum Optics (MPQ) in Germany. Hänsch, together with John Hall, was awarded the 2005 Nobel Prize in Physics for work including the frequency comb technique. Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colours, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colours rather than distances, with an extremely accurate and fine grid. New, extremely precise spectrographs will be needed in experiments planned for the future European Extremely Large Telescope (E-ELT), which is being designed by ESO, the European Southern Observatory. These new spectrographs will need to be calibrated with even more accurate 'rulers'. In fact, they must be accurate to about one part in 30 billions - a feat equivalent to measuring the circumference of the Earth to about a millimetre! "We'll need something beyond what current technology can offer, and that's where the laser frequency comb comes in. It is

  11. Mechanical Properties of Microcrystalline Metal-Organic Frameworks (MOFs) Measured by Bimodal Amplitude Modulated-Frequency Modulated Atomic Force Microscopy. (United States)

    Sun, Yao; Hu, Zhigang; Zhao, Dan; Zeng, Kaiyang


    Direct measurement of the mechanical properties of microcrystalline metal-organic framework (MOF) nanoparticles is challenging and rarely explored. In this work, we apply an effective method to realize elastic modulus mapping of a series of isostructural single MOF nanoparticles (100-500 nm) via bimodal amplitude modulated-frequency modulated atomic force microscopy. By probing five types of zirconium (Zr) and hafnium (Hf) isostructural UiO-66-type MOFs, we experimentally found that UiO-66(Hf)-type MOFs possess the higher elastic modulus (46-104 GPa) than that of UiO-66(Zr)-type MOFs (34-100 GPa), both of which are higher than that of reported zinc/copper based MOFs (3-10 GPa). We also experimentally demonstrate that the mechanical properties of MOFs can be tuned by adjusting the chemical functionalities of the ligands or using different metal nodes. In detail, the sterically bulky functional groups increase the mechanical properties of the resultant UiO-66-type MOFs, possibly due to the increased atomic density. These results pave a way to the direct measurement of mechanical properties of MOFs crystalline particles and provide an incisive perspective to the design of MOFs with high mechanical properties.

  12. Integrated Kerr comb-based reconfigurable transversal differentiator for microwave photonic signal processing (United States)

    Xu, Xingyuan; Wu, Jiayang; Shoeiby, Mehrdad; Nguyen, Thach G.; Chu, Sai T.; Little, Brent E.; Morandotti, Roberto; Mitchell, Arnan; Moss, David J.


    An arbitrary-order intensity differentiator for high-order microwave signal differentiation is proposed and experimentally demonstrated on a versatile transversal microwave photonic signal processing platform based on integrated Kerr combs. With a CMOS-compatible nonlinear micro-ring resonator, high quality Kerr combs with broad bandwidth and large frequency spacings are generated, enabling a larger number of taps and an increased Nyquist zone. By programming and shaping individual comb lines' power, calculated tap weights are realized, thus achieving a versatile microwave photonic signal processing platform. Arbitrary-order intensity differentiation is demonstrated on the platform. The RF responses are experimentally characterized, and systems demonstrations for Gaussian input signals are also performed.

  13. Femtosecond optical parametric oscillators toward real-time dual-comb spectroscopy (United States)

    Jin, Yuwei; Cristescu, Simona M.; Harren, Frans J. M.; Mandon, Julien


    We demonstrate mid-infrared dual-comb spectroscopy with an optical parametric oscillator (OPO) toward real-time field measurement. A singly resonant OPO based on a MgO-doped periodically poled lithium niobate (PPLN) crystal is demonstrated. Chirped mirrors are used to compensate the dispersion caused by the optical cavity and the crystal. A low threshold of 17 mW has been achieved. The OPO source generates a tunable idler frequency comb between 2.7 and 4.7 μm. Dual-comb spectroscopy is achieved by coupling two identical Yb-fiber mode-locked lasers to this OPO with slightly different repetition frequencies. A measured absorption spectrum of methane is presented with a spectral bandwidth of , giving an instrumental resolution of . In addition, a second OPO containing two MgO-doped PPLN crystals in a singly resonant ring cavity is demonstrated. As such, this OPO generates two idler combs (average power up to 220 mW), covering a wavelength range between 2.7 and 4.2 μm, from which a mid-infrared dual-comb Fourier transform spectrometer is constructed. By detecting the heterodyned signal between the two idler combs, broadband spectra of molecular gases can be observed over a spectral bandwidth of more than . This special cavity design allows the spectral resolution to be improved to without locking the OPO cavity, indicating that this OPO represents an ideal high-power broadband mid-infrared source for real-time gas sensing.

  14. Molecular Combing of DNA: Methods and Applications

    DEFF Research Database (Denmark)

    Nazari, Zeniab Esmail; Gurevich, Leonid


    First proposed in 1994, molecular combing of DNA is a technique that allows adsorption and alignment of DNA on the surface with no need for prior modification of the molecule. Since then, many variations of the original method have been devised and used in a wide range of applications from genomi...... of the main methods in molecular combing as well as its major applications in nanotechnology.......First proposed in 1994, molecular combing of DNA is a technique that allows adsorption and alignment of DNA on the surface with no need for prior modification of the molecule. Since then, many variations of the original method have been devised and used in a wide range of applications from genomic...

  15. An etalon stabilized 10-GHz comb source using a slab coupled waveguide amplifier (United States)

    Davila-Rodriguez, Josue; Ozdur, Ibrahim T.; Mandridis, Dimitrios; Williams, Charles; Delfyett, Peter J.; Plant, Jason J.; Juodawlkis, Paul W.


    An optical comb source based on a slab-coupled optical waveguide amplifier (SCOWA) is presented. The laser is harmonically mode-locked at 10.287 GHz repetition rate and stabilized to an intra-cavity Fabry-Pérot etalon via Pound- Drever-Hall locking. The Fabry-Pérot etalon serves as a reference for the optical frequency of the comb-lines and suppresses the fiber cavity modes to allow only a single longitudinal mode-set to oscillate, generating a frequency comb spaced by the repetition rate. The pulse-to-pulse timing jitter and energy fluctuations are amplifier as the gain medium and the use of an ultra-low noise sapphire-loaded cavity oscillator to mode-lock the laser. The SCOWA has higher saturation power than commercially available gain media, permitting higher intra-cavity power as well as available power at the output, increasing the power of the photodetected RF tones which increases their signal-to-noise ratio. A high visibility optical frequency comb is observed spanning ~3 nm (at -10 dB), with optical SNR > 60 dB for a cavity with no dispersion compensation. Initial results of a dispersion compensated cavity are presented. A spectral width of ~7.6 nm (-10 dB) was obtained for this case and the pulses can be compressed to near the transform limit at ~930 fs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Niemi, K.; O' Connell, D.; Gans, T. [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Oliveira, N. de; Joyeux, D.; Nahon, L. [Synchrotron Soleil, l' Orme des Merisiers, St. Aubin BP 48, 91192 Gif sur Yvette Cedex (France); Booth, J. P. [Laboratoire de Physique des Plasmas-CNRS, Ecole Polytechnique, 91128 Palaiseau (France)


    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. %.

  17. Synonymy of Maladera rubida (Moser, 1915) comb. N. (Coleoptera ...

    African Journals Online (AJOL)

    During a revision of type material of Afrotropical and Asian Sericini, the following new synonymy was established: Maladera rubida (Moser, 1915) comb. n. (= Autoserica errata Moser, 1916, syn. n.), Maladera laminifera (Moser, 1916) comb. n. and Maladera fuscescens (Moser, 1917) comb. n. Lectotypes for Autoserica ...

  18. Measurements of amplitude and frequencies of subwavelength oscillations of atoms using resonance fluorescence of three levels atom in two standing waves (United States)

    Enaki, Nicolae; Bazgan, Sergiu; Mihailescu, Ion


    The resonance fluorescence of an atomic (or ion) system implanted in the materials driving two standing waves of the optical cavity is studied taking into consideration the delocalization of the atom. It is demonstrated that the resonance fluorescence depends on the position of atoms (or ions) relative the nodes or antinodes of standing waves. This situation gives us the possibility to measure the amplitude of mechanical oscillations of these radiators implanted in organic or inorganic materials. It is proposed to measure the amplitude of the mechanical oscillations relative to the equilibrium position using the time changes in the positions of the five peaks of the resonance fluorescence spectrum. In this case, the small oscillation amplitude relative to the standing wave length can drastically change the spectrum of resonance fluorescence of such atoms. The proposed method can be used in the measurements of the nanostructure temperature (or bio-molecule temperature deformation).

  19. Absolute frequency determination of molecular transition in the Doppler regime at kHz level of accuracy (United States)

    Bielska, K.; Wójtewicz, S.; Morzyński, P.; Ablewski, P.; Cygan, A.; Bober, M.; Domysławska, J.; Zawada, M.; Ciuryło, R.; Masłowski, P.; Lisak, D.


    We measured absolute frequency of the unperturbed P7 P7 O2 B-band transition ν0 = 434783.5084857(82) GHz and the collisional self-shift coefficient δ = - 9.381(62) ×10-21 GHz/(molecule/cm3). With Doppler-limited spectroscopy we achieved the relative standard uncertainty of 2 ×10-11 on line position, typical for Doppler-free techniques. Shapes of the spectral line were measured with a Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectrometer referenced to an 88Sr optical atomic clock via an optical frequency comb.

  20. Comb-drive actuators for large displacements

    NARCIS (Netherlands)

    Legtenberg, Rob; Legtenberg, R.; Groeneveld, A.W.; Elwenspoek, Michael Curt

    The design, fabrication and experimental results of lateral-comb-drive actuators for large displacements at low driving voltages is presented. A comparison of several suspension designs is given, and the lateral large deflection behaviour of clamped-clamped beams and a folded flexure design is

  1. Time sequence photography of Roosters Comb (United States)

    The importance of understanding natural landscape changes is key in properly determining rangeland ecology. Time sequence photography allows a landscape snapshot to be documented and enables the ability to compare natural changes overtime. Photographs of Roosters Comb were taken from the same vantag...

  2. Comb-like polymers inside nanoscale pores


    Gay, Cyprien; Raphael, Elie


    A new method of polymer characterization, based on permeation studies using nanoscale pores, was recently proposed by Brochard and de Gennes. In the present paper, we study how this method, initially developped for star polymers can be extended to comb-like polymers.

  3. Dynamics of comb-of-comb-network polymers in random layered flows. (United States)

    Katyal, Divya; Kant, Rama


    We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength W_{α}. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν=2-α/2. Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t^{-α/2}. We show that the network with greater total mass moves faster.

  4. Monitoring nano-flow rate of water by atomic emission detection using helium radio-frequency plasma. (United States)

    Nakagama, Tatsuro; Maeda, Tsuneaki; Uchiyama, Katsumi; Hobo, Toshiyuki


    Recently, high-performance nano-scale flow pumping systems have been developed for micro and miniaturized analysis systems. A novel device capable of measuring and monitoring nanoliter scale flow rates has been required for the further development of the pumping system. In this study, an atomic emission detector using helium radio-frequency plasma (RFP-AED) was used for the measurement of the nanoliter scale flow rate of water by quantitatively detecting the emission from hydrogen in the water molecules. Monitoring nano-flow rates of water in the range up to 1.0 microl min(-1), and the change in the flow rate by the indication of the ratio of the emissions of H (656.3 nm) and He (667.8 nm) were successful. At present, the lowest flow rate that could be determined reproducibly was 4 nl min(-1) calculated as five times the standard deviation of the background noise. Additionally, similar evaluations for the deviation of each flow rate by using the RFP-AED and a flow-injection system were produced.

  5. Self-assembled monolayers of sulfonate-terminated alkanethiols investigated by frequency modulation atomic force microscopy in liquid (United States)

    Asakawa, Hitoshi; Inada, Natsumi; Hirata, Kaito; Matsui, Sayaka; Igarashi, Takumi; Oku, Norihisa; Yoshikawa, Norinobu; Fukuma, Takeshi


    A molecular-scale understanding of self-assembled monolayers (SAMs) of sulfonate-terminated alkanethiols is crucial for interfacial studies of functionalized SAMs and their various applications. However, such an understanding has been difficult to achieve because of the lack of direct information on these molecular-scale structures in real space. In this study, we investigated the structures of sulfonate SAMs of sodium 11-mercapto-1-undecanesulfonate (MUS) by frequency modulation atomic force microscopy (FM-AFM) in liquid. The subnanometer-resolution FM-AFM images showed that the single-component MUS SAM prepared in pure water had random surface structures. In contrast, the MUS SAM prepared in a water-ethanol mixed solvent showed periodic striped structures with a flat-lying conformation. The results suggest a significant solvent effect on molecular-scale structures of long-chain sulfonate SAMs. In addition, we investigated the molecular-scale structures of mixed SAMs of MUS and 11-mercapto-1-undecanol (MUO) with alkane chains of the same length. The FM-AFM images of the mixed SAMs showed clear phase separation between MUS SAM and MUO SAM domains. In the MUO SAM domains, the incorporated MUS molecules appeared as protrusions. The results obtained in this study provide direct structural information on long-chain sulfonate and mixed SAMs.

  6. The effect of drive frequency and set point amplitude on tapping forces in atomic force microscopy: simulation and experiment. (United States)

    Legleiter, Justin


    In tapping mode atomic force microscopy (AFM), a sharp probe tip attached to an oscillating cantilever is allowed to intermittently strike a surface. By raster scanning the probe while monitoring the oscillation amplitude of the cantilever via a feedback loop, topographical maps of surfaces with nanoscale resolution can be acquired. While numerous studies have employed numerical simulations to elucidate the time-resolved tapping force between the probe tip and surface, until recent technique developments, specific read-outs from such models could not be experimentally verified. In this study, we explore, via numerical simulation, the impact of imaging parameters, i.e. set point ratio and drive frequency as a function of resonance, on time-varying tip-sample force interactions, which are directly compared to reconstructed tapping forces from real AFM experiments. As the AFM model contains a feedback loop allowing for the simulation of the entire scanning process, we further explore the impact that various tip-sample force have on the entire imaging process.

  7. Laser frequency locking with 46 GHz offset using an electro-optic modulator for magneto-optical trapping of francium atoms

    CERN Document Server

    Harada, K; Ezure, S; Kato, K; Hayamizu, T; Kawamura, H; Inoue, T; Arikawa, H; Ishikawa, T; Aoki, T; Uchiyama, A; Sakamoto, K; Ito, S; Itoh, M; Ando, S; Hatakeyama, A; Hatanaka, K; Imai, K; Murakami, T; Nataraj, H S; Shimizu, Y; Sato, T; Wakasa, T; Yoshida, H P; Sakemi, Y


    We demonstrated a frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I2. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr.

  8. Laser frequency locking with 46  GHz offset using an electro-optic modulator for magneto-optical trapping of francium atoms. (United States)

    Harada, K; Aoki, T; Ezure, S; Kato, K; Hayamizu, T; Kawamura, H; Inoue, T; Arikawa, H; Ishikawa, T; Aoki, T; Uchiyama, A; Sakamoto, K; Ito, S; Itoh, M; Ando, S; Hatakeyama, A; Hatanaka, K; Imai, K; Murakami, T; Nataraj, H S; Shimizu, Y; Sato, T; Wakasa, T; Yoshida, H P; Sakemi, Y


    We demonstrate frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I₂. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr.

  9. Laser frequency locking with 46 GHz offset using an electro-optic modulator for magneto-optical trapping of francium atoms (United States)

    Harada, K.; Aoki, T.; Ezure, S.; Kato, K.; Hayamizu, T.; Kawamura, H.; Inoue, T.; Arikawa, H.; Ishikawa, T.; Aoki, T.; Uchiyama, A.; Sakamoto, K.; Ito, S.; Itoh, M.; Ando, S.; Hatakeyama, A.; Hatanaka, K.; Imai, K.; Murakami, T.; Nataraj, H. S.; Shimizu, Y.; Sato, T.; Wakasa, T.; Yoshida, H. P.; Sakemi, Y.


    We demonstrated a frequency offset locking between two laser sources using a waveguide-type electro-optic modulator (EOM) with 10th-order sidebands for magneto-optical trapping of Fr atoms. The frequency locking error signal was successfully obtained by performing delayed self-homodyne detection of the beat signal between the repumping frequency and the 10th-order sideband component of the trapping light. Sweeping the trapping-light and repumping-light frequencies with keeping its frequency difference of 46 GHz was confirmed over 1 GHz by monitoring the Doppler absorption profile of I2. This technique enables us to search for a resonance frequency of magneto-optical trapping of Fr.

  10. The Physics of Ultrabroadband Frequency Comb Generation and Optimized Combs for Measurements in Fundamental Physics (United States)


    nonlinear physics as it is a key mechanism in fiber SC generation but also because of similarities with rogue instabilities in hydrodynamics [5]. It... boat suddenly stopped – not so the mass of water in the channel which it had put in motion … a large, solitary, progressive wave” Systematic Studies...unlimited. Motivating experiments in hydrodynamics 1/70 scale DISTRIBUTION A. Approved for public release: distribution unlimited. Light & gravity

  11. The Rose-comb mutation in chickens constitutes a structural rearrangement causing both altered comb morphology and defective sperm motility.

    Directory of Open Access Journals (Sweden)

    Freyja Imsland


    Full Text Available Rose-comb, a classical monogenic trait of chickens, is characterized by a drastically altered comb morphology compared to the single-combed wild-type. Here we show that Rose-comb is caused by a 7.4 Mb inversion on chromosome 7 and that a second Rose-comb allele arose by unequal crossing over between a Rose-comb and wild-type chromosome. The comb phenotype is caused by the relocalization of the MNR2 homeodomain protein gene leading to transient ectopic expression of MNR2 during comb development. We also provide a molecular explanation for the first example of epistatic interaction reported by Bateson and Punnett 104 years ago, namely that walnut-comb is caused by the combined effects of the Rose-comb and Pea-comb alleles. Transient ectopic expression of MNR2 and SOX5 (causing the Pea-comb phenotype occurs in the same population of mesenchymal cells and with at least partially overlapping expression in individual cells in the comb primordium. Rose-comb has pleiotropic effects, as homozygosity in males has been associated with poor sperm motility. We postulate that this is caused by the disruption of the CCDC108 gene located at one of the inversion breakpoints. CCDC108 is a poorly characterized protein, but it contains a MSP (major sperm protein domain and is expressed in testis. The study illustrates several characteristic features of the genetic diversity present in domestic animals, including the evolution of alleles by two or more consecutive mutations and the fact that structural changes have contributed to fast phenotypic evolution.

  12. Long distance measurement up to 1.2 km by electro-optic dual-comb interferometry (United States)

    Wu, Hanzhong; Zhao, Tuo; Wang, Zhiyang; Zhang, Kai; Xue, Bin; Li, Jianshuang; He, Mingzhao; Qu, Xinghua


    We perform a long distance measurement up to 1.2 km on the outdoor baseline by electro-optic dual-comb interferometry. A frequency comb pair is developed by phase modulating a continuous laser with a narrow linewidth, and the slightly different repetition frequencies are synchronized to the Rb clock via the signal generators. A RF electrical comb can be generated by multi-wavelength heterodyne interferometry, and thus, a series of synthetic wavelengths can be obtained, whose phases can be used to determine the distances. Compared with the reference values, the experimental results show an agreement within 379 μm in the 1180 m range. In the long-time experiments, the Allan deviation can be below 20 μm with an averaging time of 10 s, and can be further improved to be less than 600 nm when the averaging time is above 350 s at 435 m and 1180 m, respectively.

  13. Silicon-chip-based mid-infrared dual-comb spectroscopy

    CERN Document Server

    Yu, Mengjie; Griffith, Austin G; Picqué, Nathalie; Lipson, Michal; Gaeta, Alexander L


    On-chip spectroscopy that could realize real-time fingerprinting with label-free and high-throughput detection of trace molecules is one of the 'holy grails" of sensing. Such miniaturized spectrometers would greatly enable applications in chemistry, bio-medicine, material science or space instrumentation, such as hyperspectral microscopy of live cells or pharmaceutical quality control. Dual-comb spectroscopy (DCS), a recent technique of Fourier transform spectroscopy without moving parts, is particularly promising since it measures high-precision spectra in the gas phase using only a single detector. Here, we present a microresonator-based platform designed for mid-infrared (mid-IR) DCS. A single continuous-wave (CW) low-power pump source generates two mutually coherent mode-locked frequency combs spanning from 2.6 $\\mu$m to 4.1 $\\mu$m in two silicon micro-resonators. Thermal control and free-carrier injection control modelocking of each comb and tune the dual-comb parameters. The large line spacing of the co...

  14. Transport properties on a random comb (United States)

    Balakrishnan, V.; Van den Broeck, C.


    We study the random walk of a particle in a random comb structure, both in the presence of a biasing field and an the field-free case. We show that the mean-field treatment of the quenched disorder can be exactly mapped on to a continuous time random walk (CTRW) on the backbone of the comb, with a definite waiting time density. We find an exact expression for this central quantity. The Green function for the CTRW is then obtained. Its first and second moments determine the drift and diffusion at all times. We show that the drift velocity v vanishes asymptotically for power-law and stretched-exponential distributions of branch lengths on the comb, whatever be the biasing field strength. For an exponential branch-length distribution, v is a nonmonotonic function of the bias, increasing initially to a maximum and then decreasing to zero at a critical value. In the field-free case, anomalous diffusion occurs for a range of power-law distributions of the branch length. The corresponding exponent for the mean square displacement is obtained, as is the asymptotic form of the positional probability distribution for the random walk. We show that normal diffusion occurs whenever the mean branch length is finite, and present a simple formula for the effective diffusion constant; these results are extended to regular (nonrandom) combs as well. The physical reason for anomalous drift or diffusion is traced to the properties of the distribution of a first passage time (on a finite chain) that controls the effective waiting time density of the CTRW.

  15. A tunable CW UV laser with <35 kHz absolute frequency instability for precision spectroscopy of Sr Rydberg states

    CERN Document Server

    Bridge, Elizabeth M; Bounds, Alistair D; Boddy, Danielle; Sadler, Daniel P; Jones, Matthew P A


    We present a solid-state laser system that generates over 200 mW of continuous-wave, narrowband light, tunable between 316.3 nm and 319.3 nm. The laser is based on commercially available fiber amplifiers and optical frequency doubling technology, along with sum frequency generation in a periodically poled stoichiometric lithium tantalate crystal. The laser frequency is stabilized to an atomic-referenced high finesse optical transfer cavity. Using a GPS-referenced optical frequency comb we measure a long term frequency instability of <35 kHz. As an application we perform spectroscopy of Sr Rydberg states from n = 37 - 81, demonstrating mode-hop-free scans of 24 GHz. In a cold atomic sample we measure Doppler-limited linewidths of 350 kHz.

  16. Generation of Optical Combs in a WGM Resonator from a Bichromatic Pump (United States)

    Strekalov, Dmitry V.; Yu, Nan; Matsko, Andrey B.


    Optical combs generated by a monolithic resonator with Kerrmedium can be used in a number of applications, including orbital clocks and frequency standards of extremely high accuracy, such as astronomy, molecular spectroscopy, and the like. The main difficulty of this approach is the relatively high pump power that has to be used in such devices, causing undesired thermorefractive effects, as well as stimulated Raman scattering, and limiting the optical comb quality and utility. In order to overcome this problem, this innovation uses a different approach to excitation of the nonlinear oscillations in a Kerr-nonlinear whispering gallery mode (WGM) resonator and generation of the optical comb. By coupling to the resonator two optical pump frequencies instead of just one, the efficiency of the comb source can be increased considerably. It therefore can operate in a lowerpower regime where the undesirable effects are not present. This process does not have a power threshold; therefore, the new optical component can easily be made strong enough to generate further components, making the optical comb spread in a cascade fashion. Additionally, the comb spacing can be made in an arbitrary number of the resonator free spectral ranges (FSR). The experimental setup for this innovation used a fluorite resonator with OMEGA= 13.56 GHz. This material has very low dispersion at the wavelength of 1.5 microns, so the resonator spectrum around this wavelength is highly equidistant. Light was coupled in and out of the resonator using two optical fibers polished at the optimal coupling angle. The gap between the resonator and the fibers, affecting the light coupling and the resonator loading, was controlled by piezo positioners. The light from the input fiber that did not go into the resonator reflected off of its rim, and was collected by a photodetector. This enabled observation and measurement of the (absorption) spectrum of the resonator. The input fiber combined light from two

  17. Evanescent-wave comb spectroscopy of liquids with strongly dispersive optical fiber cavities (United States)

    Avino, S.; Giorgini, A.; Salza, M.; Fabian, M.; Gagliardi, G.; De Natale, P.


    We demonstrate evanescent-wave fiber cavity-enhanced spectroscopy in the liquid phase using a near-infrared frequency comb. Exploiting strong fiber-dispersion effects, we show that liquid absorption spectra can be recorded without any external dispersive element. The fiber cavity is used both as sensor and spectrometer. The resonance modes are frequency locked to the comb teeth while the cavity photon lifetime is measured over 155 nm, from 1515 nm to 1670 nm, where absorption bands of liquid polyamines are detected as a proof of concept. Our fiber spectrometer lends itself to in situ, real-time chemical analysis in environmental monitoring, biomedical assays, and micro-opto-fluidic systems.

  18. Tracing Paths - A Study of Combs from Viking Age ICeland


    Eckhoff, Nicolai Andreas


    The present study is a technological and comparative analysis of combs from Viking Age Iceland. Recent research suggests that it was important for people in the Viking Age that the comb they caried was affiliated with their own culture; hence combs seem to have an inherent ability to portray cultural patterns. Such patterns are difficult to find in Iceland as few artefact studies have been completed in Icelandic archaeology. This thesis focuses on this fact, as the regional variations in the ...

  19. Wet combing for the eradication of head lice. (United States)


    Manual removal (using conditioner and comb or a wet comb) can be used in the treatment of head lice. Head lice infestation (Pediculosis humanus capitis) is a common problem. It is diagnosed by visualising the lice. As half of people infested with head lice will not scratch, all people in contact with a person affected with head lice should be manually checked for infestations. Wet combing is easily and safely performed at home, but persistence is needed. This article describes the process of head lice removal using a wet comb. It has NHMRC Level 2 evidence of efficacy and no serious adverse effects have been reported.

  20. Autler-Townes splitting via frequency upconversion at ultra-low power levels in cold $^{87}$Rb atoms using an optical nanofiber

    CERN Document Server

    Kumar, Ravi; Deasy, Kieran; Chormaic, Síle Nic


    The tight confinement of the evanescent light field around the waist of an optical nanofiber makes it a suitable tool for studying nonlinear optics in atomic media. Here, we use an optical nanofiber embedded in a cloud of laser-cooled 87Rb for near-infrared frequency upconversion via a resonant two-photon process. Sub-nW powers of the two-photon beams, at 780 nm and 776 nm, co-propagate through the optical nanofiber and generation of 420 nm photons is observed. A measurement of the Autler-Townes splitting provides a direct measurement of the Rabi frequency of the 780 nm transition. Through this method, dephasings of the system can be studied. In this work, the optical nanofiber is used as an excitation and detection tool simultaneously, and it highlights some of the advantages of using fully fibered systems for nonlinear optics with atoms.

  1. Characterisation of the membrane affinity of an isoniazide peptide conjugate by tensiometry, atomic force microscopy and sum-frequency vibrational spectroscopy, using a phospholipid Langmuir monolayer model. (United States)

    Hill, Katalin; Pénzes, Csanád Botond; Schnöller, Donát; Horváti, Kata; Bosze, Szilvia; Hudecz, Ferenc; Keszthelyi, Tamás; Kiss, Eva


    Tensiometry, sum-frequency vibrational spectroscopy, and atomic force microscopy were employed to assess the cell penetration ability of a peptide conjugate of the antituberculotic agent isoniazide. Isoniazide was conjugated to peptide (91)SEFAYGSFVRTVSLPV(106), a functional T-cell epitope of the immunodominant 16 kDa protein of Mycobacterium tuberculosis. As a simple but versatile model of the cell membrane a phospholipid Langmuir monolayer at the liquid/air interface was used. Changes induced in the structure of the phospholipid monolayer by injection of the peptide conjugate into the subphase were followed by tensiometry and sum-frequency vibrational spectroscopy. The drug penetrated lipid films were transferred to a solid support by the Langmuir-Blodgett technique, and their structures were characterized by atomic force microscopy. Peptide conjugation was found to strongly enhance the cell penetration ability of isoniazide.

  2. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals. (United States)

    Peng, Fulai; Liu, Hongyun; Wang, Weidong


    A photoplethysmographic (PPG) signal can provide very useful information about a subject's cardiovascular status. Motion artifacts (MAs), which usually deteriorate the waveform of a PPG signal, severely obstruct its applications in the clinical diagnosis and healthcare area. To reduce the MAs from a PPG signal, in the present study we present a comb filter based signal processing method. Firstly, wavelet de-noising was implemented to preliminarily suppress a part of the MAs. Then, the PPG signal in the time domain was transformed into the frequency domain by a fast Fourier transform (FFT). Thirdly, the PPG signal period was estimated from the frequency domain by tracking the fundamental frequency peak of the PPG signal. Lastly, the MAs were removed by the comb filter which was designed based on the obtained PPG signal period. Experiments with synthetic and real-world datasets were implemented to validate the performance of the method. Results show that the proposed method can effectively restore the PPG signals from the MA corrupted signals. Also, the accuracy of blood oxygen saturation (SpO2), calculated from red and infrared PPG signals, was significantly improved after the MA reduction by the proposed method. Our study demonstrates that the comb filter can effectively reduce the MAs from a PPG signal provided that the PPG signal period is obtained.

  3. Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case


    Daniel Ebeling; Solares, Santiago D


    Summary We present an overview of the bimodal amplitude?frequency-modulation (AM-FM) imaging mode of atomic force microscopy (AFM), whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with con...

  4. Signatures of Anderson localization excited by an optical frequency comb

    KAUST Repository

    Gentilini, S.


    We investigate Anderson localization of light as occurring in ultrashort excitations. A theory based on time dependent coupled-mode equations predicts universal features in the spectrum of the transmitted pulse. In particular, the process of strong localization of light is shown to correspond to the formation of peaks in both the amplitude and in the group delay of the transmitted pulse. Parallel ab initio simulations made with finite-difference time-domain codes and molecular dynamics confirm theoretical predictions, while showing that there exists an optimal degree of disorder for the strong localization. © 2010 The American Physical Society.

  5. Mid-IR Microresonator-Based Optical Frequency Combs (United States)


    DISTRIBUTION A: Distribution approved for public release. AF Office Of Scientific Research (AFOSR)/ RTB1 Arlington, Virginia 22203 Air Force Research Laboratory...Kärtner, M. A. Belkin, A. Belyanin, X. Li, D. Ham , H. Schneider, P. Grant, C. Y. Song, S. Haffouz, Z. R. Wasilewski, H.C. Liu, and F. Capasso, “Mode

  6. Compact Ultra-Wideband Optical Frequency Comb Fiber Laser Project (United States)

    National Aeronautics and Space Administration — Based on our success in developing the world first commercial 10 W femtosecond fiber laser system and our leading technology development in ultrashort pulsed fiber...

  7. Wax combs mediate nestmate recognition by guard honeybees

    DEFF Research Database (Denmark)

    D'Ettorre, Patrizia; Wenseleers, Tom; Dawson, Jenny


    Research has shown that the wax combs are important in the acquisition of colony odour in the honeybee, Apis mellifera. However, many of these studies were conducted in the laboratory or under artificial conditions. We investigated the role of the wax combs in nestmate recognition in the natural...

  8. Comb-like optical transmission spectra generated from one-dimensional two-segment-connected two-material waveguide networks optimized by genetic algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yu [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China); Yang, Xiangbo, E-mail: [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China); School of Physical Education and Sports Science, South China Normal University, Guangzhou 510006 (China); Lu, Jian; Zhang, Guogang [MOE Key Laboratory of Laser Life Science and Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631 (China); Liu, Chengyi Timon [School of Physical Education and Sports Science, South China Normal University, Guangzhou 510006 (China)


    In this Letter, a one-dimensional (1D) two-segment-connected two-material waveguide network (TSCTMWN) is designed to produce comb-like frequency passbands, where each waveguide segment is composed of normal and anomalous dispersion materials and the length ratio of sub-waveguide segments is optimized by genetic algorithm (GA). It is found that 66 comb-like frequency passbands are created in the second frequency unit, maximal relative width difference of which is less than 2×10{sup −5}. It may be useful for the designing of dense wavelength division multiplexings (DWDMs) and multi-channel filters, etc., and provide new applications for GA.

  9. Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case. (United States)

    Ebeling, Daniel; Solares, Santiago D


    We present an overview of the bimodal amplitude-frequency-modulation (AM-FM) imaging mode of atomic force microscopy (AFM), whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM) while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM) technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with constant frequency and constant excitation amplitude. General as well as particular characteristics of the different driving schemes are highlighted from theoretical and experimental points of view, revealing the advantages and disadvantages of each. This study provides information and guidelines that can be useful in selecting the most appropriate operation mode to characterize different samples in the most efficient and reliable way.

  10. Bimodal atomic force microscopy driving the higher eigenmode in frequency-modulation mode: Implementation, advantages, disadvantages and comparison to the open-loop case

    Directory of Open Access Journals (Sweden)

    Daniel Ebeling


    Full Text Available We present an overview of the bimodal amplitude–frequency-modulation (AM-FM imaging mode of atomic force microscopy (AFM, whereby the fundamental eigenmode is driven by using the amplitude-modulation technique (AM-AFM while a higher eigenmode is driven by using either the constant-excitation or the constant-amplitude variant of the frequency-modulation (FM-AFM technique. We also offer a comparison to the original bimodal AFM method, in which the higher eigenmode is driven with constant frequency and constant excitation amplitude. General as well as particular characteristics of the different driving schemes are highlighted from theoretical and experimental points of view, revealing the advantages and disadvantages of each. This study provides information and guidelines that can be useful in selecting the most appropriate operation mode to characterize different samples in the most efficient and reliable way.

  11. Tunable Surface Properties from Bioinspired Comb Copolymers (United States)

    van Zoelen, Wendy; Buss, Hilda; Ellebracht, Nathan; Zuckermann, Ronald; Segalman, Rachel


    A modular polymer system which incorporates multiple functionalities simultaneously while keeping an identical backbone chemistry is a useful tool in determining necessary functionalities for marine antifouling properties. We have investigated the surface properties and antifouling behavior of polypeptoids, a class of non-natural biomimetic polymers based on an N-substituted glycine backbone, that combine many of the advantageous properties of bulk polymers with those of synthetically produced proteins, including controllable chain shape, sequence, and self-assembled structure. Using thiol-ene click chemistry, thiol functionalized amphiphilic peptoid sequences consisting of hydrophilic methoxyethyl and hydrophobic heptafluorobutyl side chains were attached to polystyrene-block-poly(ethylene oxide-stat-allyl glycidyl ether), creating comb-shaped molecules. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) was used to study the surface characteristics as a function of peptoid length and composition. Only 20% of fluorinated groups in the peptoid were sufficient for promoting surface display of the otherwise hydrophilic PEO/peptoid comb block. Antifouling experiments with spores of the green algae Ulva indicated an influence of sequence.

  12. Absolute spectroscopy near 7.8 {\\mu} m with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco


    We report the first experimental demonstration of frequency-locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locking scheme is applied to carry out absolute spectroscopy of N2O lines near 7.87 {\\\\mu}m with an accuracy of ~60 kHz. Thanks to a single mode operation over more than 100 cm^{-1}, the comb-locked EC-QCL shows great potential for the accurate retrieval of line center frequencies in a spectral region that is currently outside the reach of broadly tunable cw sources, either based on difference frequency generation or optical parametric oscillation. The approach described here can be straightforwardly extended up to 12 {\\\\mu}m, which is the current wavelength limit for commercial cw EC-QCLs.

  13. Static response, collective frequencies, and ground-state thermodynamical properties of spin-saturated two-component cold atoms and neutron matter (United States)

    Boulet, A.; Lacroix, D.


    The thermodynamical ground-state properties and static response in both cold atoms at or close to unitarity and neutron matter are determined using a recently proposed density functional theory (DFT) based on the s -wave scattering length as, effective range re, and unitary gas limit. In cold atoms, when the effective range may be neglected, we show that the pressure, chemical potential, compressibility modulus, and sound velocity obtained with the DFT are compatible with experimental observations or exact theoretical estimates. The static response in homogeneous infinite systems is also obtained and a possible influence of the effective range on the response is analyzed. The neutron matter differs from unitary gas due to the noninfinite scattering length and to a significant influence of effective range, which affects all thermodynamical quantities as well as the static response. In particular, we show for neutron matter that the latter response recently obtained in auxiliary-field diffusion Monte Carlo (AFDMC) can be qualitatively reproduced when the p -wave contribution is added to the functional. Our study indicates that the close similarity between the exact AFDMC static response and the free-gas response might stem from the compensation of the as effect by the effective range and p -wave contributions. We finally consider the dynamical response of both atoms or neutron droplets in anisotropic traps. Assuming the hydrodynamical regime and a polytropic equation of state, a reasonable description of the radial and axial collective frequencies in cold atoms is obtained. Following a similar strategy, we estimate the equivalent collective frequencies of neutron drops in anisotropic traps.

  14. Dissolution Processes at Step Edges of Calcite in Water Investigated by High-Speed Frequency Modulation Atomic Force Microscopy and Simulation. (United States)

    Miyata, Kazuki; Tracey, John; Miyazawa, Keisuke; Haapasilta, Ville; Spijker, Peter; Kawagoe, Yuta; Foster, Adam S; Tsukamoto, Katsuo; Fukuma, Takeshi


    The microscopic understanding of the crystal growth and dissolution processes have been greatly advanced by the direct imaging of nanoscale step flows by atomic force microscopy (AFM), optical interferometry, and X-ray microscopy. However, one of the most fundamental events that govern their kinetics, namely, atomistic events at the step edges, have not been well understood. In this study, we have developed high-speed frequency modulation AFM (FM-AFM) and enabled true atomic-resolution imaging in liquid at ∼1 s/frame, which is ∼50 times faster than the conventional FM-AFM. With the developed AFM, we have directly imaged subnanometer-scale surface structures around the moving step edges of calcite during its dissolution in water. The obtained images reveal that the transition region with typical width of a few nanometers is formed along the step edges. Building upon insight in previous studies, our simulations suggest that the transition region is most likely to be a Ca(OH)2 monolayer formed as an intermediate state in the dissolution process. On the basis of this finding, we improve our understanding of the atomistic dissolution model of calcite in water. These results open up a wide range of future applications of the high-speed FM-AFM to the studies on various dynamic processes at solid-liquid interfaces with true atomic resolution.

  15. A Compact, Waveguide Based Programmable Optical Comb Generator Project (United States)

    National Aeronautics and Space Administration — This NASA Phase I STTR effort will establish the feasibility of developing a compact broadband near to mid-IR programmable optical comb for use in laser based remote...

  16. Atomic frequency reference at 1033 nm for ytterbium (Yb)-doped fiber lasers and applications exploiting a rubidium (Rb) 5S_1/2 to 4D_5/2 one-colour two-photon transition (United States)

    Roy, Ritayan; Condylis, Paul C.; Johnathan, Yik Jinen; Hessmo, Björn


    We demonstrate a two-photon transition of rubidium (Rb) atoms from the ground state (5$S_{1/2}$) to the excited state (4$D_{5/2}$), using a home-built ytterbium (Yb)-doped fiber amplifier at 1033 nm. This is the first demonstration of an atomic frequency reference at 1033 nm as well as of a one-colour two-photon transition for the above energy levels. A simple optical setup is presented for the two-photon transition fluorescence spectroscopy, which is useful for frequency stabilization for a broad class of lasers. This spectroscopy has potential applications in the fiber laser industry as a frequency reference, particularly for the Yb-doped fiber lasers. This two-photon transition also has applications in atomic physics as a background- free high- resolution atom detection and for quantum communication, which is outlined in this article.

  17. Observation by fluorescence microscopy of transcription on single combed DNA (United States)

    Gueroui, Z.; Place, C.; Freyssingeas, E.; Berge, B.


    Molecular combing is a powerful procedure for aligning a large array of DNA molecules onto a surface. This technique usually leads to an overstretching of about 150% of the molecules' contour length. By changing the magnitude of capillary forces during the combing process, we were able to reduce the relative extension of the DNA molecules. Thus we achieved combing of T7 DNA with an extension close to its molecule contour length. We checked the ability of combed DNA to interact with DNA binding proteins. Using the T7 bacteriophage transcription system, we investigated the transcription activity of RNA polymerase on combed DNA by direct visualization of newly synthesized fluorescent RNAs. Our experiments show that no transcription activity occurs on overstretched DNA molecules, whereas we observe a transcription activity for nonoverstretched molecules. This activity is observed both in multiple initiation experiments and for one immobilized T7 RNA polymerase per promoter. These results open possibilities for the study of single enzyme actions on combed DNA by optical methods. PMID:11983896


    Directory of Open Access Journals (Sweden)

    M. I. Evstifeev


    Full Text Available Subject of Research.The reasons for subharmonic resonances in RR-type micromechanical gyro output under linear vibrations are investigated. In ideal case, this type of gyro should be insensitive to this kind of impact due to primary and secondary angular oscillations. However, experimental results reveal significant increase in output signal under external vibrations in 20 Hz - 2 kHz bandwidth, though the device natural frequencies are above 3 kHz. This effect is caused by characteristicsnonlinearity of plate-type and comb-type capacitive sensors. Method. Mathematical model of the capacitive comb-type sensors is clarified. Electromechanical interactions in the sensors under external vibrations are described. Simulink modeling of specified mathematical model is carried out. External vibration modeling is doneby “oscillating frequency” method with constant accelerationamplitude in 20 Hz - 2 kHz bandwidth. Main Results.We have received good agreement of modeling and experimental results in the form of occurrence of subharmonic resonances under linear vibrations in three orthogonal directions. Obtained effects are explained by proposed mathematical models. The main reason for subharmonic resonances in RR-type micromechanical gyro output is that combs of stator and combs of proof mass jump out of mesh. Practical Relevance. The provided investigation gives the possibility to determine algorithmic and construction compensation methods of studied interactions for enhancing vibration resistance of RR-type micromechanical gyro.

  19. Comb-assisted subkilohertz linewidth quantum cascade laser for high-precision mid-infrared spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Galli, I.; Cappelli, F.; Bartalini, S.; Mazzotti, D.; Giusfredi, G.; Cancio, P.; De Natale, P. [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy); LENS-European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino, FI (Italy); Siciliani de Cumis, M. [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy); Borri, S. [CNR-IFN-Istituto di Fotonica e Nanotecnologie, Via Amendola 173, 70126 Bari, BA (Italy); Montori, A. [LENS-European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino, FI (Italy); Akikusa, N. [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan); Yamanishi, M. [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)


    We report on the linewidth narrowing of a room-temperature mid-infrared quantum cascade laser by phase-locking to a difference-frequency-generated radiation referenced to an optical frequency comb synthesizer. A locking bandwidth of 250 kHz, with a residual rms phase-noise of 0.56 rad, has been achieved. The laser linewidth is narrowed by more than 2 orders of magnitude below 1 kHz, and its frequency is stabilized with an absolute traceability of 2 Multiplication-Sign 10{sup -12}. This source has allowed the measurement of the absolute frequency of a CO{sub 2} molecular transition with an uncertainty of about 1 kHz.

  20. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin


    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  1. Imaginary-frequency polarizability and van der Waals force constants of two-electron atoms, with rigorous bounds (United States)

    Glover, R. M.; Weinhold, F.


    Variational functionals of Braunn and Rebane (1972) for the imagery-frequency polarizability (IFP) have been generalized by the method of Gramian inequalities to give rigorous upper and lower bounds, valid even when the true (but unknown) unperturbed wavefunction must be represented by a variational approximation. Using these formulas in conjunction with flexible variational trial functions, tight error bounds are computed for the IFP and the associated two- and three-body van der Waals interaction constants of the ground 1(1S) and metastable 2(1,3S) states of He and Li(+). These bounds generally establish the ground-state properties to within a fraction of a per cent and metastable properties to within a few per cent, permitting a comparative assessment of competing theoretical methods at this level of accuracy. Unlike previous 'error bounds' for these properties, the present results have a completely a priori theoretical character, with no empirical input data.

  2. Energy resolved actinometry for simultaneous measurement of atomic oxygen densities and local mean electron energies in radio-frequency driven plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Greb, Arthur, E-mail:; Niemi, Kari; O' Connell, Deborah; Gans, Timo [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)


    A diagnostic method for the simultaneous determination of atomic oxygen densities and mean electron energies is demonstrated for an atmospheric pressure radio-frequency plasma jet. The proposed method is based on phase resolved optical emission measurements of the direct and dissociative electron-impact excitation dynamics of three distinct emission lines, namely, Ar 750.4 nm, O 777.4 nm, and O 844.6 nm. The energy dependence of these lines serves as basis for analysis by taking into account two line ratios. In this frame, the method is highly adaptable with regard to pressure and gas composition. Results are benchmarked against independent numerical simulations and two-photon absorption laser-induced fluorescence experiments.

  3. Legal Time of the Republic of Colombia and its international traceability using the Cesium Atomic Clock - Time and Frequency National Standard (United States)

    Hernández Forero, Liz Catherine; Bahamón Cortés, Nelson


    Around the world, there are different providers of timestamp (mobile, radio or television operators, satellites of the GPS network, astronomical measurements, etc.), however, the source of the legal time for a country is either the national metrology institute or another designated laboratory. This activity requires a time standard based on an atomic time scale. The International Bureau of Weights and Measures (BIPM) calculates a weighted average of the time kept in more than 60 nations and produces a single international time scale, called Coordinated Universal Time (UTC). This article presents the current time scale that generates Legal Time for the Republic of Colombia produced by the Instituto Nacional de Metrología (INM) using the time and frequency national standard, a cesium atomic oscillator. It also illustrates how important it is for the academic, scientific and industrial communities, as well as the general public, to be synchronized with this time scale, which is traceable to the International System (SI) of units, through international comparisons that are made in real time.

  4. Low-frequency dielectric properties of intrinsic and Al-doped rutile TiO{sub 2} thin films grown by the atomic layer deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Kassmi, M. [Microelectronics Technology Laboratory (LTM), Grenoble Alpes University (UGA) and National Center for Scientific Research - CNRS, Grenoble 38000 (France); LMOP, El Manar University, Tunis 2092 (Tunisia); Pointet, J.; Gonon, P., E-mail:; Bsiesy, A.; Vallée, C. [Microelectronics Technology Laboratory (LTM), Grenoble Alpes University (UGA) and National Center for Scientific Research - CNRS, Grenoble 38000 (France); Jomni, F. [LMOP, El Manar University, Tunis 2092 (Tunisia)


    Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO{sub 2} rutile films which are deposited on RuO{sub 2} by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz–100 kHz range, for ac electric fields up to 1 MV{sub rms}/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreases the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MV{sub rms}/cm range, strong voltage non-linearities are evidenced in undoped films. The conductance increases exponentially with the ac field and the capacitance displays negative values (inductive behavior). Hopping barrier lowering is proposed to explain high-field effects. Finally, it is shown that Al doping strongly improves the high-field dielectric behavior.

  5. Device Characterization of High Performance Quantum Dot Comb Laser

    KAUST Repository

    Rafi, Kazi


    The cost effective comb based laser sources are considered to be one of the prominent emitters used in optical communication (OC) and photonic integrated circuits (PIC). With the rising demand for delivering triple-play services (voice, data and video) in FTTH and FTTP-based WDM-PON networks, metropolitan area network (MAN), and short-reach rack-to-rack optical computer communications, a versatile and cost effective WDM transmitter design is required, where several DFB lasers can be replaced by a cost effective broadband comb laser to support on-chip optical signaling. Therefore, high performance quantum dot (Q.Dot) comb lasers need to satisfy several challenges before real system implementations. These challenges include a high uniform broadband gain spectrum from the active layer, small relative intensity noise with lower bit error rate (BER) and better temperature stability. Thus, such short wavelength comb lasers offering higher bandwidth can be a feasible solution to address these challenges. However, they still require thorough characterization before implementation. In this project, we briefly characterized the novel quantum dot comb laser using duty cycle based electrical injection and temperature variations where we have observed the presence of reduced thermal conductivity in the active layer. This phenomenon is responsible for the degradation of device performance. Hence, different performance trends, such as broadband emission and spectrum stability were studied with pulse and continuous electrical pumping. The tested comb laser is found to be an attractive solution for several applications but requires further experiments in order to be considered for photonic intergraded circuits and to support next generation computer-communications.

  6. An astro-comb calibrated solar telescope to study solar activity and search for the radial velocity signature of Venus (United States)

    Phillips, David; HARPS-N Collaboration


    We recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope, which is calibrated with a laser frequency comb calibrator optimized for calibrating high resolution spectrographs and referred to as an astro-comb. We are using the solar telescope to characterize the effects of stellar (solar) RV jitter due to activity on the solar surface over the course of many hours every clear day. With the help of solar satellites such as the Solar Dynamics Observatory (SDO), we are characterizing the correlation between observed RV and detailed imaging of the solar photosphere. We plan to use these tools to mitigate the effects of stellar jitter with the goal of the detection of Venus from its solar RV signature, thus showing the potential of the RV technique to detect true Earth-twins.

  7. Chileotrecha romero (Kraus, 1966) comb. nov. and Pseudocleobis patagonicus (Roewer, 1934) comb. nov. transferral from Mummuciidae to Ammotrechidae (Arachnida, Solifugae). (United States)

    Botero-Trujillo, Ricardo; Iuri, Hernán A


    The solifuge species Mummucina romero Kraus, 1966, from Chile, and Mummucia patagonica Roewer, 1934, from Argentina, are here transferred from Mummuciidae Roewer, 1934 to Ammotrechidae Roewer, 1934. Chileotrecha romero (Kraus, 1966) comb. nov. and Pseudocleobis patagonicus (Roewer, 1934) comb. nov. are proposed. Comments on their morphology are made and previous distributional records are discussed. Pseudocleobis patagonicus is proposed as a nomen dubium. In addition, we confirm that female and immature specimens of the family Mummuciidae, just like males, can be reliably recognized based on features that had been suggested by Maury (1984).

  8. Design and Analysis of Wet Etching Based Comb Type Capacitive Accelerometer

    Directory of Open Access Journals (Sweden)

    Shankar DUTTA


    Full Text Available A wet etching based tilted comb type microaccelerometer has been proposed. This paper deals with the analytical estimation of sensitivity and operating frequency of this oriented silicon-based accelerometer. The mechanical and electrical behaviour of the structure have been simulated by Finite Element Method (FEM by using Intellisuite 6.1 software. Static, modal and dynamic simulations were done. The theoretical and simulated results are compared and found in reasonable agreement. The sensitivity of the structure is found to be ~21 fF/g with a first resonant frequency 843 Hz of twisting mode. The Von Misses stress analysis was done for the beam region. Bandwidth of the structure was found to be 70 Hz for the accelerometer using a 15 mm deep pit in a glass mount.

  9. Phase transition behaviors of the supported DPPC bilayer investigated by sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). (United States)

    Wu, Heng-Liang; Tong, Yujin; Peng, Qiling; Li, Na; Ye, Shen


    The phase transition behaviors of a supported bilayer of dipalmitoylphosphatidyl-choline (DPPC) have been systematically evaluated by in situ sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM). By using an asymmetric bilayer composed of per-deuterated and per-protonated monolayers, i.e., DPPC-d75/DPPC and a symmetric bilayer of DPPC/DPPC, we were able to probe the molecular structural changes during the phase transition process of the lipid bilayer by SFG spectroscopy. It was found that the DPPC bilayer is sequentially melted from the top (adjacent to the solution) to bottom leaflet (adjacent to the substrate) over a wide temperature range. The conformational ordering of the supported bilayer does not decrease (even slightly increases) during the phase transition process. The conformational defects in the bilayer can be removed after the complete melting process. The phase transition enthalpy for the bottom leaflet was found to be approximately three times greater than that for the top leaflet, indicating a strong interaction of the lipids with the substrate. The present SFG and AFM observations revealed similar temperature dependent profiles. Based on these results, the temperature-induced structural changes in the supported lipid bilayer during its phase transition process are discussed in comparison with previous studies.

  10. Simple Comb Generator Design for SWaP Constrained Applications (United States)


    transistor ( BJT ) [5], or another non-linear element could have been used instead of the SRD and could possibly have overcome some of the SRD’s disadvantages...pp. 454–456, June 2007. [5] E. Prapuchanay, D. Sakulhirirak, H. Zenkner, and S. Chalermwisutkul, “Design and implementation of a low cost bjts comb

  11. The effect of drone comb on a honey bee colony's production of honey


    Seeley, Thomas


    International audience; This study examined the impact on a colony's honey production of providing it with a natural amount (20%) of drone comb. Over 3 summers, for the period mid May to late August, I measured the weight gains of 10 colonies, 5 with drone comb and 5 without it. Colonies with drone comb gained only 25.2 $\\pm$ 16.0 kg whereas those without drone comb gained 48.8 $\\pm$ 14.8 kg. Colonies with drone comb also had a higher mean rate of drone flights and a lower incidence of drone ...

  12. Realization of a frequency standard at 778 nm: absolute frequency measurement of the 2S-8S/D transitions in hydrogen and deuterium and determination of the Rydberg constant; Realisation d'un etalon de frequence a 778 nm: mesure absolue des frequences 2S-8S/D des atomes d'hydrogene et de deuterium et determination de la constante de rydberg

    Energy Technology Data Exchange (ETDEWEB)

    Beauvoir, B. de


    The purpose of this work is to design a 778 nm standard laser for performing an absolute measurement of 2S-8S/D frequencies of hydrogen and deuterium atoms. This frequency calibration is based on a 5S-5D two-photon transition of the rubidium atom. Metrological performance of this laser is 10 times as good as that of He-Ne laser calibrated on iodine. It has been shown that the passage of a laser radiation through an optic fiber does not deteriorate its metrological properties. 2S-8S/8D transitions have been excited in an atomic jet by a titanium-sapphire laser. Spurious effects can shift and broaden lines. In order to prevent these effects, a theoretical line has been shaped and adjusted on experimental signals. The frequency comparison between the excitation laser and the standard laser has led to the measurement of the absolute frequency of the line concerned. The value of the Rydberg constant has been deduced: R{sub {infinity}} = 109737.3156859 (10) cm{sup -1}. The comparison of experimental data between deuterium and hydrogen has allowed us to determine the value of the Lamb shift of the 2S state of deuterium: L(2S-2P) = 1059,230 (9) MHz.

  13. In-situ determination of astro-comb calibrator lines to better than 10 cm s(-1). (United States)

    Li, Chih-Hao; Glenday, Alexander G; Benedick, Andrew J; Chang, Guoqing; Chen, Li-Jin; Cramer, Claire; Fendel, Peter; Furesz, Gabor; Kärtner, Franz X; Korzennik, Sylvain; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L


    Improved wavelength calibrators for high-resolution astrophysical spectrographs will be essential for precision radial velocity (RV) detection of Earth-like exoplanets and direct observation of cosmological deceleration. The astro-comb is a combination of an octave-spanning femtosecond laser frequency comb and a Fabry-Pérot cavity used to achieve calibrator line spacings that can be resolved by an astrophysical spectrograph. Systematic spectral shifts associated with the cavity can be 0.1-1 MHz, corresponding to RV errors of 10-100 cm/s, due to the dispersive properties of the cavity mirrors over broad spectral widths. Although these systematic shifts are very stable, their correction is crucial to high accuracy astrophysical spectroscopy. Here, we demonstrate an in-situ technique to determine the systematic shifts of astro-comb lines due to finite Fabry-Pérot cavity dispersion. The technique is practical for implementation at a telescope-based spectrograph to enable wavelength calibration accuracy better than 10 cm/s.

  14. Cross-Sectional Imaging of Boundary Lubrication Layer Formed by Fatty Acid by Means of Frequency-Modulation Atomic Force Microscopy. (United States)

    Hirayama, Tomoko; Kawamura, Ryota; Fujino, Keita; Matsuoka, Takashi; Komiya, Hiroshi; Onishi, Hiroshi


    To observe in situ the adsorption of fatty acid onto metal surfaces, cross-sectional images of the adsorption layer were acquired by frequency-modulation atomic force microscopy (FM-AFM). Hexadecane and palmitic acid were used as the base oil and typical fatty acid, respectively. A Cu-coated silicon wafer was prepared as the target substrate. The solvation structure formed by hexadecane molecules at the interface between the Cu substrate and the hexadecane was observed, and the layer pitch was found to be about 0.6 nm, which corresponds to the height of hexadecane molecules. This demonstrates that hexadecane molecules physically adsorbed onto the surface due to van der Waals forces with lying orientation because hexadecane is a nonpolar hydrocarbon. When hexadecane with palmitic acid was put on the Cu substrate instead of pure hexadecane, an adsorption layer of palmitic acid was observed at the interface. The layer pitch was about 2.5-2.8 nm, which matches the chain length of palmitic acid molecules well. This indicates that the original adsorption layer was monolayer or single bilayer in the local area. In addition, a cross-sectional image captured 1 h after observation started to reveal that the adsorbed additive layer gradually grew up to be thicker than about 20 nm due to an external stimulus, such as cantilever oscillation. This is the first report of in situ observation of an adsorbed layer by FM-AFM in the tribology field and demonstrates that FM-AFM is useful for clarifying the actual boundary lubrication mechanism.

  15. Cantharellus gallaecicus (Blanco-Dios Olariaga, comb. & stat. nov (Cantharellaceae

    Directory of Open Access Journals (Sweden)

    Olariaga, Ibai


    Full Text Available Cantharellus gallaecicus comb. & stat. nov. is proposed, after the examination of its holotype and additional material. Based on the characters observed in all the studied material (i.e., thinwalled hyphae of the pileipelis, minute basidiomata with white to grey pileus, and surface that turns yellow when bruised it is considered that C. gallaecicus is more closely related to C. romagnesianus than to C. cibarius.Se propone Cantharellus gallaecicus comb. & stat. nov. tras revisar su holótipo y material adicional disponible. Dado que todo el material examinado posee hifas del pileipelis de pared delgada, basidiomas pequeños con píleo de blanco a gris, y superficie que vira a amarillo al roce, se considera que C. gallaecicus es una especie más estrechamente relacionada con C. romagnesianus que con C. cibarius.

  16. Dual Comb Unit High-g Accelerometer Based on CMOS-MEMS Technology

    Directory of Open Access Journals (Sweden)

    Mehrdad Mottaghi


    Full Text Available In this paper a capacitive based high-g accelerometer with superior level of sensitivity is presented. It takes advantage of dual comb unit configuration and surface micromachining fabrication process. All aspects of mechanical design such as sensor structure, modal analysis, energy dissipations, dynamic response and stresses in moving structure as well as anchors are described. Electrical circuit based on CMOS technology and its output signal is presented. Fabrication process and packaging are also discussed. The proposed sensor can endure impact loads up to 120,000 g (g = 9.81 m.s-2 and achieves 16.75 µV.g-1 sensitivity with 5 V bridge excitation voltage. Main resonant frequency of structure is found to be 42.4 kHz. Intended applications of suggested sensor include military and aerospace industries as well as field of impact engineering.

  17. Reclassification of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov. (United States)

    Blackall, Patrick J; Christensen, Henrik; Beckenham, Tim; Blackall, Linda L; Bisgaard, Magne


    This paper describes a phenotypic and genotypic investigation of the taxonomy of [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium, a major subcluster within the avian 16S rRNA cluster 18 of the family Pasteurellaceae. An extended phenotypic characterization was performed of the type strain of [Haemophilus] paragallinarum, which is NAD-dependent, and eight NAD-independent strains of [Haemophilus] paragallinarum. Complete 16S rRNA gene sequences were obtained for one NAD-independent and four NAD-dependent [Haemophilus] paragallinarum strains. These five sequences along with existing 16S rRNA gene sequences for 11 other taxa within avian 16S rRNA cluster 18 as well as seven other taxa from the Pasteurellaceae were subjected to phylogenetic analysis. The analysis demonstrated that [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium formed a monophyletic group with a minimum of 96.8 % sequence similarity. This group can also be separated by phenotypic testing from all other recognized and named taxa within the Pasteurellaceae. As both genotypic and phenotypic testing support the separate and distinct nature of this subcluster, the transfer is proposed of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium to a new genus Avibacterium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov. The type strains are NCTC 1118T (Avibacterium gallinarum), NCTC 11296T (Avibacterium paragallinarum), NCTC 11297T (Avibacterium avium) and NCTC 3438T (Avibacterium volantium). Key characteristics that separate these four species are catalase activity (absent only in Avibacterium paragallinarum) and production of acid from galactose (negative only in Avibacterium paragallinarum), maltose (negative only in Avibacterium avium) and mannitol (negative

  18. Characterization of Capacitive Comb-finger MEMS Accelerometers


    Joshi, Aaditi; Redkar, Sangram; Sugar, Thomas


    This paper discusses various methods for testing the performance of MEMS capacitive comb-finger accelerometers manufactured by Sandia National Laboratories. The use of Capacitive MEMS devices requires complex circuits for measurement of capacitance. Sandia MEMS accelerometer's capacitance changes in a very small femto-farad (fF) range. The performance of accelerometer is tested using Analog Devices AD7747 sigma-delta capacitance to digital converter. The response of a MEMS capacitive accelero...

  19. Reclassification of Vibrio fischeri, Vibrio logei, Vibrio salmonicida and Vibrio wodanis as Aliivibrio fischeri gen. nov., comb. nov., Aliivibrio logei comb. nov., Aliivibrio salmonicida comb. nov. and Aliivibrio wodanis comb. nov. (United States)

    Urbanczyk, Henryk; Ast, Jennifer C; Higgins, Melissa J; Carson, Jeremy; Dunlap, Paul V


    Four closely related species, Vibrio fischeri, Vibrio logei, Vibrio salmonicida and Vibrio wodanis, form a clade within the family Vibrionaceae; the taxonomic status and phylogenetic position of this clade have remained ambiguous for many years. To resolve this ambiguity, we tested these species against other species of the Vibrionaceae for phylogenetic and phenotypic differences. Sequence identities for the 16S rRNA gene were > or =97.4 % among members of the V. fischeri group, but were Vibrio, with which they overlap in G+C content, and Enterovibrio, Grimontia and Salinivibrio, with which they do not overlap in G+C content). Combined analysis of the recA, rpoA, pyrH, gyrB and 16S rRNA gene sequences revealed that the species of the V. fischeri group form a tightly clustered clade, distinct from these other genera. Furthermore, phenotypic traits differentiated the V. fischeri group from other genera of the Vibrionaceae, and a panel of 13 biochemical tests discriminated members of the V. fischeri group from type strains of Photobacterium and Vibrio. These results indicate that the four species of the V. fischeri group represent a lineage within the Vibrionaceae that is distinct from other genera. We therefore propose their reclassification in a new genus, Aliivibrio gen. nov. Aliivibrio is composed of four species: Aliivibrio fischeri comb. nov. (the type species) (type strain ATCC 7744(T) =CAIM 329(T) =CCUG 13450(T) =CIP 103206(T) =DSM 507(T) =LMG 4414(T) =NCIMB 1281(T)), Aliivibrio logei comb. nov. (type strain ATCC 29985(T) =CCUG 20283(T) =CIP 104991(T) =NCIMB 2252(T)), Aliivibrio salmonicida comb. nov. (type strain ATCC 43839(T) =CIP 103166(T) =LMG 14010(T) =NCIMB 2262(T)) and Aliivibrio wodanis comb. nov. (type strain ATCC BAA-104(T) =NCIMB 13582(T) =LMG 24053(T)).

  20. Magnetostatic wave oscillator frequencies (United States)

    Sethares, J. C.; Stiglitz, M. R.; Weinberg, I. J.


    The frequencies of magnetostatic wave (MSW) oscillators employing three principal modes of propagation, surface (MSSW), forward (MSFVW), and backward (MSBVW) volume waves, have been investigated. Previous (MSW) oscillator papers dealt with MSSW. Oscillators were fabricated using LPE-YIG MSW delay lines in a feedback loop of a 2-4 GHz amplifier. Wide and narrow band transducers were employed. Oscillator frequency as a function of biasing field is in agreement with a theoretical analysis. The analysis predicts frequency in terms of material parameters, biasing field, and transducer geometry. With wide band transducers a comb of frequencies is generated. Narrow band transducers for MSSW and MSFVW select a single mode; and MSBVW selects two modes. Spurious modes, attributed to instrumentation, are more than 20 dB below the main response, and bandwidths are less than 0.005 percent. No other spurious modes are observed. MSW oscillators produce clean electronically tunable signals and appear attractive in frequency agile systems.

  1. Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing (United States)

    Hu, Gao-ming; Lin, Yu; Ran, Shi-yong; Wang, Yan-wei; Yang, Guang-can


    We investigated the interaction between DNA and hexammine cobalt III [Co(NH3)6]3+ by a simple molecular combing method and dynamic light scattering. The average extension of λ-DNA-YOYO-1 complex is found to be 20.9 μm, about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris, 1 mmol/L EDTA, pH=8.0), due to bis-intercalation of YOYO-1. A multivalent cation, hexammine cobalt, is used for DNA condensation. We find that the length of DNA-[Co(NH3)6]3+ complexes decrease from 20.9 μ to 5.9 μ as the concentration of the [Co(NH3)6]3+ vary from 0 to 3 μmol/L. This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt. The results from the molecular combing studies are supported by dynamic light scattering investigation, where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions. It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.

  2. Adsorption and combing of DNA on HOPG surfaces of bulk crystals and nanosheets: application to the bridging of DNA between HOPG/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Rose, F [Laboratory for Integrated Micro Mechatronic Systems/Centre National de la Recherche Scientifique (UMI 2820) Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Martin, P [Laboratory for Integrated Micro Mechatronic Systems/Centre National de la Recherche Scientifique (UMI 2820) Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Fujita, H [Laboratory for Integrated Micro Mechatronic Systems/Centre National de la Recherche Scientifique (UMI 2820) Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Kawakatsu, H [Laboratory for Integrated Micro Mechatronic Systems/Centre National de la Recherche Scientifique (UMI 2820) Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan)


    Controlled and reproducible combing of {lambda}-phage DNA molecules can be realized in predetermined orientations on highly oriented pyrolitic graphite (HOPG) surfaces. Observations by atomic force microscopy (AFM) show that DNA adsorption onto HOPG surfaces leads to different hierarchical organizations such as balls, networks, films, and fractal structures. HOPG nanosheets (3.5-100 nm thick) were created by simply rubbing a HOPG crystal onto a silicon oxide surface, and then patterned with a focused ion beam (FIB) to fabricate HOPG/Si heterostructures (arrays of silicon micropillars and microtracks decorated on their top surface with HOPG nanosheets). The surface reactivity of HOPG nanosheets toward DNA is found to be the same as of HOPG bulk crystals. Finally, combing is used to attach and suspend bundles of approximately 20-50 DNA molecules between HOPG/Si heterostructures.

  3. Single- and Multiband OFDM Photonic Wireless Links in the 75−110 GHz Band Employing Optical Combs

    DEFF Research Database (Denmark)

    Beltrán, M.; Deng, Lei; Pang, Xiaodan


    The photonic generation of electrical orthogonal frequency-division multiplexing (OFDM) modulated wireless signals in the 75−110 GHz band is experimentally demonstrated employing in-phase/quadrature electrooptical modulation and optical heterodyn upconversion. The wireless transmission of 16......-quadrature-amplitude-modulation OFDM signals is demonstrated with a bit error rate performance within the forward error correction limits. Signals of 19.1 Gb/s in 6.3-GHz bandwidth are transmitted over up to 1.3-m wireless distance. Optical comb generation is further employed to support different channels...

  4. Long reach DWDM-PON with 12.5 GHz channel spacing based on comb source seeding (United States)

    Zhou, Zhao; Nie, Hai-tao; Wang, Yao-jun


    A long reach dense wavelength division multiplexing passive optical network (DWDM-PON) with 12.5 GHz channel spacing is proposed and experimentally demonstrated. An optical frequency comb source is used to provide the multiwavelength seeding light, while reflective semiconductor optical amplifiers (RSOAs) are installed in both optical line terminal (OLT) and optical network units (ONUs) as colorless transmitter. The experimental results show that the bidirectional transmission for 1.2 Gbit/s data rate is achieved over 80 km single mode fiber (SMF).

  5. Optical diagnostics of radio-frequency plasmas containing CHF3 and CHF3/O2: Laser-induced fluorescence of CF2, CF, and O atoms, and optical emission from H, F, and O (United States)

    Hancock, G.; Sucksmith, J. P.


    Laser-induced fluorescence (LIF) has been used to measure absolute concentrations of CF2, CF, and O atoms in a parallel-plate capacitatively coupled radio-frequency-driven plasma containing CHF3 and its mixtures with Ar and O2 at pressures between 50 and 500 mTorr. In CHF3 the spatial distribution of CF2 peaks at the driven electrode, and shows the importance of surface processes for its production. Time-resolved studies show evidence for its homogeneous chemical removal. CF concentrations are an order of magnitude lower than those of CF2, and removal by reaction with H atoms is consistent with time-resolved data taken on plasma extinction. For both radicals the absolute concentrations are higher than those found for similar plasmas in CF4. In the presence of O2 the fluorinated radical concentrations drop to below the detection limit, and the influence of surface removal processes is again invoked to explain the increase in O atom concentration observed when a small amount of CHF3 is added to a dominantly O2 gas flow. Optical emission from excited F, H, and O atoms is observed, and even when corrected by actinometry, is shown to be an unreliable indicator of the relative concentration of the ground-state species because of contributions from dissociative excitation of stable species in the discharge. Excited H atoms are found to be translationally hot from measurements of their linewidths, and are clearly not all formed from excitation of H atoms. Time-resolved actinometry (TRA) can be used in some cases to remove the contribution to the emission from dissociative excitation, but in the case of O atoms where both LIF and TRA were compared, the influence of a time-dependent dissociative excitation step complicates the analysis and is attributed to the presence of other species such as O2(a1Δg) in the discharge.

  6. Cavity-enhanced optical frequency combspectroscopy

    DEFF Research Database (Denmark)

    Balslev-Clausen, David Morten; Thorpe, M. J.; Kirchner, M. S.


    Broad-bandwidth, high-spectral-resolution optical detection of human breath has identified multiple important biomarkers correlated with specific diseases and metabolic processes. This optical-frequency-comb-based breath analysis system comes with excellent performance in all criteria: high...

  7. Large-scale continuous-variable dual-rail cluster entangled state based on spatial mode comb. (United States)

    Zhang, J; Wang, J J; Yang, R G; Liu, K; Gao, J R


    In recent continuous-variable (CV) multipartite entanglement researches, the number of fully inseparable light modes has been increased dramatically by the introduction of a multiplexing scheme in either the time domain or the frequency domain. In this paper, we propose a scheme that a large-scale (≥ 20) CV dual-rail cluster entangled state is established based on a spatial mode comb in a self-imaging optical parametric oscillator, which is pumped by two spatial Laguerre-Gaussian modes with different polarization and identical frequency. A sufficient condition of full inseparability for a CV dual-rail cluster entangled state is used to evaluate the degree of quantum entanglement. It is shown that entanglement exists over a wide range of analyzing frequency and pump parameter. We have found a new scheme that uses the optical parametric cavity to generate a large-scale entanglement based on optical spatial mode comb. The presented system will be hopefully as a practical entangled source for quantum information.

  8. Electrostatic Comb-Drive Actuator with High In-Plane Translational Velocity

    Directory of Open Access Journals (Sweden)

    Yomna M. Eltagoury


    Full Text Available This work reports the design and opto-mechanical characterization of high velocity comb-drive actuators producing in-plane motion and fabricated using the technology of deep reactive ion etching (DRIE of silicon-on-insulator (SOI substrate. The actuators drive vertical mirrors acting on optical beams propagating in-plane with respect to the substrate. The actuator-mirror device is a fabrication on an SOI wafer with 80 μm etching depth, surface roughness of about 15 nm peak to valley and etching verticality that is better than 0.1 degree. The travel range of the actuators is extracted using an optical method based on optical cavity response and accounting for the diffraction effect. One design achieves a travel range of approximately 9.1 µm at a resonance frequency of approximately 26.1 kHz, while the second design achieves about 2 µm at 93.5 kHz. The two specific designs reported achieve peak velocities of about 1.48 and 1.18 m/s, respectively, which is the highest product of the travel range and frequency for an in-plane microelectromechanical system (MEMS motion under atmospheric pressure, to the best of the authors’ knowledge. The first design possesses high spring linearity over its travel range with about 350 ppm change in the resonance frequency, while the second design achieves higher resonance frequency on the expense of linearity. The theoretical predications and the experimental results show good agreement.

  9. Inductor Machines with Longitudinally-Transversal Comb-Wise Tooth Zone

    Directory of Open Access Journals (Sweden)

    Serebryakov A.


    Full Text Available The method considered in the present paper concerns the operational efficiency of the inductor electric machine, which can be improved by placing on the stator and rotor teeth the combs combined from differently shaped teeth and slots. The use on the inductor electric machine stator and rotor teeth of combs as a combination of differently shaped hills (teeth and valleys (slots allows raising the specific power of the machine. This effect is determined by the chosen type of a comb element as well as by technological possibilities of the manufacturer. The proposed method could be used moderately in the inductor machines with longitudinally-transversal combing.

  10. Implementation of a data processing platform for real-time distance measurement with dual-comb lasers (United States)

    Ni, Kai; Xu, Mingfei; Zhou, Qian; Dong, Hao; Li, Xinghui; Wu, Guanhao


    Absolute distance measurement with dual femtosecond comb lasers has advantages of wide-range, high-accuracy and fast speed. It combines time-of-flight and interferometric measurement. The novelty of ranging method leads to new challenges in designing the data acquisition and processing hardware system. Currently there are no available real-time data processing system for dual-comb ranging. This paper introduces our recent progress on designing and implementing such a platform. Our platform mainly contains four different function modules. First, a clock module that accept a 250MHz maximum reference clock input was introduced to generate the sample clock for A/D converter, and the module's output clock can be delayed up to 20ns with a resolution of 714ps. Second, a high-speed data acquisition module with a 14-bit resolution and a 125 MSPS maximum sample rate was designed to convert the analog laser pulse signal to digital signal. Third, we built a real-time data processing module that allows an input of 16-bit data in the FPGA to calculate the distance from the digital signal within 83us. Finally, a data transmission module based on a 128MB DDR SDRAM and USB2.0 was added so that we can easily debug the platform in the PC. The performance of our system is evaluated in real-time. The test bench consists of two femtosecond laser sources, an optical fiber interferometer and our data processing system. The repetition frequencies of the two combs are around 50MHz, with frequency difference of 2.5kHz. The center wavelength of laser pulses is 1560nm. The target distance is from 0m to 3m. The experimental results show that our system can output measurement results at the rate of 2500 pts/s, and the measurement deviation is less than 10um.

  11. Telecom-Wavelength Atomic Quantum Memory in Optical Fiber for Heralded Polarization Qubits. (United States)

    Jin, Jeongwan; Saglamyurek, Erhan; Puigibert, Marcel lí Grimau; Verma, Varun; Marsili, Francesco; Nam, Sae Woo; Oblak, Daniel; Tittel, Wolfgang


    Polarization-encoded photons at telecommunication wavelengths provide a compelling platform for practical realizations of photonic quantum information technologies due to the ease of performing single qubit manipulations, the availability of polarization-entangled photon-pair sources, and the possibility of leveraging existing fiber-optic links for distributing qubits over long distances. An optical quantum memory compatible with this platform could serve as a building block for these technologies. Here we present the first experimental demonstration of an atomic quantum memory that directly allows for reversible mapping of quantum states encoded in the polarization degree of freedom of a telecom-wavelength photon. We show that heralded polarization qubits at a telecom wavelength are stored and retrieved with near-unity fidelity by implementing the atomic frequency comb protocol in an ensemble of erbium atoms doped into an optical fiber. Despite remaining limitations in our proof-of-principle demonstration such as small storage efficiency and storage time, our broadband light-matter interface reveals the potential for use in future quantum information processing.

  12. Integrated InAs/InP quantum-dot coherence comb lasers (Conference Presentation) (United States)

    Lu, Zhenguo; Liu, Jiaren; Poole, Philip J.; Song, Chun-Ying; Webber, John; Mao, Linda; Chang, Shoude; Ding, Heping; Barrios, Pedro J.; Poitras, Daniel; Janz, Siegfried


    Current communication networks needs to keep up with the exponential growth of today's internet traffic, and telecommunications industry is looking for radically new integrated photonics components for new generation optical networks. We at National Research Council (NRC) Canada have successfully developed nanostructure InAs/InP quantum dot (QD) coherence comb lasers (CCLs) around 1.55 μm. Unlike uniform semiconductor layers in most telecommunication lasers, in these QD CCLs light is emitted and amplified by millions of semiconductor QDs less than 60 nm in diameter. Each QD acts like an isolated light source acting independently of its neighbours, and each QD emits light at its own unique wavelength. The end result is a QD CCL is more stable and has ultra-low timing jitter. But most importantly, a single QD CCL can simultaneously produce 50 or more separate laser beams at distinct wavelengths over the telecommunications C-band. Utilizing those unique properties we have put considerable effort well to design, grow and fabricate InAs/InP QD gain materials. After our integrated packaging and using electrical feedback-loop control systems, we have successfully demonstrated ultra-low intensity and phase noise, frequency-stabilized integrated QD CCLs with the repetition rates from 10 GHz to 100 GHz and the total output power up to 60 mW at room temperature. We have investigated their relative intensity noises, phase noises, RF beating signals and other performance of both filtered individual channel and the whole CCLs. Those highly phase-coherence comb lasers are the promising candidates for flexible bandwidth terabit coherent optical networks and signal processing applications.

  13. Force correcting atom centered potentials for generalized gradient approximated density functional theory: Approaching hybrid functional accuracy for geometries and harmonic frequencies in CCl$_3$F and other small molecules

    CERN Document Server

    von Lilienfeld, O Anatole


    Generalized gradient approximated (GGA) density functional theory (DFT) typically overestimates polarizability and bond-lengths, and underestimates force constants of covalent bonds. To overcome this problem we show that one can use empirical frequency correcting atom centered potentials (FCACPs), parameterized for every nuclear species. Parameters are obtained through minimization of a penalty functional that explicitly encodes hybrid DFT geometries and static polarizabilities of reference molecules. For hydrogen, fluorine, chlorine, and carbon the respective reference molecules consist of H$_2$, F$_2$, Cl$_2$, and CH$_4$. The transferability of this approach to other systems and properties is assessed for harmonic frequencies of a small set of molecules. Numerical evidence, gathered for CCl$_3$F, HF, HCl, CFH$_3$, and CHCl$_3$, indicates that the GGA+FCACP level of theory yields significantly improved harmonic frequencies at the desired hybrid DFT geometry minima, as well as systematically reduced molecular...

  14. Whispering gallery mode resonators for frequency metrology applications (United States)

    Baumgartel, Lukas

    This dissertation describes an investigation into the use of whispering gallery mode (WGM) resonators for applications towards frequency reference and metrology. Laser stabilization and the measurement of optical frequencies have enabled myriad technologies of both academic and commercial interest. A technology which seems to span both motivations is optical atomic clocks. These devices are virtually unimaginable without the ultra stable lasers plus frequency measurement and down-conversion afforded by Fabry Perot (FP) cavities and model-locked laser combs, respectively. However, WGM resonators can potentially perform both of these tasks while having the distinct advantages of compactness and simplicity. This work represents progress towards understanding and mitigating the performance limitations of WGM cavities for such applications. A system for laser frequency stabilization to a the cavity via the Pound-Drever-Hall (PDH) method is described. While the laser lock itself is found to perform at the level of several parts in 1015, a variety of fundamental and technical mechanisms destabilize the WGM frequency itself. Owing to the relatively large thermal expansion coefficients in optical crystals, environmental temperature drifts set the stability limit at time scales greater than the thermal relaxation time of the crystal. Uncompensated, these drifts pull WGM frequencies about 3 orders of magnitude more than they would in an FP cavity. Thus, two temperature compensation schemes are developed. An active scheme measures and stabilizes the mode volume temperature to the level of several nK, reducing the effective temperature coefficient of the resonator to 1.7x10-7 K-1; simulations suggest that the value could eventually be as low as 3.5x10-8 K-1, on par with the aforementioned FP cavities. A second, passive scheme is also described, which employs a heterogeneous resonator structure that capitalizes on the thermo-mechanical properties of one material and the optical

  15. Perovskites in the comb roof base of hornets : Their possible function

    NARCIS (Netherlands)

    Ishay, JS; Joseph, Z; Galushko, D; Ermakov, N; Bergman, DJ; Barkay, Z; Stokroos, [No Value; Van der Want, J


    On the ceiling of the Oriental hornet comb cell, there are mineral granules of poly-crystalline material known to belong to the group of perovskites. In a comb cell intended to house a worker hornet, the roof base usually carries one or several such perovskite granules containing titanium (Ti),


    Directory of Open Access Journals (Sweden)

    G. Formato


    Full Text Available The Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, during August-July 2007 analyzed, for the microbial aspects, 37 samples of jar honey and 53 samples of honey in comb obtained from 37 farms of Latium Region. In the jar honey there weren’t values up to 1*103 colony-forming unit (CFU/g of bacteria mesophiles, while in the honey in comb it was not up to 2*103 CFU/g. Bacillus cereus was found in 22 samples (41,5% of honey in comb and in 18 samples (48,6% of jar honey; Clostridium perfringens was found in 6 (11,3% samples of honey in comb and in 6 samples (16,2% of jar honey; Clostridium baratii was found in 1 (1,9% sample of honey in comb and in 1 sample (2,7% of jar honey; coagulase-positive staphylococci were found in 4 (11,3% samples of honey in comb and in 4 samples (10,8% of jar honey; Clostridium sordelli was found in 2 samples (3,8% of honey in comb and in 1 sample (2,7% of jar honey. Only 2 samples of honey in comb and 1 sample of jar honey had yeasts up to 1000 CFU/g. Finally, 9 samples (24,3% of jar honey and 16 samples (30,2% of honey in jar were positives for moulds.

  17. Conjugate Fabry-Perot cavity pair for improved astro-comb accuracy. (United States)

    Li, Chih-Hao; Chang, Guoqing; Glenday, Alexander G; Langellier, Nicholas; Zibrov, Alexander; Phillips, David F; Kärtner, Franz X; Szentgyorgyi, Andrew; Walsworth, Ronald L


    We propose a new astro-comb mode-filtering scheme composed of two Fabry-Perot cavities (coined "conjugate Fabry-Perot cavity pair"). Simulations indicate that this new filtering scheme makes the accuracy of astro-comb spectral lines more robust against systematic errors induced by nonlinear processes associated with power-amplifying and spectral-broadening optical fibers.

  18. Deflection and Pull-In of a Misaligned Comb Drive Finger in an Electrostatic Field

    NARCIS (Netherlands)

    Meijaard, Jacob Philippus; Krijnen, B.; Brouwer, Dannis Michel


    The elastic deflection of a comb drive finger in an electrostatic field is considered. The finger can be symmetrically located between two rigid fingers of the matching comb, in which case the problem reduces to a pure bifurcation problem for which the critical voltage can be determined.

  19. Deflection of an eccentric tooth of a comb drive in an electrostatic field

    NARCIS (Netherlands)

    Meijaard, Jacob Philippus; Krijnen, B.; Brouwer, Dannis Michel


    The elastic deflection of a comb drive tooth in an electrostatic field is considered. The tooth can be symmetrically located between two rigid teeth of the matching comb, in which case the problem reduces to a pure bifurcation problem for which the critical voltage can be determined. Alternatively,

  20. Sub-lethal effects of pesticide residues in brood comb on worker honey bee (Apis mellifera development and longevity.

    Directory of Open Access Journals (Sweden)

    Judy Y Wu

    Full Text Available BACKGROUND: Numerous surveys reveal high levels of pesticide residue contamination in honey bee comb. We conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan. METHODOLOGY/PRINCIPAL FINDINGS: Worker bees were reared in brood comb containing high levels of known pesticide residues (treatment or in relatively uncontaminated brood comb (control. Delayed development was observed in bees reared in treatment combs containing high levels of pesticides particularly in the early stages (day 4 and 8 of worker bee development. Adult longevity was reduced by 4 days in bees exposed to pesticide residues in contaminated brood comb during development. Pesticide residue migration from comb containing high pesticide residues caused contamination of control comb after multiple brood cycles and provided insight on how quickly residues move through wax. Higher brood mortality and delayed adult emergence occurred after multiple brood cycles in contaminated control combs. In contrast, survivability increased in bees reared in treatment comb after multiple brood cycles when pesticide residues had been reduced in treatment combs due to residue migration into uncontaminated control combs, supporting comb replacement efforts. Chemical analysis after the experiment confirmed the migration of pesticide residues from treatment combs into previously uncontaminated control comb. CONCLUSIONS/SIGNIFICANCE: This study is the first to demonstrate sub-lethal effects on worker honey bees from pesticide residue exposure from contaminated brood comb. Sub-lethal effects, including delayed larval development and adult emergence or shortened adult longevity, can have indirect effects on the colony such as premature shifts in hive roles and foraging activity. In addition, longer development time for bees may provide a reproductive advantage for parasitic Varroa destructor

  1. Transcriptome analysis of comb and testis from Rose-comb Silky chicken (R1/R1) and Beijing Fatty wild type chicken (r/r). (United States)

    Wang, Y; Li, J; Feng, C; Zhao, Y; Hu, X; Li, N


    Rose-comb was one of the chicken comb-variants first used by Bateson and Punnet in 1902 to demonstrate Mendelian inheritance in animals. Rose-comb is a monogenic trait that has been widely described in chickens. It is caused by a large structural rearrangement that leads to mis-expression of transcription factor MNR2 on chromosome 7. Rose-comb has pleiotropic effects in homozygous roosters, which is associated with poor sperm mobility. It was postulated that this is caused by the disruption of the CCDC108 gene located at the distal inversion breakpoint. In this study, we did the transcriptional profiling of combs and testes from Rose-comb Silky (RS) (R1/R1) and Beijing Fatty (BF) wild type chickens (r/r) using RNA-seq. We obtained 68,694,797 unique mapped reads and over 80% of the chicken genes were covered for each sample. In combs, we found that differentially expressed genes (DEGs) were significantly enriched in the retinol metabolism (RPE65, CYP26A1, and CYP26C1) and hedgehog-signaling pathway (PTCH1, GLI1, and HHIP), while genes related to cell differentiation and morphogenesis were down-regulated in R1/R1 chickens, suggesting that the transient expression of MNR2 might affect the expression of these genes and influence the development of comb tissue. For testes, DEGs were significantly enriched in the GO terms of binding activates and mitochondrial oxidation-reduction reactions. Our results suggested that the CCDC108 might be functionally related with mitochondrial oxidation-reduction reactions and caused subfertility of roosters. Compared with the genome average, the degree of expression variations within the inversion region did not show significant differences. However, DEGs near the breakpoints showed greater expression variance. Our results demonstrated that the large-scale rearrangements affected the gene expression only around the breakpoint in this case. © 2017 Poultry Science Association Inc.

  2. Development of Unified Fabrication Process and Testing of MEMS Based Comb and Crab Type Capacitive Accelerometers for Navigational Applications

    Directory of Open Access Journals (Sweden)

    R. K. Bhan


    Full Text Available MEMS based accelerometers have already penetrated defense programs including navigation control in addition to their usual deployment in automotive, consumer and industrial markets because of their improved reliability, accuracy and excellent price performance. This paper discussed about the fabrication and testing of single axis capacitive accelerometer structures based on change in area (comb-type and change in gap (Crab type sensing principles. The accelerometers are designed for ±30 g acceleration range. A common fabrication process flow is designed for the fabrication of both types of accelerometers that are fabricated by using a three mask dissolved wafer process (DWP. Both the accelerometers showed a scale factor sensitivity of >60 mV/g at ±1 g flip test. Vibration and sensitivity testing at higher frequency was conducted on shaker table using a half sine wave shock (HSWS of 2 ms. Using HSWS test, a sensitivity in the range of ~60 mV/g was obtained for both comb or crab type structures in the 0-30 g range. It can be further tuned upto 100 mV/g by increasing the gain of the capacitance Read Out Integrated Circuit (ROIC. However, performance of the comb type of accelerometers gets affected in – 30 g to – 0 g range due to deep boron diffusion induced residual stress. The crab accelerometers showed almost linear (nonlinearity:<3 % FS behavior in the whole ±30 g range. Other tests like bias stability, bandwidth, bias temperature coefficient etc. indicate that devices are fully functional. All these observations validate our design and unified process.

  3. A single comb laser source for short reach WDM interconnects (United States)

    Wojcik, Gregory L.; Yin, Dongliang; Kovsh, Alexey R.; Gubenko, Alexey E.; Krestnikov, Igor L.; Mikhrin, Sergey S.; Livshits, Daniil A.; Fattal, David A.; Fiorentino, Marco; Beausoleil, Raymond G.


    High-channel-count WDM will eventually be used for short reach optical interconnects since it maximizes link bandwidth and efficiency. An impediment to adoption is the fact that each WDM wavelength currently requires its own DFB laser. The alternative is a single, multi-wavelength laser, but noise, size and/or expense make existing options impractical. In contrast, a new low-noise, diode comb laser based on InAs/GaAs quantum dots provides a practical and timely alternative, albeit in the O-band. Samples are being evaluated in short reach WDM development systems. Tests show this type of Fabry-Perot laser permits >10 Gb/s error-free modulation of 10 to over 50 separate channels, as well as potential for 1.25 Gb/s direct modulation. The paper describes comb laser requirements, noise measurements for external and direct modulation, O-band issues, transmitter photonic circuitry and components, future CMP applications, and optical couplers that may help drive down packaging costs to below a dollar.

  4. Molecular dynamics study of linear and comb-like polyelectrolytes in aqueous solution: effect of Ca2+ ions (United States)

    Tong, Kefeng; Song, Xingfu; Sun, Shuying; Xu, Yanxia; Yu, Jianguo


    All-atom molecular dynamics simulations were employed to provide microscopic mechanism for the salt tolerance of polyelectrolytes dispersants. The conformational variation of polyelectrolytes and interactions between COO- groups and counterions/water molecules were also studied via radius of gyration and pair correlations functions. Sodium polyacrylate (NaPA) and sodium salts of poly(acrylic acid)-poly(ethylene oxide) (NaPA-PEO) were selected as the representative linear and comb-like polyelectrolyte, respectively. The results show that Ca2+ ions interact with COO- groups much stronger than Na+ ions and can bring ion-bridging interaction between intermolecular COO- groups in the NaPA systems. While in the NaPA-PEO systems, the introduced PEO side chains can prevent backbone chains from ion-bridging interactions and weaken the conformational changes. The present results can help in selecting and designing new-type efficient polyelectrolyte dispersants with good salt tolerance.

  5. Characterization of the molecular structure and mechanical properties of polymer surfaces and protein/polymer interfaces by sum frequency generation vibrational spectroscopy and atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Koffas, Telly Stelianos [Univ. of California, Berkeley, CA (United States)


    Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and other complementary surface-sensitive techniques have been used to study the surface molecular structure and surface mechanical behavior of biologically-relevant polymer systems. SFG and AFM have emerged as powerful analytical tools to deduce structure/property relationships, in situ, for polymers at air, liquid and solid interfaces. The experiments described in this dissertation have been performed to understand how polymer surface properties are linked to polymer bulk composition, substrate hydrophobicity, changes in the ambient environment (e.g., humidity and temperature), or the adsorption of macromolecules. The correlation of spectroscopic and mechanical data by SFG and AFM can become a powerful methodology to study and engineer materials with tailored surface properties. The overarching theme of this research is the interrogation of systems of increasing structural complexity, which allows us to extend conclusions made on simpler model systems. We begin by systematically describing the surface molecular composition and mechanical properties of polymers, copolymers, and blends having simple linear architectures. Subsequent chapters focus on networked hydrogel materials used as soft contact lenses and the adsorption of protein and surfactant at the polymer/liquid interface. The power of SFG is immediately demonstrated in experiments which identify the chemical parameters that influence the molecular composition and ordering of a polymer chain's side groups at the polymer/air and polymer/liquid interfaces. In general, side groups with increasingly greater hydrophobic character will be more surface active in air. Larger side groups impose steric restrictions, thus they will tend to be more randomly ordered than smaller hydrophobic groups. If exposed to a hydrophilic environment, such as water, the polymer chain will attempt to orient more of its hydrophilic groups to

  6. Wave Atom Based Watermarking


    Bukhari, Ijaz; Nuhman-ul-Haq; Hyat, Khizar


    Watermarking helps in ensuring originality, ownership and copyrights of a digital image. This paper aims at embedding a Watermark in an image using Wave Atom Transform. Preference of Wave Atoms on other transformations has been due to its sparser expansion, adaptability to the direction of local pattern, and sharp frequency localization. In this scheme, we had tried to spread the watermark in an image so that the information at one place is very small and undetectable. In order to extract the...

  7. Synchronization of an optomechanical oscillator and thermal/free-carrier self-pulsing using optical comb forces

    CERN Document Server

    Navarro-Urrios, Daniel; Gomis-Bresco, Jordi; Alzina, Francesc; Griol, Amadeu; Martinez, Alejandro; Torres, Clivia M Sotomayor


    Optical forces can set tiny objects in states of self-sustained oscillation. When more than one oscillator comes into play, even a very weak interaction among them may lead to synchronization. This work reports a novel spontaneous synchronization process within an optomechanical crystal, which involves thermal/free-carrier self-pulsing and coherent mechanical motion. Both oscillating systems are driven and coupled by the optical energy stored in the cavity. Multiple frequency entrainment regions are observed as a result of the wide tuneability of the natural frequency of the thermal/free-carrier self-pulsing and the comb nature of the optical forces. All these features are observed at ambient conditions of pressure and temperature in a silicon compatible platform, which would allow their exploitation for advanced clocking applications or in artificial neural networks.

  8. Frequency shift due to blackbody radiation in a cesium atomic fountain and improvement of the clock performances; Deplacement de frequence du au rayonnement du corps noir dans une fontaine atomique a cesium et amelioration des performances de l'horloge

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S


    FO1 was the first caesium fountain primary frequency standard in the world. The most recent evaluation in 2002 before improvement reached an accuracy of 1*10{sup -15} when operated with optical molasses. Working as an extremely precise and stable instrument, FO1 has contributed to fundamental physics and technical measurements: - Frequency comparison between Cs and Rb fountains over an interval of 5 years sets an upper limit for a possible variation of the fine structure constant as |alpha/alpha| < 2*10{sup -15}/y. The resolution is about 5 times better than the previous test in our laboratory. The projected accuracy of the space clock PHARAO is 1*10{sup -16}. We confirmed its Ramsey cavity performance by testing the phase difference between the two interaction zones in FO1. The measured temperature T dependent frequency shift of the Cs clock induced by the blackbody radiation field is given as nu(T)=154(6)*10{sup -6}*(T/300){sup 4}[1+{epsilon}(T/300){sup 2}] Hz with the theoretical value {epsilon} = 0,014. The obtained accuracy represents a 3 times improvement over the previous measurement by the PTB group. Some improvements have been carried out on FO1. The new FO1 version works directly with optical molasses loaded by a laser slowed atomic beam. The application of the adiabatic passage method to perform the state selection allows us to determine the atom number dependent frequency shifts due to the cold collision and cavity pulling effects at a level of of 10{sup -16}. Recently, the obtained frequency stability is 2,8*10{sup -14}*{tau}{sup -1/2} for about 4*10{sup 6} detected atoms. The accuracy is currently under evaluation, the expected value is a few times 10{sup -16}. (author)

  9. Taxonomic evaluation of the genus Enterobacter based on multilocus sequence analysis (MLSA): proposal to reclassify E. nimipressuralis and E. amnigenus into Lelliottia gen. nov. as Lelliottia nimipressuralis comb. nov. and Lelliottia amnigena comb. nov., respectively, E. gergoviae and E. pyrinus into Pluralibacter gen. nov. as Pluralibacter gergoviae comb. nov. and Pluralibacter pyrinus comb. nov., respectively, E. cowanii, E. radicincitans, E. oryzae and E. arachidis into Kosakonia gen. nov. as Kosakonia cowanii comb. nov., Kosakonia radicincitans comb. nov., Kosakonia oryzae comb. nov. and Kosakonia arachidis comb. nov., respectively, and E. turicensis, E. helveticus and E. pulveris into Cronobacter as Cronobacter zurichensis nom. nov., Cronobacter helveticus comb. nov. and Cronobacter pulveris comb. nov., respectively, and emended description of the genera Enterobacter and Cronobacter. (United States)

    Brady, Carrie; Cleenwerck, Ilse; Venter, Stephanus; Coutinho, Teresa; De Vos, Paul


    The taxonomy of Enterobacter has a complicated history, with several species transferred to and from this genus. Classification of strains is difficult owing to its polyphyletic nature, based on 16S rRNA gene sequences. It has been previously acknowledged that Enterobacter contains species which should be transferred to other genera. In an attempt to resolve the taxonomy of Enterobacter, MLSA based on partial sequencing of protein-encoding genes (gyrB, rpoB, infB and atpD) was performed on the type strains and reference strains of Enterobacter, Cronobacter and Serratia species, as well as members of the closely related genera Citrobacter, Klebsiella, Kluyvera, Leclercia, Mangrovibacter, Raoultella and Yokenella. Phylogenetic analyses of the concatenated nucleotide sequences revealed that Enterobacter can be divided into five strongly supported MLSA groups, suggesting that the species should be reclassified into five different genera. Further support for this was provided by a concatenated amino acid tree, phenotypic characteristics and fatty acid profiles, enabling differentiation of the MLSA groups. Three novel genera are proposed: Lelliottia gen. nov., Pluralibacter gen. nov. and Kosakonia gen. nov. and the following new combinations: Lelliottia nimipressuralis comb. nov., Lelliottia amnigena comb. nov., Pluralibacter gergoviae comb. nov., Pluralibacter pyrinus comb. nov., Kosakonia cowanii comb. nov., Kosakonia radicincitans comb. nov., Kosakonia oryzae comb. nov., Kosakonia arachidis comb. nov., Cronobacter helveticus comb. nov. and Cronobacter pulveris comb. nov. Additionally, the novel epithet Cronobacter zurichensis nom. nov. is proposed for the reclassification of Enterobacter turicensis into the genus Cronobacter, as Cronobacter turicensis (Iversen et al., 2008) is already in use. Copyright © 2013 Elsevier GmbH. All rights reserved.

  10. A Study of the Effect of the Fringe Fields on the Electrostatic Force in Vertical Comb Drives

    Directory of Open Access Journals (Sweden)

    Else Gallagher


    Full Text Available The equation that describes the relationship between the applied voltage and the resulting electrostatic force within comb drives is often used to assist in choosing the dimensions for their design. This paper re-examines how some of these dimensions—particularly the cross-sectional dimensions of the comb teeth—affect this relationship in vertical comb drives. The electrostatic forces in several vertical comb drives fabricated for this study were measured and compared to predictions made with four different mathematical models in order to explore the amount of complexity required within a model to accurately predict the electrostatic forces in the comb drives.

  11. Mechanisms behind the metabolic flexibility of an invasive comb jelly

    DEFF Research Database (Denmark)

    Augustine, Starrlight; Jaspers, Cornelia; Kooijman, Sebastiaan A. L.M.


    Mnemiopsis leidyi is an invasive comb jellywhich has successfully established itself in European seas. The species is known to produce spectacular blooms yet it is holoplanktonic and not much is known about its population dynamics in between. One way to gain insight on how M. leidyi might survive...... between blooms and how it can bloom so fast is to study how the metabolism of this species actually responds to environmental changes in food and temperature over its different life-stages. To this end we combined modelling and data analysis to study the energy budget of M. leidyi over its full life....... Intriguingly, the onset of the acceleration appears to be delayed and the data do not yet exist which allows determining what actually triggers it. It is hypothesised that this delay confers a lot of metabolic flexibility by controlling generation time. We compared the DEB model parameters for this species...

  12. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)


    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  13. Atomic Physics

    CERN Document Server

    Foot, Christopher J


    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  14. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.


    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  15. Fermions on the low-buckled honey-comb structured lattice plane and classical Casimir-Polder force (United States)

    Goswami, Partha


    We start with the well-known expression for the vacuum polarization and suitably modify it for 2+1-dimensional spin-orbit coupled (SOC) fermions on the low-buckled honey-comb structured lattice plane described by the low-energy Liu-Yao-Feng-Ezawa (LYFE) model Hamiltonian involving the Dirac matrices in the chiral representation obeying the Clifford algebra. The silicene and germanene fit this description suitably. They have the Dirac cones similar to those of graphene and SOC is much stronger. The system could be normal or ferromagnetic in nature. The silicene turns into the latter type if there is exchange field arising due to the proximity coupling to a ferromagnet (FM) such as depositing Fe atoms to the silicene surface. For the silicene, we find that the many-body effects considerably change the bare Coulomb potential by way of the dependence of the Coulomb propagator on the real-spin, iso-spin and the potential due to an electric field applied perpendicular to the silicene plane. The computation aspect of the Casimir-Polder force (CPF) needs to be investigated in this paper. An important quantity in this process is the dielectric response function (DRF) of the material. The plasmon branch was obtained by finding the zeros of DRF in the long-wavelength limit. This leads to the plasmon frequencies. We find that the collective charge excitations at zero doping, i.e., intrinsic plasmons, in this system, are absent in the Dirac limit. The valley-spin-split intrinsic plasmons, however, come into being in the case of the massive Dirac particles with characteristic frequency close to 10 THz. Our scheme to calculate the Casimir-Polder interaction (CPI) of a micro-particle with a sheet involves replacing the dielectric constant of the sample in the CPI expression obtained on the basis of the Lifshitz theory by the static DRF obtained using the expressions for the polarization function we started with. Though the approach replaces a macroscopic constant by a microscopic

  16. Frequency ratios of Sr, Yb and Hg based optical lattice clocks and their applications

    CERN Document Server

    Takamoto, Masao; Das, Manoj; Nemitz, Nils; Ohkubo, Takuya; Yamanaka, Kazuhiro; Ohmae, Noriaki; Takano, Tetsushi; Akatsuka, Tomoya; Yamaguchi, Atsushi; Katori, Hidetoshi


    This article describes the recent progress of optical lattice clocks with neutral strontium ($^{87}$Sr), ytterbium ($^{171}$Yb) and mercury ($^{199}$Hg) atoms. In particular, we present frequency comparison between the clocks locally via an optical frequency comb and between two Sr clocks at remote sites using a phase-stabilized fibre link. We first review cryogenic Sr optical lattice clocks that reduce the room-temperature blackbody radiation shift by two orders of magnitude and serve as a reference in the following clock comparisons. Similar physical properties of Sr and Yb atoms, such as transition wavelengths and vapour pressure, have allowed our development of a compatible clock for both species. A cryogenic Yb clock is evaluated by referencing a Sr clock. We also report on a Hg clock, which shows one order of magnitude less sensitivity to blackbody radiation, while its large nuclear charge makes the clock sensitive to the variation of fine-structure constant. Connecting all three types of clocks by an o...

  17. Comb structure analysis of the capacitive sensitive element in MEMS-accelerometer (United States)

    Shalimov, Andrew; Timoshenkov, Sergey; Korobova, Natalia; Golovinskiy, Maxim; Timoshenkov, Alexey; Zuev, Egor; Berezueva, Svetlana; Kosolapov, Andrey


    In this paper analysis of comb design for the sensing element MEMS accelerometer with longitudinal displacement of the inertial mass under the influence of acceleration to obtain the necessary parameters for the further construction of an electronic circuit for removal and signal processing has been done. Fixed on the stator the inertia mass has the ability to move under the influence of acceleration along the longitudinal structure. As a result the distance between the fixed and movable combs, and hence the capacitance in the capacitors have been changed. Measuring the difference of these capacitances you can estimate the value of the applied acceleration. Furthermore, managing combs that should apply an electrostatic force for artificial deviation of the inertial mass may be used for the initial sensitive elements culling. Also in this case there is a change of capacitances, which can be measured by the comb and make a decision about the spoilage presence or absence.

  18. Description of Histiostoma Conjuncta (New Comb.) (Acari: Anoetidae), An Associate of Central American Bark Beetles (United States)

    J. P. Woodring; John C. Moser


    The adult female and male plus the tritonymph of Histiostoma conjuncta (Woodring and Moser, 1970) (new comb.) and described. The species is known to be associated with various pine bark beetles from Honduras, Guatemala, and Louisiana.

  19. Al{sub 2}O{sub 3} multi-density layer structure as a moisture permeation barrier deposited by radio frequency remote plasma atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Hyunsoo [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741 (Korea, Republic of); Jeon, Heeyoung [Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Choi, Hagyoung; Ham, Giyul; Shin, Seokyoon [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Jeon, Hyeongtag, E-mail: [Division of Materials Science and Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Department of Nano-scale Semiconductor Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)


    Al{sub 2}O{sub 3} films deposited by remote plasma atomic layer deposition have been used for thin film encapsulation of organic light emitting diode. In this study, a multi-density layer structure consisting of two Al{sub 2}O{sub 3} layers with different densities are deposited with different deposition conditions of O{sub 2} plasma reactant time. This structure improves moisture permeation barrier characteristics, as confirmed by a water vapor transmission rate (WVTR) test. The lowest WVTR of the multi-density layer structure was 4.7 × 10{sup −5} gm{sup −2} day{sup −1}, which is one order of magnitude less than WVTR for the reference single-density Al{sub 2}O{sub 3} layer. This improvement is attributed to the location mismatch of paths for atmospheric gases, such as O{sub 2} and H{sub 2}O, in the film due to different densities in the layers. This mechanism is analyzed by high resolution transmission electron microscopy, elastic recoil detection, and angle resolved X-ray photoelectron spectroscopy. These results confirmed that the multi-density layer structure exhibits very good characteristics as an encapsulation layer via location mismatch of paths for H{sub 2}O and O{sub 2} between the two layers.

  20. Photothermally driven fast responding photo-actuators fabricated with comb-type hydrogels and magnetite nanoparticles


    Eunsu Lee; Dowan Kim; Haneul Kim; Jinhwan Yoon


    To overcome the slow kinetics of the volume phase transition of stimuli-responsive hydrogels as platforms for soft actuators, thermally responsive comb-type hydrogels were prepared using synthesized poly(N-isopropylacrylamide) macromonomers bearing graft chains. Fast responding light-responsive hydrogels were fabricated by combining a comb-type hydrogel matrix with photothermal magnetite nanoparticles (MNP). The MNPs dispersed in the matrix provide heat to stimulate the volume change of the h...

  1. A comb laser-driven DWDM silicon photonic transmitter based on microring modulators. (United States)

    Chen, Chin-Hui; Ashkan Seyedi, M; Fiorentino, Marco; Livshits, Daniil; Gubenko, Alexey; Mikhrin, Sergey; Mikhrin, Vladimir; Beausoleil, Raymond G


    We demonstrate concurrent multi-channel transmission at 10 Gbps per channel of a DWDM silicon photonic transmitter. The DWDM transmitter is based on a single quantum dot comb laser and an array of microring resonator-based modulators. The resonant wavelengths of microrings are thermally tuned to align with the wavelengths provided by the comb laser. No obvious crosstalk is observed at 240 GHz channel spacing.

  2. Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers. (United States)

    Chang, Guoqing; Li, Chih-Hao; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X


    We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb's side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution approximately 100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro-comb is predicted to provide 1 cm/s (approximately 10 kHz) radial velocity calibration accuracy for an astrophysical spectrograph. Such extreme performance will be necessary for the search for and characterization of Earth-like extra-solar planets, and in direct measurements of the change of the rate of cosmological expansion.

  3. Absolute spectroscopy near 7.8 μm with a comb-locked extended-cavity quantum-cascade-laser

    KAUST Repository

    Lamperti, Marco


    We report for the first time the frequency locking of an extended-cavity quantum-cascade-laser (EC-QCL) to a near-infrared frequency comb. The locked laser source is exploited to carry out molecular spectroscopy around 7.8 μm with a line-centre frequency combined uncertainty of ~63 kHz. The strength of the approach, in view of an accurate retrieval of line centre frequencies over a spectral range as large as 100 cm-1, is demonstrated on the P(40), P(18) and R(31) lines of the fundamental rovibrational band of N2O covering the centre and edges of the P and R branches. The spectrometer has the potential to be straightforwardly extended to other spectral ranges, till 12 μm, which is the current wavelength limit for commercial cw EC-QCLs.

  4. Atomic physics

    CERN Document Server

    Born, Max


    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  5. Early Atomism

    Indian Academy of Sciences (India) Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  6. Photonic-assisted microwave frequency multiplication with a tunable multiplication factor. (United States)

    Gao, Liang; Liu, Weilin; Chen, Xiangfei; Yao, Jianping


    Photonic-assisted microwave frequency multiplication with a tunable multiplication factor (MF) based on an optical comb generator and an embedded single-passband microwave photonic filter (MPF) is proposed and demonstrated. The optical comb is generated using two cascaded modulators which are driven by a microwave reference signal. By applying the optical comb to a photodetector, a fundamental frequency corresponding to the comb spacing and its harmonics is generated. Thanks to the embedded single-passband MPF, only one harmonic is selected by the single-passband MPF. Thus, a single-frequency frequency-multiplied microwave signal is generated. In the proposed system, the embedded single-passband MPF is formed by using a sliced broadband optical source and a section of dispersion-compensating fiber (DCF). By tuning the central frequency of the passband at a frequency corresponding to that of a specific harmonic, a microwave signal at that specific frequency is generated. The proposed system is experimentally demonstrated. A frequency-multiplied microwave signal with an MF from 1 to 5 is generated. The phase noise and frequency tunability of the generated microwave signal are also investigated.

  7. Recognizing nitrogen dopant atoms in graphene using atomic force microscopy

    DEFF Research Database (Denmark)

    van der Heijden, Nadine J.; Smith, Daniel; Calogero, Gaetano


    Doping graphene by heteroatoms such as nitrogen presents an attractive route to control the position of the Fermi level in the material. We prepared N-doped graphene on Cu(111) and Ir(111) surfaces via chemical vapor deposition of two different molecules. Using scanning tunneling microscopy images...... as a benchmark, we show that the position of the dopant atoms can be determined using atomic force microscopy. Specifically, the frequency shift-distance curves Delta f(z) acquired above a N atom are significantly different from the curves measured over a C atom. Similar behavior was found for N-doped graphene...

  8. Sex combs reduced (Scr) regulatory region of Drosophila revisited. (United States)

    Calvo-Martín, Juan M; Papaceit, Montserrat; Segarra, Carmen


    The Hox gene Sex combs reduced (Scr) is responsible for the differentiation of the labial and prothoracic segments in Drosophila. Scr is expressed in several specific tissues throughout embryonic development, following a complex path that must be coordinated by an equally complex regulatory region. Although some cis-regulatory modules (CRMs) have been identified in the Scr regulatory region (~75 kb), there has been no detailed and systematic study of the distinct regulatory elements present within this region. In this study, the Scr regulatory region was revisited with the aim of filling this gap. We focused on the identification of Initiator elements (IEs) that bind segmentation factors, Polycomb response elements (PREs) that are recognized by the Polycomb and Trithorax complexes, as well as insulators and tethering elements. To this end, we summarized all currently available information, mainly obtained from high throughput ChIP data projects. In addition, a bioinformatic analysis based on the evolutionary conservation of regulatory sequences using the software MOTEVO was performed to identify IE and PRE candidates in the Scr region. The results obtained by this combined strategy are largely consistent with the CRMs previously identified in the Scr region and help to: (i) delimit them more accurately, (ii) subdivide two of them into different independent elements, (iii) identify a new CRM, (iv) identify the composition of their binding sites and (v) better define some of their characteristics. These positive results indicate that an approach that integrates functional and bioinformatic data might be useful to characterize other regulatory regions.

  9. Reclassification of Arthrobacter viscosus as Rhizobium viscosum comb. nov. (United States)

    Flores-Félix, José David; Ramírez-Bahena, Martha Helena; Salazar, Sergio; Peix, Alvaro; Velázquez, Encarna


    The species Arthrobacter viscosus was isolated from soil from Guatemala and it was classified into the genus Arthrobacter on the basis of phenotypic traits. Nevertheless, the results of16S rRNA gene analysis indicated that this species is a member of the genus Rhizobium, with Rhizobium alamii GBV016T and Rhizobium mesosinicum CCBAU 25010T as the most closely related species with 99.64 and 99.48 % similarity, respectively. The similarity values for the recA gene are 92.2 and 94.4 % with respect to R. alamii GBV016T and R. mesosinicum CCBAU 25010T, respectively, and those for the atpD gene are 92.9 and 98.7 %, respectively. Results of DNA-DNA hybridization analysis yield averages of 46 and 41 % relatedness with respect to the type strains of R. alamii and R. mesosinicum, respectively. Phenotypic characteristics also differed from those of the most closely related species of the genus Rhizobium. Therefore, based on the data obtained in this study, we propose to classify strain LMG 16473T as representing a novel species named Rhizobiumviscosum comb. nov. (type strain LMG 16473T=CECT 908T).

  10. The comb jelly opsins and the origins of animal phototransduction. (United States)

    Feuda, Roberto; Rota-Stabelli, Omar; Oakley, Todd H; Pisani, Davide


    Opsins mediate light detection in most animals, and understanding their evolution is key to clarify the origin of vision. Despite the public availability of a substantial collection of well-characterized opsins, early opsin evolution has yet to be fully understood, in large part because of the high level of divergence observed among opsins belonging to different subfamilies. As a result, different studies have investigated deep opsin evolution using alternative data sets and reached contradictory results. Here, we integrated the data and methods of three, key, recent studies to further clarify opsin evolution. We show that the opsin relationships are sensitive to outgroup choice; we generate new support for the existence of Rhabdomeric opsins in Cnidaria (e.g., corals and jellyfishes) and show that all comb jelly opsins belong to well-recognized opsin groups (the Go-coupled opsins or the Ciliary opsins), which are also known in Bilateria (e.g., humans, fruit flies, snails, and their allies) and Cnidaria. Our results are most parsimoniously interpreted assuming a traditional animal phylogeny where Ctenophora are not the sister group of all the other animals. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  11. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    National Research Council Canada - National Science Library

    Van den Berg, S.A; Van Eldik, S; Bhattacharya, N


    .... From the spectrally resolved output of a Michelson interferometer a distance is derived. The presented measurement method combines spectral interferometry, white light interferometry and multi-wavelength interferometry in a single scheme...

  12. Entangling the optical frequency comb into multiple continuous-variable cluster states (United States)

    Pfister, Olivier; Zaidi, Hussain; Menicucci, Nicolas; Flammia, Steven; Bloomer, Russell; Pysher, Matthew


    A single multimode optical parametric oscillator (OPO) can be designed so that its nonlinear gain medium (typically a two-photon parametric amplifier) generates a particular network of entangling interactions between the eigenmodes of its optical cavity. We show how this can be formulated using nonstandard graph states and how these are related to the usual graph states, an example of which is the cluster state for one-way quantum computing. We also report on the progress of our very compact experimental implementation, in a single OPO with a single pump field, of a parallel quantum register comprising several independent quadripartite cluster states.

  13. Improvement of signal-to-noise ratio of a beat note by cascading an Yb-doped fiber amplifier in an Er-fiber comb (United States)

    Liu, H.; Cao, S. Y.; Yu, Y.; Lin, B. K.; Lu, W. P.; Fang, Z. J.


    Femtosecond optical frequency combs (FOFCs) make it possible to measure the absolute frequency of a laser, which greatly simplifies quantity traceability and comparison of the absolute frequency. In order to ensure the accuracy and reliability of the measurement, the signal-to-noise ratio (SNR) of the beat note (f b) between an FOFC and a laser should be above 30 dB. In this paper, an Er-doped FOFC (Er-FOFC) is employed, at a repetition rate of 305 MHz. The spectral intensity near the 1 µm wavelength in an octave-spanning supercontinuum generated from the Er-FOFC is enhanced effectively by cascading an Yb-doped fiber amplifier after spectral broadening, which helps improve the SNR of the beat note between the comb light and an iodine-stabilized 532 nm laser. This method can effectively reduce the intensity requirements on the 1 µm wavelength when the spectrum is directly broadened in an Er-FOFC.

  14. Radio frequency phototube and optical clock: High resolution, high rate and highly stable single photon timing technique

    Energy Technology Data Exchange (ETDEWEB)

    Margaryan, Amur


    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.

  15. Optical angular momentum and atoms. (United States)

    Franke-Arnold, Sonja


    Any coherent interaction of light and atoms needs to conserve energy, linear momentum and angular momentum. What happens to an atom's angular momentum if it encounters light that carries orbital angular momentum (OAM)? This is a particularly intriguing question as the angular momentum of atoms is quantized, incorporating the intrinsic spin angular momentum of the individual electrons as well as the OAM associated with their spatial distribution. In addition, a mechanical angular momentum can arise from the rotation of the entire atom, which for very cold atoms is also quantized. Atoms therefore allow us to probe and access the quantum properties of light's OAM, aiding our fundamental understanding of light-matter interactions, and moreover, allowing us to construct OAM-based applications, including quantum memories, frequency converters for shaped light and OAM-based sensors.This article is part of the themed issue 'Optical orbital angular momentum'. © 2017 The Author(s).

  16. Worm-like mesoporous TiO2 thin films templated using comb copolymer for dye-sensitized solar cells with polymer electrolyte (United States)

    Lee, Jae Hun; Park, Cheol Hun; Jung, Jung Pyo; Kim, Jong Hak


    A comb copolymer consisting of hydrophobic poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate) (PBEM) and hydrophilic poly(oxyethylene methacrylate) (POEM) is synthesized via one-pot free radical polymerization. The PBEM-POEM comb copolymer is used as an agent to direct the structure toward one consisting of worm-like mesoporous TiO2 (WM-TiO2) films. The selective, preferential interaction between the titania precursor and the hydrophilic POEM chains is responsible for the formation of a well-organized worm-like mesostructure. The morphology of the WM-TiO2 films is characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). In particular, the effects of film thickness on the optical and electrochemical properties are systematically investigated. The introduction of the WM-TiO2 layer between the nanocrystalline TiO2 (NC-TiO2) layer and fluorine-doped tin oxide (FTO) glass results in increased transmittance of visible light due to an antireflective property, decreased interfacial resistance and suppressed charge recombination at the interfaces of NC-TiO2/FTO glass. As a result, the photovoltaic conversion efficiency of the dye-sensitized solar cell (DSSC) with a polymer electrolyte is improved from 5.3% to 6.6% at an optimum film thickness (310 nm). The obtained efficiency represents a higher efficiency for the N719-based DSSC with a solvent-free, polymer electrolyte.

  17. Enhancing V2X Communication Based on a New Comb-Pilot Estimation Approach

    Directory of Open Access Journals (Sweden)

    Aymen Sassi


    Full Text Available Vehicle to Vehicle (V2V and Vehicle to Infrastructure (V2I communication systems, known as V2X technologies, have increasingly attracted attention in current research on road safety and traffic ergonomics. The performance evaluation of these communication systems is an important step before their potential integration and use in real systems. V2X communications are based on the IEEE 802.11p standard also known as Wireless Access in Vehicular Environment (WAVE. V2X can affect human life; therefore a deep study related to V2X performance evaluation should be done in order to be sure about the system reliability. In this context, we have elaborated a deep study related to the effect of transmission range on V2X communications by considering the terminal mobility. First, we have evaluated the performance of the PHY layer on the IEEE 802.11p using simulation. Secondly, we have conducted real case measurements using the Arada LocoMate Transmission system. The obtained results shows the necessity to optimize the quality of transmission in V2X communications. Consequently, we propose in this paper a new comb-pilot technique to enhance the quality of Orthogonal Frequency Division Multiplexing (OFDM transmission. Our proposal consists in two new uses of the pilot subcarrier estimation technique in order to decrease the elevated bit error rate (BER. The quality of transmission (QoT is first evaluated relating to the pilot symbol rearranged positions. Second, we proposed to optimize the QoT by adding two supplementary pilot symbols as it can offer better channel estimation results. Based on the performance evaluation of our proposal, it is confirmed that both of rearrangement and the adding of the pilot patterns lead to performance enhancement compared to baseline model (standardized one.

  18. Magnetic field modulation spectroscopy of rubidium atoms

    Indian Academy of Sciences (India)

    phase-sensitive detection of the signal, thereby paving the way for very high sensitive measurement in the parts per billion (PPB) levels [4]. On the other hand, the saturation. FMS (SFMS) can be used as a very precise frequency reference in experiments involving laser-cooled atoms, frequency standards as in atomic clock, ...

  19. Phylogenetic analyses of the genus Glaciecola: emended description of the genus Glaciecola, transfer of Glaciecola mesophila, G. agarilytica, G. aquimarina, G. arctica, G. chathamensis, G. polaris and G. psychrophila to the genus Paraglaciecola gen. nov. as Paraglaciecola mesophila comb. nov., P. agarilytica comb. nov., P. aquimarina comb. nov., P. arctica comb. nov., P. chathamensis comb. nov., P. polaris comb. nov. and P. psychrophila comb. nov., and description of Paraglaciecola oceanifecundans sp. nov., isolated from the Southern Ocean. (United States)

    Shivaji, Sisinthy; Reddy, Gundlapally Sathyanarayana


    Phylogenetic analyses of the genus Glaciecola were performed using the sequences of the 16S rRNA gene and the GyrB protein to establish its taxonomic status. The results indicated a consistent clustering of the genus Glaciecola into two clades, with significant bootstrap values, with all the phylogenetic methods employed. Clade 1 was represented by seven species, Glaciecola agarilytica, G. aquimarina, G. arctica, G. chathamensis, G. mesophila, G. polaris and G. psychrophila, while clade 2 consisted of only three species, Glaciecola nitratireducens, G. pallidula and G. punicea. Evolutionary distances between species of clades 1 and 2, based on 16S rRNA gene and GyrB protein sequences, ranged from 93.0 to 95.0 % and 69.0 to 73.0 %, respectively. In addition, clades 1 and 2 possessed 18 unique signature nucleotides, at positions 132, 184 : 193, 185 : 192, 230, 616 : 624, 631, 632, 633, 738, 829, 1257, 1265, 1281, 1356 and 1366, in the 16S rRNA gene sequence and can be differentiated by the occurrence of a 15 nt signature motif 5'-CAAATCAGAATGTTG at positions 1354-1368 in members of clade 2. Robust clustering of the genus Glaciecola into two clades based on analysis of 16S rRNA gene and GyrB protein sequences, 16S rRNA gene sequence similarity of ≤95.0 % and the occurrence of signature nucleotides and signature motifs in the 16S rRNA gene suggested that the genus should be split into two genera. The genus Paraglaciecola gen. nov. is therefore created to accommodate the seven species of clade 1, while the name Glaciecola sensu stricto is retained to represent species of clade 2. The species of clade 1 are transferred to the genus Paraglaciecola as Paraglaciecola mesophila comb. nov. (type strain DSM 15026(T) = KMM 241(T)), P. agarilytica comb. nov. (type strain NO2(T) = KCTC 12755(T) = LMG 23762(T)), P. aquimarina comb. nov. (type strain GGW-M5(T) = KCTC 32108(T) = CCUG 62918(T)), P. arctica comb. nov. (type strain BSs20135(T

  20. Aerodynamics of a translating comb-like plate inspired by a fairyfly wing (United States)

    Lee, Seung Hun; Kim, Daegyoum


    Unlike the smooth wings of common insects or birds, micro-scale insects such as the fairyfly have a distinctive wing geometry, comprising a frame with several bristles. Motivated by this peculiar wing geometry, we experimentally investigated the flow structure of a translating comb-like wing for a wide range of gap size, angle of attack, and Reynolds number, Re = O(10) - O(103), and the correlation of these parameters with aerodynamic performance. The flow structures of a smooth plate without a gap and a comb-like plate are significantly different at high Reynolds number, while little difference was observed at the low Reynolds number of O(10). At low Reynolds number, shear layers that were generated at the edges of the tooth of the comb-like plate strongly diffuse and eventually block a gap. This gap blockage increases the effective surface area of the plate and alters the formation of leading-edge and trailing-edge vortices. As a result, the comb-like plate generates larger aerodynamic force per unit area than the smooth plate. In addition to a quasi-steady phase after the comb-like plate travels several chords, we also studied a starting phase of the shear layer development when the comb-like plate begins to translate from rest. While a plate with small gap size can generate aerodynamic force at the starting phase as effectively as at the quasi-steady phase, the aerodynamic force drops noticeably for a plate with a large gap because the diffusion of the developing shear layers is not enough to block the gap.

  1. Atomic theories

    CERN Document Server

    Loring, FH


    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  2. Frequency noise reduction performance of a feed-forward heterodyne technique: application to an actively mode-locked laser diode. (United States)

    Sahni, Mohamed Omar; Trebaol, Stéphane; Bramerie, Laurent; Joindot, Michel; Ó Dúill, Seán P; Murdoch, Stuart G; Barry, Liam P; Besnard, Pascal


    We report on the frequency noise reduction performance of a feed-forward technique. The Letter is based on frequency noise measurements that allow the spectral response of the feed-forward phase noise correction to be determined. The main limitation to the noise compensation is attributed to the local oscillator flicker noise and the noise added by the optoelectronic loop elements. The technique is applied to an actively mode-locked laser diode demonstrating, at the output of the system, an optical frequency comb source with 14 comb lines reduced to sub-kilohertz intrinsic linewidth.

  3. Atomic Power

    African Journals Online (AJOL)

    Atomic Power. By Denis Taylor: Dr. Taylor was formerly Chief UNESCO Advisor at the University. College, Nairobi, Kenya and is now Professor of Electrical Engineering in the Uni- versity of ... method of producing radioactive isotopes, which are materials .... the sealing and the pressure balancing, all can be carried out ...

  4. Comb-Type Grafted Hydrogels of PNIPAM and PDMAEMA with Reversed Network-Graft Architectures from Controlled Radical Polymerizations

    Directory of Open Access Journals (Sweden)

    Sheng-Qi Chen


    Full Text Available Dual thermo- and pH-responsive comb-type grafted hydrogels of poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA and poly(N-isopropylacrylamide (PNIPAM with reversed network-graft architectures were synthesized by the combination of atom transfer radical polymerization (ATRP, reversible addition-fragmentation chain transfer (RAFT polymerization and click chemistry. Two kinds of macro-cross-linkers with two azido groups at one chain-end and different chain length [PNIPAM–(N32 and PDMAEMA–(N32] were prepared with N,N-di(β-azidoethyl 2-halocarboxylamide as the ATRP initiator. Through RAFT copolymerization of DMAEMA or NIPAM with propargyl acrylate (ProA using dibenzyltrithiocarbonate as a chain transfer agent, two network precursors with different content of alkynyl side-groups [P(DMAEMA-co-ProA and P(NIPAM-co-ProA] were obtained. The subsequent azido-alkynyl click reaction of macro-cross-linkers and network precursors led to the formation of the network-graft hydrogels. These dual stimulus-sensitive hydrogels exhibited rapid response, high swelling ratio and reproducible swelling/de-swelling cycles under different temperatures and pH values. The influences of cross-linkage density and network-graft architecture on the properties of the hydrogels were investigated. The release of ceftriaxone sodium from these hydrogels showed both thermal- and pH-dependence, suggesting the feasibility of these hydrogels as thermo- and pH-dependent drug release devices.

  5. Ortho-Para-Dependent Pressure Effects Observed in the Near Infrared Band of Acetylene by Dual-Comb Spectroscopy (United States)

    Iwakuni, Kana; Okubo, Sho; Yamada, Koichi M. T.; Inaba, Hajime; Onae, Atsushi; Hong, Feng-Lei; Sasada, Hiroyuki


    We demonstrate that dual-comb spectroscopy, which allows one to record broadband spectra with high frequency accuracy in a relatively short time, provides a real advantage for the observation of pressure-broadening and pressure-shift effects. We illustrate this with the ν1+ν3 vibration band of 12C2 H2 . We observe transitions from P (26 ) to R (29 ) , which extend over a 3.8 THz frequency range, at six pressures ranging up to 2654 Pa. Each observed absorption line profile is fitted to a Voigt function yielding pressure-broadening and pressure-shift coefficients for each rotation-vibration transition. The effectiveness of this technique is such that we are able to discern a clear dependence of the pressure-broadening coefficients on the nuclear spin state, i.e., on the ortho or para modification. This information, combined with the pressure-shift coefficients, can facilitate a detailed understanding of the mechanism of molecular collisions.

  6. Atomic arias (United States)

    Crease, Robert P.


    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  7. Atomic rivals

    Energy Technology Data Exchange (ETDEWEB)

    Goldschmidt, B.


    This book is a memoir of rivalries among the Allies over the bomb, by a participant and observer. Nuclear proliferation began in the uneasy wartime collaboration of the United States, England, Canada, and Free France to produce the atom bomb. Through the changes of history, a young French chemist had a role in almost every act of this international drama. This memoir is based on Goldschmidt's own recollections, interviews with other leading figures, and 3,000 pages of newly declassified documents in Allied archives. From his own start as Marie Curie's lab assistant, Goldschmidt's career was closely intertwined with Frances complicated rise to membership in the nuclear club. As a refugee from the Nazis, he became part of the wartime nuclear energy project in Canada and found himself the only French scientist to work (although briefly) on the American atom bomb project.

  8. Possibility of comb-type rf shield structure for high-current accelerators

    Directory of Open Access Journals (Sweden)

    Y. Suetsugu


    Full Text Available A novel rf shield structure for bellows chambers or gate valves in high-current accelerators is proposed. The rf shield has no thin fingers, but nested comb teeth instead at the inner surface of the beam duct. The comb-type rf shield has a higher thermal strength structurally than the conventional finger-type one. A simulation also indicates its lower impedance. Especially, the leak of a TE modelike higher order mode through the axial slits, which causes mainly heating of these components, is almost suppressed due to thick teeth. An abrasion test in a vacuum using a test piece of the comb-type rf shield shows less dust generation compared to the finger type. Another preliminary test transmitting 508 MHz microwaves through a prototype rf shield in the atmosphere found no abnormal heating or arcing. A trial model of bellows chambers with the comb-type rf shield will be installed and tested using a real beam in the KEK B-factory positron ring this year.

  9. Wooden combs from the Roman fort at Vechten: the bodily appearance of soldiers

    NARCIS (Netherlands)

    Derks, A.M.J.; Vos, W.K.


    Abstract Excavations in the late 19th century and surveys carried out in the 1970s have produced 12 boxwood combs from the Roman fort at Vechten (NL). They are to be considered waste material that was dumped in the river Rhine which in the Roman period ran just north of the camp. In this article,

  10. Controlled deposition and combing of DNA across lithographically defined patterns on silicon

    DEFF Research Database (Denmark)

    Nazari, Zeniab Esmail; Gurevich, Leonid


    We have developed a new procedure for efficient combing of DNA on a silicon substrate, which allows reproducible deposition and alignment of DNA molecules across lithographically defined patterns. The technique involves surface modification of Si/SiO2 substrates with a hydrophobic silane by using...

  11. Functional materials based on self-assembled comb-shaped supramolecules

    NARCIS (Netherlands)

    ten Brinke, G; Ikkala, O; KorugicKarasz, LS; MacKnight, WJ; Martuscelli, E


    In this paper we will review the main features of our approach to create functional materials using self-assembly of hydrogenbonded comb-shaped supramolecules. Typically, the supramolecules consist of homopolymers or diblock copolymers, where short chain amphiphiles are hydrogenbonded to the

  12. Synthesis of ZnO comb-like nanostructures for high sensitivity H2S ...

    Indian Academy of Sciences (India)


    Sep 15, 2017 ... Small response time (48–22s) and long recovery time. (540 s) were found at H2S gas .... gold electrodes with a thickness of 50 nm was deposited on the surface of the sensing films by using the ... Abdulqader Dawood Faisal. Figure 10. Typical response and recovery characteristics of ZnO comb-like sensor.

  13. Sexual selection and the evolution of secondary sexual traits: sex comb evolution in Drosophila. (United States)

    Snook, Rhonda R; Gidaszewski, Nelly A; Chapman, Tracey; Simmons, Leigh W


    Sexual selection can drive rapid evolutionary change in reproductive behaviour, morphology and physiology. This often leads to the evolution of sexual dimorphism, and continued exaggerated expression of dimorphic sexual characteristics, although a variety of other alternative selection scenarios exist. Here, we examined the evolutionary significance of a rapidly evolving, sexually dimorphic trait, sex comb tooth number, in two Drosophila species. The presence of the sex comb in both D. melanogaster and D. pseudoobscura is known to be positively related to mating success, although little is yet known about the sexually selected benefits of sex comb structure. In this study, we used experimental evolution to test the idea that enhancing or eliminating sexual selection would lead to variation in sex comb tooth number. However, the results showed no effect of either enforced monogamy or elevated promiscuity on this trait. We discuss several hypotheses to explain the lack of divergence, focussing on sexually antagonistic coevolution, stabilizing selection via species recognition and nonlinear selection. We discuss how these are important, but relatively ignored, alternatives in understanding the evolution of rapidly evolving sexually dimorphic traits. © 2013 The Authors. Journal of Evolutionary Biology © 2013 European Society For Evolutionary Biology.

  14. Fabrication Challenges for Realization of Wet Etching Based Comb Type Capacitive Microaccelerometer Structure

    Directory of Open Access Journals (Sweden)

    Shankar DUTTA


    Full Text Available The current paper presents fabrication of wet etching based comb-type microaccelerometer structure consisting of 47 interdigitated fingers attached to a large proof mass, which is suspended by two narrow torsional beams. Silicon (, p-type was oxidized and the microaccelerometer structure was patterned by photolithography. Desired device thickness was achieved by combination of wet anisotropic etching of 15μm depth and formation of 12 μm thick p++ etch stop layer. Pits of 15 μm were formed in Pyrex glass and metallic lines with bonding pads were formed by UHV Ti-Au metallization and pattern plating (Au. Patterned glass and silicon wafers were aligned and anodically bonded; whereas, the metallic lines and the microaccelerometer anchors are eutectically bonded. Finally, the suspended comb-type device structure consisting of two torsional beams of 5μm width and interdigitated comb fingers of 10μm width is achieved by Dissolve Wafer Process (DWP. The paper highlights the fabrication challenges faced during the realization of the comb-type structure.

  15. Optical Fourier transform based in-plane vibration characterization for MEMS comb structure. (United States)

    Gao, Yongfeng; Cao, Liangcai; You, Zheng; Zhao, Jiahao; Zhang, Zichen; Yang, Jianzhong


    On-line and on-wafer characterizations of mechanical properties of Micro-Electro-Mechanical-System (MEMS) with efficiency are very important to the mass production of MEMS foundry in the near future. However, challenges still remain. In this paper, we present an in-plane vibration characterizing method for MEMS comb using optical Fourier transform (OFT). In the experiment, the intensity distribution at the focal plane was captured to characterize the displacement of the vibrator in the MEMS comb structure. A typical MEMS comb was tested to verify the principle. The shape and the movement of MEMS comb was imitated and tested to calibrate the measurement by using a spatial light modulator (SLM). The relative standard deviations (RSD) of the measured displacements were better than 5%, where the RSD is defined as the ratio of the standard deviation to the mean. It is convinced that the presented method is feasible for on-line and on-wafer characterizations for MEMS with great convenience, high efficiency and low cost.

  16. Power, Prayers, and Protection: Comb Ridge as a Case Study in Navajo Thought (United States)

    McPherson, Robert S.


    Beginning in 2005, a five-year survey of cultural resources began to unfold in southeastern Utah along a prominent sandstone rock formation known as Comb Ridge. This visually dramatic monocline stretches a considerable distance from the southwestern corner of Blue Mountain (Abajos) in Utah to Kayenta, Arizona, approximately one hundred miles to…

  17. Gravity orientation in social wasp comb cells (Vespinae) and the possible role of embedded minerals (United States)

    Ishay, Jacob S.; Barkay, Zahava; Eliaz, Noam; Plotkin, Marian; Volynchik, Stanislav; Bergman, David J.


    Social wasps and hornets maintain their nest in the dark. The building of the combs by all Vespinae is always in the direction of the gravitational force of Earth, and in each cell’s ceiling, at least one ‘keystone’ is embedded and fastened by saliva. The sensory mechanisms that enable both building of sizeable symmetrical combs and nursing of the brood in the darkness merit investigation, and the aim of the present study was to identify and characterize the ‘keystones’ that exist in the ceiling and in the walls of the social wasp comb cells. Bio-ferrography was used to isolate magnetic particles on slides. These slides, as well as original cells, were analyzed in an environmental scanning electron microscope by a variety of analytical tools. It was found that both the roof and the walls of each comb cell bear minerals, like ferrites, as well as Ti and Zr. The latter two elements are less abundant in the soil around the nest. Ti and Zr are known to reflect infrared (IR) light. IR imaging showed a thermoregulatory center in the dorsal thorax of the adult Oriental hornet. It is not known yet whether these insects can sense IR light.

  18. Synthesis of ZnO comb-like nanostructures for high sensitivity H2S ...

    Indian Academy of Sciences (India)

    Zinc oxide (ZnO) comb-like nanostructures were successfully synthesized on the silicon substrate without a catalyst via chemical vapour deposition. The morphology and crystal structure of the product were characterized by scanning electron microscope and X-ray diffractometer. In this research, a simple gas sensor was ...

  19. Spontaneous curvature of comb copolymers strongly adsorbed at a flat interface : A computer simulation study

    NARCIS (Netherlands)

    de Jong, Johan; Subbotin, A; ten Brinke, G


    Using a modified bond fluctuation model, with only excluded-volume interactions, we demonstrate spontaneous curvature of 2D comb copolymer molecules, provided the side chains are allowed to flip from one side of the backbone to the other. When the side chains are not allowed to flip, the polymer

  20. Look closer: Time sequence photography of Roosters Comb in the Sheep Creek Range, Nevada (United States)

    The importance of understanding natural landscape changes is key in properly determining rangeland ecology. Time sequence photography allows a snapshot of a landscape to be documented and enables the ability to compare natural changes overtime. Photographs of Roosters Comb were taken from the same v...

  1. Effect of partial comb and wattle trim on pullet behavior and thermoregulation (United States)

    The wattles and comb of chickens are important for thermoregulation allowing for heat exchange during high temperatures. These integumentary tissues are sometimes trimmed to prevent tears if caught on cage equipment and to also improve feed efficiency; however, the procedure itself could be painful ...

  2. Reclassification of Thermoanaerobium acetigenum as Caldicellulosiruptor acetigenus comb. nov and emendation of the genus description

    DEFF Research Database (Denmark)

    Onyenwoke, R.U.; Lee, Y.J.; Dabrowski, Slawomir


    -examination of physiological properties of the type strain, X6B(T) (= DSM 7040(T) = ATCC BAA-11149(T)), we propose that Thermoanaerobium acetigenum should be reclassified as Caldicellulosiruptor acetigenus comb. nov. Strain X6B(T) contains two separate 16S rRNA genes bracketing another species in the phylogenetic 16S r...

  3. Searching for Scandinavians in pre-Viking Scotland : Molecular fingerprinting of Early Medieval combs

    NARCIS (Netherlands)

    Von Holstein, Isabella C C; Ashby, Steven P.; van Doorn, Nienke L.; Sachs, Stacie M.; Buckley, Michael; Meiri, Meirav; Barnes, Ian; Brundle, Anne; Collins, Matthew J.

    The character and chronology of Norse colonisation in Early Medieval northern Scotland (8th-10th centuries AD) is hotly debated. The presence of reindeer antler raw material in 'native' or 'Pictish' type combs from the Orkney Isles, northern Scotland has been put forward as evidence for a long and

  4. Laser stabilisation for velocity-selective atomic absorption

    NARCIS (Netherlands)

    Meijer, H.A.J.; Meulen, H.P. van der; Ditewig, F.; Wisman, C.J.; Morgenstern, R.


    A relatively simple method is described for stabilising a dye laser at a frequency ν = ν0 + νc in the vicinity of an atomic resonance frequency ν0. The Doppler effect is exploited by looking for atomic fluorescence when a laser beam is crossed with an atomic beam at certain angles αi. Absolute

  5. Acceleration effects on atomic clocks

    CERN Document Server

    Dahia, F


    We consider a free massive particle inside a box which is dragged by Rindler observers. Admitting that the particle obeys the Klein-Gordon equation, we find the frequencies of the stationary states of this system. Transitions between the stationary states are employed to set a standard frequency for a toy atomic clock. Comparing the energy spectrum of the accelerated system with the energy spectrum of an identical system in an inertial frame, we determine the influence of the instantaneous acceleration on the rate of atomic clocks. We argue that our result does not violate the clock hypothesis.

  6. In Situ Adsorption Studies at the Solid/Liquid Interface:Characterization of Biological Surfaces and Interfaces Using SumFrequency Generation Vibrational Spectroscopy, Atomic Force Microscopy,and Quartz Crystal Microbalance

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Diana Christine [Univ. of California, Berkeley, CA (United States)


    Sum frequency generation (SFG) vibrational spectroscopy, atomic force microscopy (AFM), and quartz crystal microbalance (QCM) have been used to study the molecular surface structure, surface topography and mechanical properties, and quantitative adsorbed amount of biological molecules at the solid-liquid interface. The molecular-level behavior of designed peptides adsorbed on hydrophobic polystyrene and hydrophilic silica substrates has been examined as a model of protein adsorption on polymeric biomaterial surfaces. Proteins are such large and complex molecules that it is difficult to identify the features in their structure that lead to adsorption and interaction with solid surfaces. Designed peptides which possess secondary structure provide simple model systems for understanding protein adsorption. Depending on the amino acid sequence of a peptide, different secondary structures (α-helix and β-sheet) can be induced at apolar (air/liquid or air/solid) interfaces. Having a well-defined secondary structure allows experiments to be carried out under controlled conditions, where it is possible to investigate the affects of peptide amino acid sequence and chain length, concentration, buffering effects, etc. on adsorbed peptide structure. The experiments presented in this dissertation demonstrate that SFG vibrational spectroscopy can be used to directly probe the interaction of adsorbing biomolecules with a surface or interface. The use of well designed model systems aided in isolation of the SFG signal of the adsorbing species, and showed that surface functional groups of the substrate are sensitive to surface adsorbates. The complementary techniques of AFM and QCM allowed for deconvolution of the effects of surface topography and coverage from the observed SFG spectra. Initial studies of biologically relevant surfaces are also presented: SFG spectroscopy was used to study the surface composition of common soil bacteria for use in bioremediation of nuclear waste.

  7. Electrochemical frequency modulation and inductively coupled plasma atomic emission spectroscopy methods for monitoring corrosion rates and inhibition of low alloy steel corrosion in HCl solutions and a test for validity of the Tafel extrapolation method

    Energy Technology Data Exchange (ETDEWEB)

    Amin, Mohammed A. [Chemistry Department, Faculty of Science, Ain Shams University, Al-Khalefah Al-Maamoon St., Abbassia, Cairo 11566 (Egypt)], E-mail:; Abd El Rehim, Sayed S. [Chemistry Department, Faculty of Science, Ain Shams University, Al-Khalefah Al-Maamoon St., Abbassia, Cairo 11566 (Egypt); Abdel-Fatah, Hesham T.M. [Central Chemical Laboratories, Egyptian Electricity Holding Company, Sabtia, Cairo (Egypt)


    The inhibition effect of glycine (Gly) towards the corrosion of low alloy steel ASTM A213 grade T22 boiler steel was studied in aerated stagnant 0.50 M HCl solutions in the temperature range 20-60 deg. C using potentiodynamic polarization (Tafel polarization and linear polarization) and impedance techniques, complemented with scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Electrochemical frequency modulation (EFM), a non-destructive corrosion measurement technique that can directly give values of corrosion current without prior knowledge of Tafel constants, is also presented here. Experimental corrosion rates determined by the Tafel extrapolation method are compared with corrosion rates obtained by electrochemical, namely EFM technique, and chemical (i.e., non-electrochemical) method for steel in HCl. The chemical method of confirmation of the corrosion rates involved determination of the dissolved cation, using ICP-AES (inductively coupled plasma atomic emission spectrometry) method of analysis. Corrosion rates (in mm y{sup -1}) obtained from the electrochemical (Tafel extrapolation and EFM) and the chemical method, ICP, are in a good agreement. Polarization studies have shown that Gly is a good 'green', mixed-type inhibitor with cathodic predominance. The inhibition process was attributed to the formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. Scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) examinations of the electrode surface confirmed the existence of such an adsorbed film. The inhibition efficiency increases with increase in Gly concentration, while it decreases with solution temperature. Temkin isotherm is successfully applied to describe the adsorption process. Thermodynamic functions for the adsorption process were determined.

  8. Linear and Nonlinear Elasticity of Networks Made of Comb-like Polymers and Bottle-Brushes (United States)

    Liang, H.; Dobrynin, A.; Everhart, M.; Daniel, W.; Vatankhah-Varnoosfaderani, M.; Sheiko, S.

    We study mechanical properties of networks made of combs and bottle-brushes by computer simulations, theoretical calculations and experimental techniques. The networks are prepared by cross-linking backbones of combs or bottle-brushes with linear chains. This results in ``hybrid'' networks consisting of linear chains and strands of combs or bottle-brushes. In the framework of the phantom network model, the network modulus at small deformations G0 can be represented as a sum of contributions from linear chains, G0 , l, and strands of comb or bottle-brush, G0 , bb. If the length of extended backbone between crosslinks, Rmax, is much longer than the Kuhn length, bk, the modulus scales with the degree of polymerization of the side chains, nsc, and number of monomers between side chains, ng, as G0 , bb (nsc/ng + 1)-1. In the limit when bk becomes of the order of Rmax, the combs and bottle-brushes can be considered as semiflexible chains, resulting in a network modulus to be G0 , bb (nsc/ng + 1)-1(nsc2/2/ng) . In the nonlinear deformation regime, the strain-hardening behavior is described by the nonlinear network deformation model, which predicts that the true stress is a universal function of the structural modulus, G, first strain invariant, I1, and deformation ratio, β. The results of the computer simulations and predictions of the theoretical model are in a good agreement with experimental results. NSF DMR-1409710, DMR-1407645, DMR-1624569, DMR-1436201.

  9. Atom Skimmers and Atom Lasers Utilizing Them (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.


    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  10. PREFACE: Atomic Spectra and Oscillator Strengths (ASOS9) Atomic Spectra and Oscillator Strengths (ASOS9) (United States)

    Wahlgren, Glenn M.; Wiese, Wolfgang L.; Beiersdorfer, Peter


    For the first time since its inaugural meeting in Lund in 1983, the triennial international conference on Atomic Spectroscopy and Oscillator Strengths for Astrophysical and Laboratory Plasmas (ASOS) returned to Lund, Sweden. Lund has been a home to atomic spectroscopy since the time of Janne Rydberg, and included the pioneering work in laboratory and solar spectroscopy by Bengt Edlén, who presented the initial ASOS talk in 1983. The ninth ASOS was hosted by the Lund Observatory and Physics Department of Lund University, 7-10 August 2007, and was attended by 99 registrants. An encouraging sign for the field was the number of young researchers in attendance. This volume of Physica Scripta contains contributions from the invited presentations of the conference. For the first time, papers from the ASOS9 poster presentations have been made feely available online in a complementary volume of Journal of Physics: Conference Series. With these two volumes the character of ASOS9 is more evident, and together they serve as a review of the state of atomic spectroscopy for spectrum analysis and the determination of oscillator strengths and their applications. The goal of ASOS is to be a forum for atomic spectroscopy, where both the providers and the users of atomic data, which includes wavelengths, energy levels, lifetimes, oscillator strengths and line shape parameters, can meet to discuss recent advances in experimental and theoretical techniques and their application to understanding the physical processes that are responsible for producing observed spectra. The applications mainly originate from the fields of astrophysics and plasma physics, which includes fusion energy and lighting research. The oral presentations, all but one of which are presented in this volume, provided an extensive synopsis of techniques currently in use and those that are being planned. New to ASOS9 was the extent to which techniques such as cold, trapped atoms and molecules and frequency combs are

  11. Dual-Comb Spectroscopy of the ν_1+ ν_3 Band of Acetylene: Intensity and Transition Dipole Moment (United States)

    Iwakuni, Kana; Okubo, Sho; Yamada, Koichi MT; Inaba, Hajime; Onae, Atsushi; Hong, Feng-Lei; Sasada, Hiroyuki


    The ν_1+ν_3 vibration band of ^{12}C_2H_2 is recorded with a homemade dual-comb spectrometer. The spectral resolution and the accuracy of frequency determination are high, and the bandwidth is broad enough to take spectrum of the whole band in one shot. The last remarkable competence enables us to record all the spectral lines under constant experimental conditions. The linewidth and line strength of the P(26) to R(29) transitions are determined by fitting the line profile to Lambert-Beer's law with a Voigt function. In the course of analysis, we found the ortho-para dependence of the pressure-broadening coefficient. This time, we have determined the transition dipole moment of the ν_1+ν_3 band. It is noted that the transition dipole moment determined from the ortho lines agrees with that from the para lines. S. Okubo et al., Applied Physics Express 8, 082402 (2015). K.Iwakuni et al., 71th ISMS, WK15 K. Iwakuni et al., Physical Review Letters 117, 143902 (2016).

  12. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui


    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  13. Wavelength and bandwidth-tunable silicon comb filter based on Sagnac loop mirrors with Mach-Zehnder interferometer couplers. (United States)

    Jiang, Xinhong; Wu, Jiayang; Yang, Yuxing; Pan, Ting; Mao, Junming; Liu, Boyu; Liu, Ruili; Zhang, Yong; Qiu, Ciyuan; Tremblay, Christine; Su, Yikai


    We propose and experimentally demonstrate a wavelength and bandwidth-tunable comb filter based on silicon Sagnac loop mirrors (SLMs) with Mach-Zehnder interferometer (MZI) couplers. By thermally tuning the MZI couplers in common and differential modes, the phase shift and reflectivity of the SLMs can be changed, respectively, leading to tunable wavelength and bandwidth of the comb filter. The fabricated comb filter has 93 comb lines in the wavelength range from 1535 nm to 1565 nm spaced by ~0.322 nm. The central wavelength can be red-shifted by ~0.462 nm with a tuning efficiency of ~0.019 nm/mW. A continuously tunable bandwidth from 5.88 GHz to 24.89 GHz is also achieved with a differential heating power ranging from 0.00 mW to 0.53 mW.

  14. Quantum gates between superconducting and atomic qubits (United States)

    Saffman, Mark; Wilhelm, Frank; McDermott, Robert


    We propose methods for performing entangling gate operations between superconducting phase qubits and neutral atom hyperfine qubits. The gate is mediated by mapping the superconducting qubit onto a microwave excitation of a coplanar waveguide resonator (CPW). The large transition dipole moments of atomic Rydberg states at microwave frequencies enable bidirectional entanglement between a single atom and a single CPW photon. Specific gate protocols and fidelity calculations are presented for experimentally realistic geometries.

  15. Afroleius floridus (Mahunka, 1985) comb. nov. and three new Afroleius Mahunka, 1984 species (Acari: Oribatida: Mycobatidae) from South Africa. (United States)

    Coetzee, Louise


    Three new species of the genus Afroleius Mahunka, 1984 are described: A. amieae sp. nov. with round notogastral foveae and long rostral and lamellar setae, A. inae sp. nov. with long lamellae and rostral and lamellar setae of similar length, and A. valerieae sp. nov. with ventrally directed bothridium and octotaxic system consisting of porose areas. Magyaria florida Mahunka, 1985 is recombined in the genus Afroleius as A. floridus comb. nov. Juvenile instars of A. floridus comb. nov. are described.

  16. High Atom Number in Microsized Atom Traps (United States)


    Final Performance Report on ONR Grant N00014-12-1-0608 High atom number in microsized atom traps for the period 15 May 2012 through 14 September...TYPE Final Technical Report 3. DATES COVERED (From - To) 05/15/2012-09/14/2012 4. TITLE AND SUBTITLE High atom number in microsized atom traps...forces for implementing a small-footprint, large-number atom -chip instrument. Bichromatic forces rely on absorption and stimulated emission to produce

  17. Innovation and reliability of atomic standards for PTTI applications (United States)

    Kern, R.


    Innovation and reliability in hyperfine frequency standards and clock systems are discussed. Hyperfine standards are defined as those precision frequency sources and clocks which use a hyperfine atomic transition for frequency control and which have realized significant commercial production and acceptance (cesium, hydrogen, and rubidium atoms). References to other systems such as thallium and ammonia are excluded since these atomic standards have not been commercially exploited in this country.

  18. Modeling and System-level Simulation of Force-balance MEMS Comb Accelerometers

    Directory of Open Access Journals (Sweden)

    Hao CHEN


    Full Text Available This paper presents a quick system-level modeling and simulation of force-balance MEMS comb accelerometers. The derivation of the system-level model including the sense element and interface electronics is elaborated and the simulation results are obtained from COVENTOR and MATLAB respectively. The force-balance MEMS comb accelerometer, with the size of 1920 µm ´ 960 µm ´ 50 µm, the static capacitance of 2.25 pF, and the inertial mass of 5.47 µg, can endure with over load of 2000 g. Through the system-level simulation, the sensitivity is 100 mv/g, the full scale range is ± 50 g, the nonlinear distortion is smaller than 0.5 % and the system bandwidth is 2.2 kHz.

  19. Characterization of Comb-Shaped Copolymers by Multidetection SEC, DLS and SANS

    Directory of Open Access Journals (Sweden)

    Giulia Gelardi


    Full Text Available PolyCarboxylate ether-based superplasticizers (PCEs are a type of comb-shaped copolymers used as polymeric dispersants in cementitious materials. PCEs have a high degree of dispersity, which limits the suitability of conventional characterization techniques, such as Size Exclusion Chromatography (SEC. Properties of PCEs strongly depend on their molecular structure and a comprehensive characterization is needed to fully understand the structure–property relationships. PCEs with well-defined molecular structures were synthesized to study their solution conformation by SEC and scattering techniques. The combined use of SEC, dynamic light scattering and small-angle neutron scattering allowed us to demonstrate the validity of a scaling law describing the radius of gyration of comb-shaped copolymers as a function of their molecular structure. Moreover, we show that the use of SEC with standard calibration, although widely spread, is not adequate for PCEs.

  20. Optical properties of the iridescent organ of the comb-jellyfish Beroë cucumis (Ctenophora) (United States)

    Welch, Victoria; Vigneron, Jean Pol; Lousse, Virginie; Parker, Andrew


    Using transmission electron microscopy, analytical modeling, and detailed numerical simulations, the iridescence observed from the comb rows of the ctenophore Beroë cucumis was investigated. It is shown that the changing coloration which accompanies the beating of comb rows as the animal swims can be explained by the weakly-contrasted structure of the refractive index induced by the very coherent packing of locomotory cilia. The colors arising from the narrow band-gap reflection are shown to be highly saturated and, as a function of the incidence angle, cover a wide range of the visible and ultraviolet spectrum. The high transparency of the structure at the maximal bioluminescence wavelength is also explained.

  1. Transmission comb of a distributed Bragg reflector with two surface dielectric gratings

    KAUST Repository

    Zhao, Xiaobo


    The transmission behaviour of a distributed Bragg reector (DBR) with surface dielectric gratings on top and bottom is studied. The transmission shows a comb-like spectrum in the DBR band gap, which is explained in the Fano picture. The number density of the transmission peaks increases with increasing number of cells of the DBR, while the ratio of the average full width at half maximum to the corresponding average free spectral range, being only few percent for both transversal electric and magnetic waves, is almost invariant. The transmission peaks can be narrower than 0.1 nm and are fully separated from each other in certain wavebands. We further prove that the transmission combs are robust against randomness in the heights of the DBR layers. Therefore, the proposed structure is a candidate for an ultra-narrow-band multichannel filter or polarizer.

  2. Thermosensitive mPEG-b-PA-g-PNIPAM comb block copolymer micelles: effect of hydrophilic chain length and camptothecin release behavior. (United States)

    Yang, Xiao-Li; Luo, Yan-Ling; Xu, Feng; Chen, Ya-Shao


    Block copolymer micelles are extensively used as drug controlled release carriers, showing promising application prospects. The comb or brush copolymers are especially of great interest, whose densely-grafted side chains may be important for tuning the physicochemical properties and conformation in selective solvents, even in vitro drug release. The purpose of this work was to synthesize novel block copolymer combs via atom transfer radical polymerization, to evaluate its physicochemical features in solution, to improve drug release behavior and to enhance the bioavailablity, and to decrease cytotoxicity. The physicochemical properties of the copolymer micelles were examined by modulating the composition and the molecular weights of the building blocks. A dialysis method was used to load hydrophobic camptothecin (CPT), and the CPT release and stability were detected by UV-vis spectroscopy and high-performance liquid chromatography, and the cytotoxicity was evaluated by MTT assays. The copolymers could self-assemble into well-defined spherical core-shell micelle aggregates in aqueous solution, and showed thermo-induced micellization behavior, and the critical micelle concentration was 2.96-27.64 mg L(-1). The micelles were narrow-size-distribution, with hydrodynamic diameters about 128-193 nm, depending on the chain length of methoxy polyethylene glycol (mPEG) blocks and poly(N-isopropylacrylamide) (PNIPAM) graft chains or/and compositional ratios of mPEG to PNIPAM. The copolymer micelles could stably and effectively load CPT but avoid toxicity and side-effects, and exhibited thermo-dependent controlled and targeted drug release behavior. The copolymer micelles were safe, stable and effective, and could potentially be employed as CPT controlled release carriers.

  3. Could Atomic clocks be affected by neutrinos?

    CERN Document Server

    Hanafi, Hanaa


    An atomic clock is a clock device that uses an electronic transition frequency of the electromagnetic spectrum of atoms as a frequency standard in order to derive a time standard since time is the reciprocal of frequency. If the electronic transition frequencies are in an "optical region", we are talking in this case about optical atomic clocks. If they are in an "microwave region" these atomic clocks are made of the metallic element cesium so they are called Cesium atomic clocks. Atomic clocks are the most accurate time and frequency standards known despite the different perturbations that can affect them, a lot of researches were made in this domain to show how the transitions can be different for different type of perturbations..Since atomic clocks are very sensitive devices, based on coherent states (A coherent state tends to loose coherence after interacting). One question can arise (from a lot of questions) which is why cosmic neutrinos are not affecting these clocks? The answer to this question requir...

  4. Atom-by-Atom Construction of a Quantum Device. (United States)

    Petta, Jason R


    Scanning tunneling microscopes (STMs) are conventionally used to probe surfaces with atomic resolution. Recent advances in STM include tunneling from spin-polarized and superconducting tips, time-domain spectroscopy, and the fabrication of atomically precise Si nanoelectronics. In this issue of ACS Nano, Tettamanzi et al. probe a single-atom transistor in silicon, fabricated using the precision of a STM, at microwave frequencies. While previous studies have probed such devices in the MHz regime, Tettamanzi et al. probe a STM-fabricated device at GHz frequencies, which enables excited-state spectroscopy and measurements of the excited-state lifetime. The success of this experiment will enable future work on quantum control, where the wave function must be controlled on a time scale that is much shorter than the decoherence time. We review two major approaches that are being pursued to develop spin-based quantum computers and highlight some recent progress in the atom-by-atom fabrication of donor-based devices in silicon. Recent advances in STM lithography may enable practical bottom-up construction of large-scale quantum devices.

  5. Resonant interaction modified by the atomic environment

    Energy Technology Data Exchange (ETDEWEB)

    Sainz, I; Klimov, A B; Chumakov, S M [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jal. (Mexico)


    The dynamics of a resonant atom interacting with a quantum cavity field in the presence of many off-resonant atoms is studied. In the framework of the effective Hamiltonian approach we show that the results of elimination of non-resonant transitions are (a) a dynamical Stark shift of the field frequency, dependent on the populations of non-resonant atoms, (b) dependence of the coupling constant between the resonant atom and the field on the populations of non-resonant atoms, and (c) an effective dipole-dipole interaction between non-resonant atoms. Two effects (the coherent influence and dephasing) of the off-resonant environment on the dynamics of the resonant atom are discussed.

  6. The oldest vertebrate trace fossils from Comb Ridge (Bears Ears Region, southeastern Utah)


    Gay, Robert J.; Jenkins, Xavier A.; Lepore, Taormina


    Vertebrate trace fossils are common in Upper Triassic deposits across the American southwest. These ichnofauna are dominated by Grallator, Brachychirotherium, and Pseudotetrasauropus, and lack ichnotaxa traditionally considered to be Early Jurassic in age, such as Eubrontes and Anomoepus. While known from Indian Creek and Lisbon Valley, Utah, vertebrate trace fossils have not been previously reported from Comb Ridge, Utah. This is significant considering that lithostratigraphic work has been ...

  7. Update on Breast Cancer Detection Using Comb-push Ultrasound Shear Elastography


    Denis, Max; Bayat, Mahdi; Mehrmohammadi, Mohammad; Gregory, Adriana; Song, Pengfei; Whaley, Dana H; Pruthi, Sandhya; Chen, Shigao; Fatemi, Mostafa; Alizad, Azra


    In this work, tissue stiffness estimates are used to differentiate between benign and malignant breast masses in a group of pre-biopsy patients. The rationale being that breast masses are often stiffer than healthy tissue; furthermore, malignant masses are stiffer than benign masses. The comb-push ultrasound shear elastography (CUSE) method is used to noninvasively assess a tissue’s mechanical properties. CUSE utilizes a simultaneous multiple laterally spaced radiation force (ARF) excitations...

  8. Wintering Reserve Queens in Mini-Plus and 3-Comb Nuclei

    Directory of Open Access Journals (Sweden)

    Siuda Maciej


    Full Text Available The aim of this study was to develop an effective method of overwintering reserve honey bee queens in two-storey mini-plus mating nuclei and in 3-comb nuclei (frames 36 x 26 cm, Wielkopolski hive. The assay was performed during three wintering seasons (2005 - 2008 parallel at two centers in Poland: the Division of Apiculture at the University of Life Sciences (SGGW in Warsaw, and the Apiculture Division at the University of Warmia and Mazury (UWM in Olsztyn. The results showed that 59% of queens overwintered in mini-plus nuclei and 77% in 3-comb nuclei. Among queens in mini-plus nuclei 63% overwintered in bee yard and only 55% in cellar. Within queens in 3-comb nuclei, 62% overwintered in Olsztyn and 91% in Warsaw. The highest survival rate of 93% was observed in Warsaw during the first season. Due to low survival rate, it is not recommended to overwinter the queens in miniplus nuclei.

  9. Validity of the mean-field approximation for diffusion on a random comb (United States)

    Revathi, S.; Balakrishnan, V.; Lakshmibala, S.; Murthy, K. P. N.


    We consider unbiased diffusion on a random comb structure (an infinitely long backbone with loopless branches of arbitrary length emanating from it). If w=T0 is the mean time (averaged over all random walks) for first passage from an arbitrary origin 0 on the backbone to either of the sites +j or -j on it in a given realization of the structure, the exact diffusion constant for the problem is defined as K=limj-->∞j2c, where c stands for the configuration average over the realizations of the random comb. The diffusion constant in the mean-field approximation is given by KMF=limj-->∞j2/c. We compute T0 exactly for an arbitrary realization of the comb and then show rigorously that, owing to the suppression of the relative fluctuations in T0 in the ``thermodynamic limit'' j-->∞, we have KMF=K whenever the moments of certain random variables Γ(L,α,β) are finite; here the site-dependent random variables L, α, and β are, respectively, the branch length, stay probability at the tip of a branch, and the backbone-to-branch jump probability. Finally, we discuss different situations in which K will not be equal to KMF, although the transport remains diffusive, as opposed to those in which anomalous diffusion occurs.

  10. A mummified duck-billed dinosaur with a soft-tissue cock's comb. (United States)

    Bell, Phil R; Fanti, Federico; Currie, Philip J; Arbour, Victoria M


    Among living vertebrates, soft tissues are responsible for labile appendages (combs, wattles, proboscides) that are critical for activities ranging from locomotion to sexual display [1]. However, soft tissues rarely fossilize, and such soft-tissue appendages are unknown for many extinct taxa, including dinosaurs. Here we report a remarkable "mummified" specimen of the hadrosaurid dinosaur Edmontosaurus regalis from the latest Cretaceous Wapiti Formation, Alberta, Canada, that preserves a three-dimensional cranial crest (or "comb") composed entirely of soft tissue. Previously, crest function has centered on the hypertrophied nasal passages of lambeosaurine hadrosaurids, which acted as resonance chambers during vocalization [2-4]. The fleshy comb in Edmontosaurus necessitates an alternative explanation most likely related to either social signaling or sexual selection [5-7]. This discovery provides the first view of bizarre, soft-tissue signaling structures in a dinosaur and provides additional evidence for social behavior. Crest evolution within Hadrosaurinae apparently culminated in the secondary loss of the bony crest at the terminal Cretaceous; however, the new specimen indicates that cranial ornamentation was in fact not lost but substituted in Edmontosaurus by a fleshy display structure. It also implies that visual display played a key role in the evolution of hadrosaurine crests and raises the possibility of similar soft-tissue structures among other dinosaurs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  11. Clustering of comb and propolis waxes based on the distribution of aliphatic constituents

    Directory of Open Access Journals (Sweden)

    Custodio Angela R.


    Full Text Available Chemical composition data for 41 samples of propolis waxes and 9 samples of comb waxes of Apis mellifera collected mainly in Brazil were treated using Principal Component Analysis (PCA and Hierarchical Cluster Analysis (HCA. For chemometrical analysis, the distribution of hydrocarbons and residues of alcohols and carboxylic acids of monoesters were considered. The clustering obtained revealed chemical affinities and differences not previously grasped by simple eye-inspection of the data. No consistent differences were detected between comb and propolis waxes. These and previous results suggest that hydrocarbons, carboxylic acids, aliphatic alcohols and esters from both comb and propolis waxes are bee-produced compounds and, hence, the differences detected between one and another region are dependent on genetic factors related to the insects rather than the local flora. The samples analyzed were split into two main clusters, one of them comprising exclusively material collected in the State of São Paulo. The results are discussed with respect to the africanization of honeybees that first took place in that State and therefrom irradiated to other parts of Brazil.

  12. Long term stability of atomic time scales (United States)

    Petit, Gérard; Arias, Elisa Felicitas


    International Atomic Time TAI gets its stability from some 400 atomic clocks worldwide that generate the free atomic scale EA L and its accuracy from a small number of primary frequency standards (PFS) which frequency measurements are used to steer the EAL frequency. Because TAI is computed in "real - time" (every month) and has operational constraints, it is not optimal and the BIPM computes in deferred time another time scale TT(BIPM), which is based on a weighted average of the evaluations of TAI frequency by the PFS. We show that a point has been reached where the stability of atomic time scales, the accuracy of primary frequency standards, and the capabilities of frequency transfer are approximately at a similar level, in the low 10 - 16 in relative frequency. The goal is now to reach and surpass 1x10 - 16 and the three fields are in various stages of advancement towards this aim. We review the stability and accuracy recently achieved by frequency standards, focusing on primary frequency standards on one hand, and on new secondary realizations e.g. based on optical transitions on the other hand. We study how these performances can translate to the performance of atomic time scales, and the possible implications of the availability of new high - accuracy frequency standards operating on a regular basis. Finally we show how time transfer is trying to keep up with the progresses of frequency standards. Time transfer is presently the limiting factor at short averaging time (e.g. 1 - 2 weeks) but it should not be limiting the long term stability of atomic time scales, which is the main need of many applications in astronomy.

  13. Atom-atom interactions around the band edge of a photonic crystal waveguide. (United States)

    Hood, Jonathan D; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E; Kimble, H J


    Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields [Formula: see text] outside the bandgap to localized fields [Formula: see text] within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the [Formula: see text] line of atomic cesium for [Formula: see text] atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.

  14. "Bohr's Atomic Model." (United States)

    Willden, Jeff


    "Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

  15. Laser Technology in Commercial Atomic Clocks (United States)

    Lutwak, R.


    Commercial atomic frequency standards (AFS) are deployed in diverse civilian, military, and aerospace applications, ranging from high-precision measurement and calibration to navigation, communications and, of course, timekeeping. Currently, commercially available AFS include magnetically-selected cesium beam frequency standards and hydrogen masers and lamp-pumped rubidium oscillators. Despite the revolution in atomic physics and laboratory-scale AFS brought about by the advent of the tunable laser in the early 1970s, commercial AFS invariably rely on more conventional atomic physics technology developed in the 1950s. The reason for this lack of advancement of commercial AFS technology is the relatively poor reliability and environmental sensitivity of narrow-linewidth single-mode laser sources at atomic resonance wavelengths. Over the past 8 years, Symmetricom, in collaboration with laser manufacturers, has developed specialized laser sources for commercial AFS applications. These laser devices, optimized for high spectral purity and long-term reliability, will enable a new generation of commercial AFS. This talk will briefly describe two laser-based atomic frequency standard development programs at Symmetricom. The Chip-Scale Atomic Clock, two orders of magnitude smaller and lower power than any commercial AFS, will enable atomic timing accuracy in portable battery-powered applications. The Optically-Pumped Cesium Beam Frequency Standard, under development for deployment onboard the GPS-III satellite constellation, will provide enhanced short-term stability and longer lifetime compared to magnetically-selected cesium beam AFS.

  16. Teach us atom structure

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Suh Yeon


    This book is written to teach atom structure in very easy way. It is divided into nine chapters, which indicates what is the components of matter? when we divide matter continuously, it becomes atom, what did atom look like? particles comprised of matter is not only atom, discover of particles comprised of atom, symbol of element, various radiation, form alchemy to nuclear transmutation, shape of atom is evolving. It also has various pictures in each chapters to explain easily.

  17. Playing pinball with atoms. (United States)

    Saedi, Amirmehdi; van Houselt, Arie; van Gastel, Raoul; Poelsema, Bene; Zandvliet, Harold J W


    We demonstrate the feasibility of controlling an atomic scale mechanical device by an external electrical signal. On a germanium substrate, a switching motion of pairs of atoms is induced by electrons that are directly injected into the atoms with a scanning tunneling microscope tip. By precisely controlling the tip current and distance we make two atom pairs behave like the flippers of an atomic-sized pinball machine. This atomic scale mechanical device exhibits six different configurations.

  18. Microfabricated ion frequency standard (United States)

    Schwindt, Peter; Biedermann, Grant; Blain, Matthew G.; Stick, Daniel L.; Serkland, Darwin K.; Olsson, III, Roy H.


    A microfabricated ion frequency standard (i.e. an ion clock) is disclosed with a permanently-sealed vacuum package containing a source of ytterbium (Yb) ions and an octupole ion trap. The source of Yb ions is a micro-hotplate which generates Yb atoms which are then ionized by a ultraviolet light-emitting diode or a field-emission electron source. The octupole ion trap, which confines the Yb ions, is formed from suspended electrodes on a number of stacked-up substrates. A microwave source excites a ground-state transition frequency of the Yb ions, with a frequency-doubled vertical-external-cavity laser (VECSEL) then exciting the Yb ions up to an excited state to produce fluorescent light which is used to tune the microwave source to the ground-state transition frequency, with the microwave source providing a precise frequency output for the ion clock.

  19. A spread spectrum system with frequency hopping and sequentially balanced modulation. II - Operation in jamming and multipath (United States)

    Mathis, R. F.; Pawula, R. F.


    The performance of a spread spectrum system which incorporates frequency hopping, sequentially balanced modulation, phase-comparison tone ranging, and pseudoorthogonal block coding of BPSK data with maximum likelihood of soft decision decoding, is evaluated in jamming environments and multipath. The jamming models considered include partial-band noise jamming, comb-type partial-band noise jamming, multitone jamming, and comb-type multitone jamming. Specular multipath with broad-band noise are shown to be the most serious form of interference. Bit-error probability and ranging accuracy curves are presented.

  20. Tapered amplifier laser with frequency-shifted feedback

    Directory of Open Access Journals (Sweden)

    A. Bayerle, S. Tzanova, P. Vlaar, B. Pasquiou, F. Schreck


    Full Text Available We present a frequency-shifted feedback (FSF laser based on a tapered amplifier. The laser operates as a coherent broadband source with up to 370GHz spectral width and 2.3us coherence time. If the FSF laser is seeded by a continuous-wave laser a frequency comb spanning the output spectrum appears in addition to the broadband emission. The laser has an output power of 280mW and a center wavelength of 780nm. The ease and flexibility of use of tapered amplifiers makes our FSF laser attractive for a wide range of applications, especially in metrology.

  1. Tuning of successively scanned two monolithic Vernier-tuned lasers and selective data sampling in optical comb swept source optical coherence tomography. (United States)

    Choi, Dong-Hak; Yoshimura, Reiko; Ohbayashi, Kohji


    Monolithic Vernier tuned super-structure grating distributed Bragg reflector (SSG-DBR) lasers are expected to become one of the most promising sources for swept source optical coherence tomography (SS-OCT) with a long coherence length, reduced sensitivity roll-off, and potential capability for a very fast A-scan rate. However, previous implementations of the lasers suffer from four main problems: 1) frequencies deviate from the targeted values when scanned, 2) large amounts of noise appear associated with abrupt changes in injection currents, 3) optically aliased noise appears due to a long coherence length, and 4) the narrow wavelength coverage of a single chip limits resolution. We have developed a method of dynamical frequency tuning, a method of selective data sampling to eliminate current switching noise, an interferometer to reduce aliased noise, and an excess-noise-free connection of two serially scanned lasers to enhance resolution to solve these problems. An optical frequency comb SS-OCT system was achieved with a sensitivity of 124 dB and a dynamic range of 55-72 dB that depended on the depth at an A-scan rate of 3.1 kHz with a resolution of 15 μm by discretely scanning two SSG-DBR lasers, i.e., L-band (1.560-1.599 μm) and UL-band (1.598-1.640 μm). A few OCT images with excellent image penetration depth were obtained.

  2. Stochastic models for atomic clocks (United States)

    Barnes, J. A.; Jones, R. H.; Tryon, P. V.; Allan, D. W.


    For the atomic clocks used in the National Bureau of Standards Time Scales, an adequate model is the superposition of white FM, random walk FM, and linear frequency drift for times longer than about one minute. The model was tested on several clocks using maximum likelihood techniques for parameter estimation and the residuals were acceptably random. Conventional diagnostics indicate that additional model elements contribute no significant improvement to the model even at the expense of the added model complexity.

  3. Dispersing multi-component and unstable powders in aqueous media using comb-type anionic polymers

    DEFF Research Database (Denmark)

    Laarz, E.; Kauppi, A.; Andersson, K.M.


    We have investigated the effect of polymeric dispersants on the rheological properties and consolidation behavior of concentrated cemented carbide (WC-Co) and magnesia (MgO) suspensions. The relatively novel types of comb-type anionic polymers with grafted non-ionic side chains are effective...... of the grafted ethylene oxide side chains showed that the dispersants adsorb onto a MgO surface and infer a repulsion where the range scales with the length of the poly ethylene oxide side chains. The compressibility and the consolidation behavior of MgO particle networks in response to a centrifugal force field...

  4. Dual-comb spectroscopy for rapid characterization of complex optical properties of solids. (United States)

    Asahara, Akifumi; Nishiyama, Akiko; Yoshida, Satoru; Kondo, Ken-Ichi; Nakajima, Yoshiaki; Minoshima, Kaoru


    We demonstrate rapid characterization of complex optical properties of solids via dual-comb spectroscopy (DCS) in the near-infrared region. The fine spectral structures in the complex refractive index of an Er:YAG are successfully deduced using the developed system and Fourier analysis. Moreover, simultaneous determination of the refractive index and the thickness is demonstrated for a silicon semiconductor wafer through the use of multireflected echo signals. The results indicate the potential of DCS as a powerful measurement tool for the rapid and full characterization of solid materials.

  5. Pesticides for apicultural and/or agricultural application found in Belgian honey bee wax combs


    Ravoet, Jorgen; Reybroeck, Wim; de Graaf, Dirk


    In a Belgian pilot study honey bee wax combs from ten hives were analyzed on the presence of almost 300 organochlorine and organophosphorous compounds by LC?MS/MS and GC?MS/MS. Traces of 18 pesticides were found and not a single sample was free of residues. The number of residues found per sample ranged from 3 to 13, and the pesticides found could be categorized as (1) pesticides for solely apicultural (veterinary) application, (2) pesticides for solely agricultural (crop protection) applicat...

  6. An astro-comb calibrated solar telescope to search for the radial velocity signature of Venus (United States)

    Phillips, David F.; Glenday, Alex G.; Dumusque, Xavier; Buchschacher, Nicolas; Cameron, Andrew Collier; Cecconi, Massimo; Charbonneau, David; Cosentino, Rosario; Ghedina, Adriano; Haywood, Raphäelle; Latham, David W.; Li, Chih-Hao; Lodi, Marcello; Lovis, Christophe; Molinari, Emilio; Pepe, Francesco; Sasselov, Dimitar; Szentgyorgyi, Andrew; Udry, Stephane; Walsworth, Ronald L.


    We recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope, which is calibrated with a green astro-comb. We are using the solar telescope to characterize the effects of stellar (solar) RV jitter due to activity on the solar surface with the goal of detecting the solar RV signal from Venus, thereby demonstrating the sensitivity of these instruments to detect true Earth-twin exoplanets.

  7. Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules

    Directory of Open Access Journals (Sweden)

    Rose Franck


    Full Text Available AbstractMicrotubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed.

  8. Laser Graphic Video Display using Silicon Scanning Mirrors with Vertical Comb Fingers (United States)

    Lee, Jin-Ho; Ko, Young-Chul; Mun, Yong-Kweun; Choi, Byoung-So; Kim, Jong-Min; Jeon, Duk Young


    We acquired a two-dimensional (2D) laser vector graphic video image using 1500 μm× 1200 μm silicon scanning mirrors with vertical comb fingers. Vector image signals from the graphic board were applied to two scanning mirrors, and a SHG green laser was directly modulated to shape independent graphic images. These scanning mirrors were originally designed for laser raster video display as a galvanometric vertical scanner, and are controlled perfectly by the ramp waveform of 60 Hz with the duty cycle of 90%.

  9. Graphene oxide scrolls on hydrophobic substrates fabricated by molecular combing and their application in gas sensing. (United States)

    Li, Hai; Wu, Jumiati; Qi, Xiaoying; He, Qiyuan; Liusman, Cipto; Lu, Gang; Zhou, Xiaozhu; Zhang, Hua


    Well-aligned graphene oxide (GO) scrolls are prepared through the controlled folding/scrolling of single-layer GO sheets using molecular combing on hydrophobic substrates, such as aged gold substrate, polydimethylsiloxane film, poly(L-lactic acid) film, and octadecyltrimethoxysilane-modified silicon dioxide. As a proof of concept, the gas sensor fabricated with a single reduced GO scroll is used to detect NO(2) gas with a concentration as low as 0.4 ppm. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Control the fear atomic

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Gwan [I and Book, Seoul (Korea, Republic of)


    This book has a lot of explanation of nuclear energy with articles. Their titles are the bad man likes atomic, the secret of atom, nuclear explosion, NPT?, the secret of uranium fuel rod, nuclear power plant vs nuclear bomb, I hate atomic, keep plutonium in control, atomic in peace and find out alternative energy.

  11. Discussion Problems Related to the Study of Pit-Comb Ware Sites in the Middle Volga Region

    Directory of Open Access Journals (Sweden)

    Stavitsky Vladimir V.


    Full Text Available A number of issues concerning the origin and chronology of the Neolithic Pit-Сomb Ware culture monuments, as well as their correlation with those referring to other cultures are tackled in the article. The spread of pit-combed pottery bearers as a result of their eastward migration from the territory of the Volga-Oka river interfluve seems most likely. Still, the problem of correspondence between radiocarbon dating and stratigraphy data from the Neolithic sites located in the Volga region has not lost actuality. The results of radiocarbon dating show that in the middle reaches of the Sura river pit-comb ware cultures had preceded the combed pottery sites, which requires a revision of the issues of their synchronization based on typological data. In the forest-steppe zone, the sequence of ceramic traditions development could probably differ from that prevalent in the territories located further north

  12. EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2013 . Scientific Opinion on Rooster Combs Extract

    DEFF Research Database (Denmark)

    Tetens, Inge; Poulsen, Morten

    and objections of a scientific nature raised by Member States. Rooster combs extract results from a production process involving enzymatic hydrolysis of rooster combs and subsequent filtration, concentration and precipitation steps. The principle constituents of RCE are the glycosaminoglycans hyaluronic acid......Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to carry out the additional assessment for „Rooster Combs Extract‟ (RCE) as a food ingredient in the context of Regulation (EC) No 258/97, taking into account the comments......, chondroitin sulphate A and dermatan sulphate. The applicant intends to add RCE to a number of dairy products with a recommended maximum intake of 80 mg RCE per portion and per day. The target population is the general population, with the exception of pregnant women, children and people with adverse reactions...

  13. Asymmetrical two-atom entanglement in a coated microsphere

    Energy Technology Data Exchange (ETDEWEB)

    Burlak, G.N. [Center for Research on Engineering and Applied Sciences, Autonomous State University of Morelos, Cuernavaca, Mor. 62210 (Mexico)]. E-mail:; Klimov, A.B. [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, Guadalajara, Jalisco, 44420 (Mexico)]. E-mail:


    We study evolution of entanglement of two two-level atoms placed inside a multilayered microsphere. We show that due to inhomogeneity of the optical field modes this entanglement essentially depends on the atomic positions (asymmetrical entanglement) and also on the detuning between the atomic transitions and field frequencies. The robust and complete entanglement can be achieved even in the resonant case when the atoms have different effective coupling constants, and it can be extended in time if the detuning is large enough.

  14. Generation of three-octave-spanning transient Raman comb in hydrogen-filled hollow-core PCF. (United States)

    Tani, F; Belli, F; Abdolvand, A; Travers, J C; Russell, P St J


    A noise-seeded transient comb of Raman sidebands spanning three octaves from 180 to 2400 nm, is generated by pumping a hydrogen-filled hollow-core photonic crystal fiber with 26-μJ, 300-fs pulses at 800 nm. The pump pulses are spectrally broadened by both Kerr and Raman-related self-phase modulation (SPM), and the broadening is then transferred to the Raman lines. In spite of the high intensity, and in contrast to bulk gas-cell based experiments, neither SPM broadening nor ionization are detrimental to comb formation.

  15. Optical lattice clock with strontium atoms; Horloge a reseau optique a atomes de strontium

    Energy Technology Data Exchange (ETDEWEB)

    Baillard, X.; Le Targat, R.; Fouche, M.; Brusch, A.; Westergaard, Ph.G.; Lecallier, A.; Lodewyck, J.; Lemonde, P. [Observatoire de Paris, LNE-SYRTE, Systemes de Reference Temps Espace, 75 (France)


    Optical lattice clocks, which were first imagined in 2000, should allow one to achieve unprecedented performances in the domain of atomic clocks. We present here the Strontium lattice clock, developed at LNE-SYRTE. The principle, in particular trapping atoms in the Lamb-Dicke regime and the notion of magic wavelength, is first explained. We then present the results obtained for the {sup 87}Sr isotope, with a frequency accuracy of 2,6.10{sup -15}, and the {sup 88}Sr isotope, with. which we perform the first frequency measurement of an optical lattice clock with bosonic atoms. (authors)

  16. Micro Ion Frequency Standard (United States)


    Figure 6. (a) Fabricated VCSEL . (b) Emission spectrum of VCSEL at 1 mA drive current . As expected, our initial VCSEL wafers produced much less...light source at 369 nm. (a) (b) Figure 7. (a) 740-nm VCSEL output power and voltage versus current . (b) Periodically poled KTP crystal with...micro ion frequency standard and relevant current results. INTRODUCTION Vapor cell atomic clocks have seen extreme miniaturization within the past

  17. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    KAUST Repository

    Elshurafa, Amro M.


    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression for the electrostatic force generated between the combs of the rotor and the stator is derived and takes into account both the transverse and longitudinal capacitances present. After formulating the problem, the resulting stiff differential equations are solved analytically using the method of multiple scales, and a closed-form solution is obtained. Furthermore, the nonlinear boundary value problem that describes the dynamics of inextensional spring beams is solved using straightforward perturbation to obtain the linear and nonlinear spring constants of the beam. The analytical solution is verified numerically using a Matlab/Simulink environment, and the results from both analyses exhibit excellent agreement. Stability analysis based on phase plane trajectory is also presented and fully explains previously reported empirical results that lacked sufficient theoretical description. Finally, the proposed solutions are, once again, verified with previously published measurement results. The closed-form solutions provided are easy to apply and enable predicting the actual behavior of resonators and gyroscopes with similar structures. © 2011 IEEE.

  18. Modeling high signal-to-noise ratio in a novel silicon MEMS microphone with comb readout (United States)

    Manz, Johannes; Dehe, Alfons; Schrag, Gabriele


    Strong competition within the consumer market urges the companies to constantly improve the quality of their devices. For silicon microphones excellent sound quality is the key feature in this respect which means that improving the signal-to-noise ratio (SNR), being strongly correlated with the sound quality is a major task to fulfill the growing demands of the market. MEMS microphones with conventional capacitive readout suffer from noise caused by viscous damping losses arising from perforations in the backplate [1]. Therefore, we conceived a novel microphone design based on capacitive read-out via comb structures, which is supposed to show a reduction in fluidic damping compared to conventional MEMS microphones. In order to evaluate the potential of the proposed design, we developed a fully energy-coupled, modular system-level model taking into account the mechanical motion, the slide film damping between the comb fingers, the acoustic impact of the package and the capacitive read-out. All submodels are physically based scaling with all relevant design parameters. We carried out noise analyses and due to the modular and physics-based character of the model, were able to discriminate the noise contributions of different parts of the microphone. This enables us to identify design variants of this concept which exhibit a SNR of up to 73 dB (A). This is superior to conventional and at least comparable to high-performance variants of the current state-of-the art MEMS microphones [2].

  19. Multiresidue method for trace pesticide analysis in honeybee wax comb by GC-QqQ-MS. (United States)

    García, M D Gil; Duque, S Uclés; Fernández, A B Lozano; Sosa, A; Fernández-Alba, A R


    The aim of this analytical study is to develop an improved multi-residue methodology of high sensitivity and expanded scope for pesticide residue analysis in honeybee wax combs. The method was validated for 160 pesticide residues (including acaricides, insecticides, fungicides and herbicides) gas chromatography amenable and covering a wide variety of polarity and chemical structure. This method of analysis applied gas chromatography coupled to a triple quadrupole mass spectrometer for the quantitative analysis of pesticide residues. The extraction procedure applied was based QuEChERs method allowing acceptable recoveries for most of the pesticides (98%), within the range 60-120% with an associated precision (RSD) wax comb samples randomly collected from different apiaries in Spain. A total of 32 pesticide residues (14 insecticides/acaricides, 10 insecticides, 6 fungicides and 2 herbicides) were detected in the samples. The highest pesticide concentrations were found for those with insecticide-acaricide activity like acrinathrin, chlorfenvinphos, coumaphos and fluvalinate-tau, some of them are mainly applied in apiculture for controlling the honeybee parasite Varroa destructor. The total load of pesticide residues ranged from 69 to 1000µgkg(-1) for 40% of the analysed samples, 22% contained pesticide residues in the ranges of 1000-2000µgkg(-1), 24% between 2000 and 5000µgkg(-1) and 14% of the samples contained residues between 5000 and 9557µgkg(-1). Copyright © 2016 Elsevier B.V. All rights reserved.

  20. A keystone-like grain in hornet comb cells: its nature and physical properties. (United States)

    Ishay, Jacob S; Riabinin, Ksenia; Kozhevnikov, Maria; van der Want, Hans; Stokroos, Ietse


    In the roof of cells built by the Oriental hornet, Vespa orientalis (Vespinae, Hymenoptera), there is one or more grains differing in their composition and shape from the surrounding structures. These grains have a diameter of 100-200 microm and protrude slightly from the roof inward. They contain primarily a large percentage of Ti but also Fe and occasionally Si. The mineral makeup in the grains is still uncertain, but it seems that the minerals belong to the group called perovskite. These grains in the hornet's comb may originate from the soil around the nest, that is, comprised of ceramic matter, but it is also possible that they are secreted from a gland within the frons plate of the hornet because the fungus-like secretion in this gland contains elements similar to those in the roof of the comb cells. We conjecture that the grain in question serves as a reference point for the hornets that build the cell walls in the direction of gravity. The cement whereby the building hornets conjoin the various building materials, whether organic (cellulose and the like) or inorganic (sand grains or tiny stones), is a saliva that is secreted from their oral gland, which upon release hardens into a polymeric glue. The ceramic grain embedded within this polymeric matrix is endowed with different physical properties and can therefore respond differently to the tension or pressure of the surrounding walls.

  1. Finite Element Analysis of the Vertical Levitation Force in an Electrostatic MEMS Comb Drive Actuator (United States)

    Wooldridge, J.; Blackburn, J.; Muniz-Piniella, A.; Stewart, M.; Shean, T. A. V.; Weaver, P. M.; Cain, M. G.


    A vertical levitation electrostatic comb drive actuator was manufactured for the purpose of measuring piezoelectric coefficients in small-scale materials and devices. Previous modelling work on comb drive levitation has focussed on control of the levitation in standard poly-silicon devices in order to minimize effects on lateral modes of operation required for the accelerometer and gyroscope applications. The actuator developed in this study was manufactured using a 20 μm electroplated Ni process with a 25 μm trench created beneath the released structure through chemical wet etching. A finite element analysis using ZINC was used to model electrostatic potential around a cross section of one static and one movable electrode, from which the net levitation force per unit electrode was calculated. The model was first verified using the electrode geometry from previously studied systems, and then used to study the variation of force as a function of decreasing substrate-electrode distance. With the top electrode surfaces collinear the calculated force density is 0.00651 epsilon0V2Mμm-1, equivalent to a total force for the device of 36.4 μN at an applied voltage of VM=100 V, just 16% larger than the observed value. The measured increase in force with distance was smaller than predicted with the FEA, due to the geometry of the device in which the electrodes at the anchored ends of the supporting spring structure displace by a smaller amount than those at the centre.

  2. On the partition dimension of comb product of path and complete graph (United States)

    Darmaji, Alfarisi, Ridho


    For a vertex v of a connected graph G(V, E) with vertex set V(G), edge set E(G) and S ⊆ V(G). Given an ordered partition Π = {S1, S2, S3, …, Sk} of the vertex set V of G, the representation of a vertex v ∈ V with respect to Π is the vector r(v|Π) = (d(v, S1), d(v, S2), …, d(v, Sk)), where d(v, Sk) represents the distance between the vertex v and the set Sk and d(v, Sk) = min{d(v, x)|x ∈ Sk}. A partition Π of V(G) is a resolving partition if different vertices of G have distinct representations, i.e., for every pair of vertices u, v ∈ V(G), r(u|Π) ≠ r(v|Π). The minimum k of Π resolving partition is a partition dimension of G, denoted by pd(G). Finding the partition dimension of G is classified to be a NP-Hard problem. In this paper, we will show that the partition dimension of comb product of path and complete graph. The results show that comb product of complete grapph Km and path Pn namely p d (Km⊳Pn)=m where m ≥ 3 and n ≥ 2 and p d (Pn⊳Km)=m where m ≥ 3, n ≥ 2 and m ≥ n.

  3. Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb. (United States)

    de Oliveira, Sabrina Alves; da Silva, Bruno Campos; Riegel-Vidotti, Izabel Cristina; Urbano, Alexandre; de Sousa Faria-Tischer, Paula Cristina; Tischer, Cesar Augusto


    The bacterial cellulose (BC), from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid (HA) is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration. In this study, polymeric composites were produced in presence of hyaluronic acid isolated from chicken comb on different days of fermentation, specifically on the first (BCHA-SABT0) and third day (BCHA-SABT3) of fermentation. The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The results demonstrate that the polymeric composites (BC/HA-SAB) can be produced in situ. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Comb jellies (ctenophora): a model for Basal metazoan evolution and development. (United States)

    Pang, Kevin; Martindale, Mark Q


    INTRODUCTIONCtenophores, or comb jellies, are a group of marine organisms whose unique biological features and phylogenetic placement make them a key taxon for understanding animal evolution. These gelatinous creatures are clearly distinct from cnidarian medusae (i.e., jellyfish). Key features present in the ctenophore body plan include biradial symmetry, an oral-aboral axis delimited by a mouth and an apical sensory organ, two tentacles, eight comb rows composed of interconnected cilia, and thick mesoglea. Other morphological features include definitive muscle cells, a nerve net, basal lamina, a sperm acrosome, and light-producing photocytes. Aspects of their development made them attractive to experimental embryologists as early as the 19th century. Recently, because of their role as an invasive species, studies on their role in ecology and fisheries-related fields have increased. Although the phylogenetic placement of ctenophores with respect to other animals has proven difficult, it is clear that, along with poriferans, placozoans, and cnidarians, ctenophores are one of the earliest diverging extant animal groups. It is important to determine if some of the complex features of ctenophores are examples of convergence or if they were lost in other animal branches. Because ctenophores are amenable to modern technical approaches, they could prove to be a highly useful emerging model.

  5. Genomic data do not support comb jellies as the sister group to all other animals. (United States)

    Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert


    Understanding how complex traits, such as epithelia, nervous systems, muscles, or guts, originated depends on a well-supported hypothesis about the phylogenetic relationships among major animal lineages. Traditionally, sponges (Porifera) have been interpreted as the sister group to the remaining animals, a hypothesis consistent with the conventional view that the last common animal ancestor was relatively simple and more complex body plans arose later in evolution. However, this premise has recently been challenged by analyses of the genomes of comb jellies (Ctenophora), which, instead, found ctenophores as the sister group to the remaining animals (the "Ctenophora-sister" hypothesis). Because ctenophores are morphologically complex predators with true epithelia, nervous systems, muscles, and guts, this scenario implies these traits were either present in the last common ancestor of all animals and were lost secondarily in sponges and placozoans (Trichoplax) or, alternatively, evolved convergently in comb jellies. Here, we analyze representative datasets from recent studies supporting Ctenophora-sister, including genome-scale alignments of concatenated protein sequences, as well as a genomic gene content dataset. We found no support for Ctenophora-sister and conclude it is an artifact resulting from inadequate methodology, especially the use of simplistic evolutionary models and inappropriate choice of species to root the metazoan tree. Our results reinforce a traditional scenario for the evolution of complexity in animals, and indicate that inferences about the evolution of Metazoa based on the Ctenophora-sister hypothesis are not supported by the currently available data.

  6. PH- and salt-dependent molecular combing of DNA: experiments and phenomenological model

    Energy Technology Data Exchange (ETDEWEB)

    Benke, Annegret; Pompe, Wolfgang [Institut fuer Werkstoffwissenschaft and Max-Bergmann-Zentrum fuer Biomaterialien, Technische Universitaet Dresden, D-01062 Dresden (Germany); Mertig, Michael, E-mail: [Physikalische Chemie, Technische Universitaet Dresden, D-01062 Dresden (Germany)


    {lambda}-DNA as well as plasmids can be successfully deposited by molecular combing on hydrophobic surfaces, for pH values ranging from 4 to 10. On polydimethylsiloxane (PDMS) substrates, the deposited DNA molecules are overstretched by about 60-100%. There is a significant influence of sodium ions (NaCl) on the surface density of the deposited DNA, with a maximum near to 100 mM NaCl for a DNA solution (28 ng {mu}l{sup -1}) at pH 8. The combing process can be described by a micromechanical model including: (i) the adsorption of free moving coiled DNA at the substrate; (ii) the stretching of the coiled DNA by the preceding meniscus; (iii) the relaxation of the deposited DNA to the final length. The sticky ends of {lambda}-DNA cause an adhesion force in the range of about 400 pN which allows a stable overstretching of the DNA by the preceding meniscus. The exposing of hidden hydrophobic bonds of the overstretched DNA leads to a stable deposition on the hydrophobic substrate. The pH-dependent density of deposited DNA as well as the observed influence of sodium ions can be explained by their screening of the negatively charged DNA backbone and sticky ends, respectively. The final DNA length can be derived from a balance of the stored elastic energy of the overstretched molecules and the energy of adhesion.

  7. Characterization of non-Lorentzian line shapes in atom-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Dehesa, J.S. (Granada Univ. (Spain). Dept. de Fisica Nuclear; Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Kernphysik)

    Two different characterizations of the spectral line shape in the core region of resonance lines of atoms perturbed by other atoms in terms of 1) its moments about the origin and 2) its frequency moments are given. Simple expressions relating the line width and the asymmetry parameter of these collision-broadened lines with two of these moments are obtained. These expressions might lead to a new experimental determination of the average time of duration of atom-atom collisions since the involved moments are measurable.

  8. Microfabricated Waveguide Atom Traps.

    Energy Technology Data Exchange (ETDEWEB)

    Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading cold atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.

  9. Atomic and molecular manipulation

    CERN Document Server

    Mayne, Andrew J


    Work with individual atoms and molecules aims to demonstrate that miniaturized electronic, optical, magnetic, and mechanical devices can operate ultimately even at the level of a single atom or molecule. As such, atomic and molecular manipulation has played an emblematic role in the development of the field of nanoscience. New methods based on the use of the scanning tunnelling microscope (STM) have been developed to characterize and manipulate all the degrees of freedom of individual atoms and molecules with an unprecedented precision. In the meantime, new concepts have emerged to design molecules and substrates having specific optical, mechanical and electronic functions, thus opening the way to the fabrication of real nano-machines. Manipulation of individual atoms and molecules has also opened up completely new areas of research and knowledge, raising fundamental questions of "Optics at the atomic scale", "Mechanics at the atomic scale", Electronics at the atomic scale", "Quantum physics at the atomic sca...

  10. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J


    This fifth volume of the successful series Advances in Atomic Spectroscopy continues to discuss and investigate the area of atomic spectroscopy.It begins with a description of the use of various atomic spectroscopic methods and applications of speciation studies in atomic spectroscopy. The emphasis is on combining atomic spectroscopy with gas and liquid chromatography. In chapter two the authors describe new developments in tunable lasers and the impact they will have on atomic spectroscopy. The traditional methods of detection, such as photography and the photomultiplier, and how they are being replaced by new detectors is discussed in chapter three. The very active area of glow discharge atomic spectrometry is presented in chapter four where, after a brief introduction and historical review, the use of glow discharge lamps for atomic spectroscopy and mass spectrometry are discussed. Included in this discussion is geometry and radiofrequency power. The future of this source in atomic spectroscopy is also dis...

  11. High-speed cinematography of gas-metal atomization

    Energy Technology Data Exchange (ETDEWEB)

    Ting, Jason [ALCOA Specialty Metals Division, 100 Technical Drive, Alcoa Center, PA 15069 (United States)]. E-mail:; Connor, Jeffery [Material Science Engineering Department, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Ridder, Stephen [Metallurgical Processing Group, NIST, 100 Bureau Dr. Stop 8556, Gaithersburg, MD 20899 (United States)


    A high-speed cinematographic footage of a 304L stainless steel gas atomization, recorded at the National Institute of Standard and Technology (NIST), was analyzed using a discrete Fourier transform (DFT) algorithm. The analysis showed the gas atomization process possesses two prominent frequency ranges of melt oscillation (pulsation). A low-frequency oscillation in the melt flow occurring between 5.41 and 123 Hz, with a dominant frequency at 9.93 Hz, was seen in the recirculation zone adjacent to the melt orifice. A high-frequency melt oscillation range was observed above 123 Hz, and was more prominent one melt-tip-diameter downstream in the melt atomization image than upstream near the melt tip. This high-frequency range may reflect the melt atomization frequency used to produce finely atomized powder. This range also included a prominent high frequency at 1273 Hz, which dominated in the image further away downstream from the melt tip. This discrete high-frequency oscillation is most probably caused by the aeroacoustic ''screech'' phenomenon, intrasound (<20 kHz), a result of the atomizing gas jets undergoing flow resonance. It is hypothesized that this discrete intrinsic aeroacoustic tone may enhance melt breakup in the atomization process with evidence of this fact in the melt images.

  12. A compact and robust diode laser system for atom interferometry on a sounding rocket

    CERN Document Server

    Schkolnik, V; Wenzlawski, A; Grosse, J; Kohfeldt, A; Döringshoff, K; Wicht, A; Windpassinger, P; Sengstock, K; Braxmaier, C; Krutzik, M; Peters, A


    We present a diode laser system optimized for laser cooling and atom interferometry with ultra-cold rubidium atoms aboard sounding rockets as an important milestone towards space-borne quantum sensors. Design, assembly and qualification of the system, combing micro-integrated distributed feedback (DFB) diode laser modules and free space optical bench technology is presented in the context of the MAIUS (Matter-wave Interferometry in Microgravity) mission. This laser system, with a volume of 21 liters and total mass of 27 kg, passed all qualification tests for operation on sounding rockets and is currently used in the integrated MAIUS flight system producing Bose-Einstein condensates and performing atom interferometry based on Bragg diffraction. The MAIUS payload is being prepared for launch in fall 2016. We further report on a reference laser system, comprising a rubidium stabilized DFB laser, which was operated successfully on the TEXUS 51 mission in April 2015. The system demonstrated a high level of technol...

  13. Novel Concept of Frequency-Combs Interferometric Spectroscopy in the Mid-IR for Significantly Enhanced Detection of Explosives (United States)


    continuous-wave photonic THz source tunable from 1 to 4.5 THz for nonlinear molecular spectroscopy " International Symposium on Photoelectronic... spectroscopy in the mid-ir for significantly enhanced detection of explosives" . For technical questions, please contact Dr. Vodopyanov at vodopyanov... spectroscopy in the mid- IR for significantly enhanced detection of explosives Sb. GRANT NUMBER N0001 4-14-1 -0447 Sc. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Sd

  14. Optical atomic phase reference and timing (United States)

    Hollberg, L.; Cornell, E. H.; Abdelrahmann, A.


    Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space-time science. Those systems require strain measurements at less than or equal to 10-20. As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, ΔΦ/Φtotal ≤ 10-20, that could make an important impact in gravity wave science. This article is part of the themed issue 'Quantum technology for the 21st century'.

  15. Study on the fine control of atoms by coherent interaction

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jae Min; Rho, S. P.; Park, H. M.; Lee, K. S.; Rhee, Y. J.; Yi, J. H.; Jeong, D. Y.; Jung, E. C.; Choe, A. S.; Lee, J. M


    The basic research on the control of atoms using the coherent interaction, such as the development of the generator of the thermal atomic beam with high directionality, the photodeflection of atomic beam and the coherent excitation of atoms, has been performed. Yb atomic beam with small divergence was generated and the deflection mechanism of the atomic beam was studied by using a broad band dye laser and a narrow band laser. It has been proved that the single mode dye laser with narrow bandwidth was suitable for deflection of atoms but the frequency locking system was indispensable. And the apparatus for intermodulated optogalvanic (IMOG) experiment was developed and the high resolution optogalvanic spectroscopy was studied for laser frequency stabilization. (author). 74 refs., 1 tab., 26 figs

  16. Atomic clock ensemble in space (United States)

    Cacciapuoti, L.; Salomon, C.


    Atomic Clock Ensemble in Space (ACES) is a mission using high-performance clocks and links to test fundamental laws of physics in space. Operated in the microgravity environment of the International Space Station, the ACES clocks, PHARAO and SHM, will generate a frequency reference reaching instability and inaccuracy at the 1 · 10-16 level. A link in the microwave domain (MWL) and an optical link (ELT) will make the ACES clock signal available to ground laboratories equipped with atomic clocks. Space-to-ground and ground-to-ground comparisons of atomic frequency standards will be used to test Einstein's theory of general relativity including a precision measurement of the gravitational red-shift, a search for time variations of fundamental constants, and Lorentz Invariance tests. Applications in geodesy, optical time transfer, and ranging will also be supported. ACES has now reached an advanced technology maturity, with engineering models completed and successfully tested and flight hardware under development. This paper presents the ACES mission concept and the status of its main instruments.

  17. Atom Wavelike Nature Solved Mathematically (United States)

    Sven, Charles


    Like N/S poles of a magnet the strong force field surrounding, confining the nucleus exerts an equal force [noted by this author] driving electrons away from the attraction of positively charged protons force fields in nucleus -- the mechanics for wavelike nature of electron. Powerful forces corral closely packed protons within atomic nucleus with a force that is at least a million times stronger than proton's electrical attraction that binds electrons. This then accounts for the ease of electron manipulation in that electron is already pushed away by the very strong atomic N/S force field; allowing electrons to drive photons when I strike a match. Ageless atom's electron requirements, used to drive light/photons or atom bomb, without batteries, must be supplied from a huge, external, super high frequency, super-cooled source, undetected by current technology, one that could exist 14+ billion years without degradation -- filling a limitless space prior to Big Bang. Using only replicable physics, I show how our Universe emanated from that event.

  18. Frequency measurement of the 2S(1/2)-2D(3/2) electric quadrupole transition in a single 171Yb+ ion. (United States)

    Webster, Stephen; Godun, Rachel; King, Steven; Huang, Guilong; Walton, Barney; Tsatourian, Veronika; Margolis, Helen; Lea, Stephen; Gill, Patrick


    We report on precision laser spectroscopy of the 2S(1/2)(F = 0)-2D(3/2) (F = 2, m(F) = 0) clock transition in a single ion of 171Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 +/- 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 x 10(-14).

  19. Bacterial communities in termite fungus combs are comprised of consistent gut deposits and contributions from the environment

    DEFF Research Database (Denmark)

    Otani, Saria; Hansen, Lars Hestbjerg; Sørensen, Søren J


    -throughput sequencing of the 16S rRNA gene, we explored the bacterial community compositions of 33 fungus comb samples from four termite species (three genera) collected at four South African geographic locations in 2011 and 2013. We identified 33 bacterial phyla, with Firmicutes, Bacteroidetes, Proteobacteria...

  20. A magnetostrictive phased array sensor using a nickel comb patch for guided Lamb wave-based damage detection (United States)

    Yoo, Byungseok; Pines, Darryll J.


    This paper presents the development of an ultrasonic guided Lamb wave (GLW)-based magnetostrictive phased array sensor (MPAS) using a circular comb-shaped nickel disc patch with 1" in diameter. And its damage detection capability to identify loosened joint bolts is experimentally demonstrated. The compact sized MPAS was comprised of the nickel disc patch and a detachable magnetic circuit device. The disc patch was machined with 24 comb fingers along its radial direction and the magnetic circuit device contained 6 sensing coils and cylindrical biasing magnets. The individual sensing coils appear to have distinct directional sensing preferences designated by the normal direction of coil winding. The directional sensing feature of the developed MPAS is offered by the combined effect of the magnetic shape anisotropy of comb finger formation in the nickel patch and the sensing directionality of the coil sensor. The MPAS detects the strain-induced magnetic property change on the nickel comb patch due to the mechanical interaction between the patch and GLWs. Although the MPAS holds only the 6 physical coil sensors, the array sensor enables to acquire additional GLW signal data from different sensing sections within the nickel patch, by simply altering the rotational orientation of the magnetic circuit device. Such signal data additions allow to provide a higher resolution damage detection scheme for the advanced phased array signal processing technique. The MPAS apparatus and its damage detection capability were experimentally validated by GLW inspection testing with a thin aluminum plate installed with numerous joint bolts.