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Sample records for sex combs asx

  1. Additional sex combs-like 1 belongs to the enhancer of trithorax and Polycomb Group and genetically interacts with Cbx2 in mice

    PubMed Central

    Fisher, C.L.; Lee, I.; Bloyer, S.; Bozza, S.; Chevalier, J.; Dahl, A; Bodner, C.; Helgason, C. D.; Hess, J.L.; Humphries, R.K.; Brock, H.W.

    2009-01-01

    The Additional sex combs (Asx) gene of Drosophila behaves genetically as an enhancer of trithorax and Polycomb (ETP) in displaying bidirectional homeotic phenotypes, suggesting that is required for maintenance of both activation and silencing of Hox genes. There are 3 murine homologs of Asx called Additional sex combs-like1, 2, and-3. Asxl1 is required for normal adult hematopoiesis; however its embryonic function is unknown. We used a targeted mouse mutant line Asxl1tm1Bc to determine if Asxl1 is required to silence and activate Hox genes in mice during axial patterning. The mutant embryos exhibit simultaneous anterior and posterior transformations of the axial skeleton, consistent with a role for Asxl1 in activation and silencing of Hox genes. Transformations of the axial skeleton are enhanced in compound mutant embryos for the Polycomb group gene M33/Cbx2. Hox a4, a7, and c8 are derepressed in Asxl1tm1Bc mutants in the antero-posterior axis, but Hox c8 expression is reduced in the brain of mutants, consistent with Asxl1 being required both for activation and repression of Hox genes. We discuss the genetic and molecular definition of ETPs, and suggest that the function of Asxl1 depends on its cellular context. PMID:19833123

  2. Sex-specific repression of dachshund is required for Drosophila sex comb development.

    PubMed

    Atallah, Joel; Vurens, Gerard; Mavong, Setong; Mutti, Alexa; Hoang, Don; Kopp, Artyom

    2014-02-15

    The origin of new morphological structures requires the establishment of new genetic regulatory circuits to control their development, from initial specification to terminal differentiation. The upstream regulatory genes are usually the first to be identified, while the mechanisms that translate novel regulatory information into phenotypic diversity often remain obscure. In particular, elaborate sex-specific structures that have evolved in many animal lineages are inevitably controlled by sex-determining genes, but the genetic basis of sexually dimorphic cell differentiation is rarely understood. In this report, we examine the role of dachshund (dac), a gene with a deeply conserved function in sensory organ and appendage development, in the sex comb, a recently evolved male-specific structure found in some Drosophila species. We show that dac acts during metamorphosis to restrict sex comb development to the appropriate leg region. Localized repression of dac by the sex determination pathway is necessary for male-specific morphogenesis of sex comb bristles. This pupal function of dac is separate from its earlier role in leg patterning, and Dac at this stage is not dependent on the pupal expression of Distalless (Dll), the main regulator of dac during the larval period. Dll acts in the epithelial cells surrounding the sex comb during pupal development to promote sex comb rotation, a complex cellular process driven by coordinated cell rearrangement. Our results show that genes with well-conserved developmental functions can be re-used at later stages in development to regulate more recently evolved traits. This mode of gene co-option may be an important driver of evolutionary innovations. PMID:24361261

  3. The Polycomb-group gene, extra sex combs, encodes a nuclear member of the WD-40 repeat family.

    PubMed Central

    Gutjahr, T; Frei, E; Spicer, C; Baumgartner, S; White, R A; Noll, M

    1995-01-01

    We have delimited the extra sex combs (esc) gene to < 4 kb that include a single transcript and are able to rescue both the maternal and zygotic esc phenotypes. Several mutations have been identified within the esc transcript. In agreement with earlier genetic studies, esc is expressed maternally and its product is most abundant during the early embryonic stages. It encodes a protein of the WD-40 repeat family, which localizes predominantly to the nucleus. During germ band extension, it is expressed in a stereotypic pattern of neuroblasts. We propose a model in which Esc is recruited by gap proteins both to act as a corepressor that competes with the TAFII80 coactivator to block transcription and also to mediate the transition to permanent repression by Polycomb-group proteins. Images PMID:7556071

  4. A Logical OR Redundancy within the Asx-Pro-Asx-Gly Type 1 {Beta}-Turn Motif

    SciTech Connect

    Lee, Jihun; Dubey, Vikash Kumar; Longo, Lian M.; Blaber, Michael

    2008-04-19

    Turn secondary structure is essential to the formation of globular protein architecture. Turn structures are, however, much more complex than either {alpha}-helix or {beta}-sheet, and the thermodynamics and folding kinetics are poorly understood. Type I {beta}-turns are the most common type of reverse turn, and they exhibit a statistical consensus sequence of Asx-Pro-Asx-Gly (where Asx is Asp or Asn). A comprehensive series of individual and combined Asx mutations has been constructed within three separate type I 3:5 G1 bulge {beta}-turns in human fibroblast growth factor-1, and their effects on structure, stability, and folding have been determined. The results show a fundamental logical OR relationship between the Asx residues in the motif, involving H-bond interactions with main-chain amides within the turn. These interactions can be modulated by additional interactions with residues adjacent to the turn at positions i + 4 and i + 6. The results show that the Asx residues in the turn motif make a substantial contribution to the overall stability of the protein, and the Asx logical OR relationship defines a redundant system that can compensate for deleterious point mutations. The results also show that the stability of the turn is unlikely to be the prime determinant of formation of turn structure in the folding transition state.

  5. Distinct self-interaction domains promote Multi Sex Combs accumulation in and formation of the Drosophila histone locus body

    PubMed Central

    Terzo, Esteban A.; Lyons, Shawn M.; Poulton, John S.; Temple, Brenda R. S.; Marzluff, William F.; Duronio, Robert J.

    2015-01-01

    Nuclear bodies (NBs) are structures that concentrate proteins, RNAs, and ribonucleoproteins that perform functions essential to gene expression. How NBs assemble is not well understood. We studied the Drosophila histone locus body (HLB), a NB that concentrates factors required for histone mRNA biosynthesis at the replication-dependent histone gene locus. We coupled biochemical analysis with confocal imaging of both fixed and live tissues to demonstrate that the Drosophila Multi Sex Combs (Mxc) protein contains multiple domains necessary for HLB assembly. An important feature of this assembly process is the self-interaction of Mxc via two conserved N-terminal domains: a LisH domain and a novel self-interaction facilitator (SIF) domain immediately downstream of the LisH domain. Molecular modeling suggests that the LisH and SIF domains directly interact, and mutation of either the LisH or the SIF domain severely impairs Mxc function in vivo, resulting in reduced histone mRNA accumulation. A region of Mxc between amino acids 721 and 1481 is also necessary for HLB assembly independent of the LisH and SIF domains. Finally, the C-terminal 195 amino acids of Mxc are required for recruiting FLASH, an essential histone mRNA-processing factor, to the HLB. We conclude that multiple domains of the Mxc protein promote HLB assembly in order to concentrate factors required for histone mRNA biosynthesis. PMID:25694448

  6. Sex comb on midleg (Scm) is a functional link between PcG-repressive complexes in Drosophila

    PubMed Central

    Kang, Hyuckjoon; McElroy, Kyle A.; Jung, Youngsook Lucy; Alekseyenko, Artyom A.; Zee, Barry M.; Park, Peter J.

    2015-01-01

    The Polycomb group (PcG) proteins are key regulators of development in Drosophila and are strongly implicated in human health and disease. How PcG complexes form repressive chromatin domains remains unclear. Using cross-linked affinity purifications of BioTAP-Polycomb (Pc) or BioTAP-Enhancer of zeste [E(z)], we captured all PcG-repressive complex 1 (PRC1) or PRC2 core components and Sex comb on midleg (Scm) as the only protein strongly enriched with both complexes. Although previously not linked to PRC2, we confirmed direct binding of Scm and PRC2 using recombinant protein expression and colocalization of Scm with PRC1, PRC2, and H3K27me3 in embryos and cultured cells using ChIP-seq (chromatin immunoprecipitation [ChIP] combined with deep sequencing). Furthermore, we found that RNAi knockdown of Scm and overexpression of the dominant-negative Scm-SAM (sterile ? motif) domain both affected the binding pattern of E(z) on polytene chromosomes. Aberrant localization of the Scm-SAM domain in long contiguous regions on polytene chromosomes revealed its independent ability to spread on chromatin, consistent with its previously described ability to oligomerize in vitro. Pull-downs of BioTAP-Scm captured PRC1 and PRC2 and additional repressive complexes, including PhoRC, LINT, and CtBP. We propose that Scm is a key mediator connecting PRC1, PRC2, and transcriptional silencing. Combined with previous structural and genetic analyses, our results strongly suggest that Scm coordinates PcG complexes and polymerizes to produce broad domains of PcG silencing. PMID:26063573

  7. Compact electrostatic comb actuator

    DOEpatents

    Rodgers, M. Steven (Albuquerque, NM); Burg, Michael S. (Albuquerque, NM); Jensen, Brian D. (Albuquerque, NM); Miller, Samuel L. (Albuquerque, NM); Barnes, Stephen M. (Albuquerque, NM)

    2000-01-01

    A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

  8. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    DOE PAGESBeta

    Novikov, S. V.; Ting, M.; Yu, K. M.; Sarney, W. L.; Martin, R. W.; Svensson, S. P.; Walukiewicz, W.; Foxon, C. T.

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×10²? cm?³. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×10¹? cm?³ and mobilities of ~1 cm²/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  9. Frequency comb swept lasers

    PubMed Central

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

    2010-01-01

    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 ~?1.2dB sensitivity roll off over ~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. PMID:19997365

  10. Dual-comb MIXSEL

    NASA Astrophysics Data System (ADS)

    Link, S. M.; Zaugg, C. A.; Klenner, A.; Mangold, M.; Golling, M.; Tilma, B. W.; Keller, U.

    2015-03-01

    We present a single semiconductor disk laser simultaneously emitting two different gigahertz modelocked pulse trains. A birefringent crystal inside a modelocked integrated external-cavity surface-emitting laser (MIXSEL) separates the cavity beam into two spatially separated beams with perpendicular polarizations on the MIXSEL chip. This MIXSEL then generates two orthogonally polarized collinear modelocked pulse trains from one simple straight cavity. Superimposing the beams on a photo detector creates a microwave beat signal, representing a strikingly simple setup to down-convert the terahertz optical frequencies into the electronically accessible microwave regime. This makes the dual-comb MIXSEL scheme an ultra-compact and cost-efficient candidate for dual-comb spectroscopy applications.

  11. Native Chemical Ligation at Asx-Cys, Glx-Cys: Chemical Synthesis and High-Resolution Xray Structure of ShK Toxin by Racemic Protein

    E-print Network

    Bezanilla, Francisco

    Native Chemical Ligation at Asx-Cys, Glx-Cys: Chemical Synthesis and High-Resolution Xray Structure Supporting Information ABSTRACT: We have re-examined the utility of native chemical ligation at -Gln- mercaptophenylacetic acid (MPAA), native chemical ligation could be performed at -Gln-Cys- and Asn-Cys- sites without

  12. Structural characterization of GaN and GaAsxN1-x grown by electron cyclotron resonance-metalorganic molecular beam epitaxy

    E-print Network

    Florida, University of

    of increasing importance due to their potential for use as visible optical devices and high-power electronic January 1994) Electron cyclotron resonance-metalorganic molecular beam epitaxy has been used to deposit GaStructural characterization of GaN and GaAsxN1-x grown by electron cyclotron resonance

  13. Molecular Comb Development

    SciTech Connect

    Ferrell, T.L.; Thundat, G.T.; Witkowski, C.E., III

    2007-07-17

    This CRADA was developed to enable ORNL to assist Protein Discovery, Inc. to develop a novel biomolecular separation system based on an ORNL patent application 'Photoelectrochemical Molecular Comb' by Thundat, Ferrell, and Brown. The Molecular Comb concept is based on creating light-induced charge carriers at a semiconductor-liquid interface, which is kept at a potential control such that a depletion layer is formed in the semiconductor. Focusing light from a low-power illumination source creates electron-hole pairs, which get separated in the depletion layer. The light-induced charge carriers reaching the surface attract oppositely charged biomolecules present in the solution. The solution is a buffer solution with very small concentrations of biomolecules. As the focused light is moved across the surface of the semiconductor-liquid interface, the accumulated biomolecules follow the light beam. A thin layer of gel or other similar material on the surface of the semiconductor can act as a sieving medium for separating the biomolecules according to their sizes.

  14. Mid-infrared frequency combs

    E-print Network

    Schliesser, Albert; Hänsch, Theodor W

    2012-01-01

    Laser frequency combs are coherent light sources that emit a broad spectrum consisting of discrete, evenly spaced narrow lines, each having an absolute frequency measurable within the accuracy of an atomic clock. Their development, a decade ago, in the near-infrared and visible domains has revolutionized frequency metrology with numerous windfalls into other fields such as astronomy or attosecond science. Extension of frequency comb techniques to the mid-infrared spectral region is now under exploration. Versatile mid-infrared frequency comb generators, based on novel laser gain media, nonlinear frequency conversion or microresonators, promise to significantly expand the tree of applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the fingerprint region, with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may spark off new discoveries in the various fields relevant to molecular sciences.

  15. Surface Acoustic Wave Frequency Comb

    E-print Network

    Savchenkov, A A; Ilchenko, V S; Seidel, D; Maleki, L

    2011-01-01

    We report on realization of an efficient triply-resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyper-parametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb observing the modulation of the modulated light escaping the resonator.

  16. On-chip Dual-comb based on Quantum Cascade Laser Frequency Combs

    E-print Network

    Villares, Gustavo; Kazakov, Dmitry; Süess, Martin J; Hugi, Andreas; Beck, Mattias; Faist, Jérôme

    2015-01-01

    Dual-comb spectroscopy is emerging as one of the most appealing applications of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs combined with the high sensitivities achievable by mid-infrared molecular spectroscopy. Here we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs, where two frequency combs are integrated on a single chip. Control of the combs repetition and offset frequencies is obtained by integrating micro-heaters next to each laser. We show that a full control of the dual-comb system is possible, by measuring a multi-heterodyne beating corresponding to an optical bandwidth of 32 cm$^{-1}$ at a center frequency of 1330 cm$^{-1}$ (7.52 $\\mu$m), demonstrating that this device is ideal for compact dual-comb spectroscopy systems.

  17. Ultrafast electrooptic dual-comb interferometry

    E-print Network

    Duran, Vicente; Torres-Company, Victor

    2015-01-01

    The femtosecond laser frequency comb has enabled the 21st century revolution in optical synthesis and metrology. A particularly compelling technique that relies on the broadband coherence of two laser frequency combs is dual-comb interferometry. This method is rapidly advancing the field of optical spectroscopy and empowering new applications, from nonlinear microscopy to laser ranging. Up to now, most dual-comb interferometers were based on modelocked lasers, whose repetition rates have restricted the measurement speed to ~ kHz. Here we demonstrate a novel dual-comb interferometer that is based on electrooptic frequency comb technology and measures consecutive complex spectra at a record-high refresh rate of 25 MHz. These results pave the way for novel scientific and metrology applications of frequency comb generators beyond the realm of molecular spectroscopy, where the measurement of ultrabroadband waveforms is of paramount relevance.

  18. Optimization of filtering schemes for broadband astro-combs

    E-print Network

    Walsworth, Ronald L.

    nonlinear optical fiber to spectrally broaden the filtered and amplified narrowband frequency comb a narrowband, femtosecond laser frequency comb ("source-comb"), one must integrate the source-comb with three). We find that even a small nonlinear phase can reduce suppression of filtered comb lines, and increase

  19. Broadband midinfrared frequency comb with tooth scanning

    NASA Astrophysics Data System (ADS)

    Lee, Kevin F.; Mas?owski, P.; Mills, A.; Mohr, C.; Jiang, Jie; Schunemann, Peter G.; Fermann, M. E.

    2015-03-01

    Frequency combs are a massively parallel source of extremely accurate optical frequencies. Frequency combs generally operate at the visible or near-infrared wavelengths, but fundamental molecular vibrations occur at midinfrared wavelengths. We demonstrate an optically-referenced, broadband midinfrared frequency comb based on a doublyresonant optical parametric oscillator (OPO). By tuning the wavelength of the reference laser, the comb line frequencies are tuned as well. By scanning the reference wavelength, any frequency can be accessed, not just the frequencies of the base comb. Combined with our comb-resolving Fourier transform spectrometer, we can measure 200 wavenumber wide broadband absorption spectra with 200 kHz linewidth comb teeth. Our OPO is pumped by an amplified Tm fiber frequency comb, with phase-locked carrier envelope offset frequency, and repetition rate fixed by phase-locking a frequency comb line to a narrow linewidth diode laser at a telecom channel. The frequency comb is referenced to GPS by long-term stabilization of the repetition rate to a selected value using the temperature of the reference laser as the control. The resulting pump comb is about 3W of 100 fs pulses at 418 MHz repetition rate at 1950 nm. Part of the comb is used for supercontinuum generation for frequency stabilization, and the rest pumps an orientation-patterned gallium arsenide (OP-GaAs) crystal in a doubly-resonant optical parametric oscillator cavity, yielding collinear signal and idler beams from about 3 to 5.5 ?m. We verify comb scanning by resolving the 200 MHz wide absorption lines of the entire fundamental CO vibrational manifold at 11 Torr pressure.

  20. Stabilization of a Kerr frequency comb oscillator.

    PubMed

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

    2013-08-01

    We study stability and spectral purity of a microresonator-based Kerr frequency comb oscillator experimentally and observe a correlation between the frequency of the continuous wave laser pumping the nonlinear resonator and the repetition frequency of the comb. This correlation is used in a proof-of-principle demonstration of a Kerr frequency comb stabilized with an optical transition of 87Rb. PMID:23903097

  1. Atomic quantum memory for multimode frequency combs

    E-print Network

    Z. Zheng; O. Mishina; N. Treps; C. Fabre

    2015-04-06

    We propose a Raman quantum memory scheme that uses several atomic ensembles to store and retrieve the multimode highly entangled state of an optical quantum frequency comb, such as the one produced by parametric down-conversion of a pump frequency comb. We analyse the efficiency and the fidelity of such a quantum memory. Results show that our proposal may be helpful to multimode information processing using the different frequency bands of an optical frequency comb.

  2. Scaling of Yb-Fiber Frequency Combs

    NASA Astrophysics Data System (ADS)

    Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E.; Hartl, Ingmar

    2010-06-01

    Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

  3. Visible wavelength astro-comb.

    PubMed

    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

    2010-08-30

    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. PMID:20940813

  4. Quantum Cascade Laser Frequency Combs

    E-print Network

    Faist, Jérôme; Scalari, Giacomo; Rösch, Markus; Bonzon, Christopher; Hugi, Andreas; Beck, Mattias

    2015-01-01

    It was recently demonstrated that broadband quantum cascade lasers can operate as frequency combs. As such, they operate under direct electrical pumping at both mid-infrared and THz frequencies, making them very attractive for dual-comb spectroscopy. Performance levels are continuously improving, with average powers over 100 mW and frequency coverage of 100 cm$^{-1}$ in the mid-infrared. In the THz range, 10 mW of average power and 600 GHz of frequency coverage are reported. As a result of the very short upper state lifetime of the gain medium, the mode proliferation in these sources arises from four wave mixing rather than saturable absorption. As a result, their optical output is characterized by the tendency of small intensity modulation of the output power, and the relative phases of the modes to be similar to the ones of a frequency modulated laser. Recent results include the proof of comb operation down to a metrological level, the observation of a Schawlow-Townes broadened linewidth, as well as the fir...

  5. A Josephson radiation comb generator

    NASA Astrophysics Data System (ADS)

    Solinas, P.; Gasparinetti, S.; Golubev, D.; Giazotto, F.

    2015-07-01

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of ? and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1?GHz can deliver up to a 0.5?nW at 200?GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

  6. A Josephson radiation comb generator.

    PubMed

    Solinas, P; Gasparinetti, S; Golubev, D; Giazotto, F

    2015-01-01

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of ? and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a 0.5 nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation. PMID:26193628

  7. A Josephson radiation comb generator

    PubMed Central

    Solinas, P.; Gasparinetti, S.; Golubev, D.; Giazotto, F.

    2015-01-01

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of ? and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1?GHz can deliver up to a 0.5?nW at 200?GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation. PMID:26193628

  8. Calculation of tunable type-II band alignments in InAsxSbyP1?x?y/InAs heterojunctions

    NASA Astrophysics Data System (ADS)

    Shim, Kyurhee

    2016-01-01

    The energy band gaps of the alloy InAsxSbyP1?x?y are calculated using the correlated function expansion (CFE) technique over the entire composition space x and y, for which the CFE band gap composition contour for the mid-infrared (MIR) spectral region of 2 (0.62)–5 µm (0.25 eV) is presented. The composition dependence of the valence-band maximum (VBM) is obtained using the universal tight binding (UTB) method, and the corresponding conduction-band minimum (CBM) can be computed from the difference between the band gap and the VBM. By organizing the relative positions of the VBM and CBM between the quaternary alloy InAsSbP and the binary compound InAs, the band alignments and band types of InAsSbP/InAs heterojunctions (HJs) along the lattice-matching conditions x and y [i.e., y = 0.311(1 ? x)] are determined. It is found that the VBMs of the alloy InAsxSbyP1?x?y are located within the band gap of InAs, whereas the CBMs of the alloy lie outside the band gap of InAs over the entire composition range. This implies that the InAsxSbyP1?x?y/InAs HJs exhibit composition-tunable, type-II (staggered) band alignments. In addition, the conduction-band offset (CBO) and valence-band offset (VBO) of InAsSbP/InAs HJs both present the upward bowing trend, with the CBO curves appearing sharp and the VBO curves appearing smooth.

  9. Phononic frequency combs through nonlinear resonances

    NASA Astrophysics Data System (ADS)

    Peng, Ru-Wen; Cao, Lu-Shuai; Qi, Dong-Xiang; Wang, Mu; Schmelcher, Peter

    2015-03-01

    It is well known that optical frequency combs have become important coherent optical sources with diverging applications, ranging from optical frequency metrology to ultracold gases. In this work, we explore an analogue of optical frequency combs in driven nonlinear phononic systems, and present a mechanism for generating phononic frequency combs through nonlinear resonances. In the underlying process, a set of phonon modes is simultaneously excited by the external driving which yields frequency combs with an array of discrete and equidistant spectral lines of each nonlinearly excited phonon mode. Frequency combs through nonlinear resonance of different orders are investigated, and in particular the possibility of correlation tailoring in higher-order cases is revealed. We suggest that our results can be applied in various nonlinear acoustic processes, such as phonon harvesting, and can also be generalized to other nonlinear systems. Supported by NSF and MOST of China.

  10. Specific-heat critical behavior of the structural random-field system Dy(AsxV1-x)O4

    NASA Astrophysics Data System (ADS)

    Slani?, Z.; Belanger, D. P.; Wang, J.; Taylor, D. R.

    1996-01-01

    The specific-heat critical behaviors of the pure Ising transition in DyVO4 and the random-field Ising transition in Dy(AsxV1-x)O4 have been measured. The critical exponent ? and amplitude ratio A+/A- for DyVO4, which has Tc=14.82 K, are in excellent agreement with the known pure d=3 Ising exponents. The random fields generated by the local strain fields in Dy(AsxV1-x)O4 depress the transitions to Tc=13.45 K and Tc=7.7 K for x=0.05 and x=0.15, respectively. With increasing x, the transition becomes rounded and severely depressed in size. The value of ? appears large and negative for x=0.15. As the random-field strength increases, i.e., the value of x gets larger, the amount of entropy change associated with the transition rapidly decreases. Where the missing entropy reappears is not adequately understood.

  11. Localized states on comb lattices

    NASA Astrophysics Data System (ADS)

    Baldi, G.; Burioni, R.; Cassi, D.

    2004-09-01

    Complex networks and graphs provide a general description of a great variety of inhomogeneous discrete systems. These range from polymers and biomolecules to complex quantum devices, such as arrays of Josephson junctions, microbridges, and quantum wires. We introduce a technique, based on the analysis of the motion of a random walker, that allows us to determine the density of states of a general local Hamiltonian on a graph, when the potential differs from zero on a finite number of sites. We study in detail the case of the comb lattice and we derive an analytic expression for the elements of the resolvent operator of the Hamiltonian, giving its complete spectrum.

  12. Bichromatically pumped microresonator frequency combs

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Wabnitz, S.

    2014-07-01

    A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrödinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.

  13. Structural, Electronic, Thermodynamic and Thermal Properties of Zinc-Blende InP, InAs and Their InAsx P1-x Ternary Alloys via First Principles Calculations

    NASA Astrophysics Data System (ADS)

    Nemiri, O.; Ghemid, S.; Chouahda, Z.; Meradji, H.; El Haj Hassan, F.

    2013-10-01

    First-principles calculations are performed to study the structural, electronic, thermodynamic and thermal properties of the InP and InAs bulk materials and InAsxP1-x ternary alloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The dependence of the lattice constant, bulk modulus, band gap, Debye temperature, heat capacity and mixing entropy on the composition x was analyzed. The lattice constant for InAsxP1-x alloys exhibits a marginal deviation from the Vegard's law. A large deviation of the bulk modulus from linear concentration dependence (LCD) was observed for our alloys. We found that the composition dependence of the energy band gap is almost linear by using the mBJ and EV-GGA approximations. The microscopic origins of the gap bowing were explained and detailed by using the approach of Zunger and co-workers. Furthermore, the calculated phase diagram shows a miscibility gap for these alloys with a high critical temperature. Thermal effects on some macroscopic properties of InAsxP1-x alloys are predicted using the quasi-harmonic Debye model, in which the phononic effects are considered. This is the first quantitative theoretical prediction of the thermal properties of the InAsxP1-x alloys, and we still expect the confirmation of experimental studies.

  14. Frequency Comb Generation in Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Erickson, R. P.; Vissers, M. R.; Sandberg, M.; Jefferts, S. R.; Pappas, D. P.

    2014-10-01

    We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? /2 resonators at T =3 K . Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 1 08. The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves.

  15. Femtosecond optical parametric oscillator frequency combs

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yohei; Torizuka, Kenji; Marandi, Alireza; Byer, Robert L.; McCracken, Richard A.; Zhang, Zhaowei; Reid, Derryck T.

    2015-09-01

    Techniques to measure and manipulate the carrier-envelope phase within femtosecond optical parametric oscillators (OPOs) allow their outputs to be stabilized in a way that produces a frequency comb structure, potentially tunable throughout the transparency band of the gain material. In this review we describe the fundamental principles of phase control, on which the development of singly- and doubly-resonant OPO frequency combs is based. We give examples of practical embodiments of such combs, and discuss in detail several applications, including spectroscopy, metrology, quantum computation and astrophotonics.

  16. Fractional diffusion on a fractal grid comb

    NASA Astrophysics Data System (ADS)

    Sandev, Trifce; Iomin, Alexander; Kantz, Holger

    2015-03-01

    A grid comb model is a generalization of the well known comb model, and it consists of N backbones. For N =1 the system reduces to the comb model where subdiffusion takes place with the transport exponent 1 /2 . We present an exact analytical evaluation of the transport exponent of anomalous diffusion for finite and infinite number of backbones. We show that for an arbitrarily large but finite number of backbones the transport exponent does not change. Contrary to that, for an infinite number of backbones, the transport exponent depends on the fractal dimension of the backbone structure.

  17. Frequency combs from crystalline resonators: influence of cavity parameters on comb dynamics

    E-print Network

    Grudinin, Ivan S

    2014-01-01

    We experimentally study the factors that influence the span in frequency combs derived from the crystalline whispering gallery mode resonators. We observe that cavity dispersion plays an important role in generation of combs by cascaded four wave mixing process. We observed combs from the resonators with anomalous dispersion and nearly zero dispersion at the pump wavelength. In addition, the comb generation efficiency is found to be affected by the crossing of modes of different families. The influence of Raman gain is discussed as well as the role of cavity diameter and pump power. Copyright 2014 California Institute of Technology. Government sponsorship acknowledged.

  18. Ultrabroadband coherent supercontinuum frequency comb

    SciTech Connect

    Ruehl, Axel; McKay, Hugh; Thomas, Brian; Dong, Liang; Fermann, Martin E.; Hartl, Ingmar; Martin, Michael J.; Cossel, Kevin C.; Chen Lisheng; Benko, Craig; Ye Jun; Dudley, John M.

    2011-07-15

    We present detailed studies of the coherence properties of an ultrabroadband supercontinuum, enabled by a comprehensive approach involving continuous-wave laser sources to independently probe both the amplitude and phase noise quadratures across the entire spectrum. The continuum coherently spans more than 1.5 octaves, supporting Hz-level comparison of ultrastable lasers at 698 nm and 1.54 {mu}m. We present a complete numerical simulation of the accumulated comb coherence in the limit of many pulses, in contrast to the single-pulse level, with systematic experimental verification. The experiment and numerical simulations reveal the presence of quantum-seeded broadband amplitude noise without phase coherence degradation, including the discovery of a dependence of the supercontinuum coherence on the fiber fractional Raman gain.

  19. Phononic Frequency Combs via Nonlinear Resonances

    E-print Network

    Lushuai Cao; Dongxiang Qi; Ruwen Peng; Mu Wang; Peter Schmelcher

    2014-02-22

    We study the analogue of optical frequency combs in driven nonlinear phononic systems, and present a new generation mechanism for phononic frequency combs via nonlinear resonances. The nonlinear resonance refers to the simultaneous excitation of a set of phonon modes by the external driving, and thereby generated frequency combs are characterized by an array of equidistant spectral lines in the spectrum of each nonlinearly excited phonon mode. Frequency combs via nonlinear resonance of different orders are investigated, and particularly we reveal the possibility for correlation tailoring in higher order cases. The investigation contributes to potential applications in various nonlinear acoustic processes, such as harvesting phonons and generating phonon entanglements, and can also be generalized to other nonlinear systems.

  20. Phononic Frequency Combs via Nonlinear Resonances

    E-print Network

    Cao, Lushuai; Peng, Ruwen; Wang, Mu; Schmelcher, Peter

    2013-01-01

    We study the analogue of optical frequency combs in driven nonlinear phononic systems, and present a new generation mechanism for phononic frequency combs via nonlinear resonances. The nonlinear resonance refers to the simultaneous excitation of a set of phonon modes by the external driving, and thereby generated frequency combs are characterized by an array of equidistant spectral lines in the spectrum of each nonlinearly excited phonon mode. Frequency combs via nonlinear resonance of different orders are investigated, and particularly we reveal the possibility for correlation tailoring in higher order cases. The investigation contributes to potential applications in various nonlinear acoustic processes, such as harvesting phonons and generating phonon entanglements, and can also be generalized to other nonlinear systems.

  1. Frequency Comb Generation in Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Pappas, David; Erickson, Robert; Vissers, Michael; Ku, Hsiang-Sheng

    2015-03-01

    We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? = 2 resonators at T =3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 108 The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves. Generation of combs in this frequency range allows for unprecedented analysis of this non-linear phenomena in the time domain. We acknowledge DARPA and the NIST Quantum Information program.

  2. Phase steps and resonator detuning measurements in microresonator frequency combs

    NASA Astrophysics Data System (ADS)

    Del'Haye, Pascal; Coillet, Aurélien; Loh, William; Beha, Katja; Papp, Scott B.; Diddams, Scott A.

    2015-01-01

    Experiments and theoretical modelling yielded significant progress toward understanding of Kerr-effect induced optical frequency comb generation in microresonators. However, the simultaneous Kerr-mediated interaction of hundreds or thousands of optical comb frequencies with the same number of resonator modes leads to complicated nonlinear dynamics that are far from fully understood. An important prerequisite for modelling the comb formation process is the knowledge of phase and amplitude of the comb modes as well as the detuning from their respective microresonator modes. Here, we present comprehensive measurements that fully characterize optical microcomb states. We introduce a way of measuring resonator dispersion and detuning of comb modes in a hot resonator while generating an optical frequency comb. The presented phase measurements show unpredicted comb states with discrete ? and ?/2 steps in the comb phases that are not observed in conventional optical frequency combs.

  3. Phase steps and resonator detuning measurements in microresonator frequency combs.

    PubMed

    Del'Haye, Pascal; Coillet, Aurélien; Loh, William; Beha, Katja; Papp, Scott B; Diddams, Scott A

    2015-01-01

    Experiments and theoretical modelling yielded significant progress toward understanding of Kerr-effect induced optical frequency comb generation in microresonators. However, the simultaneous Kerr-mediated interaction of hundreds or thousands of optical comb frequencies with the same number of resonator modes leads to complicated nonlinear dynamics that are far from fully understood. An important prerequisite for modelling the comb formation process is the knowledge of phase and amplitude of the comb modes as well as the detuning from their respective microresonator modes. Here, we present comprehensive measurements that fully characterize optical microcomb states. We introduce a way of measuring resonator dispersion and detuning of comb modes in a hot resonator while generating an optical frequency comb. The presented phase measurements show unpredicted comb states with discrete ? and ?/2 steps in the comb phases that are not observed in conventional optical frequency combs. PMID:25565467

  4. 2.8 ?m emission from type-I quantum wells grown on InAsxP1-x/InP metamorphic graded buffers

    NASA Astrophysics Data System (ADS)

    Jung, Daehwan; Song, Yuncheng; Yu, Lan; Wasserman, Daniel; Larry Lee, Minjoo

    2012-12-01

    We report 2.8 ?m emission from compressively strained type-I quantum wells (QWs) grown on InP-based metamorphic InAsxP1-x step-graded buffers. High quality metamorphic graded buffers showed smooth surface morphology and low threading dislocation densities of approximately 2.5 × 106 cm-2. High-resolution x-ray diffraction scans showed strong satellites from multiple quantum wells grown on metamorphic buffers, and cross-sectional transmission electron microscopy revealed smooth and coherent quantum well interfaces. Room-temperature photoluminescence emission at 2.8 ?m with a narrow linewidth (˜50 meV) shows the promise of metamorphic growth for mid-infrared laser diodes on InP.

  5. Wideband RF channelizer based on parametric combs

    NASA Astrophysics Data System (ADS)

    Zlatanovic, S.; Adleman, J. R.; Huynh, C. K.; Jester, S. B.; Lin, C.; Wiberg, A. O...; Myslivets, E.; Radic, S.; Jacobs, E. W.

    2015-05-01

    RF photonic channelizers can overcome limitations of conventional electronic methods for analysis of wideband RF spectral content. Here, we will present a recent progress on the RF photonic channelizer systems that are based on optical parametric combs. These systems can analyze very wide RF bandwidths exceeding 100GHz, therefore providing essential capability for the applications demanding a wide-bandwidth spectral analysis. The RF channelizers being presented utilize parametric processes in the highly non-linear fiber mixers to generate a large number of RF signal copies in the optical domain. Two different implementations for generation of RF signal copies will be presented and compared: one using a parametric multicasting and another utilizing a direct comb modulation. Generation of optical combs spanning more than 10THz will be shown. We will also present two distinct system architectures for RF photonic channelizer system: one employing a periodic optical filter such as Fabry-Perot etalon to select channels from the signal comb, and another one utilizing a coherent detection between a frequency-locked signal comb and a parametrically generated local oscillator (LO) comb. The second scheme gives benefit of providing both in-phase and quadrature (I/Q) information on channelized intermediate frequency (IF) signals. We will present a system with 32 implemented channels using a filtered scheme and a 32-channel coherent system with a full-field detection implemented on one tunable channel. Sensitivity and dynamic range as well as benefits of both system architectures will be discussed.

  6. Laboratory duplication of comb layering in the Rhum pluton. [igneous rocks with comb layered texture

    NASA Technical Reports Server (NTRS)

    Donaldson, C. H.

    1977-01-01

    A description is provided of the texture of harrisite comb layers, taking into account the results of crystallization experiments at controlled cooling rates, which have reproduced the textural change from 'cumulate' to comb-layered harrisite. Melted samples of harrisite were used in the dynamic crystallization experiments considered. The differentiation of a cooling rate run with respect to olivine grain size and shape is shown and three possible origins of hopper olivine in differentiated crystallization runs are considered. It is found that olivine nucleation occurred throughout cooling, except for the incubation period during early cooling. The elongate combed olivines in harrisite apparently grew as the magma locally supercooled to at least 30 C. It is suggested that the branching crystals in most comb layers, including comb-layered harrisite, probably grew along thermal gradients.

  7. Analytical Model for Comb Capacitance Fringe Hanno Hammer

    E-print Network

    the analytic result, an approximation to the levitation force acting on the upper finger surfaces is derived interdigitated comb drive, levitation effect, length of electric field lines. I. INTRODUCTION ELECTROSTATIC comb

  8. Electrostatic comb drive for vertical actuation

    SciTech Connect

    Lee, A. P., LLNL

    1997-07-10

    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.

  9. Direct Frequency Comb Spectroscopy of Alkali Atoms

    NASA Astrophysics Data System (ADS)

    Pradhananga, Trinity; Palm, Christopher; Nguyen, Khoa; Guttikonda, Srikanth; Kimball, Derek Jackson

    2011-11-01

    We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

  10. Optical Nyquist channel generation using a comb-based

    E-print Network

    Touch, Joe

    Optical Nyquist channel generation using a comb-based tunable optical tapped-delay-line Morteza 18, 2014 We demonstrate optical Nyquist channel generation based on a comb-based optical tapped-delay-line. The frequency lines of an optical frequency comb are used as the taps of the optical tapped

  11. Frequency comb generation in quadratic nonlinear media

    NASA Astrophysics Data System (ADS)

    Ricciardi, Iolanda; Mosca, Simona; Parisi, Maria; Maddaloni, Pasquale; Santamaria, Luigi; De Natale, Paolo; De Rosa, Maurizio

    2015-06-01

    We experimentally demonstrate and theoretically explain the onset of optical frequency combs in a simple cavity-enhanced second-harmonic-generation system, exploiting second-order nonlinear interactions. Two combs are simultaneously generated around the fundamental pump frequency, with a spectral bandwidth up to about 10 nm, and its second harmonic. We observe different regimes of generation, depending on the phase-matching condition for second-harmonic generation. Moreover, we develop an elemental model which provides a deep physical insight into the observed dynamics. Despite the different underlying physical mechanism, the proposed model is remarkably similar to the description of third-order effects in microresonators, revealing a potential variety of new effects to be explored and laying the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

  12. Nonlinear transmission spectroscopy with dual frequency combs

    NASA Astrophysics Data System (ADS)

    Glenn, Rachel; Mukamel, Shaul

    2014-08-01

    We show how two frequency combs E1, E2 can be used to measure single-photon, two-photon absorption (TPA), and Raman resonances in a molecule with three electronic bands, by detecting the radio frequency modulation of the nonlinear transmission signal. Some peaks are independent of the carrier frequency of the comb and others shift with that frequency and have a width close to the comb width. TPA and Raman resonances independent of the carrier frequency are selected by measuring the transmission signal ˜E12E22 and the single-photon resonances are selected by measuring the transmission signal ˜E13E2. Sinusoidal spectral phase shaping strongly affects the TPA, but not the Raman resonances.

  13. Frequency comb generation in quadratic nonlinear media

    E-print Network

    Ricciardi, Iolanda; Parisi, Maria; Maddaloni, Pasquale; Santamaria, Luigi; De Natale, Paolo; De Rosa, Maurizio

    2014-01-01

    Optical frequency combs are nowadays routinely used tools in a wide range of scientific and technological applications. Different techniques have been developed for generating optical frequency combs, like mode-locking in lasers and third-order interactions in microresonators, or to extend their spectral capabilities, using frequency conversion processes in nonlinear materials. Here, we experimentally demonstrate and theoretically explain the onset of optical frequency combs in a simple cavity-enhanced second-harmonic-generation system, exploiting second-order nonlinear interactions. We develop an elemental model which provides a deep physical insight into the observed dynamics. Moreover, despite the different underlying physical mechanism, the proposed model is remarkably similar to the description of third-order effects in microresonators, revealing a potential variety of new effects to be explored. Finally, exploiting a nonlinearity intrinsically stronger than the third-order one, our work lays the groundw...

  14. Nonlinear transmission spectroscopy with dual frequency combs

    E-print Network

    Glenn, Rachel

    2014-01-01

    We show how two frequency combs $\\mathcal{E}_1$, $\\mathcal{E}_2$ can be used to measure single-photon, two-photon absorption (TPA), and Raman resonances in a molecule with three electronic bands, by detecting the radio frequency modulation of the nonlinear transmission signal. Some peaks are independent of the carrier frequency of the comb and others shift with that frequency and have a width close to the comb width. TPA and Raman resonances independent of the carrier frequency are selected by measuring the transmission signal $\\sim\\mathcal{E}_1^2 \\mathcal{E}_2^2$ and the single-photon resonances are selected by measuring the transmission signal $\\sim\\mathcal{E}_1^3\\mathcal{E}_2$. Sinusoidal spectral phase shaping strongly affects the TPA, but not the Raman resonances.

  15. Frequency-agile dual-comb spectroscopy

    E-print Network

    Millot, Guy; Yan, Ming; Hovannysyan, Tatevik; Bendahmane, Abdelkrim; Hänsch, Theodor W; Picqué, Nathalie

    2015-01-01

    We propose a new approach to near-infrared molecular spectroscopy, harnessing advanced concepts of optical telecommunications and supercontinuum photonics. We generate, without mode-locked lasers, two frequency combs of slightly different repetition frequencies and moderate, but rapidly tunable, spectral span. The output of a frequency-agile continuous wave laser is split and sent into two electro-optic intensity modulators. Flat-top low-noise frequency combs are produced by wave-breaking in a nonlinear optical fiber of normal dispersion. With a dual-comb spectrometer, we record Doppler-limited spectra spanning 60 GHz within 13 microseconds and 80-kHz refresh rate, at a tuning speed of 10 nm.s^(-1). The sensitivity for weak absorption is enhanced by a long gas-filled hollow-core fiber.

  16. Microresonator-based optical frequency combs.

    PubMed

    Kippenberg, T J; Holzwarth, R; Diddams, S A

    2011-04-29

    The series of precisely spaced, sharp spectral lines that form an optical frequency comb is enabling unprecedented measurement capabilities and new applications in a wide range of topics that include precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. A new optical frequency comb generation principle has emerged that uses parametric frequency conversion in high resonance quality factor (Q) microresonators. This approach provides access to high repetition rates in the range of 10 to 1000 gigahertz through compact, chip-scale integration, permitting an increased number of comb applications, such as in astronomy, microwave photonics, or telecommunications. We review this emerging area and discuss opportunities that it presents for novel technologies as well as for fundamental science. PMID:21527707

  17. Safe sex

    MedlinePLUS

    Safe sex means taking steps before and during sex that can prevent you from getting an infection, or from ... the skin around the genital area. Before having sex: Get to know your partner and discuss your ...

  18. Kerr frequency comb generation in overmoded resonators.

    PubMed

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

    2012-11-19

    We show that scattering-based interaction among nearly degenerate optical modes is the key factor in low threshold generation of Kerr frequency combs in nonlinear optical resonators with small group velocity dispersion (GVD). Mode interaction is capable of producing drastic changes in the local GVD, resulting in either a significant reduction, or an increase, in the oscillation threshold. Furthermore, we show that mode interaction is also responsible for majority of observed optical frequency combs in resonators characterized with large normal GVD. We present results of our numerical simulations together with supporting experimental data. PMID:23187584

  19. High-Temperature Thermoelectric Properties of the Solid–Solution Zintl Phase Eu11Cd6Sb12–xAsx (x < 3)

    SciTech Connect

    Kazem, Nasrin; Xie, Weiwei; Ohno, Saneyuki; Zevalkink, Alexandra; Miller, Gordon J; Snyder, G Jeffrey; Kauzlarich, Susan M

    2014-02-11

    Zintl phases are compounds that have shown promise for thermoelectric applications. The title solid–solution Zintl compounds were prepared from the elements as single crystals using a tin flux for compositions x = 0, 1, 2, and 3. Eu11Cd6Sb12–xAsx (x < 3) crystallize isostructurally in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58). Efforts to make the As compositions for x exceeding ?3 resulted in structures other than the Sr11Cd6Sb12 structure type. Single-crystal X-ray diffraction indicates that As does not randomly substitute for Sb in the structure but is site specific for each composition. The amount of As determined by structural refinement was verified by electron microprobe analysis. Electronic structures and energies calculated for various model structures of Eu11Cd6Sb10As2 (x = 2) indicated that the preferred As substitution pattern involves a mixture of three of the six pnicogen sites in the asymmetric unit. In addition, As substitution at the Pn4 site opens an energy gap at the Fermi level, whereas substitution at the other five pnicogen sites remains semimetallic with a pseudo gap. Thermoelectric properties of these compounds were measured on hot-pressed, fully densified pellets. Samples show exceptionally low lattice thermal conductivities from room temperature to 775 K: 0.78–0.49 W/mK for x = 0; 0.72–0.53 W/mK for x = 1; and 0.70–0.56 W/mK for x = 2. Eu11Cd6Sb12 shows a high p-type Seebeck coefficient (from +118 to 153 ? V/K) but also high electrical resistivity (6.8 to 12.8 m?·cm). The value of zT reaches 0.23 at 774 K. The properties of Eu11Cd6Sb12–xAsx are interpreted in discussion with the As site substitution.

  20. Dual-comb spectroscopy based on quantum-cascade-laser frequency combs.

    PubMed

    Villares, Gustavo; Hugi, Andreas; Blaser, Stéphane; Faist, Jérôme

    2014-01-01

    Dual-comb spectroscopy performed in the mid-infrared-where molecules have their strongest rotovibrational absorption lines-offers the promise of high spectral resolution broadband spectroscopy with very short acquisition times (?s) and no moving parts. Recently, we demonstrated frequency comb operation of a quantum-cascade-laser. We now use that device in a compact, dual-comb spectrometer. The noise properties of the heterodyne beat are close to the shot noise limit. Broadband (15?cm(-1)) high-resolution (80?MHz) absorption spectroscopy of both a GaAs etalon and water vapour is demonstrated, showing the potential of quantum-cascade-laser frequency combs as the basis for a compact, all solid-state, broadband chemical sensor. PMID:25307936

  1. Dispersion engineering of Quantum Cascade Lasers frequency combs

    E-print Network

    Villares, Gustavo; Wolf, Johanna; Kazakov, Dmitry; Süess, Martin J; Beck, Mattias; Faist, Jérôme

    2015-01-01

    Quantum cascade lasers are compact sources capable of generating frequency combs. Yet key characteristics - such as optical bandwidth and power-per-mode distribution - have to be improved for better addressing spectroscopy applications. Group delay dispersion plays an important role in the comb formation. In this work, we demonstrate that a dispersion compensation scheme based on a Gires-Tournois Interferometer integrated into the QCL-comb dramatically improves the comb operation regime, preventing the formation of high-phase noise regimes previously observed. The continuous-wave output power of these combs is typically $>$ 100 mW with optical spectra centered at 1330 cm$^{-1}$ (7.52 $\\mu$m) with $\\sim$ 70 cm$^{-1}$ of optical bandwidth. Our findings demonstrate that QCL-combs are ideal sources for chip-based frequency comb spectroscopy systems.

  2. The microrheology of polystyrene sulfonate combs in aqueous solution

    NASA Astrophysics Data System (ADS)

    Papagiannopoulos, A.; Fernyhough, C. M.; Waigh, T. A.

    2005-12-01

    Video particle tracking (VPT) and diffusing wave spectroscopy were used to characterize the microrheology of polystyrene sulfonate combs in aqueous solutions. At low frequencies VPT demonstrated predominantly viscous behavior. The manner in which the viscosity scaled as a function of monomer concentration was a sensitive function of the comb architecture. Densely branched combs or combs with long side chains demonstrated entangled polyelectrolyte scaling above the overlap concentration, whereas sparsely branched combs had unentangled polyelectrolyte scaling. A dynamic scaling model was developed for the viscosity of unentangled semidilute solutions of comb polyelectrolytes. Diffusing wave spectroscopy demonstrated Rouse modes (G'˜G?˜?1/2) for the high-frequency dynamics of the semidilute comb solutions. The form of the high-frequency viscoelasticity was independent of the chain architecture and the modulus scaled as expected for linear flexible polyelectrolytes.

  3. Quantum cascade laser Kerr frequency comb

    E-print Network

    Lecaplain, Caroline; Lucas, Erwan; Jost, John D; Kippenberg, Tobias J

    2015-01-01

    The mid-infrared (mid-IR) regime (typically the wavelength regime of $\\lambda \\sim 2.5-20 \\ \\mathrm{\\mu m}$) is an important spectral range for spectroscopy as many molecules have their fundamental rotational-vibrational absorption in this band. Recently optical frequency combs based on optical microresonators ("Kerr" combs) at the onset of the mid-IR region have been generated using crystalline resonators and integrated planar silicon micro-resonators. Here we extend for the first time Kerr combs deep into the mid-IR i.e. the 'molecular fingerprint' region. This is achieved by combining an ultra high quality (Q) factor mid-IR microresonator based on crystalline $\\mathrm{MgF_{2}}$ with the quantum cascade laser (QCL) technology. Using a tapered chalgogenide (ChG) fiber and a QCL continuous wave pump laser, frequency combs at $\\lambda\\sim 4.4\\ \\mathrm{\\mu m}$ (i.e. 2270cm$^{-1}$) are generated, that span over 600nm (i.e. 300cm$^{-1}$) in bandwidth, with a mode spacing of 14.3GHz (0.5cm$^{-1}$), corresponding t...

  4. Coherence and Incoherence in an Optical Comb

    NASA Astrophysics Data System (ADS)

    Viktorov, Evgeny A.; Habruseva, Tatiana; Hegarty, Stephen P.; Huyet, Guillaume; Kelleher, Bryan

    2014-06-01

    We demonstrate a coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. This is experimentally achieved by means of optical linewidth, radio frequency spectrum, and optical spectrum measurements and confirmed numerically by a delay-differential equation model showing excellent agreement with the experiment. We interpret the state as a chimera state.

  5. Pellet Fueling Technology Development S. K. Combs

    E-print Network

    Pellet Fueling Technology Development S. K. Combs Fusion Energy Division, Oak Ridge National Laboratory Peer Review: Plasma Fueling Program Oak Ridge National Laboratory Oak Ridge, Tennessee May 10, 2000 1 #12;SKC Peer Review: Plasma Fueling Program 5/10/00 Main Objective of Plasma Fueling R&D Has

  6. Time sequence photography of Roosters Comb

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  7. High temperature and composition induced phase transitions in LiZnV?-xAsxO? phenacites: Crystal structure and Raman spectroscopy studies.

    PubMed

    Manoun, B; Azrour, M; Lazor, P; Azdouz, M; Bih, L; Benmokhtar, S; Essehli, R; El Ammari, L

    2015-12-01

    In this work, using techniques of X-ray diffraction and Raman spectroscopy, we report the composition and high-temperature induced phase transition in the system LiZnV1-xAsxO4 (0?x?1). Both techniques showed that the increase of arsenic amount induced a structural transition from R-3 LiZnVO4 type to LiZnAsO4 type belonging to R3 space group, the transition occurring between x=0.7 and x=0.8. Furthermore, increasing temperature for the compositions (0.8?x?1) manifests a transition from the LiZnAsO4 structural type with R3 space group to the R-3 LiZnVO4 structural type. For this series, the transition from the space group R3 to the centro-symmetric space group R-3 shows considerable changes in the compositional and temperature dependencies of the bands: spectral positions of all the observed Raman bands exhibit shifts linearly proportional to the temperature increase, with points of shift-rate changes revealing a symmetry change. The Raman-spectra based temperature-composition phase diagram confirms the results obtained using the method of Rietveld refinements, thus showing the R-3 to R3 transition occurring between x=0.7 and 0.8. PMID:26186614

  8. Stephen C. Pratt Decentralized control of drone comb construction in honey bee colonies

    E-print Network

    Pratt, Stephen

    Stephen C. Pratt Decentralized control of drone comb construction in honey bee colonies Received with two types of comb distinguished by cell size: large cells for rearing males (drone comb) and small of drone comb in a nest is governed by negative feedback from drone comb already constructed. This feedback

  9. Conjugate FabryPerot cavity pair for improved astro-comb accuracy

    E-print Network

    Walsworth, Ronald L.

    (>10 GHz) optical frequency combs referenced to atomic clocks and optimized for wavelength calibra-year observation periods. An astro-comb consists of an octave-spanning laser frequency comb ("source comb length, that improves the performance of astro-combs containing nonlinear elements such as photonic

  10. Operation of a broadband visible-wavelength astro-comb with a high-resolution

    E-print Network

    Walsworth, Ronald L.

    frequency comb [12] stabilized to an atomic clock (the "source comb"), (ii) a nonlinear element to shift be achievable using an astro-comb, a laser frequency comb optimized for astrophysical spectrograph wavelengthOperation of a broadband visible-wavelength astro-comb with a high-resolution astrophysical

  11. Broadband 2.5-6?m frequency comb source for dual-comb molecular spectroscopy

    NASA Astrophysics Data System (ADS)

    Smolski, V. O.; Vodopyanov, K. L.

    2015-02-01

    Absorption spectroscopy with frequency combs in the molecular fingerprint portion of the spectrum (2-10 ?m) has great potential for trace molecular detection and in particular for such applications as monitoring of the atmosphere and medical breath analysis. Especially attractive is dual-comb Fourier transform spectroscopy where full advantage is taken of temporal and spatial coherence of frequency combs as well as of their broadband nature. The promise is high speed, broad spectral coverage, superior sensitivity, high spectral resolution, and the possibility of absolute frequency calibration of molecular resonances. Here we report a system suitable for performing dual-comb spectroscopy in the range of 2.5-6 ?m and beyond. Broadband mid-IR frequency combs are obtained via a doubly-resonant near-degenerate synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned GaAs (OP-GaAs) pumped by a femtosecond Tm-fiber laser at 2-?m wavelength. Low pump threshold (7 mW), high coherence, and broad instantaneous spectral coverage make this system extremely promising for spectroscopic studies.

  12. Tunable optical correlator using an optical frequency comb and a nonlinear multiplexer

    E-print Network

    Touch, Joe

    Tunable optical correlator using an optical frequency comb and a nonlinear multiplexer Morteza frequency comb to generate the coherent signals and multiplex them coherently in a single PPLN waveguide, "Comb-Based Radio-Frequency Photonic Filters with Rapid Tunab

  13. Coherent data transmission with microresonator Kerr frequency combs

    E-print Network

    Pfeifle, Joerg; Wegner, Daniel; Brasch, Victor; Herr, Tobias; Hartinger, Klaus; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J; Koos, Christian

    2013-01-01

    Optical frequency combs enable coherent data transmission on hundreds of wavelength channels and have the potential to revolutionize terabit communications. Generation of Kerr combs in nonlinear integrated microcavities represents a particularly promising option enabling line spacings of tens of GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr combs may exhibit strong phase noise and multiplet spectral lines, and this has made high-speed data transmission impossible up to now. Recent work has shown that systematic adjustment of pump conditions allows generating low phase-noise Kerr combs with singlet spectral lines. Here, by employing an integrated Si3N4 microresonator, we demonstrate that Kerr combs are suited for coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the optical source. In our experiment, we encode a data stream of 392 Gbit/s on subsequent lines of a Kerr comb using quadrature phase shift keying (...

  14. Laser frequency combs for astronomical observations

    E-print Network

    Tilo Steinmetz; Tobias Wilken; Constanza Araujo-Hauck; Ronald Holzwarth; Theodor W. Hänsch; Luca Pasquini; Antonio Manescau; Sandro D'Odorico; Michael T. Murphy; Thomas Kentischer; Wolfgang Schmidt; Thomas Udem

    2008-09-09

    A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at about 1.5 micrometers - beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.

  15. Laser frequency combs for astronomical observations.

    PubMed

    Steinmetz, Tilo; Wilken, Tobias; Araujo-Hauck, Constanza; Holzwarth, Ronald; Hänsch, Theodor W; Pasquini, Luca; Manescau, Antonio; D'Odorico, Sandro; Murphy, Michael T; Kentischer, Thomas; Schmidt, Wolfgang; Udem, Thomas

    2008-09-01

    A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of approximately 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrated the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at approximately 1.5 micrometers-beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration. PMID:18772434

  16. Conformation of adsorbed comb copolymer dispersants.

    PubMed

    Flatt, Robert J; Schober, Irene; Raphael, Elie; Plassard, Cédric; Lesniewska, Eric

    2009-01-20

    Comb copolymers with an adsorbing backbone and nonadsorbing side chains can be very effective dispersants, particularly when a high ionic strength strongly penalizes electrostatic stabilization. For this reason, they have become essential components of concrete over the past decade. This article examines the steric hindrance characteristics of such polymers through the use of atomic force microscopy (AFM) on calcium silicate hydrate, the main hydration product of Portland cement. It is found that solution and surface properties (hydrodynamic radius, radius of gyration, surface coverage, steric layer thickness) and force-distance curves obtained during AFM measurements can be well described by a scaling approach derived in this paper. This represents the first real quantitative step in relating these properties directly to the molecular structure of such comb copolymer dispersants. PMID:19086886

  17. Sex ratios 

    E-print Network

    West, Stuart A; Reece, S E; Sheldon, Ben C

    2002-01-01

    Sex ratio theory attempts to explain variation at all levels (species, population, individual, brood) in the proportion of offspring that are male (the sex ratio). In many cases this work has been extremely successful, ...

  18. Phone Sex 

    E-print Network

    Flamingo

    1995-01-01

    is that it lacks obvious sex chromosomes and possesses a poorly understood monogenic sex determination system in which females produce all male or female clutches. This species also engages in facultative predation on other blow fly species, but the proximate...

  19. Coherence and incoherence in an optical comb.

    PubMed

    Viktorov, Evgeny A; Habruseva, Tatiana; Hegarty, Stephen P; Huyet, Guillaume; Kelleher, Bryan

    2014-06-01

    We demonstrate a coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. This is experimentally achieved by means of optical linewidth, radio frequency spectrum, and optical spectrum measurements and confirmed numerically by a delay-differential equation model showing excellent agreement with the experiment. We interpret the state as a chimera state. PMID:24949771

  20. Intrinsic linewidth of quantum cascade laser frequency combs

    E-print Network

    Cappelli, Francesco; Riedi, Sabine; Faist, Jerome

    2015-01-01

    The frequency noise power spectral density of a free-running quantum cascade laser frequency comb is investigated. A plateau is observed at high frequencies, attributed to the quantum noise limit set by the Schawlow-Townes formula for the total laser power on all comb lines. In our experiment, a linewidth of 292 Hz is measured for a total power of 25 mW. This result proves that the four-wave mixing process, responsible for the comb operation, effectively correlates the quantum noise of the individual comb lines.

  1. Universality of comb structures in strong-field QED

    E-print Network

    Krajewska, Katarzyna

    2013-01-01

    We demonstrate a new mechanism for coherent comb generation in both radiation and matter domains, which is by using strong-field quantum electrodynamics processes. Specifically, we demonstrate this for nonlinear Compton scattering which has the potential to generate frequency combs extending towards the $\\gamma$-ray spectral region as well as combs of ultra-relativistic electrons extending towards the MeV regime. Moreover, we show that coherent energy combs of positrons (or electrons) emerge in laser-induced pair creation processes such as the Breit-Wheeler process, proving the universality of the proposed mechanism.

  2. Universality of comb structures in strong-field QED

    E-print Network

    Katarzyna Krajewska; Jerzy Z. Kaminski

    2013-07-20

    We demonstrate a new mechanism for coherent comb generation in both radiation and matter domains, which is by using strong-field quantum electrodynamics processes. Specifically, we demonstrate this for nonlinear Compton scattering which has the potential to generate frequency combs extending towards the $\\gamma$-ray spectral region as well as combs of ultra-relativistic electrons extending towards the MeV regime. Moreover, we show that coherent energy combs of positrons (or electrons) emerge in laser-induced pair creation processes such as the Breit-Wheeler process, proving the universality of the proposed mechanism.

  3. Optimization of filtering schemes for broadband astro-combs.

    PubMed

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

    2012-10-22

    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 <1 cm/s RV calibration error with >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. PMID:23187265

  4. A microresonator frequency comb optical clock

    E-print Network

    Papp, Scott B; DelHaye, Pascal; Quinlan, Franklyn; Lee, Hansuek; Vahala, Kerry J; Diddams, Scott A

    2013-01-01

    Optical-frequency combs enable measurement precision at the 20th digit, and accuracy entirely commensurate with their reference oscillator. A new direction in experiments is the creation of ultracompact frequency combs by way of nonlinear parametric optics in microresonators. We refer to these as microcombs, and here we report a silicon-chip-based microcomb optical clock that phase-coherently converts an optical-frequency reference to a microwave signal. A low-noise comb spectrum with 25 THz span is generated with a 2 mm diameter silica disk and broadening in nonlinear fiber. This spectrum is stabilized to rubidium frequency references separated by 3.5 THz by controlling two teeth 108 modes apart. The optical clocks output is the electronically countable 33 GHz microcomb line spacing, which features an absolute stability better than the rubidium transitions by the expected factor of 108. Our work demonstrates the comprehensive set of tools needed for interfacing microcombs to state-of-the-art optical clocks.

  5. Direct Frequency Comb Spectroscopy and High-Resolution Coherent Control

    E-print Network

    Jin, Deborah

    :Sapphire laser, creat- ing a broad-bandwidth optical frequency comb. By referencing the optical comb directly in 87 Rb. To reduce Doppler broadening the atoms were laser cooled in a magneto-optical trap. We present-broadening, and incoherent optical pumping. After careful study and suppression of these systematic error sources, we

  6. Generation of Kerr Frequency Combs in Resonators with Normal GVD

    E-print Network

    Matsko, Andrey B; Maleki, Lute

    2011-01-01

    We show via numerical simulation that Kerr frequency combs can be generated in a nonlinear resonator characterized with normal group velocity dispersion (GVD). We find the spectral shape of the comb and temporal envelope of the corresponding optical pulses formed in the resonator.

  7. On timing jitter of mode locked Kerr frequency combs.

    PubMed

    Matsko, Andrey B; Maleki, Lute

    2013-11-18

    We study fundamental timing jitter in repetition rate of a mode locked Kerr frequency comb generated in an externally pumped nonlinear ring resonator. We show that the increase in the integrated power of the comb harmonics, and the corresponding decrease of the duration of the associated pulse, results in the increase of low frequency noise, and a decrease in high frequency noise. PMID:24514400

  8. Normal group-velocity dispersion Kerr frequency comb.

    PubMed

    Matsko, A B; Savchenkov, A A; Maleki, L

    2012-01-01

    We show via numerical simulation that Kerr frequency combs can be generated in a nonlinear resonator characterized with normal group-velocity dispersion. We find the spectral shape of the comb and temporal envelope of the corresponding optical pulses formed in the resonator. PMID:22212785

  9. Coherent Raman dual-comb spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Ideguchi, Takuro; Holzner, Simon; Bernhardt, Birgitta; Guelachvili, Guy; Hänsch, Theodor W.; Picqué, Nathalie

    2014-11-01

    The invention of the optical frequency comb technique has revolutionized the field of precision spectroscopy, providing a way to measure the absolute frequency of any optical transition. Since, frequency combs have become common equipment for frequency metrology. In the last decade, novel applications for the optical frequency comb have been demonstrated beyond its original purpose. Broadband molecular spectroscopy is one of those. One such technique of molecular spectroscopy with frequency combs, dual-comb Fourier transform spectroscopy provides short measurement times with resolution and accuracy. Two laser frequency combs with slightly different repetition frequencies generate pairs of pulses with a linearly-scanned delay between pulses in a pair. The system without moving parts mimics a fast scanning Fourier transform interferometer. The measurement speed may be several orders of magnitude faster than that of a Michelson-based Fourier transform spectrometer, which opens up new opportunities for broadband molecular spectroscopy. Recently, dual-comb spectroscopy has been extended to nonlinear phenomena. A broadband Raman spectrum of molecular fingerprints may be measured within a few tens of microseconds with coherent Raman dual-comb spectroscopy. Raster scanning the sample leads to hyperspectral images. This rapid and broadband label-free vibrational spectroscopy and imaging technique might provide new diagnostic methods in a variety of scientific and industrial fields.

  10. Dual-Comb Spectroscopy in the Open Air

    NASA Astrophysics Data System (ADS)

    Rieker, Greg B.; Klose, Andrew; Diddams, Scott; Coddington, Ian; Giorgetta, Fabrizio; Sinclair, Laura; Baumann, Esther; Truong, Gar-Wing; Ycas, Gabriel; Swann, William C.; Newbury, Nathan R.

    2015-06-01

    Dual-comb spectroscopy is arguably the natural successor to FTIR. Based on the interference between two frequency combs, this technique can record broadband spectra with a resolution better than 0.0003 wn. Like FTIR, dual-comb spectroscopy measures an entire spectrum simultaneously, allowing for suppression of systematic errors related to temporal dynamics of the sample. Unlike FTIR it records the entire spectrum with virtually no instrument lineshape or error in the frequency axis. The lack of moving parts in dual-comb spectroscopy means that spectra can be recorded in milliseconds to microseconds with the desired signal-to-noise being the only real constrain on the minimum recording time. Finally the high spacial beam quality of the frequency combs allows for increased sensitivity through long interaction paths either in free-space, multi-pass cells or enhancement cavities. This talk will explore the recent use of dual-comb spectroscopy in the near-infrared to measure atmospheric carbon dioxide, methane and water concentrations over a 2-km outdoor open-air path. Due to many of the strengths just mentioned, precisions of <1 ppm for CO_2 and <3 ppb for CH_4 in 5 min are achieved making this system very attractive for carbon monitoring at length scales relevant to carbon transport models. Additionally this presentation will address recent work on robust, compact, and portable dual-comb spectrometers as well as dual-comb spectroscopy further into the IR.

  11. Comparative analysis of spectral coherence in microresonator frequency combs.

    PubMed

    Torres-Company, Victor; Castelló-Lurbe, David; Silvestre, Enrique

    2014-02-24

    Microresonator combs exploit parametric oscillation and nonlinear mixing in an ultrahigh-Q cavity. This new comb generator offers unique potential for chip integration and access to high repetition rates. However, time-domain studies reveal an intricate spectral coherence behavior in this type of platform. In particular, coherent, partially coherent or incoherent combs have been observed using the same microresonator under different pumping conditions. In this work, we provide a numerical analysis of the coherence dynamics that supports the above experimental findings and verify particular design rules to achieve spectrally coherent microresonator combs. A particular emphasis is placed in understanding the differences between so-called Type I and Type II combs. PMID:24663786

  12. A Silicon-Based Monolithic Optical Frequency Comb Source

    E-print Network

    Foster, Mark A; Kuzucu, Onur; Saha, Kasturi; Lipson, Michal; Gaeta, Alexander L

    2011-01-01

    Recently developed techniques for generating precisely equidistant optical frequencies over broad wavelength ranges are revolutionizing precision physical measurement [1-3]. These frequency "combs" are produced primarily using relatively large, ultrafast laser systems. However, recent research has shown that broad-bandwidth combs can be produced using highly-nonlinear interactions in microresonator optical parametric oscillators [4-11]. Such devices not only offer the potential for developing extremely compact optical atomic clocks but are also promising for astronomical spectroscopy [12-14], ultrashort pulse shaping [15], and ultrahigh-speed communications systems. Here we demonstrate the generation of broad-bandwidth optical frequency combs from a CMOS-compatible integrated microresonator [16,17], which is a fully-monolithic and sealed chip-scale device making it insensitive to the surrounding environment. We characterize the comb quality using a novel self-referencing method and verify that the comb line f...

  13. Spectral noise correlations of an ultrafast frequency comb.

    PubMed

    Schmeissner, Roman; Roslund, Jonathan; Fabre, Claude; Treps, Nicolas

    2014-12-31

    Cavity-based noise detection schemes are combined with ultrafast pulse shaping as a means to diagnose the spectral correlations of both the amplitude and phase noise of an ultrafast frequency comb. The comb is divided into ten spectral regions, and the distribution of noise as well as the correlations between all pairs of spectral regions are measured against the quantum limit. These correlations are then represented in the form of classical noise matrices, which furnish a complete description of the underlying comb dynamics. Their eigendecomposition reveals a set of theoretically predicted, decoupled noise modes that govern the dynamics of the comb. These matrices also contain the information necessary to deduce macroscopic noise properties of the comb. PMID:25615340

  14. Feshbach resonances in Kerr frequency combs

    NASA Astrophysics Data System (ADS)

    Matsko, Andrey B.; Maleki, Lute

    2015-01-01

    We show that both the power and repetition rate of a frequency comb generated in a nonlinear ring resonator, pumped with continuous-wave (cw) coherent light, are modulated. The modulation is brought about by the interaction of the cw background with optical pulses excited in the resonator, and occurs in resonators with nonzero high-order chromatic dispersion and wavelength-dependent quality factor. The modulation frequency corresponds to the detuning of the pump frequency from the eigenfrequency of the pumped mode in the resonator.

  15. Efficiency optimization for atomic frequency comb storage

    SciTech Connect

    Bonarota, M.; Ruggiero, J.; Le Goueet, J.-L.; Chaneliere, T.

    2010-03-15

    We study the efficiency of the atomic frequency comb storage protocol. We show that for a given optical depth, the preparation procedure can be optimize to significantly improve the retrieval. Our prediction is well supported by the experimental implementation of the protocol in a Tm{sup 3+}:YAG crystal. We observe a net gain in efficiency from 10 to 17% by applying the optimized preparation procedure. In the perspective of high bandwidth storage, we investigate the protocol under different magnetic fields. We analyze the effect of the Zeeman and superhyperfine interaction.

  16. Toward a Broadband Astro-comb: Effects of Nonlinear Spectral Broadening in Optical Fibers

    E-print Network

    Walsworth, Ronald L.

    Toward a Broadband Astro-comb: Effects of Nonlinear Spectral Broadening in Optical Fibers Guoqing astro- comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber frequency combs," Mon. Not. R. Astron. Soc. 380, 839 (2007). 2. C.-H. Li, A. J. Benedick, P. Fendel, A. G

  17. Print this article Close Astro-comb enables search for Earth-like planet

    E-print Network

    Walsworth, Ronald L.

    Print this article Close Astro-comb enables search for Earth-like planet June 5, 2008--A new-mass planet in an Earth-like orbit (see figure, #12;above). The astro-comb is a filtered laser comb linked, or source comb. To see the tiny spectral line shifts like those indicating Earth-like planets, the source

  18. Sex Offenders.

    ERIC Educational Resources Information Center

    Hayes, Susan

    1991-01-01

    This paper on the problem of sex offending among individuals with intellectual disabilities examines the incidence of this problem, characteristics of intellectually disabled sex offenders, determination of whether the behavior is a paraphilia or functional age-related behavior, and treatment options, with emphasis on the situation in New South…

  19. Coherent terabit communications with microresonator Kerr frequency combs

    PubMed Central

    Pfeifle, Joerg; Brasch, Victor; Lauermann, Matthias; Yu, Yimin; Wegner, Daniel; Herr, Tobias; Hartinger, Klaus; Schindler, Philipp; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Weimann, Claudius; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J.; Koos, Christian

    2014-01-01

    Optical frequency combs have the potential to revolutionize terabit communications1. Generation of Kerr combs in nonlinear microresonators2 represents a particularly promising option3 enabling line spacings of tens of GHz. However, such combs may exhibit strong phase noise4-6, which has made high-speed data transmission impossible up to now. Here we demonstrate that systematic adjustment of pump conditions for low phase noise4,7-9 enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit/s on a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment demonstrates feedback-stabilization of the comb and transmission of a 1.44 Tbit/s data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive solution towards chip-scale terabit/s transceivers. PMID:24860615

  20. Coherent terabit communications with microresonator Kerr frequency combs.

    PubMed

    Pfeifle, Joerg; Brasch, Victor; Lauermann, Matthias; Yu, Yimin; Wegner, Daniel; Herr, Tobias; Hartinger, Klaus; Schindler, Philipp; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Weimann, Claudius; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J; Koos, Christian

    2014-05-01

    Optical frequency combs have the potential to revolutionize terabit communications(1). Generation of Kerr combs in nonlinear microresonators(2) represents a particularly promising option(3) enabling line spacings of tens of GHz. However, such combs may exhibit strong phase noise(4-6), which has made high-speed data transmission impossible up to now. Here we demonstrate that systematic adjustment of pump conditions for low phase noise(4,7-9) enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit/s on a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment demonstrates feedback-stabilization of the comb and transmission of a 1.44 Tbit/s data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive solution towards chip-scale terabit/s transceivers. PMID:24860615

  1. XUV frequency combs based on intracavity high harmonic generation

    NASA Astrophysics Data System (ADS)

    Jones, R. Jason

    2014-05-01

    Intracavity high harmonic generation utilizing femtosecond enhancement cavities (fsEC's) has been established as an efficient route for the generation of femtosecond frequency combs in the vacuum-ultraviolet (VUV) to the extreme-ultraviolet (XUV) spectral regions. Such VUV/XUV frequency combs enable precision spectroscopy of atomic and potentially molecular spectra in an otherwise difficult to access spectral region. An improved understanding of the intracavity ionization dynamics that currently limit pulse enhancement has enabled a new generation of XUV frequency comb sources with significantly higher powers, at the >10 microwatt level per harmonic order extending below 50nm. We have developed a novel time-resolved pump-probe measurement technique to monitor and characterize the intracavity ionization dynamics by utilizing the sensitive response of the fsEC resonance itself to plasma induced nonlinear phase shifts. In recent work, we have developed a high power dual-frequency comb system based on Yb-fiber laser technology. The two phase-coherent frequency combs can be up-converted to the VUV/XUV using the fsEC. Dual-comb spectroscopy has already been established as a powerful spectroscopic method in the infrared. It's extension to the VUV/XUV spectral region will enable robust and high precision direct frequency comb spectroscopy of complex atomic and molecular structure in this spectral region.

  2. Coherent terabit communications with microresonator Kerr frequency combs

    NASA Astrophysics Data System (ADS)

    Pfeifle, Joerg; Brasch, Victor; Lauermann, Matthias; Yu, Yimin; Wegner, Daniel; Herr, Tobias; Hartinger, Klaus; Schindler, Philipp; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Weimann, Claudius; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J.; Koos, Christian

    2014-05-01

    Optical frequency combs have the potential to revolutionize terabit communications. The generation of Kerr combs in nonlinear microresonators is particularly promising, enabling line spacings of tens of gigahertz. However, such combs may exhibit strong phase noise, which has made high-speed data transmission impossible up to now. Here, we demonstrate that systematic adjustment of the pump conditions for low phase noise enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit s-1 on a Kerr comb using quadrature phase-shift keying and 16-state quadrature amplitude modulation. A second experiment demonstrates feedback stabilization of the comb and transmission of a 1.44 Tbit s-1 data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive route towards chip-scale terabit-per-second transceivers.

  3. A phase-stabilized carbon nanotube fiber laser frequency comb.

    PubMed

    Lim, Jinkang; Knabe, Kevin; Tillman, Karl A; Neely, William; Wang, Yishan; Amezcua-Correa, Rodrigo; Couny, François; Light, Philip S; Benabid, Fetah; Knight, Jonathan C; Corwin, Kristan L; Nicholson, Jeffrey W; Washburn, Brian R

    2009-08-01

    A frequency comb generated by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber is phase-stabilized for the first time. Measurements of the in-loop phase noise show an integrated phase error on the carrier envelope offset frequency of 0.35 radians. The carbon nanotube fiber laser comb is compared with a CW laser near 1533 nm stabilized to the nu(1) + nu(3) overtone transition in an acetylene-filled kagome photonic crystal fiber reference, while the CW laser is simultaneously compared to another frequency comb based on a Cr:Forsterite laser. These measurements demonstrate that the stability of a GPS-disciplined Rb clock is transferred to the comb, resulting in an upper limit on the locked comb's frequency instability of 1.2 x 10(-11) in 1 s, and a relative instability of <3 x 10(-12) in 1 s. The carbon nanotube laser frequency comb offers much promise as a robust and inexpensive all-fiber frequency comb with potential for scaling to higher repetition frequencies. PMID:19654821

  4. Dual-comb spectroscopy using frequency-doubled combs around 775 nm.

    PubMed

    Potvin, Simon; Genest, Jérôme

    2013-12-16

    Two frequency-doubled combs are generated by nonlinear frequency conversion to realize spectroscopic measurements around 775 nm. Frequency-doubled interferograms are corrected in real-time by monitoring the relative instabilities between the combs at their fundamental frequency. Rubidium absorption lines are used to demonstrate the technique's accuracy and serve as absolute references to calibrate the frequency grid of computed spectra. The method allows frequency-doubled interferograms to be averaged without distortion during long periods of time. The calibrated frequency grid is validated by the measurement of the oxygen A-band. Moreover, the measurement analysis of the acetylene ?(1) + 3?(3) overtone band has revealed some discrepancies with previous publications. PMID:24514646

  5. Nonlinear conversion efficiency in Kerr frequency comb generation.

    PubMed

    Bao, Changjing; Zhang, Lin; Matsko, Andrey; Yan, Yan; Zhao, Zhe; Xie, Guodong; Agarwal, Anuradha M; Kimerling, Lionel C; Michel, Jurgen; Maleki, Lute; Willner, Alan E

    2014-11-01

    We analytically and numerically investigate the nonlinear conversion efficiency in ring microresonator-based mode-locked frequency combs under different dispersion conditions. Efficiency is defined as the ratio of the average round trip energy values for the generated pulse(s) to the input pump light. We find that the efficiency degrades with growth of the comb spectral width and is inversely proportional to the number of comb lines. It depends on the cold-cavity properties of a microresonator only and can be improved by increasing the coupling coefficient. Also, it can be increased in the multi-soliton state. PMID:25361295

  6. A Genomic Duplication is Associated with Ectopic Eomesodermin Expression in the Embryonic Chicken Comb and Two Duplex-comb Phenotypes

    PubMed Central

    Dorshorst, Ben; Rubin, Carl-Johan; Ashwell, Chris; Gourichon, David; Tixier-Boichard, Michèle; Hallböök, Finn; Andersson, Leif

    2015-01-01

    Duplex-comb (D) is one of three major loci affecting comb morphology in the domestic chicken. Here we show that the two Duplex-comb alleles, V-shaped (D*V) and Buttercup (D*C), are both associated with a 20 Kb tandem duplication containing several conserved putative regulatory elements located 200 Kb upstream of the eomesodermin gene (EOMES). EOMES is a T-box transcription factor that is involved in mesoderm specification during gastrulation. In D*V and D*C chicken embryos we find that EOMES is ectopically expressed in the ectoderm of the comb-developing region as compared to wild-type embryos. The confinement of the ectopic expression of EOMES to the ectoderm is in stark contrast to the causal mechanisms underlying the two other major comb loci in the chicken (Rose-comb and Pea-comb) in which the transcription factors MNR2 and SOX5 are ectopically expressed strictly in the mesenchyme. Interestingly, the causal mutations of all three major comb loci in the chicken are now known to be composed of large-scale structural genomic variants that each result in ectopic expression of transcription factors. The Duplex-comb locus also illustrates the evolution of alleles in domestic animals, which means that alleles evolve by the accumulation of two or more consecutive mutations affecting the phenotype. We do not yet know whether the V-shaped or Buttercup allele correspond to the second mutation that occurred on the haplotype of the original duplication event. PMID:25789773

  7. A genomic duplication is associated with ectopic eomesodermin expression in the embryonic chicken comb and two duplex-comb phenotypes.

    PubMed

    Dorshorst, Ben; Harun-Or-Rashid, Mohammad; Bagherpoor, Alireza Jian; Rubin, Carl-Johan; Ashwell, Chris; Gourichon, David; Tixier-Boichard, Michèle; Hallböök, Finn; Andersson, Leif

    2015-03-01

    Duplex-comb (D) is one of three major loci affecting comb morphology in the domestic chicken. Here we show that the two Duplex-comb alleles, V-shaped (D*V) and Buttercup (D*C), are both associated with a 20 Kb tandem duplication containing several conserved putative regulatory elements located 200 Kb upstream of the eomesodermin gene (EOMES). EOMES is a T-box transcription factor that is involved in mesoderm specification during gastrulation. In D*V and D*C chicken embryos we find that EOMES is ectopically expressed in the ectoderm of the comb-developing region as compared to wild-type embryos. The confinement of the ectopic expression of EOMES to the ectoderm is in stark contrast to the causal mechanisms underlying the two other major comb loci in the chicken (Rose-comb and Pea-comb) in which the transcription factors MNR2 and SOX5 are ectopically expressed strictly in the mesenchyme. Interestingly, the causal mutations of all three major comb loci in the chicken are now known to be composed of large-scale structural genomic variants that each result in ectopic expression of transcription factors. The Duplex-comb locus also illustrates the evolution of alleles in domestic animals, which means that alleles evolve by the accumulation of two or more consecutive mutations affecting the phenotype. We do not yet know whether the V-shaped or Buttercup allele correspond to the second mutation that occurred on the haplotype of the original duplication event. PMID:25789773

  8. Parentage and relatedness in polyandrous comb-crested jacanas using ISSRs

    USGS Publications Warehouse

    Haig, Susan M.; Mace, Terrence R.; Mullins, Thomas D.

    2003-01-01

    In this article we present the first analysis of parentage and relatedness in a natural vertebrate population, using Intersimple Sequence Repeat (ISSR) markers. Thus, 28 ISSR markers were used in a study of a sex-role reversed, simultaneously polyandrous shorebird from northeastern Australia, the comb-crested jacana (Irediparra gallinacea). Assessment of parentage was based on comparison of field observations, novel bands, individual-specific bands found in 7/9 males and 4/6 females, and a 99% CI exclusion criteria. Integrating results from these approaches resulted in confirmation of paternity in all 36 chicks. In only one case (2.8% of chicks) was a co-mate assigned paternity. Thus, comb-crested jacanas appear to be genetically monogamous. These results showed resemblance to sequentially polyandrous birds but differed from the simultaneously polyandrous wattled jacana ( Jacana jacana; Emlen et al. 1998). A significant relationship between relatedness and ISSR similarity resulted in recognition that 14/15 adults sampled may be related to at least one other adult by 0.25 or more. Lack of dispersal may be explained by physical limitations and adequate regional habitat. ISSRs proved to be simple and helpful in resolving these issues.

  9. All-optically stabilized frequency comb

    NASA Astrophysics Data System (ADS)

    Okubo, Sho; Gunji, Kenta; Onae, Atsushi; Schramm, Malte; Nakamura, Keisuke; Hong, Feng-Lei; Hattori, Toshiaki; Hosaka, Kazumoto; Inaba, Hajime

    2015-12-01

    We present an all-optically stabilized, erbium-doped mode-locked fiber laser with an optically pumped ytterbium-doped fiber. The mode-locked fiber laser has two frequency-control actuators that are pump laser powers for erbium-doped and ytterbium-doped fibers. We investigate the frequency-control characteristics of the mode-locked laser and find that the fixed points for the two actuators are sufficiently apart from each other, realizing the simultaneous phase locking of the repetition and carrier envelope offset frequencies. We describe a long-term frequency measurement of an acetylene-stabilized laser at 1542 nm using an all-optically stabilized frequency comb.

  10. Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design

    PubMed Central

    Troncoso Romero, David Ernesto

    2014-01-01

    Comb filters are a class of low-complexity filters especially useful for multistage decimation processes. However, the magnitude response of comb filters presents a droop in the passband region and low stopband attenuation, which is undesirable in many applications. In this work, it is shown that, for stringent magnitude specifications, sharpening compensated comb filters requires a lower-degree sharpening polynomial compared to sharpening comb filters without compensation, resulting in a solution with lower computational complexity. Using a simple three-addition compensator and an optimization-based derivation of sharpening polynomials, we introduce an effective low-complexity filtering scheme. Design examples are presented in order to show the performance improvement in terms of passband distortion and selectivity compared to other methods based on the traditional Kaiser-Hamming sharpening and the Chebyshev sharpening techniques recently introduced in the literature. PMID:24578674

  11. High density terahertz frequency comb produced by coherent synchrotron radiation.

    PubMed

    Tammaro, S; Pirali, O; Roy, P; Lampin, J-F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G

    2015-01-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1?THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846?kHz, a linewidth of about 200?Hz, a fractional precision of about 2 × 10(-10) and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile. PMID:26190043

  12. Spectro-temporal dynamics of Kerr combs with parametric seeding.

    PubMed

    Lin, Guoping; Martinenghi, Romain; Diallo, Souleymane; Saleh, Khaldoun; Coillet, Aurélien; Chembo, Yanne K

    2015-03-20

    We report a joint theoretical and experimental investigation of the parametric seeding of a primary Kerr optical frequency comb. Electro-optic modulation sidebands matching multiple free-spectral ranges of an ultrahigh-Q millimeter-size magnesium fluoride disk resonator are used as seed signals. These seed signals interact through four-wave mixing with the spectral components of a stable primary comb and give rise to complex spectro-temporal patterns. We show that the new frequency combs feature multiscale frequency spacing, with major frequency gaps in the order of a few hundred gigahertz, and minor frequency spacing in the order of a few tens of gigahertz. The experimental results are in agreement with numerical simulations using the Lugiato-Lefever equation. We expect such versatile and coherent optical frequency combs to have potential applications in optical communications systems where frequency management assigns predefined spectral windows at the emitter stage. PMID:25968529

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

    PubMed

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

    2015-06-01

    This paper evaluates the opportunities for using materials other than silica for optical frequency comb generation in whispering gallery mode microsphere resonators. Different materials are shown to satisfy the requirement of dispersion compensation in interesting spectral regions such as the visible or mid-infrared and for smaller microspheres. This paper also analyses the prospects of comb generation in microspheres within aqueous solution for potential use in applications such as biosensing. It is predicted that to achieve comb generation with microspheres in aqueous solution the visible low-loss wavelength window of water needs to be exploited. This is because efficient comb generation necessitates ultra-high Q-factors, which are only possible for cavities with low absorption of the evanescent field outside the cavity. This paper explores the figure of merit for nonlinear interaction efficiency and the potential for dispersion compensation at unique wavelengths for a host of microsphere materials and dimensions and in different surroundings. PMID:26072837

  14. Raman-induced Kerr-effect dual-comb spectroscopy.

    PubMed

    Ideguchi, T; Bernhardt, B; Guelachvili, G; Hänsch, T W; Picqué, N

    2012-11-01

    We report on the first (to our knowledge) demonstration of nonlinear dual-frequency-comb spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy, the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally narrow pump is imprinted onto the femtosecond laser frequency comb probe spectrum. The birefringence signal induced by the nonlinear interaction of these beams and the sample is heterodyned against a frequency comb local oscillator with a repetition frequency slightly different from that of the comb probe. Such time-domain interference provides multiplex access to the phase and amplitude Raman spectra over a broad spectral bandwidth within a short measurement time. PMID:23114342

  15. Universality of comb structures in strong-field quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Krajewska, Katarzyna; Kami?ski, Jerzy

    2015-05-01

    We demonstrate a new mechanism for coherent comb generation in both radiation and matter domains, which is by using strong-field quantum electrodynamics processes. Specifically, we demonstrate this for nonlinear Compton scattering which has the potential to generate frequency combs extending towards the ?-ray spectral region and combs of ultra-relativistic electrons extending towards the MeV regime. Moreover, we show that coherent energy combs of positrons (electrons) emerge in laser-induced pair creation processes such as the Breit-Wheeler process, proving the universality of the proposed mechanism. We acknowledge the support from the Kosciuszko Foundation (KK) and from the Polish National Science Center (NCN), under Grant No. 2012/05/B/ST2/02547 (JZK).

  16. Frequency stabilisation of femtosecond frequency combs with a reference laser

    SciTech Connect

    Bagayev, S N; Pivtsov, V S; Zheltikov, Aleksei M

    2002-04-30

    A solution to the key problem of femtosecond metrology - elimination of the frequency offset related to the intracavity dispersion of a femtosecond laser - is proposed. The proposed method involves stabilisation of the intermode interval between equidistant spectral components in a frequency comb produced by a mode-locked femtosecond laser by phase-locking the frequency difference between a pair of discrete spectral components in this comb to the frequency of a reference laser. An introduction of a nonlinear-optical crystal for frequency doubling into the scheme for frequency-comb stabilisation allows the frequency offset related to the intracavity dispersion of the femtosecond laser to be eliminated, thus suggesting the way for absolute stabilisation of frequency combs generated by femtosecond mode-locked lasers. Radiation of a reference laser with such an approach plays the role of an anchor in the femtosecond clockwork. (control of laser radiation parameters)

  17. Raman-induced Kerr-effect dual-comb spectroscopy

    E-print Network

    Ideguchi, Takuro; Guelachvili, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2012-01-01

    We report on the first demonstration of nonlinear dual-frequency-comb spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy, the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally-narrow pump is imprinted onto the femtosecond laser frequency comb probe spectrum. The birefringence signal induced by the nonlinear interaction of these beams and the sample is heterodyned against a frequency comb local oscillator with a repetition frequency slightly different from that of the comb probe. Such time-domain interference provides multiplex access to the phase and amplitude Raman spectra over a broad spectral bandwidth within a short measurement time. Experimental demonstration, at a spectral resolution of 200 GHz, a measurement time of 293 {\\mu}s and a sensitivity of 10^-6, is given on liquid samples exhibiting a C-H stretch Raman shift.

  18. Frequency comb selection enabled flexible all optical Nyquist pulse generation

    NASA Astrophysics Data System (ADS)

    Fang, Yuan; Yu, Jianjun; Zhang, Junwen; Li, Xinying; Chi, Nan; Xiao, Jiangnan

    2015-08-01

    In this paper, we propose and experimentally demonstrate flexible all optical Nyquist pulse generation enabled by frequency comb selection with cascaded intensity modulators and tunable optical band-pass filters. Cascaded intensity modulators are used to generate frequency-locked optical comb with flat amplitude and linear phase with up to 15 tones. Arbitrary frequency comb selection based on tunable optical band-pass filters allows the control of the pulse width and repetitive period of the high quality sinc-shaped Nyquist pulse. The optical spectra of the selected 3 and 7 tones frequency comb and the corresponding time-domain waveforms are measured in experiment and simulated by software, respectively. Experimental results conform well to the simulation results which verifies the feasibility of our scheme. The scheme we propose is with excellent flexibility in Nyquist pulse generation and is suitable for high capacity optical transmission system.

  19. MICROWAVE PHOTONIC FILTER DESIGN VIA OPTICAL FREQUENCY COMB SHAPING

    E-print Network

    Purdue University

    MICROWAVE PHOTONIC FILTER DESIGN VIA OPTICAL FREQUENCY COMB SHAPING A Dissertation Submitted a lot when I joined the group and first started the microwave photonic filtering research. My special ......................................................................4 1.4. Multi-tap Microwave Photonic (MWP) Filters

  20. High density terahertz frequency comb produced by coherent synchrotron radiation

    PubMed Central

    Tammaro, S.; Pirali, O.; Roy, P.; Lampin, J.-F.; Ducournau, G.; Cuisset, A.; Hindle, F.; Mouret, G.

    2015-01-01

    Frequency combs have enabled significant progress in frequency metrology and high-resolution spectroscopy extending the achievable resolution while increasing the signal-to-noise ratio. In its coherent mode, synchrotron radiation is accepted to provide an intense terahertz continuum covering a wide spectral range from about 0.1 to 1?THz. Using a dedicated heterodyne receiver, we reveal the purely discrete nature of this emission. A phase relationship between the light pulses leads to a powerful frequency comb spanning over one decade in frequency. The comb has a mode spacing of 846?kHz, a linewidth of about 200?Hz, a fractional precision of about 2 × 10?10 and no frequency offset. The unprecedented potential of the comb for high-resolution spectroscopy is demonstrated by the accurate determination of pure rotation transitions of acetonitrile. PMID:26190043

  1. Optical combing to align photoreceptors in detached retinas

    NASA Astrophysics Data System (ADS)

    Yin, Shizhuo; Gardner, Thomas W.; Wu, Fei; Cholker, Milind S.

    2004-07-01

    In this paper, we presented a novel micro-manipulating method, called 'optical combing', that could improve the retina reattachment surgery results. Optical combing adopts the working principle of optical tweezers (i.e., focused Gaussian beam produces a trapping force when it incidents onto a micro-object. The trapping force can pull the micro-object to the central point of focused laser beam. Optical combing is implemented by scanning a focused laser beam on the misaligned micro objects (such as misaligned photoreceptors). In our preliminary experiment, a set of misaligned micro glass rods was re-aligned by applying this optical combing technology, which verified our theory. In the future, this technique will be used to re-align misaligned photoreceptors in real retina.

  2. Flow-Through Comb Electroporation Device for Delivery of Macromolecules

    E-print Network

    Adamo, Andrea

    We present a microfluidic electroporation device with a comb electrode layout fabricated in polydimethylsiloxane (PMDS) and glass. Characterization experiments with HeLa cells and fluorescent dextran show efficient delivery ...

  3. Multicolor Detection of Combed DNA Molecules Using Quantum Dots

    NASA Astrophysics Data System (ADS)

    Escudé, Christophe; Géron-Landre, Bénédicte; Crut, Aurélien; Desbiolles, Pierre

    DNA combing is a useful strategy for manipulating single DNA molecules and has a wide range of applications in genetics, single molecule studies, and nanobiotechnology. Visualization of combed DNA molecules is usually performed by using DNA binding organic dyes. Such dyes are not suitable in all circumstances, especially because of their photoreactivity. We have developed a method for the detection of combed DNA molecules by fluorescence microscopy that avoids the use of DNA-staining agents and does not perturb the structure of the DNA molecule. Biotin- and/or digoxigenin-modified DNA fragments are covalently linked at both ends of a DNA molecule via sequence-specific hybridization and subsequent ligation. After the modified DNA molecules have been combed on a polystyrene-coated surface, their ends are visualized by multicolor fluorescence microscopy using conjugated quantum dots.

  4. Femtosecond laser frequency comb for precision astrophysical spectroscopy

    E-print Network

    Kaertner, Franz X.

    High-resolution spectroscopy is a crucial tool for cosmology and the search for extrasolar planets. We present a laser comb with up to 40-GHz line spacing for use as a new spectrographic calibration source.

  5. Distance Measurement in Air with a Femtosecond Frequency Comb Laser

    E-print Network

    Distance Measurement in Air with a Femtosecond Frequency Comb Laser Proefschrift ter verkrijging.3 Distance measurements using lasers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.4 Inter . . . . . . . . . . . . . . . . . . . . . . 4 2 Distance Measurement Interferometry 5 2.1 Laser interferometry

  6. Direct frequency comb spectroscopy in the extreme ultraviolet.

    PubMed

    Cingöz, Arman; Yost, Dylan C; Allison, Thomas K; Ruehl, Axel; Fermann, Martin E; Hartl, Ingmar; Ye, Jun

    2012-02-01

    The development of the optical frequency comb (a spectrum consisting of a series of evenly spaced lines) has revolutionized metrology and precision spectroscopy owing to its ability to provide a precise and direct link between microwave and optical frequencies. A further advance in frequency comb technology is the generation of frequency combs in the extreme-ultraviolet spectral range by means of high-harmonic generation in a femtosecond enhancement cavity. Until now, combs produced by this method have lacked sufficient power for applications, a drawback that has also hampered efforts to observe phase coherence of the high-repetition-rate pulse train produced by high-harmonic generation, which is an extremely nonlinear process. Here we report the generation of extreme-ultraviolet frequency combs, reaching wavelengths of 40?nanometres, by coupling a high-power near-infrared frequency comb to a robust femtosecond enhancement cavity. These combs are powerful enough for us to observe single-photon spectroscopy signals for both an argon transition at 82?nanometres and a neon transition at 63?nanometres, thus confirming the combs' coherence in the extreme ultraviolet. The absolute frequency of the argon transition has been determined by direct frequency comb spectroscopy. The resolved ten-megahertz linewidth of the transition, which is limited by the temperature of the argon atoms, is unprecedented in this spectral region and places a stringent upper limit on the linewidth of individual comb teeth. Owing to the lack of continuous-wave lasers, extreme-ultraviolet frequency combs are at present the only promising route to extending ultrahigh-precision spectroscopy to the spectral region below 100?nanometres. At such wavelengths there is a wide range of applications, including the spectroscopy of electronic transitions in molecules, experimental tests of bound-state and many-body quantum electrodynamics in singly ionized helium and neutral helium, the development of next-generation 'nuclear' clocks and searches for variation of fundamental constants using the enhanced sensitivity of highly charged ions. PMID:22297971

  7. XUV frequency comb metrology on the ground state of helium

    E-print Network

    Kandula, Dominik Z; Pinkert, Tjeerd J; Ubachs, Wim; Eikema, Kjeld S E

    2011-01-01

    The operation of a frequency comb at extreme ultraviolet (XUV) wavelengths based on pair-wise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency comb laser in the near-infrared range is reported. Following a first account of the experiment [Kandula et al., Phys. Rev. Lett. 105, 063001 (2010)], an extensive review is given of the demonstration that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1P_1 states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure yields an estimated timing jitter between the two upconverted comb laser pulses of 50 attoseconds, whch indicates that e...

  8. Adaptive real-time dual-comb spectroscopy

    PubMed Central

    Ideguchi, Takuro; Poisson, Antonin; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W.

    2014-01-01

    The spectrum of a laser frequency comb consists of several hundred thousand equally spaced lines over a broad spectral bandwidth. Such frequency combs have revolutionized optical frequency metrology and they now hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite an intriguing potential for the measurement of molecular spectra spanning tens of nanometres within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the demanding stability requirements of the laser combs. Here we overcome this difficulty and experimentally demonstrate a concept of real-time dual-comb spectroscopy, which compensates for laser instabilities by electronic signal processing. It only uses free-running mode-locked lasers without any phase-lock electronics. We record spectra spanning the full bandwidth of near-infrared fibre lasers with Doppler-limited line profiles highly suitable for measurements of concentrations or line intensities. Our new technique of adaptive dual-comb spectroscopy offers a powerful transdisciplinary instrument for analytical sciences. PMID:24572636

  9. A Frequency Comb calibrated Solar Atlas

    E-print Network

    Molaro, P; Monai, S; Hernandez, J I Gonzalez; Hansch, T W; Holzwarth, R; Manescau, A; Pasquini, L; Probst, R A; Rebolo, R; Steinmetz, T; Udem, Th; Wilken, T

    2013-01-01

    The solar spectrum is a primary reference for the study of physical processes in stars and their variation during activity cycles. In Nov 2010 an experiment with a prototype of a Laser Frequency Comb (LFC) calibration system was performed with the HARPS spectrograph of the 3.6m ESO telescope at La Silla during which high signal-to-noise spectra of the Moon were obtained. We exploit those Echelle spectra to study the optical integrated solar spectrum . The DAOSPEC program is used to measure solar line positions through gaussian fitting in an automatic way. We first apply the LFC solar spectrum to characterize the CCDs of the HARPS spectrograph. The comparison of the LFC and Th-Ar calibrated spectra reveals S-type distortions on each order along the whole spectral range with an amplitude of +/-40 m/s. This confirms the pattern found by Wilken et al. (2010) on a single order and extends the detection of the distortions to the whole analyzed region revealing that the precise shape varies with wavelength. A new da...

  10. Broadband Comb-Resolved Cavity Enhanced Spectrometer with Graphene Modulator

    NASA Astrophysics Data System (ADS)

    Lee, Kevin; Mohr, Christian; Jiang, Jie; Fermann, Martin; Lee, Chien-Chung; Schibli, Thomas R.; Kowzan, Grzegorz; Maslowski, Piotr

    2015-06-01

    Optical cavities enhance sensitivity in absorption spectroscopy. While this is commonly done with single wavelengths, broad bandwidths can be coupled into the cavity using frequency combs. The combination of cavity enhancement and broad bandwidth allows simultaneous measurement of tens of transitions with high signal-to-noise for even weak near-infrared transitions. This removes the need for time-consuming sequencing acquisition or long-term averaging, so any systematic errors from long-term drifts of the experimental setup or slow changes of sample composition are minimized. Resolving comb lines provides a high accuracy, absolute frequency axis. This is of great importance for gas metrology and data acquisition for future molecular lines databases, and can be applied to simultaneous trace-gas detection of gas mixtures. Coupling of a frequency comb into a cavity can be complex, so we introduce and demonstrate a simplification. The Pound-Drever-Hall method for locking a cavity and a frequency comb together requires a phase modulation of the laser output. We use the graphene modulator that is already in the Tm fiber laser cavity for controlling the carrier envelope offset of the frequency comb, rather than adding a lossy external modulator. The graphene modulator can operate at frequencies of over 1~ MHz, which is sufficient for controlling the laser cavity length actuator which operates below 100~kHz. We match the laser cavity length to fast variations of the enhancement cavity length. Slow variations are stabilized by comparison of the pulse repetition rate to a GPS reference. The carrier envelope offset is locked to a constant value chosen to optimize the transmitted spectrum. The transmitted pulse train is a stable frequency comb suitable for long measurements, including the acquisition of comb-resolved Fourier transform spectra with a minimum absorption coefficient of about 2×10-7 wn. For our 38 cm long enhancement cavity, the comb spacing is 394~MHz. With our 300 wn bandwidth at 2 ?m, we simultaneously measure the full comb line resolved CO_2 vibrational manifold at 4850 wn. Other spectral ranges can be accessed by using graphene with different gain fibers or nonlinear frequency conversion.

  11. A quantitative mode-resolved frequency comb spectrometer.

    PubMed

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

    2015-06-01

    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. PMID:26072768

  12. Optimizing intracavity high harmonic generation for XUV fs frequency combs.

    PubMed

    Lee, Jane; Carlson, David R; Jones, R Jason

    2011-11-01

    Previous work has shown that use of a passive enhancement cavity designed for ultrashort pulses can enable the up-conversion of the fs frequency comb into the extreme ultraviolet (XUV) spectral region utilizing the highly nonlinear process of high harmonic generation. This promising approach for an efficient source of highly coherent light in this difficult to reach spectral region promises to be a unique tool for precision spectroscopy and temporally resolved measurements. Yet to date, this approach has not been extensively utilized due in part to the low powers so far achieved and in part due to the challenges in directly probing electronic transitions with the frequency comb itself. We report on a dramatically improved XUV frequency comb producing record power levels to date in the 50-150 nm spectral region based on intracavity high harmonic generation. We measure up to 77 ?W at the 11th harmonic of the fundamental (72 nm) with ?W levels down to the 15th harmonic (53nm). Phase-matching and related design considerations unique to intracavity high harmonic generation are discussed, guided by numerical simulations which provide insight into the role played by intracavity ionization dynamics. We further propose and analyze dual-comb spectroscopy in the XUV and show that the power levels reported here permit this approach for the first time. Dual-comb spectroscopy in this physically rich spectral region promises to enable the study of a significantly broader range of atomic and molecular spectra with unprecedented precision and accuracy. PMID:22109209

  13. Laser cooling and trapping with optical frequency combs

    NASA Astrophysics Data System (ADS)

    Long, Xueping; Jayich, Andrew; Ransford, Anthony; Wang, Anna; Campbell, Wesley

    2015-05-01

    A large number of atoms and molecules are difficult to control with continuous wave lasers because generating sufficient power at all of the necessary wavelengths is technologically challenging. Mode-locked lasers, through their enhanced efficiency of nonlinear frequency conversion, provide some of these hard to access wavelengths. As a step towards control of exotic atoms and molecules we report on laser cooling and trapping of atoms using an optical frequency comb in two different regimes. Using a single comb, we have created a simultaneous dual-species (isotopes) MOT, demonstrating that multiple comb teeth can be used in parallel to cool and confine species requiring many cw lasers. Separately, we demonstrate comb-based laser cooling on a two-photon transition, which efficiently uses the full time-averaged optical power of the entire comb. Our progress toward extending this to include trapping by making a MOT using this two-photon transition is presented. This work is supported by the National Science Foundation.

  14. Brood comb as a humidity buffer in honeybee nests

    NASA Astrophysics Data System (ADS)

    Ellis, Michael B.; Nicolson, Sue W.; Crewe, Robin M.; Dietemann, Vincent

    2010-04-01

    Adverse environmental conditions can be evaded, tolerated or modified in order for an organism to survive. During their development, some insect larvae spin cocoons which, in addition to protecting their occupants against predators, modify microclimatic conditions, thus facilitating thermoregulation or reducing evaporative water loss. Silk cocoons are spun by honeybee ( Apis mellifera) larvae and subsequently incorporated into the cell walls of the wax combs in which they develop. The accumulation of this hygroscopic silk in the thousands of cells used for brood rearing may significantly affect nest homeostasis by buffering humidity fluctuations. This study investigates the extent to which the comb may influence homeostasis by quantifying the hygroscopic capacity of the cocoons spun by honeybee larvae. When comb containing cocoons was placed at high humidity, it absorbed 11% of its own mass in water within 4 days. Newly drawn comb composed of hydrophobic wax and devoid of cocoons absorbed only 3% of its own mass. Therefore, the accumulation of cocoons in the comb may increase brood survivorship by maintaining a high and stable humidity in the cells.

  15. Two-photon Direct Frequency Comb Spectroscopy of Alkali Atoms

    NASA Astrophysics Data System (ADS)

    Nguyen, Khoa; Pradhananga, Trinity; Palm, Christopher; Stalnaker, Jason; Kimball, Derek Jackson

    2012-06-01

    We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

  16. Phrenology, heredity and progress in George Combe's Constitution of Man.

    PubMed

    Jenkins, Bill

    2015-09-01

    The Constitution of Man by George Combe (1828) was probably the most influential phrenological work of the nineteenth century. It not only offered an exposition of the phrenological theory of the mind, but also presented Combe's vision of universal human progress through the inheritance of acquired mental attributes. In the decades before the publication of Darwin's Origin of Species, the Constitution was probably the single most important vehicle for the dissemination of naturalistic progressivism in the English-speaking world. Although there is a significant literature on the social and cultural context of phrenology, the role of heredity in Combe's thought has been less thoroughly explored, although both John van Wyhe and Victor L. Hilts have linked Combe's views on heredity with the transformist theories of Jean-Baptiste Lamarck. In this paper I examine the origin, nature and significance of his ideas and argue that Combe's hereditarianism was not directly related to Lamarckian transformism but formed part of a wider discourse on heredity in the early nineteenth century. PMID:25998794

  17. Self-referenceable frequency comb from an ultrafast thin disk laser

    E-print Network

    Keller, Ursula

    extreme nonlinear optics experiments such as high harmonic generation and VUV frequency comb generationSelf-referenceable frequency comb from an ultrafast thin disk laser Clara J. Saraceno,1,* Selina current with a slope of 33 kHz/mA. This result opens the door towards high-power frequency combs from

  18. Supercontinuum-based 10-GHz flat-topped optical frequency comb generation

    E-print Network

    Purdue University

    Supercontinuum-based 10-GHz flat-topped optical frequency comb generation Rui Wu,1,* Victor Torres: The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum waveform generation. Usually, nonlinear broadening techniques of comb-based sources do not provide

  19. PHYSICAL REVIEW A 90, 023804 (2014) Nonlinear transmission spectroscopy with dual frequency combs

    E-print Network

    Mukamel, Shaul

    2014-01-01

    PHYSICAL REVIEW A 90, 023804 (2014) Nonlinear transmission spectroscopy with dual frequency combs coherent broadband optical frequency combs and records the nonlinear transmission in the time domain the nonlinear signal obtained with two frequency combs and connect them to the third-order susceptibility (3

  20. Optical generation of a precise microwave frequency comb by harmonic frequency locking

    E-print Network

    Chan, Sze-Chun

    comb through the nonlinear dynamics. The laser system is operated in a harmonic frequency- lockedOptical generation of a precise microwave frequency comb by harmonic frequency locking Sze pulsing state, where its power spectrum is a microwave frequency comb that consists of multiples

  1. Comparative reproduction of Varroa destructor in different types of Russian and Italian honey bee combs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We studied whether or not older comb supported less varroa reproduction in both Russian and Italian honey bees, whether Russian bees produced comb which inhibited varroa reproduction and whether comb foundation contained enough acaricides to influence varroa reproduction. The major differences foun...

  2. LETTER doi:10.1038/nature10711 Direct frequency comb spectroscopy in the

    E-print Network

    LETTER doi:10.1038/nature10711 Direct frequency comb spectroscopy in the extreme ultraviolet Arman a precise and direct link between microwave and optical frequencies1,2 . A further advance in frequency comb technology is the generation of frequency combs in the extreme-ultraviolet spectral range by means of high

  3. [Lethal sex].

    PubMed

    Rabinerson, David; Ben-Shitrit, Gadi; Glezerman, Marek

    2011-03-01

    Asphyxiophilic sex is a form of autoerotic activity, in which the user creates mechanical means (such as hanging or bondage) in order to achieve cerebral hypoxia, which, in turn, enhances sexual, as well as orgasmic, stimulus. Failure of safety mechanisms, created by the user, may lead to instant death as a result of asphyxiation or strangulation. This kind of sexual practice is more prevalent among men than in women. In cases of death, it is difficult to relate it to the sexual practice itself. Suicide and homicide are the main differential diagnoses. Closely related derivatives of asphyxiophilic sex are anesthesiophilia (inhalation of variable volatile substances) and electrophilia (use of electric current during sexual activity)--both also intended to enhance the sexual stimulation. These forms of sexual practice are less prevalent than asphyxiophilia. PMID:21574359

  4. Enabling Arbitrary Wavelength Optical Frequency Combs on Chip

    E-print Network

    Soltani, Mohammad; Maleki, Lute

    2015-01-01

    A necessary condition for generation of bright soliton Kerr frequency combs in microresonators is to achieve anomalous group velocity dispersion (GVD) for the resonator modes. This condition is hard to implement in visible as well as ultraviolet since the majority of optical materials are characterized with large normal GVD in these wavelength regions. We overcome this challenge by borrowing ideas from strongly dispersive coupled systems in solid state physics and optics. We show that photonic compound ring resonators can possess large anomalous GVD at any desirable wavelength, even if each individual resonator is characterized with normal GVD. Based on this concept we design a mode locked frequency comb with thin-film silicon nitride compound ring resonators in the vicinity of Rubidium D1 line (794.6nm) and propose to use this optical comb as a flywheel for chip-scale optical clocks.

  5. Quantum cascade laser combs: effects of modulation and dispersion.

    PubMed

    Villares, Gustavo; Faist, Jérôme

    2015-01-26

    Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs2 mm-1) but disappears when much larger values are used (30'000 fs2 mm-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs. PMID:25835922

  6. A deep-UV optical frequency comb at 205 nm.

    PubMed

    Peters, E; Diddams, S A; Fendel, P; Reinhardt, S; Hänsch, T W; Udem, Th

    2009-05-25

    By frequency quadrupling a picosecond pulse train from a Ti:sapphire laser at 820 nm we generate a frequency comb at 205 nm with nearly bandwidth-limited pulses. The nonlinear frequency conversion is accomplished by two successive frequency doubling stages that take place in resonant cavities that are matched to the pulse repetition rate of 82 MHz. This allows for an overall efficiency of 4.5 % and produces an output power of up to 70 mW for a few minutes and 25 mW with continuous operation for hours. Such a deep UV frequency comb may be employed for direct frequency comb spectroscopy in cases where it is less efficient to convert to these short wavelengths with continuous wave lasers. PMID:19466167

  7. Nonlinear amplification of side-modes in frequency combs.

    PubMed

    Probst, R A; Steinmetz, T; Wilken, T; Hundertmark, H; Stark, S P; Wong, G K L; Russell, P St J; Hänsch, T W; Holzwarth, R; Udem, Th

    2013-05-20

    We investigate how suppressed modes in frequency combs are modified upon frequency doubling and self-phase modulation. We find, both experimentally and by using a simplified model, that these side-modes are amplified relative to the principal comb modes. Whereas frequency doubling increases their relative strength by 6 dB, the growth due to self-phase modulation can be much stronger and generally increases with nonlinear propagation length. Upper limits for this effect are derived in this work. This behavior has implications for high-precision calibration of spectrographs with frequency combs used for example in astronomy. For this application, Fabry-Pérot filter cavities are used to increase the mode spacing to exceed the resolution of the spectrograph. Frequency conversion and/or spectral broadening after non-perfect filtering reamplify the suppressed modes, which can lead to calibration errors. PMID:23736390

  8. Mid-Infrared Optical Frequency Combs based on Crystalline Microresonators

    E-print Network

    Wang, C Y; Del'Haye, P; Schliesser, A; Hofer, J; Holzwarth, R; Hänsch, T W; Picqué, N; Kippenberg, T J

    2011-01-01

    The mid-infrared spectral range (\\lambda ~ 2 \\mu m to 20 \\mu m) is known as the "molecular fingerprint" region as many molecules have their highly characteristic, fundamental ro-vibrational bands in this part of the electromagnetic spectrum. Broadband mid-infrared spectroscopy therefore constitutes a powerful and ubiquitous tool for optical analysis of chemical components that is used in biochemistry, astronomy, pharmaceutical monitoring and material science. Optical frequency combs, i.e. broad spectral bandwidth coherent light sources consisting of equally spaced sharp lines, have revolutionized optical frequency metrology one decade ago. They now demonstrate dramatically improved acquisition rates, resolution and sensitivity for molecular spectroscopy mostly in the visible and near-infrared ranges. Mid-infrared frequency combs have therefore become highly desirable and recent progress in generating such combs by nonlinear frequency conversion has opened access to this spectral region. Here we report on a pr...

  9. Decade-Spanning High-Precision Terahertz Frequency Comb

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Good, Jacob T.; Holland, Daniel B.; Carroll, P. Brandon; Allodi, Marco A.; Blake, Geoffrey A.

    2015-04-01

    The generation and detection of a decade-spanning terahertz (THz) frequency comb is reported using two Ti:sapphire femtosecond laser oscillators and asynchronous optical sampling THz time-domain spectroscopy. The comb extends from 0.15 to 2.4 THz, with a tooth spacing of 80 MHz, a linewidth of 3.7 kHz, and a fractional precision of 1.8 ×10-9 . With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional accuracy of 6.1 ×10-8 . Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies.

  10. Methods and apparatus for broadband frequency comb stabilization

    DOEpatents

    Cox, Jonathan A; Kaertner, Franz X

    2015-03-17

    Feedback loops can be used to shift and stabilize the carrier-envelope phase of a frequency comb from a mode-locked fibers laser or other optical source. Compared to other frequency shifting and stabilization techniques, feedback-based techniques provide a wideband closed-loop servo bandwidth without optical filtering, beam pointing errors, or group velocity dispersion. It also enables phase locking to a stable reference, such as a Ti:Sapphire laser, continuous-wave microwave or optical source, or self-referencing interferometer, e.g., to within 200 mrad rms from DC to 5 MHz. In addition, stabilized frequency combs can be coherently combined with other stable signals, including other stabilized frequency combs, to synthesize optical pulse trains with pulse durations of as little as a single optical cycle. Such a coherent combination can be achieved via orthogonal control, using balanced optical cross-correlation for timing stabilization and balanced homodyne detection for phase stabilization.

  11. Honeybee combs: how the circular cells transform into rounded hexagons

    PubMed Central

    Karihaloo, B. L.; Zhang, K.; Wang, J.

    2013-01-01

    We report that the cells in a natural honeybee comb have a circular shape at ‘birth’ but quickly transform into the familiar rounded hexagonal shape, while the comb is being built. The mechanism for this transformation is the flow of molten visco-elastic wax near the triple junction between the neighbouring circular cells. The flow may be unconstrained or constrained by the unmolten wax away from the junction. The heat for melting the wax is provided by the ‘hot’ worker bees. PMID:23864500

  12. Routes to spatiotemporal chaos in Kerr optical frequency combs

    SciTech Connect

    Coillet, Aurélien; Chembo, Yanne K.

    2014-03-15

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

  13. Spatiotemporal dynamics of Kerr-Raman optical frequency combs

    NASA Astrophysics Data System (ADS)

    Chembo, Yanne K.; Grudinin, Ivan S.; Yu, Nan

    2015-10-01

    Optical frequency combs generated with ultrahigh-Q whispering-gallery-mode resonators are expected to provide a compact, versatile, and energy-efficient source for the generation of coherent lightwave and microwave signals. So far, Kerr and Raman nonlinearities in these resonators have predominantly been investigated separately, even though both effects originate from the same third-order susceptibility. We present a spatiotemporal formalism for the theoretical understanding of these Kerr-Raman combs, which allows us to describe the complex interplay between both nonlinearities and all-order dispersion. These theoretical findings are successfully compared with experiments performed with ultrahigh-Q calcium and magnesium fluoride resonators.

  14. Optical Kerr Frequency Comb Generation in Overmoded Resonators

    E-print Network

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

    2012-01-01

    We show that scattering-based interaction among nearly degenerate optical modes is the key factor in low threshold generation of Kerr frequency combs in nonlinear optical resonators possessing small group velocity dispersion (GVD). The mode interaction is capable of producing drastic change in the local GVD, resulting in either a significant reduction or increase of the oscillation threshold. It is also responsible for the majority of observed combs in resonators characterized with large normal GVD. We present results of our numerical simulations as well as supporting experimental data.

  15. Optical frequency comb generation from aluminum nitride microring resonator.

    PubMed

    Jung, Hojoong; Xiong, Chi; Fong, King Y; Zhang, Xufeng; Tang, Hong X

    2013-08-01

    Aluminum nitride (AlN) is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high-quality-factor AlN microring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single-wavelength continuous-wave pump laser. Further, the Kerr coefficient (n?) of AlN is extracted from our experimental results. PMID:23903149

  16. Low loss silicon microring resonator as comb filter

    NASA Astrophysics Data System (ADS)

    Deng, Qingzhong; Yi, Huaxiang; Long, Qifeng; Wang, Xingjun; Zhou, Zhiping

    2015-11-01

    Scattering loss caused by roughness of waveguide sidewalls is a key problem for long circumference microring based applications, such as comb filters. This paper presents a Si microring resonator incorporated with the multimode waveguide and single-mode waveguide, which suppresses the unwanted resonance of high-order modes while allowing the fundamental mode resonance with low loss. Both numerical and experimental results proved that the proposed solution is capable to achieve ~88.5% scattering loss reduction which is promising for narrow channel spacing comb filters.

  17. The generation of Continuous-Variable Entanglement Frequency Comb

    PubMed Central

    Yu, Youbin; Cheng, Xiaomin; Wang, Huaijun; Shi, Zhongtao; Zhao, Junwei; Ji, Fengmin; Yin, Zhi; Wang, Yajuan

    2015-01-01

    Continuous-variable (CV) entanglement frequency comb can be produced by enhanced Raman scattering in an above-threshold optical oscillator cavity in which a hexagonally-poled LiTaO3 crystal resides as a Raman gain medium. The Stokes and anti-Stokes Raman signals are enhanced by a coupled quasi-phase-matching optical parametric process and the entanglement natures among these Raman signals and pump are demonstrated by applying a sufficient inseparability criterion for CV entanglement. Such entanglement frequency comb source with different frequencies and continuously tunable frequency interval may be very significant for the applications in quantum communication and networks. PMID:25600617

  18. Target micro-displacement measurement by a "comb" structure of intensity distribution in laser plasma propulsion

    NASA Astrophysics Data System (ADS)

    Zheng, Z. Y.; Zhang, S. Q.; Gao, L.; Gao, H.

    2015-05-01

    A "comb" structure of beam intensity distribution is designed and achieved to measure a target displacement of micrometer level in laser plasma propulsion. Base on the "comb" structure, the target displacement generated by nanosecond laser ablation solid target is measured and discussed. It is found that the "comb" structure is more suitable for a thin film target with a velocity lower than tens of millimeters per second. Combing with a light-electric monitor, the `comb' structure can be used to measure a large range velocity.

  19. Spectral characterization of a frequency comb based on cascaded quadratic nonlinearities inside an optical parametric oscillator

    E-print Network

    Ulvila, Ville; Halonen, Lauri; Vainio, Markku

    2015-01-01

    We present an experimental study of optical frequency comb generation based on cascaded quadratic nonlinearities inside a continuous-wave-pumped optical parametric oscillator. We demonstrate comb states which produce narrow-linewidth intermode beat note signals, and we verify the mode spacing uniformity of the comb at the Hz level. We also show that spectral quality of the comb can be improved by modulating the parametric gain at a frequency that corresponds to the comb mode spacing. We have reached a high average output power of over 4 W in the near-infrared region, at ~2 {\\mu}m.

  20. Mid-infrared frequency comb for broadband high precision and sensitivity molecular spectroscopy.

    PubMed

    Galli, I; Bartalini, S; Cancio, P; Cappelli, F; Giusfredi, G; Mazzotti, D; Akikusa, N; Yamanishi, M; De Natale, P

    2014-09-01

    We report on the experimental demonstration of the metrological and spectroscopic performances of a mid-infrared comb generated by a nonlinear downconversion process from a Ti:sapphire-based near-infrared comb. A quantum cascade laser at 4330 nm was phase-locked to a single tooth of this mid-infrared comb and its frequency-noise power spectral density was measured. The mid-infrared comb itself was also used as a multifrequency highly coherent source to perform ambient air direct comb spectroscopy with the Vernier technique, by demultiplexing it with a high-finesse Fabry-Perot cavity. PMID:25166071

  1. Spectral characterization of a frequency comb based on cascaded quadratic nonlinearities inside an optical parametric oscillator

    NASA Astrophysics Data System (ADS)

    Ulvila, Ville; Phillips, C. R.; Halonen, Lauri; Vainio, Markku

    2015-09-01

    We present an experimental study of optical frequency comb generation based on cascaded quadratic nonlinearities inside a continuous-wave-pumped optical parametric oscillator. We demonstrate comb states which produce narrow-linewidth intermode beat note signals, and we verify the mode-spacing uniformity of the comb at the Hertz level. We also show that the spectral quality of the comb can be improved by modulating the parametric gain at a frequency that corresponds to the comb mode spacing. We have reached a high average output power of over 4 W in the near-infrared region, at ˜2 ? m .

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

    SciTech Connect

    Hou, Dong; Wu, Jiutao; Zhang, Shuangyou; Ren, Quansheng; Zhang, Zhigang; Zhao, Jianye

    2014-03-17

    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.

  3. Spectral and temporal characterization of a fused-quartz-microresonator optical frequency comb

    SciTech Connect

    Papp, Scott B.; Diddams, Scott A.

    2011-11-15

    We report on the fabrication of high-Q, fused-quartz microresonators and the parametric generation of a frequency comb with 36-GHz line spacing using them. We have characterized the intrinsic stability of the comb in both the time and frequency domains to assess its suitability for future precision metrology applications. Intensity autocorrelation measurements and line-by-line comb control reveal near-transform-limited picosecond pulse trains that are associated with good relative phase and amplitude stability of the comb lines. The comb's 36-GHz line spacing can be readily photodetected, which enables measurements of its intrinsic and absolute phase fluctuations.

  4. Comparative efficacy of commercial combs in removing head lice (Pediculus humanus capitis) (Phthiraptera: Pediculidae).

    PubMed

    Gallardo, Anabella; Toloza, Ariel; Vassena, Claudia; Picollo, María Inés; Mougabure-Cueto, Gastón

    2013-03-01

    The use of a fine comb for removing lice from the head of the human host is a relevant tool both in the diagnosis of infestations and as part of an integrated control strategy of head lice. The effectiveness of a fine comb depends, in part, on the design and material they are built. The aim of this study was to compare in vivo the efficacy of metal and plastic combs that are currently used in the removal of head lice and eggs worldwide. The space between comb teeth and the length was 0.23 and 13 mm in KSL® plastic, 0.3 and 10.7 mm in NOPUCID® plastic, 0.15 and 31 mm in KSL® metal and 0.09 and 37 mm in ASSY® metal. The assays were performed comparing the combs in pairs: (a) KSL® vs. NOPUCID® plastic combs, (b) KSL® vs. ASSY® metal combs and (c) KSL® plastic comb vs. ASSY® metal comb. The most effective plastic comb was KSL®, removing a higher number of individuals of all stages. The most effective metal comb was ASSY®, removing more insects of all stages (except adults). The comparative test between KSL® plastic and ASSY® metal showed that ASSY® was the most effective in removing head lice and their eggs. PMID:23212391

  5. Actin polymerization front propagation in a comb-reaction system

    E-print Network

    A. Iomin; V. Zaburdaev; T. Pfohl

    2015-02-24

    Anomalous transport and reaction dynamics are considered by providing the theoretical grounds for the possible experimental realization of actin polymerization in comb-like geometry. Two limiting regimes are recovered, depending on the concentration of reagents (magnesium and actin). These are both the failure of the reaction front propagation and a finite speed corresponding to the Fisher-KPP long time asymptotic regime.

  6. Dynamics of the Modulational Instability in Microresonator Frequency Combs

    E-print Network

    Hansson, T; Wabnitz, S

    2013-01-01

    A study is made of frequency comb generation described by the driven and damped nonlinear Schr\\"odinger equation on a finite interval. It is shown that frequency comb generation can be interpreted as a modulational instability of the continuous wave pump mode, and a linear stability analysis, taking into account the cavity boundary conditions, is performed. Further, a truncated three-wave model is derived, which allows one to gain additional insight into the dynamical behaviour of the comb generation. This formalism describes the pump mode and the most unstable sideband and is found to connect the coupled mode theory with the conventional theory of modulational instability. An in-depth analysis is done of the nonlinear three-wave model. It is demonstrated that stable frequency comb states can be interpreted as attractive fixed points of a dynamical system. The possibility of soft and hard excitation states in both the normal and the anomalous dispersion regime is discussed. Investigations are made of bistable...

  7. Hard and Soft Excitation Regimes of Kerr Frequency Combs

    E-print Network

    Matsko, Andrey B; Ilchenko, Vladimir S; Seidel, David; Maleki, Lute

    2011-01-01

    We theoretically study the stability conditions and excitation regimes of hyper-parametric oscillation and Kerr frequency comb generation in continuously pumped nonlinear optical resonators possessing anomalous group velocity dispersion. We show that both hard and soft excitation regimes are possible in the resonators. Selection between the regimes is achieved via change in the parameters of the pumping light.

  8. Frequency comb offset detection using supercontinuum generation in silicon nitride

    E-print Network

    Keller, Ursula

    Frequency comb offset detection using supercontinuum generation in silicon nitride waveguides A. S) frequency detection of a modelocked laser based on supercontinuum generation (SCG) in a CMOS.7370) Waveguides; (130.4310) Nonlinear; (190.4390) Nonlinear optics, integrated optics. References and links 1. H

  9. Direct Frequency Comb Spectroscopy in the Extreme Ultraviolet

    E-print Network

    Cingoz, Arman; Allison, Thomas K; Ruehl, Axel; Fermann, Martin E; Hartl, Ingmar; Ye, Jun

    2011-01-01

    Development of the optical frequency comb has revolutionised metrology and precision spectroscopy due to its ability to provide a precise and direct link between microwave and optical frequencies. A novel application of frequency comb technology that leverages both the ultrashort duration of each laser pulse and the exquisite phase coherence of a train of pulses is the generation of frequency combs in the extreme ultraviolet (XUV) via high harmonic generation (HHG) in a femtosecond enhancement cavity. Until now, this method has lacked sufficient average power for applications, which has also hampered efforts to observe phase coherence of the high-repetition rate pulse train produced in the extremely nonlinear HHG process. Hence, the existence of a frequency comb in the XUV has not been confirmed. We have overcome both challenges. Here, we present generation of >200 {\\mu}W per harmonic reaching 50 nm, and the observation of single-photon spectroscopy signals for both an argon transition at 82 nm and a neon tra...

  10. Comb entanglement in quantum spin chains J.P. Keating,

    E-print Network

    Mezzadri, Francesco

    Comb entanglement in quantum spin chains J.P. Keating, F. Mezzadri, and M. Novaes School of Mathematics, University of Bristol, Bristol BS8 1TW, UK Bipartite entanglement in the ground state of a chain of N quantum spins can be quantified either by computing pairwise concurrence or by dividing the chain

  11. Threshold conditions and bands in attractive Dirac comb

    NASA Astrophysics Data System (ADS)

    Dharani, M.; Shastry, C. S.

    2015-06-01

    Taking into account the threshold conditions for the generation of bound states by an attractive delta comb in one dimension, we describe the band structure generated by the same when confined to a box demonstrating the correlation between the potential strength, band width and band gap.

  12. Progress with a green astro-comb for exoplanet searches

    NASA Astrophysics Data System (ADS)

    Li, Chih-Hao; Glenday, Alexander G.; Phillips, David F.; Langellier, Nicholas; Chang, Guoqing; Furesz, Gabor; Kaertner, Franz X.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

    2015-05-01

    Searches for extrasolar planets using the precision stellar radial velocity (RV) measurement technique are approaching Earth-like planet sensitivity. Astro-combs, which consist of a laser frequency comb, coherent wavelength shifting mechanism (such as a doubling crystal and photonic crystal fiber), and a mode-filtering Fabry-Perot cavity (FPC), provide a promising route to increased accuracy and long-term stability on the astrophysical spectrograph calibration. We first present the design of a green astro-comb from an octave spanning Ti:Sapphire laser, spectrally broadened by custom tapered PCF to the visible band via fiber-optic Cherenkov radiation for frequency shifting, and filtered by a broadband FPC, constructed by a pair of complementary chirped mirrors. We also present results from two years of operation of the astro-comb calibrating the HARPS-N spectrograph at the Italian National Telescope on La Palma, Canary Islands, including its use in measurements of solar radial velocities as well as its use in searches for extrasolar planets.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  14. ENGINEERING REPORTS Using Delay Estimation to Reduce Comb Filtering

    E-print Network

    Reiss, Josh

    is enough to cause a comb filter that is a 1st order low pass filter. This is equivalent to a difference. This can occur in live or studio sound production when multiple microphones reproduce a single source, and are unaffected by input signal bandwidth. 0 INTRODUCTION A common technique in live and studio production

  15. Dual-comb modelocked laser Sandro M. Link,*

    E-print Network

    Keller, Ursula

    and a microwave spectrum analyzer directly down-converts the frequency comb difference from the optical to the microwave frequency domain. With this setup, the relative carrier- envelope-offset (CEO) frequency can for the generation of visible and ultraviolet radiation," Laser Photon. Rev. 3(5), 407­434 (2009). 9. B. Rösener, M

  16. Two-photon direct frequency comb spectroscopy of alkali atoms

    NASA Astrophysics Data System (ADS)

    Palm, Christopher; Pradhananga, Trinity; Nguyen, Khoa; Montcrieffe, Caitlin; Kimball, Derek

    2012-11-01

    We have studied transition frequencies and excited state hyperfine structure in rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the rubidium vapor. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. An interesting dependence of the 2-photon spectrum on the energy of the intermediate state of the 2-photon transition is discussed. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

  17. Sex-linked dominant

    MedlinePLUS

    Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant ... type of chromosome that is affected (autosomal or sex chromosome). It also depends on whether the trait ...

  18. Sex during Pregnancy

    MedlinePLUS

    ... Kids Deal With Bullies Pregnant? What to Expect Sex During Pregnancy KidsHealth > Parents > Pregnancy & Newborn Center > Your ... satisfying and safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during ...

  19. Genomics of Sex and Sex Chromosomes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sex chromosomes are distinctive, not only because of their gender determining role, but also for genomic features that reflect their evolutionary history. The genomic sequences in the ancient sex chromosomes of humans and in the incipient sex chromosomes of medaka, stickleback, and papaya exhibit u...

  20. Direct generation of optical frequency combs in $\\chi^{(2)}$ nonlinear cavities

    E-print Network

    Mosca, S; Parisi, M; Maddaloni, P; Santamaria, L; De Natale, P; De Rosa, M

    2015-01-01

    Quadratic nonlinear processes are currently exploited for frequency comb transfer and extension from the visible and near infrared regions to other spectral ranges where direct comb generation cannot be accomplished. However, frequency comb generation has been directly observed in continuously-pumped quadratic nonlinear crystals placed inside an optical cavity. At the same time, an introductory theoretical description of the phenomenon has been provided, showing a remarkable analogy with the dynamics of third-order Kerr microresonators. Here, we give an overview of our recent work on $\\chi^{(2)}$ frequency comb generation. Furthermore, we generalize the preliminary three-wave spectral model to a many-mode comb and present a stability analysis of different cavity field regimes. Although at a very early stage, our work lays the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

  1. Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber.

    PubMed

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

    2014-09-22

    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. PMID:25321837

  2. Solar oscillations and the search for Venus enabled by a laser frequency comb

    NASA Astrophysics Data System (ADS)

    Phillips, David F.; Glenday, Alexander G.; Li, Chih-Hao; Langellier, Nicholas; Chang, Guoqing; Furesz, Gabor; Kaertner, Franz X.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

    2015-05-01

    We have recently demonstrated sub-m/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple, home-built solar telescope feeding the HARPS-N spectrograph at the Italian National Telescope calibrated with our green astro-comb. The green astro-comb is a laser frequency comb optimized for calibrating astrophysical spectrographs. We plan, in the coming year, to use the astro-comb calibrated spectrograph and solar telescope to detect the solar RV signal induced by Venus and thus demonstrate sensitivity of these instruments to detect terrestrial exoplanets. Here, we will present the astro-comb, results from the astro-comb calibrating the HARPS-N exoplanet searcher spectrograph, solar RV stability and plans for observing the signature of Venus.

  3. Mode-resolved 10-GHz frequency comb from a femtosecond optical parametric oscillator.

    PubMed

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

    2015-06-15

    We report a 10-GHz frequency comb generated by filtering a 333.3-MHz OPO frequency comb with a Fabry-Perot (FP) cavity, which was directly stabilized to the incident fundamental comb. This result is supported by a detailed analysis of the Vernier-effect-induced multiple peaks in the transmitted comb power as the FP cavity spacing is detuned. Modes of the generated 10-GHz comb were clearly resolved by a Fourier transform spectrometer with a spectral resolution of 830 MHz, considerably better than the Nyquist sampling limit. The potentially broad tuning range of this mode-resolved OPO frequency comb opens unique opportunities for precise frequency metrology and high-precision spectroscopy. PMID:26076238

  4. The Tribolium castaneum ortholog of Sex combs reduced controls dorsal ridge development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In insects, the boundary between the embryonic head and thorax is formed by the dorsal ridge, a fused structure composed of portions of the maxillary and labial segments. However, the mechanisms that promote development of this unusual structure remain a mystery. In Drosophila, mutations in the Hox ...

  5. Interferometric homogeneity test using adaptive frequency comb illumination.

    PubMed

    Mantel, Klaus; Schwider, Johannes

    2013-03-20

    The homogeneity test of glass plates in a Fizeau interferometer requires the measurement of the glass sample in reflected as well as in transmitted light. For the measurement in transmitted light, the sample has to be inserted into the ray path of a Fizeau or Twyman-Green interferometer, which leads to a nested cavity setup. To separate the interference signals from the different cavities, we illuminate a Fizeau interferometer with an adaptive frequency comb. In this way, rigid glass plates can be measured, and linear variations in the homogeneity can also be detected. The adaptive frequency comb is provided by a variable Fabry-Perot filter under broadband illumination from a superluminescence diode. Compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher. PMID:23518735

  6. Mid-infrared soliton and Raman frequency comb generation in silicon microrings.

    PubMed

    Hansson, Tobias; Modotto, Daniele; Wabnitz, Stefan

    2014-12-01

    We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw-pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described. PMID:25490668

  7. Frequency comb generation for wave transmission through the nonlinear dimer

    E-print Network

    Pichugin, Konstantin N

    2015-01-01

    We study dynamical response of a nonlinear dimer to a symmetrically injected monochromatic wave. We find a domain in the space of frequency and amplitude of the injected wave where all stationary solutions are unstable. In this domain scattered waves carry multiple harmonics with equidistantly spaced frequencies (frequency comb effect). The instability is related to a symmetry protected bound state in the continuum whose response is singular as the amplitude of the injected wave tends to zero.

  8. Generation of a frequency comb and applications thereof

    DOEpatents

    Hagmann, Mark J; Yarotski, Dmitry A

    2013-12-03

    Apparatus for generating a microwave frequency comb (MFC) in the DC tunneling current of a scanning tunneling microscope (STM) by fast optical rectification, cause by nonlinearity of the DC current vs. voltage curve for the tunneling junction, of regularly-spaced, short pulses of optical radiation from a focused mode-locked, ultrafast laser, directed onto the tunneling junction, is described. Application of the MFC to high resolution dopant profiling in semiconductors is simulated. Application of the MFC to other measurements is described.

  9. Electrical tuning and switching of an optical frequency comb generated in aluminum nitride microring resonators

    E-print Network

    Jung, Hojoong; Xiong, Chi; Tang, Hong X

    2013-01-01

    Aluminum nitride has been shown to possess both strong Kerr nonlinearity and electro-optic Pockels effect. By combining these two effects, here we demonstrate on-chip reversible on/off switching of the optical frequency comb generated by an aluminum nitride microring resonator. We optimize the design of gating electrodes and the underneath resonator structure to effectively apply electric field without increasing the optical loss. The switching of the comb is monitored by measuring one of the frequency comb peaks while varying the electric field. The controlled comb electro-optic response is investigated for direct comparison with the transient thermal effect.

  10. Spectral linewidth preservation in parametric frequency combs seeded by dual pumps.

    PubMed

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

    2012-07-30

    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. PMID:23038314

  11. Calibration of an astrophysical spectrograph below 1 m/s using a laser frequency comb.

    PubMed

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

    2012-06-18

    We deployed two wavelength calibrators based on laser frequency combs ("astro-combs") at an astronomical telescope. One astro-comb operated over a 100 nm band in the deep red (? 800 nm) and a second operated over a 20 nm band in the blue (? 400 nm). We used these red and blue astro-combs to calibrate a high-resolution astrophysical spectrograph integrated with a 1.5 m telescope, and demonstrated calibration precision and stability sufficient to enable detection of changes in stellar radial velocity < 1 m/s. PMID:22714437

  12. Dual-Colored DNA Comb Polymers for Single Molecule Rheology

    NASA Astrophysics Data System (ADS)

    Mai, Danielle; Marciel, Amanda; Schroeder, Charles

    2014-03-01

    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.

  13. Kerr comb generation from the perspective of spatial dissipative structures

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  14. Combing gravitational hair in 2+1 dimensions

    E-print Network

    Donnelly, William; Mintun, Eric

    2015-01-01

    The gravitational Gauss law requires any addition of energy to be accompanied by the addition of gravitational flux. The possible configurations of this flux for a given source may be called gravitational hair, and several recent works discuss gravitational observables (`gravitational Wilson lines') which create this hair in highly-collimated `combed' configurations. We construct and analyze time-symmetric classical solutions of 2+1 Einstein-Hilbert gravity such as might be created by smeared versions of such operators. We focus on the AdS$_3$ case, where this hair is characterized by the profile of the boundary stress tensor; the desired solutions are those where the boundary stress tensor at initial time $t=0$ agrees precisely with its vacuum value outside an angular interval $[-\\alpha,\\alpha]$. At linear order in source strength the energy is independent of the combing parameter $\\alpha$, but non-linearities cause the full energy to diverge as $\\alpha \\to 0$. In general, solutions with combed gravitational...

  15. Coherent Raman spectro-imaging with laser frequency combs.

    PubMed

    Ideguchi, Takuro; Holzner, Simon; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W

    2013-10-17

    Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques. PMID:24132293

  16. Coherent Raman spectro-imaging with laser frequency combs

    NASA Astrophysics Data System (ADS)

    Ideguchi, Takuro; Holzner, Simon; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W.

    2013-10-01

    Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques.

  17. The Riddle of Sex.

    ERIC Educational Resources Information Center

    Sagan, Dorion; Margulis, Lynn

    1985-01-01

    Discusses the work of evolutionary biologists in determining how sexual reproduction arose. Topics explored include the nature of sex, bacterial sex, meiotic sex, and asexual reproduction. A diagram (which can be used as a duplicating master) illustrating types of bacterial sex is included. (DH)

  18. Broadband Mid-Infrared Comb-Resolved Fourier Transform Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Kevin; Mills, Andrew; Mohr, Christian; Jiang, Jie; Fermann, Martin; Maslowski, Piotr

    2014-06-01

    We report on a comb-resolved, broadband, direct-comb spectroscopy system in the mid-IR and its application to the detection of trace gases and molecular line shape analysis. By coupling an optical parametric oscillator (OPO), a 100 m multipass cell, and a high-resolution Fourier transform spectrometer (FTS), sensitive, comb-resolved broadband spectroscopy of dilute gases is possible. The OPO has radiation output at 3.1-3.7 and 4.5-5.5 ?m. The laser repetition rate is scanned to arbitrary values with 1 Hz accuracy around 417 MHz. The comb-resolved spectrum is produced with an absolute frequency axis depending only on the RF reference (in this case a GPS disciplined oscillator), stable to 1 part in 10^9. The minimum detectable absorption is 1.6x10-6 wn Hz-1/2. The operating range of the experimental setup enables access to strong fundamental transitions of numerous molecular species for applications based on trace gas detection such as environmental monitoring, industrial gas calibration or medical application of human breath analysis. In addition to these capabilities, we show the application for careful line shape analysis of argon-broadened CO band spectra around 4.7 ?m. Fits of the obtained spectra clearly illustrate the discrepancy between the measured spectra and the Voigt profile (VP), indicating the need to include effects such as Dicke narrowing and the speed-dependence of the collisional width and shift in the line shape model, as was shown in previous cw-laser studies. In contrast to cw-laser based experiments, in this case the entire spectrum (˜ 250 wn) covering the whole P and R branches can be measured in 16 s with 417 MHz resolution, decreasing the acquisition time by orders of magnitude. The parallel acquisition allows collection of multiple lines simultaneously, removing the correlation of possible temperature and pressure drifts. While cw-systems are capable of measuring spectra with higher precision, this demonstration opens the door for fast, massively parallel line shape parameters retrieval combined with analysis reaching beyond the VP and with absolute frequency calibration delivered by frequency combs. R. Wehr et al. J. Mol. Spec. 235 54-68 (2003) A. Cygan, et al. Eur. Phys. J. Special Topics 222 2119-2142 (2013)

  19. Physicochemical characterization of PEG-based comb-like amphiphilic copolymer structures for possible imaging and therapeutic applications

    E-print Network

    Dawson, Jin Zhou

    2008-01-01

    Comb-like copolymer structures, also known as graft/comb copolymers, have obtained a significant amount of attention in biomedical and industrial applications because of their unique compositional flexibility, which can ...

  20. Sub-Lethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis mellifera) Development and Longevity

    PubMed Central

    Wu, Judy Y.; Anelli, Carol M.; Sheppard, Walter S.

    2011-01-01

    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 mites. The impact of delayed development in bees on Varroa mite fecundity should be examined further. PMID:21373182

  1. Stable coherent dual comb generator with dual-heterodyne phase error transfer and heterodyne optical phase-locked loop

    NASA Astrophysics Data System (ADS)

    Tong, Yitian; Liu, Zhangweiyi; Li, Baiyu; Zhou, Qian; Dong, Yi; Hu, Weisheng

    2015-08-01

    We demonstrate a stable coherent dual comb generator with two phase/intensity-modulated combs. The optical fiber path induced phase fluctuation results in the coherent dual comb beating phase noise. We transfer this phase noise to a 40MHz intermediate frequency with dual-heterodyne phase error transfer, decreasing by a phase-locked loop and optical phase locked loop. Under the scheme, stable coherent dual comb with slightly different repetition rates and offset frequency is generated.

  2. 75 FR 11559 - Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules of Origin

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ...Bahrain-FTA-103-025] Certain Combed Cotton Yarns: Effect of Modification of U...Bahrain FTA-103-025, Certain Combed Cotton Yarns: Effect of Modification of U...of origin to the FTA for certain combed cotton yarns used in the production of...

  3. Optical arbitrary waveform processing of more than 100 spectral comb lines

    E-print Network

    Purdue University

    -spectrum lightwave communications and light detection and ranging, lidar). Bringing the concepts of pulse shaping-locked lasers producing combs of frequency-stabilized spectral lines have resulted in revolutionary advances both in optical science (allowing, for example, coherent control generalizations of comb-based time

  4. Frequency comb formation and transition to chaos in microresonators with near-zero dispersion.

    PubMed

    Rogov, Andrei S; Narimanov, Evgenii E

    2014-08-01

    We investigate the frequency comb formation in microresonators with near-zero dispersion, study the route from integrability to chaos in the corresponding nonlinear system, and demonstrate the key role of nonlinear dynamics of such a system for frequency comb generation and stability. PMID:25078163

  5. Gigahertz frequency comb from a diode-pumped solid-state laser

    E-print Network

    Keller, Ursula

    Gigahertz frequency comb from a diode- pumped solid-state laser Alexander Klenner,1,* Stéphane-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency f-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can

  6. SPECTRAL BROADENING OF FREQUENCY COMBS VIA PULSE APODIZATION PRIOR TO NONLINEAR PROPAGATION

    E-print Network

    Purdue University

    SPECTRAL BROADENING OF FREQUENCY COMBS VIA PULSE APODIZATION PRIOR TO NONLINEAR PROPAGATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.1 Optoelectronic Frequency Comb Source . . . . . . . . . . . . . . . . 27 3.2 Experimental Setup Compression in Dispersion Decreasing Fiber . . . 7 1.4 Spectral Broadening in Highly Nonlinear Fiber

  7. Nonlinearly broadened phase-modulated continuous-wave laser frequency combs

    E-print Network

    Purdue University

    Nonlinearly broadened phase-modulated continuous-wave laser frequency combs characterized using-wave laser combs are spectrally broadened via nonlinear propagation in normal and anomalous dispersion media are in qualitative agreement with radio-frequency spectrum analyzer measurements. © 2008 Optical Society of America

  8. Astronomical optical frequency comb generation and test in a fiber-fed MUSE spectrograph

    NASA Astrophysics Data System (ADS)

    Chavez Boggio, J. M.; Fremberg, T.; Moralejo, B.; Rutowska, M.; Hernandez, E.; Zajnulina, M.; Kelz, A.; Bodenmüller, D.; Sandin, C.; Wysmolek, M.; Sayinc, H.; Neumann, J.; Haynes, R.; Roth, M. M.

    2014-07-01

    We here report on recent progress on astronomical optical frequency comb generation at innoFSPEC-Potsdam and present preliminary test results using the fiber-fed Multi Unit Spectroscopic Explorer (MUSE) spectrograph. The frequency comb is generated by propagating two free-running lasers at 1554.3 and 1558.9 nm through two dispersionoptimized nonlinear fibers. The generated comb is centered at 1590 nm and comprises more than one hundred lines with an optical-signal-to-noise ratio larger than 30 dB. A nonlinear crystal is used to frequency double the whole comb spectrum, which is efficiently converted into the 800 nm spectral band. We evaluate first the wavelength stability using an optical spectrum analyzer with 0.02 nm resolution and wavelength grid of 0.01 nm. After confirming the stability within 0.01 nm, we compare the spectra of the astro-comb and the Ne and Hg calibration lamps: the astro-comb exhibits a much larger number of lines than lamp calibration sources. A series of preliminary tests using a fiber-fed MUSE spectrograph are subsequently carried out with the main goal of assessing the equidistancy of the comb lines. Using a P3d data reduction software we determine the centroid and the width of each comb line (for each of the 400 fibers feeding the spectrograph): equidistancy is confirmed with an absolute accuracy of 0.4 pm.

  9. CONTROL AND CHARACTERIZATION OF PHASE-MODULATED CONTINUOUS-WAVE LASER FREQUENCY COMBS

    E-print Network

    Purdue University

    CONTROL AND CHARACTERIZATION OF PHASE-MODULATED CONTINUOUS-WAVE LASER FREQUENCY COMBS birth to my super cute nephew, Bear. Most importantly, my sincere thanks go to Ling-Ti, my lovely wife................................................................4 2. LINE-BY-LINE CONTROL ON A PHASE-MODULATED CONTINUOUS- WAVE LASER FREQUENCY COMB

  10. An Optical Reference and Frequency Comb for Improved Spectroscopy of Helium

    E-print Network

    Gabrielse, Gerald

    An Optical Reference and Frequency Comb for Improved Spectroscopy of Helium A thesis presented Farkas An Optical Reference and Frequency Comb for Improved Spectroscopy of Helium Abstract An optical an improved mea- surement of the helium 23 S - 23 PJ optical transition frequencies and fine structure

  11. 10.1117/2.1201412.005730 A green astro-comb to search

    E-print Network

    Walsworth, Ronald L.

    in the Canary Islands. One of the first steps in the search for alien life is the identifi- cation of Earth10.1117/2.1201412.005730 A green astro-comb to search for Earth-like exoplanets Chih-Hao Li A new-comb. This device is a Figure 1. Illustration of the precision radial velocity method for exo- planet searches

  12. Low noise erbium fiber fs frequency comb based on a tapered-fiber carbon nanotube design

    E-print Network

    Kieu, Khanh

    Low noise erbium fiber fs frequency comb based on a tapered-fiber carbon nanotube design Tsung, and B. R. Washburn, "A phase-stabilized carbon nanotube fiber laser frequency comb," Opt. Express 17, "Generation of few-cycle pulses from an amplified carbon nanotube mode-locked fiber laser system," IEEE Photon

  13. Fourier transform spectroscopy around 3 microns with a broad difference frequency comb

    E-print Network

    Meek, Samuel A; Guelachvili, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    We characterize a new mid-infrared frequency comb generator based on difference frequency generation around 3.2 microns. High power per comb mode (>10-7 W/mode) is obtained over a broad spectral span (>700 nm). The source is used for direct absorption spectroscopy with a Michelson-based Fourier transform interferometer.

  14. Absolute distance measurement using a frequency comb , S. A. van den Berg2

    E-print Network

    Absolute distance measurement using a frequency comb M. Cui1 , S. A. van den Berg2 , J. J. M. Braat metrology. Introduction to the stabilized frequency comb Application for distance measurement The pulse often need complex metrology systems to determine the inter-satellite distances. The stabilized

  15. 2D-LC characterization of comb-shaped polymers using isotope effect.

    PubMed

    Ahn, Seonyoung; Im, Kyuhyun; Chang, Taihyun; Chambon, Pierre; Fernyhough, Christine M

    2011-06-01

    A rigorous molecular characterization of comb-shaped polystyrene (PS) was carried out taking advantage of its molecular structure, a normal hydrogenous backbone, and deuterated side chains. Normal phase LC (NPLC) can separate the comb PS species well according to their molecular weight. Nonetheless, it cannot distinguish the backbone from the side chains and the differently structured polymers having a similar molecular weight, e.g, a single backbone comb and a coupled backbone comb with fewer side chains. In contrast to NPLC, the hydrogenous polymer is retained longer than the deuterated counterpart in reversed phase LC (RPLC). When the isotope sensitivity of RPLC is taken advantage of, the comb PS is cross fractionated by NPLC and RPLC, and a two-dimensional mapping with respect to the backbone chain length and the number of branches is fully established. PMID:21510680

  16. Frequency-comb-referenced tunable diode laser spectroscopy and laser stabilization applied to laser cooling.

    PubMed

    Fordell, Thomas; Wallin, Anders E; Lindvall, Thomas; Vainio, Markku; Merimaa, Mikko

    2014-11-01

    Laser cooling of trapped atoms and ions in optical clocks demands stable light sources with precisely known absolute frequencies. Since a frequency comb is a vital part of any optical clock, the comb lines can be used for stabilizing tunable, user-friendly diode lasers. Here, a light source for laser cooling of trapped strontium ions is described. The megahertz-level stability and absolute frequency required are realized by stabilizing a distributed-feedback semiconductor laser to a frequency comb. Simple electronics is used to lock and scan the laser across the comb lines, and comb mode number ambiguities are resolved by using a separate, saturated absorption cell that exhibits easily distinguishable hyperfine absorption lines with known frequencies. Due to the simplicity, speed, and wide tuning range it offers, the employed technique could find wider use in precision spectroscopy. PMID:25402914

  17. Photothermally driven fast responding photo-actuators fabricated with comb-type hydrogels and magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Lee, Eunsu; Kim, Dowan; Kim, Haneul; Yoon, Jinhwan

    2015-10-01

    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 hydrogel matrix by converting absorbed visible light to thermal energy. In this process, the comb-type hydrogel matrix exhibited a rapid response due to the free, mobile grafted chains. The comb-type hydrogel exhibited significantly enhanced light-induced volume shrinkage and rapid recovery. The comb-type hydrogels containing MNP were successfully used to fabricate a bilayer-type photo-actuator with fast bending motion.

  18. Photothermally driven fast responding photo-actuators fabricated with comb-type hydrogels and magnetite nanoparticles

    PubMed Central

    Lee, Eunsu; Kim, Dowan; Kim, Haneul; Yoon, Jinhwan

    2015-01-01

    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 hydrogel matrix by converting absorbed visible light to thermal energy. In this process, the comb-type hydrogel matrix exhibited a rapid response due to the free, mobile grafted chains. The comb-type hydrogel exhibited significantly enhanced light-induced volume shrinkage and rapid recovery. The comb-type hydrogels containing MNP were successfully used to fabricate a bilayer-type photo-actuator with fast bending motion. PMID:26459918

  19. Precision measurements and applications of femtosecond frequency combs

    NASA Astrophysics Data System (ADS)

    Jones, R. Jason

    2002-05-01

    The merging of femtosecond (fs) laser physics with the field of optical f requency metrology over recent years has had a profound impact on both di sciplines. Precision control of the broad frequency bandwidth from fs la sers has enabled new areas of exploration in ultrafast physics and revolu tionized optical frequency measurement and precision spectroscopy. Most recently, the transition frequency of the length standard at 514.7 nm,^ 127I2 P(13) 43-0 a3 has been measured in our lab with an improvement of more than 100 times in precision. Interesting molecular dynamics and s tructure are being explored using absolute frequency map of molecular tra nsitions over a large wavelength range. The iodine transition at 532 nm h as been used to establish an optical atomic clock with a fs comb providin g both an RF standard with stability comparable to the best atomic clocks and millions of optical frequencies across the visible and near IR spect rum, each stable to the Hz level. Work is presently underway to directly compare the iodine optical clocks at JILA with the Hg and Ca optical cloc ks currently being refined at NIST via a direct optical fiber link. A wi dely tunable single frequency laser in combination with a fs comb has bee n employed to realize an optical frequency synthesizer. Frequency combs of two independent ultrafast lasers have been coherently locked, enablin g several different avenues of application such as synthesis of arbitrary waveforms, coherent control of quantum systems, and coherent anti-Stokes Raman scattering microscopy. This talk will review these recent accompl ishments from our lab and discuss plans for further improving the control and precision of fs laser based measurements. te

  20. Comb-Referenced Sub-Doppler Resolution Infrared Spectrometer

    NASA Astrophysics Data System (ADS)

    Sasada, Hiroyuki

    2015-06-01

    We have developed a sub-Doppler resolution spectrometer. A difference frequency generation source, which consists of a pump source of a Nd:YAG laser, a signal source of an extended-cavity laser diode, and a waveguide-type PPLN, covers from 87 to 93 THz (2900 to 3100 wn). An enhanced-cavity absorption cell remarkably improves the sensitivity of Lamb dips. An optical frequency comb controls the central frequency of the source with an uncertainty of a few kilohertz. Because the idler frequency is swept based on absolute frequency through the comb, recorded spectra can be repeatedly accumulated without any frequency drift. We have applied the spectrometer to resolve the hyperfine structure of the fundamental band of HCl with a spectral resolution of about 250 kHz. To reduce the transit-time broadening, a novel enhanced-cavity absorption cell coupled with an idler wave of 1.9-mm beam radius at the beam waist has been introduced. The A1-A2 splitting of the ?b{1} and ?b{4} bands of CH3D is resolved for a few tens low-J transitions with the Lamb-dip linewidth of 60 to 100 kHz. Very recently, the source linewidth has reduced to 3 kHz using a linewidth transfer technique from the Nd:YAG laser to the extended-cavity laser diode through a novel optical frequency comb with a fast servo control. When methane sample is cooled with liquid-nitrogen, and the beam radius is expanded to 3 mm, the observed Lamb dip is 20 kHz wide without any enhanced-cavity absorption cell.

  1. Full multipartite entanglement of frequency-comb Gaussian states.

    PubMed

    Gerke, S; Sperling, J; Vogel, W; Cai, Y; Roslund, J; Treps, N; Fabre, C

    2015-02-01

    An analysis is conducted of the multipartite entanglement for Gaussian states generated by the parametric down-conversion of a femtosecond frequency comb. Using a recently introduced method for constructing optimal entanglement criteria, a family of tests is formulated for mode decompositions that extends beyond the traditional bipartition analyses. A numerical optimization over this family is performed to achieve maximal significance of entanglement verification. For experimentally prepared 4-, 6-, and 10-mode states, full entanglement is certified for all of the 14, 202, and 115 974 possible nontrivial partitions, respectively. PMID:25699426

  2. Full multipartite entanglement of frequency comb Gaussian states

    E-print Network

    S. Gerke; J. Sperling; W. Vogel; Y. Cai; J. Roslund; N. Treps; C. Fabre

    2015-02-13

    An analysis is conducted of the multipartite entanglement for Gaussian states generated by the parametric down-conversion of a femtosecond frequency comb. Using a recently introduced method for constructing optimal entanglement criteria, a family of tests is formulated for mode decompositions that extends beyond the traditional bipartition analyses. A numerical optimization over this family is performed to achieve maximal significance of entanglement verification. For experimentally prepared 4-, 6-, and 10-mode states, full entanglement is certified for all of the 14, 202, and 115974 possible nontrivial partitions, respectively.

  3. Highly non-linear optical microresonators for frequency combs generation

    NASA Astrophysics Data System (ADS)

    Zhivotkov, Daniil S.; Romanova, Elena A.; Vukovic, Ana; Phang, Sendy

    2015-03-01

    Highly non-linear chalcogenide glasses are considered as a prospective material for frequency comb generation in optical microresonators. Using of a 2D microresonator for tailoring the normal material dispersion of chalcogenide glass is analyzed by evaluation of the group velocity dispersion coefficient in near- and mid- infrared. This is done for both approximate and accurate modal resonances of the whispering gallery modes of a 2D circular chalcogenide resonators. The results show that the using of a chalcogenide resonator extends the spectral range of normal dispersion regime to longer wavelengths.

  4. Adaptive dual-comb spectroscopy in the green region.

    PubMed

    Ideguchi, T; Poisson, A; Guelachvili, G; Hänsch, T W; Picqué, N

    2012-12-01

    Dual-comb spectroscopy is extended to the visible spectral range with two short-pulse frequency-doubled free-running ytterbium-doped fiber lasers. When the spectrum is shifted to other domains by nonlinear frequency conversion, tracking the relative fluctuations of the femtosecond oscillators at their fundamental wavelength automatically produces the correction signal needed for the recording of distortion-free spectra. The dense rovibronic spectrum of iodine around 19,240 cm(-1) is recorded within 12 ms at Doppler-limited resolution. PMID:23202066

  5. Atomic Frequency Comb storage as a slow-light effect

    E-print Network

    Bonarota, M; Moiseev, S A; Chanelière, T

    2011-01-01

    Atomic Frequency Comb (AFC) protocol has been particularly successful recently to demonstrate the storage of quantum information in a solid medium (rare-earth doped crystals). The AFC is inspired by the photon-echo technique. We show in this paper that the AFC is actually closely related to the slow-light based storage protocols extensively used in atomic vapours. Experimental verifications are performed in thulium doped YAG (Tm3+:YAG). We clarify the interplay between absorption and dispersion and propose a classification of the existing protocols.

  6. Atomic Frequency Comb storage as a slow-light effect

    E-print Network

    M. Bonarota; J. -L. Le Gouët; S. A. Moiseev; T. Chanelière

    2012-01-05

    Atomic Frequency Comb (AFC) protocol has been particularly successful recently to demonstrate the storage of quantum information in a solid medium (rare-earth doped crystals). The AFC is inspired by the photon-echo technique. We show in this paper that the AFC is actually closely related to the slow-light based storage protocols extensively used in atomic vapours. Experimental verifications are performed in thulium doped YAG (Tm3+:YAG). We clarify the interplay between absorption and dispersion and propose a classification of the existing protocols.

  7. Microwave photonic comb filter with ultra-fast tunability.

    PubMed

    Jiang, H Y; Yan, L S; Pan, Y; Pan, W; Luo, B; Zou, X H; Eggleton, B J

    2015-11-01

    A microwave comb filter with ultra-fast tunability is proposed based on the fundamental delay-line microwave photonic filter. The central frequency of the passband or stopband in such a filter can be rapidly adjusted, along with the independent tunability of the free spectral range (FSR). Experimental results show that the central frequency of the transfer function is electronically tuned with a frequency difference of half of the FSR at a speed of <100??ps. Such high-speed tunability is vital for high-speed microwave switching, frequency hopping, cognitive radio, and next-generation radar systems. PMID:26512477

  8. Frequency combs with weakly lasing exciton-polariton condensates.

    PubMed

    Rayanov, K; Altshuler, B L; Rubo, Y G; Flach, S

    2015-05-15

    We predict the spontaneous modulated emission from a pair of exciton-polariton condensates due to coherent (Josephson) and dissipative coupling. We show that strong polariton-polariton interaction generates complex dynamics in the weak-lasing domain way beyond Hopf bifurcations. As a result, the exciton-polariton condensates exhibit self-induced oscillations and emit an equidistant frequency comb light spectrum. A plethora of possible emission spectra with asymmetric peak distributions appears due to spontaneously broken time-reversal symmetry. The lasing dynamics is affected by the shot noise arising from the influx of polaritons. That results in a complex inhomogeneous line broadening. PMID:26024173

  9. Sex Education: Another View

    ERIC Educational Resources Information Center

    Hamilton, Jennifer

    1977-01-01

    The mother of a 14-year-old mentally retarded boy comments on the viewpoints of Dr. Sol Gordon (a sex education columnist) regarding masturbation, questions on sex, marriage, and the parents' role. (SBH)

  10. Practice Safer Sex

    MedlinePLUS

    ... This information in Spanish ( en español ) Practice safer sex Related information Men's health Screening tests and vaccines ... Return to top More information on Practice safer sex Explore other publications and websites Addressing HIV, Other ...

  11. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 9, NO. 4, JULY/AUGUST 2003 1041 Optical Frequency Combs: From Frequency

    E-print Network

    , frequency synthesizers, metrology, nonlinear spectroscopy, optical frequency comb, optical frequency Optical Frequency Combs: From Frequency Metrology to Optical Phase Control Jun Ye, Harald Schnatz, and Leo the foundation of a "femtosecond optical-frequency comb generator" with a regular comb of sharp lines with well

  12. Sex Education. Chapter Seventeen.

    ERIC Educational Resources Information Center

    Caster, Jerry A.

    Information and a framework that permits teachers to plan and initiate a successful sex education program for students with mental disabilities is provided. A major aspect of sex education should be its focus on social relationships, emotions, choice-making, and responsibilities to self and others. Sex education should not be viewed as a…

  13. Single-Sex Classrooms

    ERIC Educational Resources Information Center

    Protheroe, Nancy

    2009-01-01

    Although single-sex education was once the norm in the U.S., the practice has largely been confined to private schools for more than a century. However, with the introduction of the final version of the U.S. Department of Education's so-called single-sex regulations in 2006, public schools were allowed greater flexibility to offer single-sex

  14. Sex GENOTYPING PROTOCOL PCR PROTOCOL NAME: Sex1

    E-print Network

    Shoubridge, Eric

    Sex GENOTYPING PROTOCOL GENE NAME: PCR PROTOCOL NAME: Sex1 PCR REAGENTS: 10X NEB THERMOPOL PCR) PRIMERS: Sex1 Forward (20uM Standard Working Concentration) Sex1 Reverse (20uM Standard Working CONDITIONS: Sex (or Sex1) 95 C for 3 min 95 C for 30 sec 60 C for 1 min 35 cycles

  15. Making Healthy Decisions About Sex

    MedlinePLUS

    ... For Teens: How to Make Healthy Decisions About Sex Article Body Before you decide to have sex ... alcohol or use drugs. Are You Ready for Sex? Sex can change your life and relationships. Having ...

  16. Harnessing high-dimensional hyperentanglement through a biphoton frequency comb

    NASA Astrophysics Data System (ADS)

    Xie, Zhenda; Zhong, Tian; Shrestha, Sajan; Xu, Xinan; Liang, Junlin; Gong, Yan-Xiao; Bienfang, Joshua C.; Restelli, Alessandro; Shapiro, Jeffrey H.; Wong, Franco N. C.; Wei Wong, Chee

    2015-08-01

    Quantum entanglement is a fundamental resource for secure information processing and communications, and hyperentanglement or high-dimensional entanglement has been separately proposed for its high data capacity and error resilience. The continuous-variable nature of the energy-time entanglement makes it an ideal candidate for efficient high-dimensional coding with minimal limitations. Here, we demonstrate the first simultaneous high-dimensional hyperentanglement using a biphoton frequency comb to harness the full potential in both the energy and time domain. Long-postulated Hong-Ou-Mandel quantum revival is exhibited, with up to 19 time-bins and 96.5% visibilities. We further witness the high-dimensional energy-time entanglement through Franson revivals, observed periodically at integer time-bins, with 97.8% visibility. This qudit state is observed to simultaneously violate the generalized Bell inequality by up to 10.95 standard deviations while observing recurrent Clauser-Horne-Shimony-Holt S-parameters up to 2.76. Our biphoton frequency comb provides a platform for photon-efficient quantum communications towards the ultimate channel capacity through energy-time-polarization high-dimensional encoding.

  17. Geotropism of hornet comb construction under persistent acceleration.

    PubMed

    Ishay, J; Sadeh, D

    1978-01-01

    Social wasps (Vespinae) are insects which build in a precise geotactical orientation. The effect of persistent acceleration on comb construction by Oriental hornet (Vespa orientalis) workers was assessed experimentally within breeding boxes of various size and shape. Groups of hornets at the building phase were subjected to a centrifugal and gravitational force with a resultant ranging between 26 degrees and 45 degrees. The comb construction within such boxes was compared to that within control boxes under ordinary gravitational pull. It was found that: a) juvenile hornets (1-2 days of age) placed in quasi-rectangular boxes built in the direction of the resultant force; b) juvenile and adult hornets (3-7 days of age) placed in spherical shaped containers also built in the direction of the resultant force; c) adult hornets who had spent their first days of life in a stationary rectangular box, apparently learned the direction of the gravitational force and "tried" to build in this direction when exposed to a centrifugal force; d) adult hornets made to spin in quasi-rectangular boxes tilted in the direction of the calculated resultant force built in the direction of the resultant. These results suggest that hornets learn the direction of the gravitational force during the first days of life and that geometrical cues within the breeding box enable them to build in the direction of the force to which they have become habituated. From the standpoint of geometric cues, only the roof of the breeding box is of critical importance. PMID:11965666

  18. Quantum Information Processing with Atomic Qubits and Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Campbell, Wesley

    2010-03-01

    Pulsed optical fields from mode-locked lasers have found widespread use as tools for precision quantum control and are well suited for implementation in quantum information processing and quantum simulation. We experimentally demonstrate two distinct regimes of the interaction between hyperfine atomic ion qubits and stimulated Raman transitions driven by picosecond pulses from a far off- resonant mode-locked laser. In the weak pulse regime, the coherent accumulation of successive pulses from an optical frequency comb performs single qubit operations and is used to entangle two trapped atomic ion qubits. In the strong pulse regime, a single pulse is used to implement a fast (<10 ps) Hadamard gate and we show how a few pulses may be used to address the atom's motion by imparting state-dependent momentum kicks. To entangle multiple ions, optical frequency combs operated near the strong pulse regime may be used to implement motion-mediated gates that can be performed much faster than a collective motional period.[4pt] [1] Garc'ia-Ripoll et al., PRL 91, 157901 (2003).[0pt] [2] Duan, PRL 93, 100502 (2004).

  19. Sexing young snowy owls

    USGS Publications Warehouse

    Seidensticker, M.T.; Holt, D.W.; Detienne, J.; Talbot, S.; Gray, K.

    2011-01-01

    We predicted sex of 140 Snowy Owl (Bubo scandiacus) nestlings out of 34 nests at our Barrow, Alaska, study area to develop a technique for sexing these owls in the field. We primarily sexed young, flightless owls (3844 d old) by quantifying plumage markings on the remiges and tail, predicting sex, and collecting blood samples to test our field predictions using molecular sexing techniques. We categorized and quantified three different plumage markings: two types of bars (defined as markings that touch the rachis) and spots (defined as markings that do not touch the rachis). We predicted sex in the field assuming that males had more spots than bars and females more bars than spots on the remiges and rectrices. Molecular data indicated that we correctly sexed 100% of the nestlings. We modeled the data using random forests and classification trees. Both models indicated that the number and type of markings on the secondary feathers were the most important in classifying nestling sex. The statistical models verified our initial qualitative prediction that males have more spots than bars and females more bars than spots on flight feathers P6P10 for both wings and tail feathers T1 and T2. This study provides researchers with an easily replicable and highly accurate method for sexing young Snowy Owls in the field, which should aid further studies of sex-ratios and sex-related variation in behavior and growth of this circumpolar owl species. ?? 2011 The Raptor Research Foundation, Inc.

  20. Osho - Insights on sex

    PubMed Central

    Nagaraj, Anil Kumar Mysore

    2013-01-01

    Sex is a mysterious phenomenon, which has puzzled even great sages. Human beings have researched and mastered the biology of sex. But that is not all. Sex needs to be understood from the spiritual perspective too. The vision of Osho is an enlightening experience in this regard. Out of the thousands of lectures, five lectures on sex made Osho most notorious. Born into a Jain family of Madhya Pradesh, Rajneesh, who later wanted himself to be called Osho, is a great master. He has spoken volumes on a wide range of topics ranging from sex to super-consciousness. His contributions in the area of sex are based on the principles of “Tantra” which has its origin from Buddhism. This article focuses on his life and insights on sex, which if understood properly, can be a stepping stone for enlightenment. PMID:23858266

  1. Terabit/s communications using chip-scale frequency comb sources

    NASA Astrophysics Data System (ADS)

    Koos, Christian; Kippenberg, Tobias J.; Barry, Liam P.; Dalton, Larry; Freude, Wolfgang; Leuthold, Juerg; Pfeifle, Joerg; Weimann, Claudius; Lauermann, Matthias; Kemal, Juned N.; Palmer, Robert; Koeber, Sebastian; Schindler, Philipp C.; Herr, Tobias; Brasch, Victor; Watts, Regan T.; Elder, Delwin

    2015-03-01

    High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the necessary light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview of our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling line rates up to 1.152 Tbit/s. In a second set of experiments, we use injection locking of a gain-switched laser diode to enerate frequency combs. This approach leads to line rates of more than 2 Tbit/s. A third set of experiments is finally dedicated to using Kerr nonlinearities in integrated nonlinear microcavities for frequency comb generation. We demonstrate coherent communication using Kerr frequency comb sources, thereby achieving line rates up to 1.44 Tbit/s. Our experiments show that frequency comb generation in chip-scale devices represents a viable approach to terabit communications.

  2. Broadband mid-IR frequency comb source for standoff chemical detection

    NASA Astrophysics Data System (ADS)

    Vodopyanov, Konstantin L.

    2015-05-01

    Frequency-comb-based absorption spectroscopy in the molecular fingerprint part of the spectrum 2-12 ?m has great potential for standoff chemical sensing because of massive parallelism of data acquisition. Especially attractive is the dual-comb Fourier transform spectroscopy, with two phase-locked sources, where full advantage is taken of temporal and spatial coherence of frequency combs as well as of their broadband nature. The promise is high speed (up to 1M spectral points in less than a second), broad spectral coverage (> one octave), superior sensitivity (< 1 part per billion in gas phase), high spectral resolution (~100 MHz), and the possibility of absolute frequency calibration of molecular resonances. Here we report a broadband frequency comb source based on a degenerate optical parametric oscillator (OPO) that allows extending frequency comb technology to the mid-IR range. The OPO uses, as gain element an orientation-patterned GaAs crystal (OP-GaAs), is pumped by a femtosecond Tm-fiber lasers at 2-?m wavelength, and is suitable for performing broadband dual-comb spectroscopy. High temporal coherence and broad instantaneous spectral coverage of 2.5 - 7.5 ?m make this system promising for chemical detection and trace molecular sensing. Few examples of single- and dual-comb spectroscopic sensing are presented.

  3. Glucose sensor based on redox-cycling between selectively modified and unmodified combs of carbon interdigitated array nanoelectrodes.

    PubMed

    Sharma, Deepti; Lim, Yeongjin; Lee, Yunjeong; Shin, Heungjoo

    2015-08-19

    We present a novel electrochemical glucose sensor employing an interdigitated array (IDA) of 1:1 aspect ratio carbon nanoelectrodes for the electrochemical-enzymatic redox cycling of redox species (ferricyanide/ferrocyanide) between glucose oxidase (GOx) and the two comb-shaped nanoelectrodes of the IDA. The carbon nanoelectrodes were fabricated using a simple, cost-effective, reproducible microfabrication technology known as the carbon-microelectromechanical-systems (C-MEMS) process. One comb (comb 1) of the IDA was selectively modified with GOx via the electrochemical reduction of an aryl diazonium salt, while the other comb (comb 2) remained unmodified; this facilitates electrochemically more active surface of comb 2, resulting in sensitive glucose detection. Ferricyanide is reduced to ferrocyanide by the GOx in the presence of glucose, and ferrocyanide diffuses to both combs of the IDA where it is oxidized. The limited electrochemical current collection at the surface-modified comb 1 is counterbalanced by the efficient redox cycling between the enzyme sites at comb 1 and the bare carbon surface of comb 2. Reducing the electrode-to-electrode gap between the two combs (gap = 1.9 ?m) increases the diffusion flux of redox species at comb 2 hence, enhanced the sensitivity and limit of detection of the glucose sensor by ?2.3 and ?295 times, respectively at comb 2 compared to comb 1. The developed IDA-based glucose sensor demonstrated good amperometric response to glucose, affording two linear ranges from 0.001 to 1 mM and from 1 to 10 mM, with limits of detection of 0.4 and 61 ?M and sensitivities of 823.2 and 70.0 ?A mM(-1) cm(-2), respectively. PMID:26343443

  4. Modeling Kerr frequency combs using the Lugiato-Lefever equation: a characterization of the multistable landscape

    NASA Astrophysics Data System (ADS)

    Parra-Rivas, P.; Gomila, D.; Matias, M. A.; Leo, F.; Coen, S.; Gelens, L.

    2014-05-01

    Optical frequency combs can be used to measure light frequencies and time intervals more easily and precisely than ever before, opening a large avenue for applications. Traditional frequency combs are usually associated with trains of evenly spaced, very short pulses. More recently, a new generation of comb sources has been demonstrated in compact high-Q optical microresonators with a Kerr nonlinearity pumped by continuous-wave laser light. These combs are now referred to as Kerr frequency combs and have attracted a lot of interest in the last few years. Kerr frequency combs can be modeled in a way that is strongly reminiscent of temporal cavity solitons (CSs) in nonlinear cavities. Temporal CSs have been experimentally studied in fiber resonators and their description is based on a now classical equation, the Lugiato-Lefever equation, that describes pattern formation in optical systems. In this work, we first perform a theoretical study of the correspondence between the CSs and patterns with frequency combs. It is known that the CSs appear in reversible systems that present bistability between a pattern and a homogeneous steady state through what it is called a homoclinic snaking structure. In this snaking region, single and multi-peak CSs coexist with patterns and homogeneous solutions, creating a largely multistable landscape. We study the changes of the homoclinic snaking for different parameter regimes in the Lugiato-Lefever equation and determine the stability and shape of the frequency combs through comparison with the underlying CSs and patterns. Secondly, we include third order dispersion in the system and study its effect on the multistable snaking structure. For high dispersion strengths the CS structures and the corresponding Kerr frequency combs disappear.

  5. Ornamental comb colour predicts T-cell-mediated immunity in male red grouse Lagopus lagopus scoticus.

    PubMed

    Mougeot, Francois

    2008-02-01

    Sexual ornaments might reliably indicate the ability to cope with parasites and diseases, and a better ability to mount a primary inflammatory response to a novel challenge. Carotenoid-based ornaments are amongst the commonest sexual signals of birds and often influence mate choice. Because carotenoids are immuno-stimulants, signallers may trade-off allocating these to ornamental colouration or using them for immune responses, so carotenoid-based ornaments might be particularly useful as honest indicators of immuno-compentence. Tetraonid birds, such as the red grouse Lagopus lagopus scoticus, exhibit supra-orbital yellow-red combs, a conspicuous ornament which functions in intra- and inter-sexual selection. The colour of combs is due to epidermal pigmentation by carotenoids, while their size is testosterone-dependent. In this study, I investigated whether comb characteristics, and in particular, comb colour, indicated immuno-competence in free-living male red grouse. I assessed T-cell-mediated immunity using a standardised challenge with phytohaemagglutinin. Red grouse combs reflect in the red and in the ultraviolet spectrum of light, which is not visible to humans but that grouse most likely see, so I measured comb colour across the whole bird visible spectrum (300-700 nm) using a reflectance spectrometer. I found that males with bigger and redder combs, but with less ultraviolet reflectance, had greater T-cell-mediated immune response. Comb colour predicted T-cell-mediated immune response better than comb size, indicating that the carotenoid-based colouration of this ornament might reliably signal this aspect of male quality. PMID:17898979

  6. Towards efficient octave-spanning comb with micro-structured crystalline resonator

    NASA Astrophysics Data System (ADS)

    Grudinin, Ivan S.; Yu, Nan

    2015-03-01

    Optical frequency combs, typically produced by mode locked lasers, have revolutionized many applications in science and technology. Frequency combs were recently generated by micro resonators through nonlinear Kerr processes. However, the comb span from micro resonators was found to be limited by resonator dispersion and mode spectrum. While dispersion engineering has been reported in on-chip devices, monolithic crystalline resonators offer an advantage of high optical quality factor. Moreover, most resonators used for comb generation support many mode families, leading to unavoidable crossings in resonator spectrum. Such crossings strongly influence comb dynamics and may prevent stable coherent mode-locking and soliton states. We report a new crystalline resonator approach supporting dispersion control and single mode spectrum while maintaining high quality factor. Dispersion engineering by waveguide micro-structuring is used to flatten the dispersion in our MgF2 resonator. Both absolute magnitude of dispersion and its slopes can be altered over a wavelength span exceeding an octave. Dispersion flattening leads to generation of an octave-spanning frequency comb with repetition rate of 46 GHz and coupled pump power below 100 mW. We also demonstrate that the micro- structuring dispersion engineering approach can be used to achieve flattened and anomalous dispersion in a CaF2 resonator near 1550 nm wavelength. In addition, we describe observation of discrete steps between the modulation instability states of the primary comb and on the three-stage comb unfolding dynamics. The micro-structured resonators may enable efficient low repetition rate coherent octave spanning frequency combs without external broadening, ideal for applications in optical frequency synthesis, metrology, spectroscopy, and communications.

  7. Ornamental comb colour predicts T-cell-mediated immunity in male red grouse Lagopus lagopus scoticus

    NASA Astrophysics Data System (ADS)

    Mougeot, Francois

    2008-02-01

    Sexual ornaments might reliably indicate the ability to cope with parasites and diseases, and a better ability to mount a primary inflammatory response to a novel challenge. Carotenoid-based ornaments are amongst the commonest sexual signals of birds and often influence mate choice. Because carotenoids are immuno-stimulants, signallers may trade-off allocating these to ornamental colouration or using them for immune responses, so carotenoid-based ornaments might be particularly useful as honest indicators of immuno-compentence. Tetraonid birds, such as the red grouse Lagopus lagopus scoticus, exhibit supra-orbital yellow red combs, a conspicuous ornament which functions in intra- and inter-sexual selection. The colour of combs is due to epidermal pigmentation by carotenoids, while their size is testosterone-dependent. In this study, I investigated whether comb characteristics, and in particular, comb colour, indicated immuno-competence in free-living male red grouse. I assessed T-cell-mediated immunity using a standardised challenge with phytohaemagglutinin. Red grouse combs reflect in the red and in the ultraviolet spectrum of light, which is not visible to humans but that grouse most likely see, so I measured comb colour across the whole bird visible spectrum (300 700 nm) using a reflectance spectrometer. I found that males with bigger and redder combs, but with less ultraviolet reflectance, had greater T-cell-mediated immune response. Comb colour predicted T-cell-mediated immune response better than comb size, indicating that the carotenoid-based colouration of this ornament might reliably signal this aspect of male quality.

  8. Evaluating the coherence and time-domain profile of quantum cascade laser frequency combs.

    PubMed

    Burghoff, David; Yang, Yang; Hayton, Darren J; Gao, Jian-Rong; Reno, John L; Hu, Qing

    2015-01-26

    Recently, much attention has been focused on the generation of optical frequency combs from quantum cascade lasers. We discuss how fast detectors can be used to demonstrate the mutual coherence of such combs, and present an inequality that can be used to quantitatively evaluate their performance. We discuss several technical issues related to shifted wave interference Fourier Transform spectroscopy (SWIFTS), and show how such measurements can be used to elucidate the time-domain properties of such combs, showing that they can possess signatures of both frequency-modulation and amplitude-modulation. PMID:25835878

  9. Chaotic dynamics of frequency combs generated with continuously pumped nonlinear microresonators.

    PubMed

    Matsko, A B; Liang, W; Savchenkov, A A; Maleki, L

    2013-02-15

    We theoretically and experimentally investigate the chaotic regime of optical frequency combs generated in nonlinear ring microresonators pumped with continuous wave light. We show that the chaotic regime reveals itself by a flat top symmetric envelope of the frequency spectrum, when observed by means of an optical spectrum analyzer. The comb, demodulated on a fast photodiode, produces a noisy radio frequency signal with spectral width significantly exceeding the linear bandwidth of the microresonator mode. We discuss practical ways of excitation of a coherent frequency comb and avoiding the chaotic regime. PMID:23455124

  10. Enhancement of two-photon transition rate by selectively removing certain frequency comb teeth

    E-print Network

    Zhang, Shuangyou; Zhao, Jianye

    2015-01-01

    We present experiments demonstrating an enhancement of resonant two-photon transition rate in 87Rb utilizing spectral phase manipulation of the excitation frequency comb. By selectively removing certain comb teeth, the resonant two-photon transition rate can be improved, and reach a factor of more than 1.8. The femtosecond pulse-train excitation of two-photon transition is investigated theoretically based on general multiphoton transitions and the results are compared with the experiments. The theory presented here gives a clear insight of physical mechanism of this quantum coherent control and indicates that it is simple, effective and universal for nonlinear interactions between frequency combs and matters.

  11. Drop-Port Study of Microresonator Frequency Combs: Pump Saturation and Power Transfer

    E-print Network

    Wang, Pei-Hsun; Fan, Li; Varghese, Leo Tom; Wang, Jian; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

    2013-01-01

    We use a drop-port geometry to study power transfer in on-chip microresonator frequency comb generators. In sharp contrast with the traditional transmission geometry, we observe smooth output spectra with comparable powers in the pump and adjacent comb lines. For the first time to our knowledge, a saturation behavior of the optical pump in the microresonator is observed, suggesting clamping of the parametric gain. A nonlinear coupling effect, which results from frequency comb-induced pump saturation, is also identified through a simple model.

  12. Characterization of frequency noise on a broadband infrared frequency comb using optical heterodyne techniques.

    PubMed

    Kim, K; Nicholson, J W; Yan, M; Knight, J C; Newbury, N R; Diddams, S A

    2007-12-24

    We measure the frequency noise across a Cr:forsterite infrared frequency comb through the optical heterodyne beat of different comb teeth against stable continuous wave (CW) lasers. This sensitive measurement shows strong correlations of the frequency noise between spectral components of the comb, relative to a fixed optical frequency near the 1.3 micron carrier of the Cr:forsterite laser. The correlated frequency fluctuations are shown to arise from amplitude noise on the pump laser. We also report a preliminary comparison of excess noise that occurs during supercontinuum generation in both highly nonlinear fiber and an extruded glass microstructured fiber. PMID:19551068

  13. Demonstration of a Near-IR Laser Comb for Precision Radial Velocity Measurements in Astronomy

    E-print Network

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

    2015-01-01

    We describe a successful effort to produce a laser comb around 1.55 $\\mu$m in the astronomical H band using a method based on a line-referenced, electro-optical-modulation frequency comb. We discuss the experimental setup, laboratory results, and proof of concept demonstrations at the NASA Infrared Telescope Facility (IRTF) and the Keck-II telescope. The laser comb has a demonstrated stability of $technology, when coupled with a high spectral resolution spectrograph, offers the promise of $<$1 m/s radial velocity precision suitable for the detection of Earth-sized planets in the habitable zones of cool M-type stars.

  14. Mid-infrared optical frequency combs based on difference frequency generation for molecular spectroscopy

    NASA Astrophysics Data System (ADS)

    Cruz, Flavio C.; Maser, Daniel L.; Johnson, Todd; Ycas, Gabriel; Klose, Andrew; Giorgetta, Fabrizio R.; Coddington, Ian; Diddams, Scott A.

    2015-10-01

    Mid-infrared femtosecond optical frequency combs were produced by difference frequency generation of the spectral components of a near-infrared comb in a 3-mm-long MgO:PPLN crystal. We observe strong pump depletion and 9.3 dB parametric gain in the 1.5 \\mu m signal, which yields powers above 500 mW (3 \\mu W/mode) in the idler with spectra covering 2.8 \\mu m to 3.5 \\mu m. Potential for broadband, high-resolution molecular spectroscopy is demonstrated by absorption spectra and interferograms obtained by heterodyning two combs.

  15. A Fine-Tooth Comb to Measure the Accelerating Universe

    NASA Astrophysics Data System (ADS)

    2008-09-01

    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 worth recalling that the kind of precision required, 1 cm/s, corresponds, on the focal plane of a typical high-resolution spectrograph, to a shift of a few tenths of a nanometre, that is, the size of some molecules," explains PhD student and team member Constanza Araujo-Hauck from ESO. The new calibration technique comes from the combination of astronomy and quantum optics, in a collaboration between researchers at ESO and the Max Planck Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a 'frequency comb' - light at many frequencies separated by a constant interval - to create just the kind of precise 'ruler' needed to calibrate a spectrograph. After successful tests in the MPQ laboratory in 2007, the team have successfully tested a prototype device using the laser comb at the VTT (Vacuum Tower Telescope) solar telescope in Tenerife, on 8 March 2008, measuring the spectrum of the Sun in infrared light. The results are already impressive, and the technique promises to achieve the accuracy needed to study these big astronomical questions. "In our tests in Tenerife, we have already achieved beyond state-of-the-art accuracy. Now we are going to make the system more versatile, and develop it even further," says team member Tilo Steinmetz, from Menlo Systems GmbH, a spin-off company from the Max Planck Institute, which was founded to commercialise the frequency comb technique. Having tested the technique on a solar telescope, a new version of the system is now being built for the HARPS planet-finder instrument on ESO's 3.6-metre telescope at La Silla in Chile, before being considered for future generations of instruments. One of the ambitious project to be realised with the E-ELT, called CODEX, aims to measure the recently discovered acceleration of the universe directly, by following the velocities of distant galaxies and quasars over a 20-year period. This would let astronomers test Einstein's general relativity and the nature of the recently discovered, and mysterious, dark energy. "We have to measu

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  17. Tunable frequency combs based on dual microring resonators

    E-print Network

    Miller, Steven A; Ramelow, Sven; Luke, Kevin; Dutt, Avik; Farsi, Alessandro; Gaeta, Alexander L; Lipson, Michal

    2015-01-01

    In order to achieve efficient parametric frequency comb generation in microresonators, external control of coupling between the cavity and the bus waveguide is necessary. However, for passive monolithically integrated structures, the coupling gap is fixed and cannot be externally controlled, making tuning the coupling inherently challenging. We design a dual-cavity coupled microresonator structure in which tuning one ring resonance frequency induces a change in the overall cavity coupling condition. We demonstrate wide extinction tunability with high efficiency by engineering the ring coupling conditions. Additionally, we note a distinct dispersion tunability resulting from coupling two cavities of slightly different path lengths, and present a new method of modal dispersion engineering. Our fabricated devices consist of two coupled high quality factor silicon nitride microresonators, where the extinction ratio of the resonances can be controlled using integrated microheaters. Using this extinction tunability...

  18. High performance tunnel injection quantum dot comb laser

    SciTech Connect

    Lee, C.-S.; Guo Wei; Basu, Debashish; Bhattacharya, Pallab

    2010-03-08

    A high-speed multiwavelength quantum dot comb laser, grown by molecular beam epitaxy, is demonstrated. The device is characterized with a 75.9 nm (full width at half maximum) and a 91.4 nm (DELTA{sub -15dB}) wide lasing spectrum. There are 105 and 185 simultaneously emitted longitudinal modes with a maximum channel intensity nonuniformity of less than 3 dB in the spectral range of 1231-1252 nm and 1274-1311 nm, respectively, for a laser with 1040 mum cavity length. The channel spacing can be tuned with cavity length and remains invariant in the temperature range of 300-323 K. The small signal modulation bandwidth is 7.5 GHz.

  19. Multimode quantum memory based on atomic frequency combs

    E-print Network

    Mikael Afzelius; Christoph Simon; Hugues de Riedmatten; Nicolas Gisin

    2009-05-22

    An efficient multi-mode quantum memory is a crucial resource for long-distance quantum communication based on quantum repeaters. We propose a quantum memory based on spectral shaping of an inhomogeneously broadened optical transition into an atomic frequency comb (AFC). The spectral width of the AFC allows efficient storage of multiple temporal modes, without the need to increase the absorption depth of the storage material, in contrast to previously known quantum memories. Efficient readout is possible thanks to rephasing of the atomic dipoles due to the AFC structure. Long-time storage and on-demand readout is achieved by use of spin-states in a lambda-type configuration. We show that an AFC quantum memory realized in solids doped with rare-earth-metal ions could store hundreds of modes or more with close to unit efficiency, for material parameters achievable today.

  20. Time-Delay Interferometry with optical frequency comb

    E-print Network

    Tinto, Massimo

    2015-01-01

    Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises it has been previously suggested that additional inter-spacecraft phase measurements must be performed by modulating the laser beams. This technique, however, considerably increases system complexity and probability of subsystem failure. With the advent of self-referenced optical frequency combs, it is possible to generate the heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be cancelled directly by applying modified second-generation Time-Delay Interferometric combinations to the heterodyne phase measurements. This approach avoids use of modulated laser beams as well as the need of additional ultra-stable oscillator clocks.

  1. Time-Delay Interferometry with optical frequency comb

    E-print Network

    Massimo Tinto; Nan Yu

    2015-02-23

    Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises it has been previously suggested that additional inter-spacecraft phase measurements must be performed by modulating the laser beams. This technique, however, considerably increases system complexity and probability of subsystem failure. With the advent of self-referenced optical frequency combs, it is possible to generate the heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be cancelled directly by applying modified second-generation Time-Delay Interferometric combinations to the heterodyne phase measurements. This approach avoids use of modulated laser beams as well as the need of additional ultra-stable oscillator clocks.

  2. The shapes of simple three and four junction comb polymers

    NASA Astrophysics Data System (ADS)

    von Ferber, Christian; Bishop, Marvin; Forzaglia, Thomas; Reid, Cooper; Zajac, Gregory

    2015-01-01

    A scheme originally proposed by G. Wei [Physica A 222, 152 (1995); Physica A 222, 155 (1995)] is redesigned to produce numerical shape parameters of arbitrary tree-branched polymers based on the Kirchhoff matrix eigenvalue spectrum. This method and two different Monte Carlo techniques (pivot and growth) are employed to investigate the asphericity of three and four junction comb polymers in both the ideal and excluded volume regimes. It is found that the extrapolated g-ratio and asphericity values obtained by all of these methods are in excellent agreement with each other and the available theory in the ideal regime and that polymers with a complete set of interior branches display a more sphere-like shape.

  3. High spectral purity Kerr frequency comb radio frequency photonic oscillator

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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.

  4. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    PubMed

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

    2015-01-01

    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. PMID:26260955

  5. Time-delay interferometry with optical frequency comb

    NASA Astrophysics Data System (ADS)

    Tinto, Massimo; Yu, Nan

    2015-08-01

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

  6. Coherent Raman spectro-imaging with laser frequency combs

    E-print Network

    Ideguchi, Takuro; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W

    2013-01-01

    Optical spectroscopy and imaging of microscopic samples have opened up a wide range of applications throughout the physical, chemical, and biological sciences. High chemical specificity may be achieved by directly interrogating the fundamental or low-lying vibrational energy levels of the compound molecules. Amongst the available prevailing label-free techniques, coherent Raman scattering has the distinguishing features of high spatial resolution down to 200 nm and three-dimensional sectioning. However, combining fast imaging speed and identification of multiple - and possibly unexpected- compounds remains challenging: existing high spectral resolution schemes require long measurement times to achieve broad spectral spans. Here we overcome this difficulty and introduce a novel concept of coherent anti-Stokes Raman scattering (CARS) spectro-imaging with two laser frequency combs. We illustrate the power of our technique with high resolution (4 cm-1) Raman spectra spanning more than 1200 cm-1 recorded within le...

  7. Doing gender in sex and sex research.

    PubMed

    Vanwesenbeeck, Ine

    2009-12-01

    Gender is central to sexuality, and vice versa, but there are a number of difficulties with the treatment of gender in sex research. Apparently, it is hard to find a balance between two conflicting needs. First, obviously, it is necessary to make distinctions between women and men, for political as well as research-technical and theoretical reasons. A second requirement, at odds with the first one, is the necessity to understand gender and its relation to sexuality and the body as much more complex than simplistically referring to two sets of individuals. This is all the more necessary when one realizes the possible drawbacks of exaggerating the differences between the sexes (in particular when they are biologically explained), because of stereotyping, stigmatizing, and expectancy confirmatory processes. This essay identifies and discusses 10 difficulties in the treatment of gender in sex research, reflects on their origins, and reviews theory and evidence with the aim to (1) consider the relative strength of gender/sex as an explanatory variable compared to other factors and processes explaining differences between men and women on a number of sexual aspects, (2) inform an understanding of gender and its relation to sexuality as an ongoing, open-ended, multi-determined, situated, interactional process, with the body as a third player, and (3) argue in favor of a nuanced, well-balanced treatment of gender in sex research. PMID:19859798

  8. Full phase stabilization of a Yb:fiber femtosecond frequency comb

    E-print Network

    of an amplified Yb:fiber femtosecond frequency comb using an intracavity electro-optic modulator and an acousto in a Yb:fiber oscillator [6] and broad bandwidth of electro-optical modulators (EOMs) in Er

  9. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide

    PubMed Central

    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

    2015-01-01

    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. PMID:25697764

  10. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide.

    PubMed

    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

    2015-01-01

    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. PMID:25697764

  11. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide

    NASA Astrophysics Data System (ADS)

    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

    2015-02-01

    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.

  12. Comb structure analysis of the capacitive sensitive element in MEMS-accelerometer

    NASA Astrophysics Data System (ADS)

    Shalimov, Andrew; Timoshenkov, Sergey; Korobova, Natalia; Golovinskiy, Maxim; Timoshenkov, Alexey; Zuev, Egor; Berezueva, Svetlana; Kosolapov, Andrey

    2015-05-01

    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.

  13. Characterizing a fiber-based frequency comb with electro-optic modulator.

    PubMed

    Zhang, Wei; Lours, Michel; Fischer, Marc; Holzwarth, Ronald; Santarelli, Giorgio; Coq, Yann

    2012-03-01

    We report on the characterization of a commercial- core fiber-based frequency comb equipped with an intracavity free-space electro-optic modulator (EOM). We investigate the relationship between the noise of the pump diode and the laser relative intensity noise (RIN) and demonstrate the use of a low-noise current supply to substantially reduce the laser RIN. By measuring several critical transfer functions, we evaluate the potential of the EOM for comb repetition rate stabilization. We also evaluate the coupling to other relevant parameters of the comb. From these measurements, we infer the capabilities of the femtosecond laser comb to generate very-low-phase-noise microwave signals when phase-locked to a high-spectral-purity ultra-stable laser. PMID:22481776

  14. Characteristics of distributed-type inorganic electroluminescence panels with comb-shaped electrodes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-Ichi; Uraoka, Yukiharu; Taguchi, Nobuyoshi; Nonaka, Toshihiro

    2013-09-01

    We deposited comb electrodes with narrow gaps between the teeth on a glass substrate, thus realizing a high electric field intensity that cannot be achieved with conventional structures. Au electrodes are deposited to form a comb shape and then spin-coated with a phosphor layer obtained by mixing ZnS phosphor particles with resins in a certain ratio. An AC voltage was applied to the gaps between the teeth of the comb electrode to emit light, from which the luminance was measured for different electric field intensities. The luminance was not affected by the transmittance of the electrodes themselves when measured from the phosphor layer side. Therefore, it may be possible to produce a display that does not require transparent electrodes by using the phosphor layer side of a device with comb electrodes made of metals, such as Au, for the display.

  15. The applications of comb polymer to the study of liver cell adhesion and signaling

    E-print Network

    Yin, David, 1973-

    2004-01-01

    Comb polymer, which consists of a hydrophobic poly(methyl methacrylate) (PMMA) backbone with hydrophilic hydroxy-poly(ethylene oxide) (HPOEM) side chains, is a tool that has many possible applications for the study of liver ...

  16. Tracing part-per-billion line shifts with direct-frequency-comb Vernier spectroscopy

    NASA Astrophysics Data System (ADS)

    Siciliani de Cumis, M.; Eramo, R.; Coluccelli, N.; Cassinerio, M.; Galzerano, G.; Laporta, P.; De Natale, P.; Cancio Pastor, P.

    2015-01-01

    Accurate frequency measurements of molecular transitions around 2 ? m are performed by using a direct-frequency-comb spectroscopy approach that combines an Er+ frequency-comb oscillator at 1.5 ? m , a Tm-Ho fiber amplifier, and a Fabry-Perot-filter, high-resolution dispersive spectrometer optical multiplex-detection system. This apparatus has unique performances in terms of a wide dynamic range to integrate the intensity per comb mode, which allows one to measure molecular absorption profiles with high precision. Spectroscopic information about transition frequencies and linewidths is very accurately determined. Relative frequency uncertainties of the order of a few parts in 10-9 are achieved for rovibrational transitions of the CO2 molecule around 5100 cm-1. Moreover, tiny frequency shifts due to molecular collisions and interacting laser power using direct comb spectroscopy are investigated in a systematic way.

  17. Applications and noise properties of high repetition rate : TiSapphire frequency combs

    E-print Network

    Benedick, Andrew John

    2011-01-01

    Femtosecond mode-locked lasers are a unique laser technology due to their broad optical bandwidth and potential for linking the optical and radio frequency domains when these lasers are configured as frequency combs. ...

  18. Comb-calibrated solar spectroscopy through a multiplexed single-mode fiber channel

    E-print Network

    Probst, R A; Doerr, H-P; Steinmetz, T; Kentischer, T J; Zhao, G; Hänsch, T W; Udem, Th; Holzwarth, R; Schmidt, W

    2015-01-01

    We investigate a new scheme for astronomical spectrograph calibration using the laser frequency comb at the Solar Vacuum Tower Telescope on Tenerife. Our concept is based upon a single-mode fiber channel, that simultaneously feeds the spectrograph with comb light and sunlight. This yields nearly perfect spatial mode matching between the two sources. In combination with the absolute calibration provided by the frequency comb, this method enables extremely robust and accurate spectroscopic measurements. The performance of this scheme is compared to a sequence of alternating comb and sunlight, and to absorption lines from Earth's atmosphere. We also show how the method can be used for radial-velocity detection by measuring the well-explored 5-minute oscillations averaged over the full solar disk. Our method is currently restricted to solar spectroscopy, but with further evolving fiber-injection techniques it could become an option even for faint astronomical targets.

  19. Redescription of Trogoderma fasciolata Fairmaire, 1897, comb. rev. from Madagascar (Coleoptera: Dermestidae, Megatomini).

    PubMed

    Kadej, Marcin; Háva, Ji?í

    2015-01-01

    Trogoderma fasciolata Fairmaire, 1897, comb. rev. is redescribed, illustrated and restored to the genus Trogoderma Dejean, 1821 from Aethriostoma Motschulsky, 1858. A key to the known Trogoderma species from Madagascar is presented. PMID:25781265

  20. Decade-Spanning High-Precision Terahertz Frequency Comb Ian A. Finneran,1

    E-print Network

    Blake, Geoffrey

    precision of 1.8 × 10-9 . With time-domain detection of the comb, we measure three transitions of water calibration source for radial velocity searches for Earth-sized exoplanets [4] and in measurements

  1. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    NASA Astrophysics Data System (ADS)

    van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

    2015-09-01

    Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. 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. Comparison with a fringe counting laser interferometer shows an agreement within <10-8 for a distance of 50?m.

  2. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    PubMed Central

    van den Berg, Steven. A.; van Eldik, Sjoerd; Bhattacharya, Nandini

    2015-01-01

    Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phased array, the frequency comb modes are resolved spectrally to the level of an individual mode. Having the frequency comb stabilized against an atomic clock, thousands of accurately known wavelengths are available for interferometry. 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. Comparison with a fringe counting laser interferometer shows an agreement within <10?8 for a distance of 50?m. PMID:26419282

  3. Fiber comb filters based on UV-writing Bragg gratings in graded-index multimode fibers

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Lit, John; Gu, Xijia; Wei, Li

    2005-10-01

    We report a new kind of comb filters based on fiber Bragg gratings in graded-index multimode fibers. It produces two groups of spectra with a total of 36 reflection peaks that correspond to 18 principal modes and cross coupled modes. The mode indices and wavelength spacings have been investigated theoretically and experimentally. This kind of comb filters may be used to construct multi-wavelength light sources for sensing, optical communications, and instrumentations

  4. Optimally coherent Kerr combs generated with crystalline whispering gallery mode resonators for ultrahigh capacity fiber communications.

    PubMed

    Pfeifle, Joerg; Coillet, Aurélien; Henriet, Rémi; Saleh, Khaldoun; Schindler, Philipp; Weimann, Claudius; Freude, Wolfgang; Balakireva, Irina V; Larger, Laurent; Koos, Christian; Chembo, Yanne K

    2015-03-01

    Optical Kerr frequency combs are known to be effective coherent multiwavelength sources for ultrahigh capacity fiber communications. These combs are the frequency-domain counterparts of a wide variety of spatiotemporal dissipative structures, such as cavity solitons, chaos, or Turing patterns (rolls). In this Letter, we demonstrate that Turing patterns, which correspond to the so-called primary combs in the spectral domain, are optimally coherent in the sense that for the same pump power they provide the most robust carriers for coherent data transmission in fiber communications using advanced modulation formats. Our model is based on a stochastic Lugiato-Lefever equation which accounts for laser pump frequency jitter and amplified spontaneous emission noise induced by the erbium-doped fiber amplifier. Using crystalline whispering-gallery-mode resonators with quality factor Q?10^{9} for the comb generation, we show that when the noise is accounted for, the coherence of a primary comb is significantly higher than the coherence of their solitonic or chaotic counterparts for the same pump power. In order to confirm this theoretical finding, we perform an optical fiber transmission experiment using advanced modulation formats, and we show that the coherence of the primary comb is high enough to enable data transmission of up to 144??Gbit/s per comb line, the highest value achieved with a Kerr comb so far. This performance evidences that compact crystalline photonic systems have the potential to play a key role in a new generation of coherent fiber communication networks, alongside fully integrated systems. PMID:25793816

  5. Generation of wideband frequency combs by continuous-wave seeding of multistage mixers with synthesized dispersion.

    PubMed

    Myslivets, Evgeny; Kuo, Bill P P; Alic, Nikola; Radic, Stojan

    2012-01-30

    We numerically and experimentally demonstrate efficient generation of an equalized optical comb with 150-nm bandwidth. The comb was generated by low-power, continuous-wave seeds, eliminating the need for pulsed laser sources. The new architecture relies on efficient creation of higher-order mixing tones in phase-matched nonlinear fiber stages separated by a linear compressor. Wideband generation was enabled by precise dispersion engineering of multiple-stage parametric mixers. PMID:22330571

  6. Chaotic dynamics of frequency combs generated with continuously pumped nonlinear microresonators

    E-print Network

    Matsko, Andrey B; Savchenkov, Anatoliy A; Maleki, Lute

    2012-01-01

    We theoretically and experimentally investigate the chaotic regime of optical frequency combs generated in nonlinear ring microresonators pumped with continuous wave light. We show that the chaotic regime reveals itself, in an apparently counter-intuitive way, by a flat top symmetric envelope of the frequency spectrum, when observed by means of an optical spectrum analyzer. The comb demodulated on a fast photodiode produces a noisy radio frequency signal with an spectral width significantly exceeding the linear bandwidth of the microresonator mode.

  7. Broadband high-resolution two-photon spectroscopy with laser frequency combs

    E-print Network

    Hipke, Arthur; Ideguchi, Takuro; Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    Two-photon excitation spectroscopy with broad spectral span is demonstrated at Doppler-limited resolution. We describe first Fourier transform two-photon spectroscopy of an atomic sample with two mode-locked laser oscillators in a dual-comb technique. Each transition is uniquely identified by the modulation imparted by the interfering comb excitations. The temporal modulation of the spontaneous two-photon fluorescence is monitored with a single photodetector, and the spectrum is revealed by a Fourier transform.

  8. A new method for determining the plasma electron density using optical frequency comb interferometer

    SciTech Connect

    Arakawa, Hiroyuki Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

    2014-04-15

    A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density.

  9. Sex: Making the Right Decision

    MedlinePLUS

    MENU Return to Web version Sex: Making the Right Decision Sex: Making the Right Decision What is sex? The word sex is used in several ways. It can refer ... by the penis. It also can mean what sex you were born (male or female) or physical ...

  10. Current Views on Sex Education

    ERIC Educational Resources Information Center

    Hoch, Loren L.

    1970-01-01

    Encourages the use of sex education in the schools and reviews the literature related to these issues: problems in implementation of sex education, reasons for sex education, comparison of sex education and attitudes in the United States with Sweden, communication with youth about sex, planning a program, and inhibitions on research. Thirty-five…

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

    PubMed

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

    2015-01-01

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

  12. Supercontinuum-based 10-GHz flat-topped optical frequency comb generation.

    PubMed

    Wu, Rui; Torres-Company, Victor; Leaird, Daniel E; Weiner, Andrew M

    2013-03-11

    The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum is important for many applications in optical communications, radio-frequency photonics and optical arbitrary waveform generation. Usually, nonlinear broadening techniques of comb-based sources do not provide the required flatness over the whole available bandwidth. Here we present a 10-GHz ultra-broadband flat-topped optical frequency comb (> 3.64-THz or 28 nm bandwidth with ~365 spectral lines within 3.5-dB power variation) covering the entire C-band. The key enabling point is the development of a pre-shaping-free directly generated Gaussian comb-based 10-GHz pulse train to seed a highly nonlinear fiber with normal dispersion profile. The combination of the temporal characteristics of the seed pulses with the nonlinear device allows the pulses to enter into the optical wave-breaking regime, thus achieving a smooth flat-topped comb spectral envelope. To further illustrate the high spectral coherence of the comb, we demonstrate high-quality pedestal-free short pulse compression to the transform-limited duration. PMID:23482172

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    PubMed Central

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

    2015-01-01

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

  15. Modeling of a High Force Density Fishbone Shaped Electrostatic Comb Drive Microactuator

    PubMed Central

    Megat Hasnan, Megat Muhammad Ikhsan; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana; Nik Ghazali, Nik Nazri

    2014-01-01

    This paper presents the design and evaluation of a high force density fishbone shaped electrostatic comb drive actuator. This comb drive actuator has a branched structure similar to a fishbone, which is intended to increase the capacitance of the electrodes and hence increase the electrostatic actuation force. Two-dimensional finite element analysis was used to simulate the motion of the fishbone shaped electrostatic comb drive actuator and compared against the performance of a straight sided electrostatic comb drive actuator. Performances of both designs are evaluated by comparison of displacement and electrostatic force. For both cases, the active area and the minimum gap distance between the two electrodes were constant. An active area of 800 × 300??m, which contained 16 fingers of fishbone shaped actuators and 40 fingers of straight sided actuators, respectively, was used. Through simulation, improvement of drive force of the fishbone shaped electrostatic comb driver is approximately 485% higher than conventional electrostatic comb driver. These results indicate that the fishbone actuator design provides good potential for applications as high force density electrostatic microactuator in MEMS systems. PMID:25165751

  16. Analysis of microwave frequency combs generated by semiconductor lasers under hybrid optical injections

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Ting; Wu, Yi-Hua; Juan, Yu-Shan

    2015-03-01

    Microwave frequency combs utilizing hybrid optical injections schemes by varying the operational parameters, injection strength, repetition frequency, and detuning frequency are demonstrated and characterized. The dynamical hybrid optical injections are realized by both optical pulse injection and optical cw injection to the slave laser simultaneously under the condition of zero detuning frequency between two injecting source lasers. For pure pulse injection case, the amplitude variation of ±27.3 dB in a 30 GHz range is obtained. By further applying the injection strength of the cw injection to the pulses injected semiconductor laser, the amplitude variation of ±3.3 dB in a 30 GHz range in microwave frequency combs are observed when operating the cw injection system in a stable locking state. In order to examine the microwave frequency comb precisely, each operational parameters of the hybrid optical injections schemes are analyzed. The amplitude variation of microwave frequency combs is also strongly influenced by operating the cw injection system in different states. Comparing to the cw injection system operated in period-one states, the amplitude variation is reduced when operated in the stable locking states. Moreover, the bandwidth broadening in microwave frequency comb is expected when the cw injection system operating in a stable locking state. In this paper, strongly improve the amplitude variation of the microwave frequency combs generated utilizing hybrid injections scheme compared to single injection case are obtained and compared.

  17. Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers.

    PubMed

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

    2010-06-01

    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. PMID:20588402

  18. Ultra-precision optical metrology using highly controlled fiber-based frequency combs

    NASA Astrophysics Data System (ADS)

    Minoshima, Kaoru; Nakajima, Yoshiaki; Wu, Guanhao

    2015-05-01

    Optical Frequency combs can be used as a tool for fully controlling the phase and frequency information of light waves, i.e., "optical synthesizer". It provides powerful tools not only in frequency metrology as "ultraprecise frequency ruler" but also in broad area since light wave can be used to its full extent with an extremely wide dynamic range. Frequency-traceable length measurement using frequency combs provides direct realization of the definition of meter, remote calibration using a GPS technology, and precise measurements of wide range of lengths by taking advantage of high dynamic range in frequency measurements. In this paper, ultrahigh-precision length metrology using fiber-based optical frequency combs are presented. By precisely controlling the frequency and phase of the combs, self-correction of air refractive index and noise cancellation in fiber path in interferometer are demonstrated. Heterodyne interferometry of 61- m path-length based on two-color optical frequency combs is developed for air-refractive-index correction. Measured two-color optical-path-differences agreed with calculations with 10-11 for 10-hour. Corrected distance variation agreed with thermal expansion of base-plate. A fiber-based optical frequency comb interferometer with 168-m-length reference path was stabilized to nm-level with fiber noise cancellation technique using a single frequency CW laser. Extremely wide range interferometric fringe scanning of 3.3-m path length

  19. Adaptive sampling dual terahertz comb spectroscopy using free-running dual femtosecond lasers

    E-print Network

    Yasui, Takeshi; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2014-01-01

    Dual terahertz (THz) comb spectroscopy is a promising methods for high accuracy, high resolution, and broadband THz spectroscopy because the mode-resolved THz comb spectrum possesses both characteristics of broadband THz radiation and narrow-linewidth continuous-wave THz radiation and all frequency mode of THz comb can be phase-locked to a microwave frequency standard. However, requirement of stabilized dual femtosecond lasers has often hindered wide use of this method. In this article, we demonstrated the adaptive sampling, dual THz comb spectroscopy, enabling use of free-running dual femtosecond lasers. To correct the non-linearity of time and frequency scale caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing signal in a data acquisition board. The demonstrated results did not only indicate the implementation of dual THz comb spectroscopy with free-running dual lasers but also implied the superiority of its spect...

  20. An improved divergent synthesis of comb-type branched oligodeoxyribonucleotides (bDNA) containing multiple secondary sequences.

    PubMed Central

    Horn, T; Chang, C A; Urdea, M S

    1997-01-01

    The divergent synthesis of branched DNA (bDNA) comb structures is described. This new type of bDNA contains one unique oligonucleotide, the primary sequence, covalently attached through a comb-like branch network to many identical copies of a different oligonucleotide, the secondary sequence. The bDNA comb structures were assembled on a solid support and several synthesis parameters were investigated and optimized. The bDNA comb molecules were characterized by polyacrylamide gel electrophoretic methods and by controlled cleavage at periodate-cleavable moieties incorporated during synthesis. The developed chemistry allows synthesis of bDNA comb molecules containing multiple secondary sequences. In the accompanying article we describe the synthesis and characterization of large bDNA combs containing all four deoxynucleotides for use as signal amplifiers in nucleic acid quantification assays. PMID:9365265

  1. Sex: Who Cares? Introduction.

    ERIC Educational Resources Information Center

    Liben, Lynn S.

    2000-01-01

    Presents evidence supporting claim that sex and gender are important to the explanatory as well as the descriptive goals of developmental psychology. Maintains that studying psychosocial and biological components of gender and sex helps one to develop hypotheses about causal mechanisms for developmental outcomes more generally. Introduces the…

  2. Sex in Fungi

    PubMed Central

    Ni, Min; Feretzaki, Marianna; Sun, Sheng; Wang, Xuying; Heitman, Joseph

    2012-01-01

    Sexual reproduction enables genetic exchange in eukaryotic organisms as diverse as fungi, animals, plants, and ciliates. Given its ubiquity, sex is thought to have evolved once, possibly concomitant with or shortly after the origin of eukaryotic organisms themselves. The basic principles of sex are conserved, including ploidy changes, the formation of gametes via meiosis, mate recognition, and cell-cell fusion leading to the production of a zygote. Although the basic tenants are shared, sex determination and sexual reproduction occur in myriad forms throughout nature, including outbreeding systems with more than two mating types or sexes, unisexual selfing, and even examples in which organisms switch mating type. As robust and diverse genetic models, fungi provide insights into the molecular nature of sex, sexual specification, and evolution to advance our understanding of sexual reproduction and its impact throughout the eukaryotic tree of life. PMID:21942368

  3. The Sex Counselor and Therapist

    ERIC Educational Resources Information Center

    Schiller, Patricia

    1976-01-01

    The author discusses the differences between sex therapy and sex counseling, the goals of the sex counseling process (and consequently, of counselor training) and the advantages of dual therapy as opposed to single therapy. (HMV)

  4. Sex and Fertility After SCI

    MedlinePLUS Videos and Cool Tools

    Experts \\ Sex and Fertility After Spinal Cord Injury Topics Adult Injuries Spinal Cord Injury 101 Spinal Cord Injury 101 ... Spasticity, Physical Therapy-Lokomat Spasticity, Physical Therapy-Lokomat Sex and Fertility After Spinal Cord Injury Sex and ...

  5. Mid-infrared frequency comb based on a quantum cascade laser.

    PubMed

    Hugi, Andreas; Villares, Gustavo; Blaser, Stéphane; Liu, H C; Faist, Jérôme

    2012-12-13

    Optical frequency combs act as rulers in the frequency domain and have opened new avenues in many fields such as fundamental time metrology, spectroscopy and frequency synthesis. In particular, spectroscopy by means of optical frequency combs has surpassed the precision and speed of Fourier spectrometers. Such a spectroscopy technique is especially relevant for the mid-infrared range, where the fundamental rotational-vibrational bands of most light molecules are found. Most mid-infrared comb sources are based on down-conversion of near-infrared, mode-locked, ultrafast lasers using nonlinear crystals. Their use in frequency comb spectroscopy applications has resulted in an unequalled combination of spectral coverage, resolution and sensitivity. Another means of comb generation is pumping an ultrahigh-quality factor microresonator with a continuous-wave laser. However, these combs depend on a chain of optical components, which limits their use. Therefore, to widen the spectroscopic applications of such mid-infrared combs, a more direct and compact generation scheme, using electrical injection, is preferable. Here we present a compact, broadband, semiconductor frequency comb generator that operates in the mid-infrared. We demonstrate that the modes of a continuous-wave, free-running, broadband quantum cascade laser are phase-locked. Combining mode proliferation based on four-wave mixing with gain provided by the quantum cascade laser leads to a phase relation similar to that of a frequency-modulated laser. The comb centre carrier wavelength is 7?micrometres. We identify a narrow drive current range with intermode beat linewidths narrower than 10?hertz. We find comb bandwidths of 4.4 per cent with an intermode stability of less than or equal to 200?hertz. The intermode beat can be varied over a frequency range of 65?kilohertz by radio-frequency injection. The large gain bandwidth and independent control over the carrier frequency offset and the mode spacing open the way to broadband, compact, all-solid-state mid-infrared spectrometers. PMID:23235876

  6. Ultra-low noise all polarization-maintaining Er fiber-based optical frequency combs facilitated with a graphene modulator.

    PubMed

    Kuse, N; Lee, C-C; Jiang, J; Mohr, C; Schibli, T R; Fermann, M E

    2015-09-21

    High bandwidth carrier phase and repetition rate control are critical for the construction of low phase noise optical frequency combs. Here we demonstrate the use of a graphene modulator for the former and a bulk electro-optic modulator for the latter enabling record low phase noise operation of an Er fiber frequency comb. For applications that do not require carrier phase control, we show that the form factor of a fiber comb can be reduced by adapting a graphene modulator for rapid repetition rate control. Moreover, the whole system demonstration is performed with all-polarization maintaining Er fiber frequency combs, highly suitable for applications in the field. PMID:26406639

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

    PubMed

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

    2014-05-15

    We demonstrate experimentally, and describe theoretically, generation of a wide, fundamentally phase-locked Kerr frequency comb in a nonlinear resonator with a normal group velocity dispersion (GVD). A magnesium fluoride whispering-gallery mode resonator characterized with 10 GHz free spectral range and pumped either at 780 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 phase of the generated harmonics are fixed. PMID:24978237

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

    E-print Network

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

    2014-01-01

    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.

  9. Regeneration of ciliary comb plates in the ctenophore Mnemiopsis leidyi. i. morphology.

    PubMed

    Tamm, Sidney L

    2012-01-01

    Regeneration of missing body parts in model organisms provides information on the mechanisms underlying the regeneration process. The aim here is to use ctenophores to investigate regeneration of their giant ciliary swimming plates. When part of a row of comb plates on Mnemiopsis is excised, the wound closes and heals, greatly increasing the distance between comb plates near the former cut edges. Video differential interference contrast (DIC) microscopy of the regeneration of new comb plates between widely separated plates shows localized widenings of the interplate ciliated groove (ICG) first, followed by growth of two opposing groups of comb plate cilia on either side. The split parts of a new plate elongate as their bases extend laterally away from the ICG widening and continue ciliogenesis at both ends. The split parts of a new plate grow longer and move closer together into the ICG widening until they merge into a single plate that interrupts the ICG in a normal manner. Video DIC snapshots of dissected gap preparations 1.5-3-day postoperation show that ICG widenings and/or new plates do not all appear at the same time or with uniform spacing within a gap: the lengths and distances between young plates in a gap are quite variable. Video stereo microscopy of intact animals 3-4 days after the operation show that all the new plates that will form in a gap are present, fairly evenly spaced and similar in length, but smaller and closer together than normal. Normal development of comb plates in embryos and growing animals is compared to the pattern of comb plate regeneration in adults. Comb plate regeneration differs in the cydippid Pleurobrachia that lacks ICGs and has a firmer mesoglea than Mnemiopsis. This study provides a morphological foundation for histological, cellular, and molecular analysis of ciliary regeneration in ctenophores. PMID:21987455

  10. Juvenile Sex Offenders.

    PubMed

    Ryan, Eileen P

    2016-01-01

    Public policy has tended to treat juvenile sex offenders (JSOs) as adult sex offenders in waiting, despite research that contradicts this notion. Although as a group, JSOs are more similar to general delinquents than to adult sex offenders, atypical sexual interests and sexual victimization during childhood may be a pathway for sexual offending that differentiates some JSOs from their nonsexually delinquent peers. Developmental considerations must be considered in risk assessment evaluations of these youth. This article reviews theories of sexual offending in youth, risk factors for juvenile offending and reoffending, psychopathology in JSOs, risk assessment, and treatment. PMID:26593121

  11. Parasitic effects in SQUID-based radiation comb generators

    E-print Network

    Riccardo Bosisio; Francesco Giazotto; Paolo Solinas

    2015-05-23

    We study several parasitic effects on the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how assuming a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of this device. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is in general negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited up to a large extent with a suitable choice of fabrication parameters.

  12. Parasitic effects in SQUID-based radiation comb generators

    E-print Network

    Riccardo Bosisio; Francesco Giazotto; Paolo Solinas

    2015-11-26

    We study several parasitic effects on the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how assuming a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of this device. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is in general negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited up to a large extent with a suitable choice of fabrication parameters.

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

    SciTech Connect

    Strecker, Kevin E.; Chandler, David W.

    2010-10-01

    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.

  14. The comb jelly opsins and the origins of animal phototransduction.

    PubMed

    Feuda, Roberto; Rota-Stabelli, Omar; Oakley, Todd H; Pisani, Davide

    2014-08-01

    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. PMID:25062921

  15. The Comb Jelly Opsins and the Origins of Animal Phototransduction

    PubMed Central

    Feuda, Roberto; Rota-Stabelli, Omar; Oakley, Todd H.; Pisani, Davide

    2014-01-01

    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. PMID:25062921

  16. Testicular Cancer and Sex

    MedlinePLUS

    ... remove just one testicle, called an inguinal orchiectomy (IO), does not make a patient impotent and seldom ... everything from having sex the day after their IO (ouch!) all the way through having to go ...

  17. When Sex Is Painful

    MedlinePLUS

    ... a gynecologic problem, such as ovarian cysts or endometriosis . Pain during sex also may be caused by ... medications, or surgery. • Other causes— Pelvic inflammatory disease , endometriosis, and adhesions are all associated with pain during ...

  18. On luck and sex.

    PubMed

    Blachford, Alistair; Doebeli, Michael

    2009-01-01

    Sex has many costs with respect to asexual reproduction, so its ubiquity is a puzzle. There has been a continuing effort to identify general circumstances in which aspects of sex generate an evolutionary advantage over asexual reproduction. Here we focus on the generality that individuals can experience good and bad "luck" at various stages of their life history regardless of genotype, and on the interindividual nature of sex. Sexual outcrossing combines genetic information from individuals with potentially different experiences, so it is conceivable that sex might reduce the contribution of individual luck to noise in inheritance. In a simple way, we derive expressions for noise in inheritance in terms of some sources of within-generation ecological noise. We demonstrate that interindividual reproduction can indeed dampen the effects of ecological noise better than lone-individual modes, but there are conditions under which it does not. Empirical and theoretical work on plants, modeled here, suggest noise dampening conditions. Ecological noise dampening operates alongside other features of sex such as recombination and segregation and, because noise in inheritance weakens the role of selection in genetic change, we speculate that noise dampening may offer a benefit to be deducted from the costs of sex. We also suggest that the amount of selfing relative to outcrossing observed in natural populations may be influenced by the amount of individual-level ecological noise in a given habitat. PMID:18803688

  19. Mid-infrared optical frequency combs at 2.5??m based on crystalline microresonators

    PubMed Central

    Wang, C. Y.; Herr, T.; Del’Haye, P.; Schliesser, A.; Hofer, J.; Holzwarth, R.; Hänsch, T. W.; Picqué, N.; Kippenberg, T. J.

    2013-01-01

    The mid-infrared spectral range (?~2–20??m) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs—broadband optical sources consisting of equally spaced and mutually coherent sharp lines—are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at ?=2.5??m spanning 200?nm (?10?THz) with a line spacing of 100?GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared. PMID:23299895

  20. Phase Coherent Link of an Atomic Clock to a Self-Referenced Microresonator Frequency Comb

    E-print Network

    Del'Haye, Pascal; Fortier, Tara; Beha, Katja; Cole, Daniel C; Yang, Ki Youl; Lee, Hansuek; Vahala, Kerry J; Papp, Scott B; Diddams, Scott A

    2015-01-01

    The counting and control of optical cycles of light has become common with modelocked laser frequency combs. But even with advances in laser technology, modelocked laser combs remain bulk-component devices that are hand-assembled. In contrast, a frequency comb based on the Kerr-nonlinearity in a dielectric microresonator will enable frequency comb functionality in a micro-fabricated and chip-integrated package suitable for use in a wide-range of environments. Such an advance will significantly impact fields ranging from spectroscopy and trace gas sensing, to astronomy, communications, atomic time keeping and photonic data processing. Yet in spite of the remarkable progress shown over the past years, microresonator frequency combs ("microcombs") have still been without the key function of direct f-2f self-referencing and phase-coherent frequency control that will be critical for enabling their full potential. Here we realize these missing elements using a low-noise 16.4 GHz silicon chip microcomb that is coher...

  1. Modal expansion approach to optical-frequency-comb generation with monolithic whispering-gallery-mode resonators

    SciTech Connect

    Chembo, Yanne K.; Yu, Nan

    2010-09-15

    We describe a general framework based on modal expansion for the study of optical-frequency combs generated with monolithic whispering-gallery-mode resonators. We obtain a set of time-domain rate equations describing the dynamics of each mode as a function of the main characteristics of the cavity, namely, Kerr nonlinearity, absorption, coupling losses, and cavity dispersion (geometrical and material). A stability analysis of the various side modes is performed, which finds analytically the threshold power needed for comb generation. We show that the various whispering gallery modes are excited in a nontrivial way, strongly dependent on the value of the overall cavity dispersion. We demonstrate that the combs are not simply generated through a direct transfer of energy from the pumped mode to all their neighbors but rather through complex intermediate interactions. Anomalous cavity dispersion is also demonstrated to be critical for these cascading processes, and comb generation is thereby unambiguously linked to modulational instability. This theory accurately describes the emergence of spectral modulation and free spectral-range tunability in the comb. It also enables a clear understanding of the various phenomena responsible for the spectral span limitation. Our theoretical predictions are in excellent agreement with the numerical simulations, and they successfully explain the internal mechanisms responsible for the generation of hundreds of Kerr modes in monolithic whispering-gallery-mode resonators.

  2. Highly Stable, Anion Conductive, Comb-Shaped Copolymers for Alkaline Fuel Cells

    SciTech Connect

    Li, NW; Leng, YJ; Hickner, MA; Wang, CY

    2013-07-10

    To produce an anion-conductive and durable polymer electrolyte for alkaline fuel cell applications, a series of quaternized poly(2,6-dimethyl phenylene oxide)s containing long alkyl side chains pendant to the nitrogen-centered cation were synthesized using a Menshutkin reaction to form comb-shaped structures. The pendant alkyl chains were responsible for the development of highly conductive ionic domains, as confirmed by small-angle X-ray scattering (SAXS). The comb-shaped polymers having one alkyl side chain showed higher hydroxide conductivities than those with benzyltrimethyl ammonium moieties or structures with more than one alkyl side chain per cationic site. The highest conductivity was observed for comb-shaped polymers with benzyldimethylhexadecyl ammonium cations. The chemical stabilities of the comb-shaped membranes were evaluated under severe, accelerated-aging conditions, and degradation was observed by measuring IEC and ion conductivity changes during aging. The comb-shaped membranes retained their high ion conductivity in 1 M NaOH at 80 degrees C for 2000 h. These cationic polymers were employed as ionomers in catalyst layers for alkaline fuel cells. The results indicated that the C-16 alkyl side chain ionomer had a slightly better initial performance, despite its low IEC value, but very poor durability in the fuel cell. In contrast, 90% of the initial performance was retained for the alkaline fuel cell with electrodes containing the C-6 side chain after 60 h of fuel cell operation.

  3. Transmission comb of a distributed Bragg reflector induced by two surface dielectric gratings

    E-print Network

    Zhao, Xiaobo; Zhang, Yongyou

    2015-01-01

    With transfer matrix theory, we study the transmission of a distributed Bragg reflector (DBR) with two dielectric gratings on top and on the bottom. Owing to the diffraction of the two gratings, the transmission shows a comb-like spectrum which red shifts with increasing the grating period during the forbidden band of the DBR. The number density of the comb peaks increases with increasing the number of the DBR cells, while the ratio of the average full width at half maximum (FWHM) of the transmission peaks in the transmission comb to the corresponding average free spectral range, being about 0.04 and 0.02 for the TE and TM incident waves, is almost invariant. The average FWHM of the TM waves is about half of the TE waves, and both they could be narrower than 0.1 nm. In addition, the transmission comb peaks of the TE and TM waves can be fully separated during certain waveband. We further prove that the transmission comb is robust against the randomness of the heights of the DBR layers, even when a 15\\% randomn...

  4. Brillouin-enhanced hyperparametric generation of an optical frequency comb in a monolithic highly nonlinear fiber cavity pumped by a cw laser.

    PubMed

    Braje, Danielle; Hollberg, Leo; Diddams, Scott

    2009-05-15

    We demonstrate self-seeded generation of a broadband comb in a highly nonlinear fiber resonator. When pumped with a cw laser, the fiber cavity generates a comb with two characteristic spacings. Hyperparametric modes spaced by approximately 2 THz create the base structure of the comb, while commensurate Brillouin modes spaced by approximately 10 GHz populate the intermediate frequency gaps. The frequency modes are coherent, and the repetition rate of the comb has been locked to a microwave standard. PMID:19518952

  5. Single Sex Education. WEEA Digest.

    ERIC Educational Resources Information Center

    Pollard, Diane S.

    Title IX of the Educational Amendments of 1972 prohibits discrimination on the basis of sex in educational institutions that receive federal financial assistance. This digest focuses on the theme of single-sex education. Articles featured in this issue include: (1) "Single-Sex Education" (Diane S. Pollard); (2) "A Legal Framework for Single-Sex

  6. 75 FR 11559 - Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules of Origin

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ... Certain Combed Cotton Yarns: Effect of Modification of U.S.- Bahrain FTA Rules of Origin AGENCY: United...-103-025, Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules Of Origin...-205-2000. Background: Chapter 3, Annex 3-A and Chapter 4 of the FTA contain the rules of origin...

  7. Self-assembly of an ultra-high-molecular-weight comb block copolymer at the airwater interface

    E-print Network

    Lin, Zhiqun

    Self-assembly of an ultra-high-molecular-weight comb block copolymer at the air­water interface Lei-assembly of a newly synthesized, amphiphilic comb block copolymer (CBCP) at the air­water interface was systematically. At the air­water interface, the CBCP molecules spontaneously assembled into ribbon-like structures

  8. Experimental Demonstration of Optical Nyquist Generation of 32-Gbaud QPSK using a Comb-based Tunable Optical

    E-print Network

    Touch, Joe

    the frequency fingers of the optical frequency comb source as the OTDL taps. By using a wavelength dependentExperimental Demonstration of Optical Nyquist Generation of 32-Gbaud QPSK using a Comb.2360) Fiber optics links and subsystems; (190.4223) Nonlinear Wave Mixing. 1. Introduction Optical

  9. Tunable RF Photonics Filter using a Comb-based Optical Tapped-Delay-Line with an Optical Nonlinear Multiplexer

    E-print Network

    Touch, Joe

    Tunable RF Photonics Filter using a Comb-based Optical Tapped-Delay-Line with an Optical Nonlinear demonstrated using an optical tapped delay line based on an optical frequency comb and a PPLN waveguide.4370) Nonlinear optics, fibers. Radio frequency (RF) and microwave photonics have many applications due to the low

  10. Draft Genome Sequence of Empedobacter (Formerly Wautersiella) falsenii comb. nov. Wf282, a Strain Isolated from a Cervical Neck Abscess

    PubMed Central

    Traglia, German Matías; Dixon, Chelsea; Chiem, Kevin; Almuzara, Marisa; Barberis, Claudia; Montaña, Sabrina; Merino, Cindy; Mussi, María Alejandra; Tolmasky, Marcelo E.; Iriarte, Andres; Vay, Carlos

    2015-01-01

    Empedobacter (formerly Wautersiella) falsenii comb. nov. strain Wf282 was isolated from a cervical neck abscess sample from an 18-year-old female patient. The isolate was resistant to many antibiotics, including meropenem and colistin. The total DNA from the multidrug-resistant E. falsenii comb. nov. Wf282 clinical isolate was sequenced. PMID:25838490

  11. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL. 22, NO. 2, APRIL 2013 483 Large Stroke Electrostatic Comb-Drive Actuators

    E-print Network

    Awtar, Shorya

    paired double parallelogram (C-DP-DP) flexure mechanism. The C-DP-DP flexure mechanism design offers high paired double parallelogram (DP-DP) flexure design with comb gap G = 3 m and flexure beam length L1 = 1 mm results in a 50-m stroke before snap-in, the reinforced C-DP-DP design with the same comb gap

  12. PUBLISHED ONLINE: 20 SEPTEMBER 2009 | DOI: 10.1038/NPHYS1398 Vacuum-ultraviolet frequency combs from

    E-print Network

    Loss, Daniel

    LETTERS PUBLISHED ONLINE: 20 SEPTEMBER 2009 | DOI: 10.1038/NPHYS1398 Vacuum-ultraviolet frequency of frequency combs to the vacuum- ultraviolet range. This advance necessitates unifying optical frequency-threshold harmonic generation (photon energy above the ionization potential), for vacuum-ultraviolet frequency combs

  13. 1-GHz repetition rate femtosecond OPO with stabilized offset between signal and idler frequency combs.

    PubMed

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

    2008-04-14

    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. PMID:18542642

  14. Velocity-selective direct frequency-comb spectroscopy of atomic vapors

    E-print Network

    Stalnaker, J E; Rowan, M E; Nguyen, K; Pradhananga, T; Palm, C A; Kimball, D F Jackson

    2015-01-01

    We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect of repetition rate on the $\\textrm{5S}_{1/2}\\rightarrow \\textrm{5D}_{3/2, 5/2}$ two-photon transitions excited in a rubidium atomic vapor cell. The transitions occur via step-wise excitation through the $\\textrm{5P}_{1/2, 3/2}$ states by use of the direct output of an optical frequency comb. Experiments were performed with two different frequency combs, one with a repetition rate of $\\approx 925$ MHz and one with a repetition rate of $\\approx 250$ MHz. The experimental spectra are compared to each other and to a theoretical model.

  15. A Novel Comb Architecture for Enhancing the Sensitivity of Bulk Mode Gyroscopes

    PubMed Central

    Elsayed, Mohannad Y.; Nabki, Frederic; El-Gamal, Mourad N.

    2013-01-01

    This work introduces a novel architecture for increasing the sensitivity of bulk mode gyroscopes. It is based on adding parallel plate comb drives to the points of maximum vibration amplitude, and tuning the stiffness of the combs. This increases the drive strength and results in a significant sensitivity improvement. The architecture is targeted for technologies with ?100 nm transducer gaps in order to achieve very high performance devices. In this work, this sensitivity enhancement concept was implemented in SOIMUMPs, a commercial relatively large gap technology. Prototypes were measured to operate at frequencies of ?1.5 MHz, with quality factors of ?33,000, at a 10 mTorr vacuum level. Measurements using discrete electronics show a rate sensitivity of 0.31 ?V/°/s, corresponding to a capacitance sensitivity of 0.43 aF/°/s/electrode, two orders of magnitude higher than a similar design without combs, fabricated in the same technology.

  16. Dual electro-optic optical frequency combs for multiheterodyne molecular dispersion spectroscopy.

    PubMed

    Martín-Mateos, Pedro; Jerez, Borja; Acedo, Pablo

    2015-08-10

    In this paper, a multiheterodyne architecture for molecular dispersion spectroscopy based on a coherent dual-comb source generated using a single continuous wave laser and electro-optic modulators is presented and validated. The phase-sensitive scheme greatly simplifies previous dual-comb implementations by the use of an electro-optic dual comb and by phase-locking all the signal generators of the setup eliminating, in this way, the necessity of any reference optical path currently mandatory in absorption-based instruments. The architecture is immune to the classical baseline and normalization problems of absorption-based analyzers and provides an output linearly dependent on the gas concentration. In addition, the simultaneous parallel multi-wavelength measurement approach has the ability to deliver an improved output bandwidth (measurement speed) over gas analyzers based on tunable lasers. PMID:26367964

  17. Generation of a flexible optical comb in a periodically poled lithium niobate waveguide.

    PubMed

    Scaffardi, Mirco; Pinna, Sergio; Lazzeri, Emma; Bogoni, Antonella

    2014-04-01

    We propose and demonstrate a technique for the generation of an optical comb with tunable line spacing in a periodically poled lithium niobate (PPLN) waveguide. The technique is implemented with four input continuous waves (CWs), which generate a 19-line comb tuned to the spacing of 25 and 20 GHz. We show that each additional CW switched on out of the quasi phase-matching band at the PPLN waveguide input generates the growth of six new lines. The performance of the comb is tested modulating the lines with a 40 Gb/s differential quadrature phase shift keying data, demonstrating error-free operation. Nonuniform spacing of the input seed CWs improves the efficiency of the line generation process. PMID:24686591

  18. Mode-locked dark pulse Kerr combs in normal-dispersion microresonators

    NASA Astrophysics Data System (ADS)

    Xue, Xiaoxiao; Xuan, Yi; Liu, Yang; Wang, Pei-Hsun; Chen, Steven; Wang, Jian; Leaird, Dan E.; Qi, Minghao; Weiner, Andrew M.

    2015-09-01

    The generation of Kerr frequency combs in a coherently driven nonlinear microresonator is now extensively investigated more generally by the research community as a potentially portable technology for a variety of applications. Here, we report experiments in which dark pulse combs are formed in normal-dispersion microresonators with mode-interaction-assisted excitation, and mode-locking transitions are observed in the normal-dispersion regime. The mode-interaction-aided excitation of dark pulses appears to occur through a deterministic pathway, in sharp contrast to the situation for bright pulses in the anomalous dispersion region. The ability to mode-lock in the normal-dispersion regime increases the freedom in the microresonator design and may make it possible to extend Kerr comb generation into the visible, where material dispersion is likely to dominate.

  19. Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb

    E-print Network

    Ferdous, Fahmida; Leaird, Daniel E; Srinivasan, Kartik; Wang, Jian; Chen, Lei; Varghese, Leo Tom; Weiner, A M

    2011-01-01

    We report, for the first time to the best of our knowledge, spectral phase characterization and line-by-line pulse shaping of an optical frequency comb generated by nonlinear wave mixing in a microring resonator. Through programmable pulse shaping the comb is compressed into a train of near-transform-limited pulses of \\approx 300 fs duration (intensity full width half maximum) at 595 GHz repetition rate. An additional, simple example of optical arbitrary waveform generation is presented. The ability to characterize and then stably compress the frequency comb provides new data on the stability of the spectral phase and suggests that random relative frequency shifts due to uncorrelated variations of frequency dependent phase are at or below the 100 microHertz level.

  20. Modelocking and Femtosecond Pulse Generation in Chip-Based Frequency Combs

    E-print Network

    Saha, Kasturi; Shim, Bonggu; Levy, Jacob S; Foster, Mark A; Salem, Reza; Johnson, Adrea R; Lamont, Michael R E; Lipson, Michal; Gaeta, Alexander L

    2012-01-01

    Development of ultrashort pulse sources has had an immense impact on condensed-matter physics, biomedical imaging, high-field physics, frequency metrology, telecommunications, nonlinear optics, and molecular spectroscopy. Although numerous advancements of such sources have been made, it remains a challenge to create a highly compact, robust platform capable of producing femtosecond pulses over a wide range of wavelengths, durations, and repetition rates. Recent observations of frequency comb generation via cascaded parametric oscillation in microresonators11 suggest a path for achieving this goal. Here we investigate the temporal and spectral properties of parametric combs generated in silicon-nitride microresonators and observe a transition to passive modelocking of the comb consistent with soliton-pulse formation, resulting in the generation of 160-fs pulses at a 99-GHz repetition rate. This platform offers the prospect of producing pulses from 10 fs to a few ps at repetition rates from 10 GHz to > 1 THz an...

  1. Comparison analysis of optical frequency comb generation with nonlinear effects in highly nonlinear fibers.

    PubMed

    Yang, Ting; Dong, Jianji; Liao, Shasha; Huang, Dexiu; Zhang, Xinliang

    2013-04-01

    We compare several schemes for broadband optical frequency comb (OFC) generation based on several nonlinear effects in highly nonlinear fiber (HNLF). Cascaded four wave mixing (CFWM) and self-phase modulation (SPM) processes in HNLF are proved to be effective ways for spectrum broadening. We investigate some parameters affecting the performance of the output OFC in detail. When only CFWM occurs in the HNLF, broadband OFC can be generated with poor power flatness. When only SPM occurs in the HNLF, we obtain a 10 GHz OFC of 103 comb lines within 5-dB power deviation. When both CFWM and SPM simultaneously occur in the HNLF, we obtain a 10 GHz OFC of 143 comb lines within 4.5-dB power deviation. All the OFC generation schemes have the advantages of tunability of central wavelength and repetition frequency. PMID:23571940

  2. Generation of a 660-2100 nm laser frequency comb based on an erbium fiber laser.

    PubMed

    Ycas, Gabriel; Osterman, Steve; Diddams, Scott A

    2012-06-15

    We present a multibranch laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 THz of bandwidth, from 660 nm to 2100 nm. Light from a mode-locked Er:fiber laser is amplified and then broadened in highly-nonlinear fiber to produce substantial power at ?1050??nm. This light is subsequently amplified in Yb:fiber to produce 1.2 nJ, 73 fs pulses at 1040 nm. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1040 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser. PMID:22739854

  3. Evaluating the performance of the NPL femtosecond frequency combs: agreement at the 10-21 level

    NASA Astrophysics Data System (ADS)

    Johnson, L. A. M.; Gill, P.; Margolis, H. S.

    2015-02-01

    Results are presented from a series of comparisons between two independent femtosecond frequency comb systems at NPL, which were carried out in order to assess their systematic uncertainty. Simultaneous measurements with the two systems demonstrate agreement at the level of 5 × 10-18 when measuring an optical frequency against a common microwave reference. When simultaneously measuring the ratio of two optical frequencies, agreement at the 3 × 10-21 level is observed. The results represent the highest reported level of agreement to date between Ti:Sapphire and Er-doped femtosecond combs. The limitations of the combs when operating in these two different manners are discussed, including traceability to the SI second, which can be achieved with an uncertainty below 1 × 10-16. The technical details presented underpin recent absolute frequency measurements of the 88Sr+ and 171Yb+ optical clock transitions at NPL, as well as a frequency ratio measurement between the two optical clock transitions in 171Yb+.

  4. Doppler cooling with coherent trains of laser pulses and a tunable velocity comb

    SciTech Connect

    Ilinova, Ekaterina; Ahmad, Mahmoud; Derevianko, Andrei

    2011-09-15

    We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, nonoverlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a ''velocity comb''--a series of narrow equidistant peaks in the velocity space.

  5. Mach-zehnder based optical marker/comb generator for streak camera calibration

    DOEpatents

    Miller, Edward Kirk

    2015-03-03

    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.

  6. Parameter optimization of a dual-comb ranging system by using a numerical simulation method.

    PubMed

    Wu, Guanhao; Xiong, Shilin; Ni, Kai; Zhu, Zebin; Zhou, Qian

    2015-12-14

    Dual-comb system parameters have significant impacts on the ranging accuracy. We present a theoretical model and a numerical simulation method for the parameter optimization of a dual-comb ranging system. With this method we investigate the impacts of repetition rate difference, repetition rate, and carrier-envelope-offset frequency on the ranging accuracy. Firstly, the simulation results suggest a series of discrete zones of repetition rate difference in an optimal range, which are consistent with the experimental results. Secondly, the simulation results of the repetition rate indicate that a higher repetition rate is very favorable to improve the ranging accuracy. Finally, the simulation results suggest a series of discrete optimal ranges of the carrier-envelope-offset frequency for the dual-comb system. The simulated results were verified by our experiments. PMID:26698995

  7. Fast wavelength calibration method for spectrometers based on waveguide comb optical filter

    SciTech Connect

    Yu, Zhengang; Huang, Meizhen Zou, Ye; Wang, Yang; Sun, Zhenhua; Cao, Zhuangqi

    2015-04-15

    A novel fast wavelength calibration method for spectrometers based on a standard spectrometer and a double metal-cladding waveguide comb optical filter (WCOF) is proposed and demonstrated. By using the WCOF device, a wide-spectrum beam is comb-filtered, which is very suitable for spectrometer wavelength calibration. The influence of waveguide filter’s structural parameters and the beam incident angle on the comb absorption peaks’ wavelength and its bandwidth are also discussed. The verification experiments were carried out in the wavelength range of 200–1100 nm with satisfactory results. Comparing with the traditional wavelength calibration method based on discrete sparse atomic emission or absorption lines, the new method has some advantages: sufficient calibration data, high accuracy, short calibration time, fit for produce process, stability, etc.

  8. Doppler-Limited Spectroscopy with a Decade-Spanning Terahertz Frequency Comb

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Good, Jacob T.; Holland, Daniel; Carroll, Brandon; Allodi, Marco A.; Blake, Geoffrey

    2015-06-01

    We report the generation and detection of a decade-spanning TeraHertz (THz) frequency comb (0.15-2.4 THz) using two Ti:Sapphire femtosecond laser oscillators and ASynchronous OPtical Sampling THz Time-Domain Spectroscopy (ASOPS-THz-TDS). The measured linewidth of the comb at 1.5 THz is 3 kHz over a 60 second acquisition. With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional uncertainty of 5.9×10-8. Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies and will enable future studies of jet-cooled hydrogen-bonded clusters.

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

    NASA Astrophysics Data System (ADS)

    Lee, Sung Hun; Suh, Ho Suhng

    2014-02-01

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

  10. Numerical investigation into the injection-locking phenomena of gain switched lasers for optical frequency comb generation

    SciTech Connect

    Ó Dúill, Sean P. Anandarajah, Prince M.; Zhou, Rui; Barry, Liam P.

    2015-05-25

    We present detailed numerical simulations of the laser dynamics that describe optical frequency comb formation by injection-locking a gain-switched laser. The typical rate equations for semiconductor lasers including stochastic carrier recombination and spontaneous emission suffice to show the injection-locking behavior of gain switched lasers, and we show how the optical frequency comb evolves starting from the free-running state, right through the final injection-locked state. Unlike the locking of continuous wave lasers, we show that the locking range for gain switched lasers is considerably greater because injection locking can be achieved by injecting at frequencies close to one of the comb lines. The quality of the comb lines is formally assessed by calculating the frequency modulation (FM)-noise spectral density and we show that under injection-locking conditions the FM-noise spectral density of the comb lines tend to that of the maser laser.

  11. Uncombed Sunspot Penumbrae Are Combed by Large Flares

    NASA Astrophysics Data System (ADS)

    Wang, Haimin; Liu, C.; Deng, N.

    2011-05-01

    In the past two decades, the complex nature of sunspots is disclosed with high resolution observations. One of the most important findings is the ``uncombed'' penumbral structure, where the bright grains are more vertical while dark fibrils are more horizontal (Solanki and Montavon 1993). The Evershed flows are more closely associated with the horizontal component. On the other hand, it was found that flares may change the topology of the sunspot structure in delta configuration: the central structure at the flaring polarity inversion line becomes darkened while sections of peripheral penumbrae may disappear permanently associated with flares (Liu et al. 2005). The high spatial and temporal resolution observations obtained with Hinode/SOT on December 6, 2006 and June 4, 2007 provide an excellent opportunity to study the evolution of penumbral fine structure associated with major flares. We found that in sections of penumbrae swept by flare ribbons, the dark fibrils completely disappear, while the bright grains evolve into faculae that resemble the structure of vertical magnetic flux tubes. Therefore, the original uncombed penumbral structure seems to be combed toward the vertical direction---the dark and bright components are no longer separated in orientation after the flares. These results provide a new insight into the possible impact by the coronal transients on the photospheric magnetic structure of sunspots, and shed new light on the obscure formation and decay mechanism of penumbrae. Reference Liu, C., Deng, N., Liu, Y., Falconer, D., Goode, P.R., Denker, C. & Wang, H., 2005, Ap.J., 622, 722 Solanki, S.K. & Montavon, C.A.P., 1993, A & A, 275, 283

  12. Mechanisms behind the metabolic flexibility of an invasive comb jelly

    NASA Astrophysics Data System (ADS)

    Augustine, Starrlight; Jaspers, Cornelia; Kooijman, Sebastiaan A. L. M.; Carlotti, François; Poggiale, Jean-Christophe; Freitas, Vânia; van der Veer, Henk; van Walraven, Lodewijk

    2014-11-01

    Mnemiopsis leidyi is an invasive comb jelly which 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-cycle using Dynamic Energy Budget (DEB) theory and literature data. An analysis of data obtained at temperatures ranging from 8 to 30 °C suggests that the optimum thermal tolerance range of M. leidyi is higher than 12 °C. Furthermore M. leidyi seems to undergo a so-called metabolic acceleration after hatching. 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 with those of another holoplanktonic gelatinous zooplankton species (Pelagia noctiluca). After accounting for differences in water content, the comparison shows just how fundamentally different the two energy allocation strategies are. P. noctiluca has an extremely high reserve capacity, low turnover times of reserve compounds and high resistance to shrinking. M. leidyi adopts the opposite strategy: it has a low reserve capacity, high turnover rates of reserve compounds and fast shrinking.

  13. Symbiotic Fungi Produce Laccases Potentially Involved in Phenol Degradation in Fungus Combs of Fungus-Growing Termites in Thailand†

    PubMed Central

    Taprab, Yaovapa; Johjima, Toru; Maeda, Yoshimasa; Moriya, Shigeharu; Trakulnaleamsai, Savitr; Noparatnaraporn, Napavarn; Ohkuma, Moriya; Kudo, Toshiaki

    2005-01-01

    Fungus-growing termites efficiently decompose plant litter through their symbiotic relationship with basidiomycete fungi of the genus Termitomyces. Here, we investigated phenol-oxidizing enzymes in symbiotic fungi and fungus combs (a substrate used to cultivate symbiotic fungi) from termites belonging to the genera Macrotermes, Odontotermes, and Microtermes in Thailand, because these enzymes are potentially involved in the degradation of phenolic compounds during fungus comb aging. Laccase activity was detected in all the fungus combs examined as well as in the culture supernatants of isolated symbiotic fungi. Conversely, no peroxidase activity was detected in any of the fungus combs or the symbiotic fungal cultures. The laccase cDNA fragments were amplified directly from RNA extracted from fungus combs of five termite species and a fungal isolate using degenerate primers targeting conserved copper binding domains of basidiomycete laccases, resulting in a total of 13 putative laccase cDNA sequences being identified. The full-length sequences of the laccase cDNA and the corresponding gene, lcc1-2, were identified from the fungus comb of Macrotermes gilvus and a Termitomyces strain isolated from the same fungus comb, respectively. Partial purification of laccase from the fungus comb showed that the lcc1-2 gene product was a dominant laccase in the fungus comb. These findings indicate that the symbiotic fungus secretes laccase to the fungus comb. In addition to laccase, we report novel genes that showed a significant similarity with fungal laccases, but the gene product lacked laccase activity. Interestingly, these genes were highly expressed in symbiotic fungi of all the termite hosts examined. PMID:16332742

  14. Bacterial communities in termite fungus combs are comprised of consistent gut deposits and contributions from the environment.

    PubMed

    Otani, Saria; Hansen, Lars H; Sørensen, Søren J; Poulsen, Michael

    2016-01-01

    Fungus-growing termites (subfamily Macrotermitinae) mix plant forage with asexual spores of their plant-degrading fungal symbiont Termitomyces in their guts and deposit this blend in fungus comb structures, within which the plant matter is degraded. As Termitomyces grows, it produces nodules with asexual spores, which the termites feed on. Since all comb material passes through termite guts, it is inevitable that gut bacteria are also deposited in the comb, but it has remained unknown which bacteria are deposited and whether distinct comb bacterial communities are sustained. Using high-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, Actinobacteria, and Candidate division TM7 jointly accounting for 92 % of the reads. Analyses of gut microbiotas from 25 of the 33 colonies showed that dominant fungus comb taxa originate from the termite gut. While gut communities were consistent between 2011 and 2013, comb community compositions shifted over time. These shifts did not appear to be due to changes in the taxa present, but rather due to differences in the relative abundances of primarily gut-derived bacteria within fungus combs. This indicates that fungus comb microbiotas are largely termite species-specific due to major contributions from gut deposits and also that environment affects which gut bacteria dominate comb communities at a given point in time. PMID:26518432

  15. 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.

    PubMed

    Shivaji, Sisinthy; Reddy, Gundlapally Sathyanarayana

    2014-09-01

    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)?=?CCTCC AB 209161(T)?=?KACC 14537(T)), P. chathamensis comb. nov. (type strain E3(T)?=?CGMCC 1.7001(T)?=?JCM 15139(T)), P. polaris comb. nov. (type strain ARK 150(T)?=?CIP 108324(T)?=?LMG 21857(T)) and P. psychrophila comb. nov. (type strain 170(T)?=?CGMCC1.6130(T)?=?JCM 13954(T)). The type species of the genus Paraglaciecola is Paraglaciecola mesophila. An emended description of the genus Glaciecola is provided. In addition, a novel strain, 162Z-12(T), was isolated from seawater collected as part of an iron fertilization experiment (LOHAFEX) conducted in the Southern Ocean in 2009 and was subjected to polyphasic taxonomic characterization. Cells of 162Z-12(T) were Gram-negative, aerobic, motile, ovoid to short rod-shaped, obligatorily halophilic and possessed all the characteristics of the genus Paraglaciecola. Strain 162Z-12(T) shared the highest 16S rRNA gene sequence similarity with the type strains of P. agarilytica (99.7?%), P. chathamensis (99.7?%), P. mesophila (98.5?%) and P. polaris (98.3?%). However, it exhibited DNA-DNA relatedness of less than 70.0?% with its nearest phylogenetic relatives, well below the threshold value for species delineation. Further, strain 162Z-12(T) differed from the nearest species in several phenotypic characteristics, in addition to the occurrence of unique nucleotides G, T, T and T at positions 1194, 1269, 1270 and 1271 of the 16S rRNA gene. Based on the cumulative differences it exhibited from its nearest phylogenetic neighbours, strain 162Z-12(T) was identified as a novel member of the genus Paraglaciecola and assigned to the novel species Paraglaciecola oceanifecundans sp. nov. The type strain of Paraglaciecola oceanifecundans is 162Z-12(T) (?=?KCTC 32337(T)?=?LMG 27453(T)). PMID:24981324

  16. High-bandwidth transfer of phase stability through a fiber frequency comb

    E-print Network

    Scharnhorst, Nils; Hannig, Stephan; Jakobsen, Kornelius; Kramer, Johannes; Leroux, Ian D; Schmidt, Piet O

    2015-01-01

    We demonstrate phase locking of a 729 nm diode laser to a 1542 nm master laser via an erbium-doped-fiber frequency comb. Thanks to a transfer-oscillator feedforward scheme which suppresses the effect of comb noise in an unprecedented 1.8 MHz bandwidth, the phase lock requires no pre-stabilization of the slave diode laser. We illustrate the performance of the system by carrying out coherent manipulations of a trapped calcium ion with a fidelity in excess of 99% even at few-microsecond timescales.

  17. Coherent Frequency Combs produced by Self Frequency Modulation in Quantum Cascade Lasers

    E-print Network

    Khurgin, Jacob; Hugi, Andreas; Faist, Jerome

    2013-01-01

    One salient characteristic of Quantum Cascade Laser (QCL) is its very shor gain recovery time that so far thwarted the attempts to achieve self-mode locking of the device into a train of single pulses. We show theoretically that four wave mixing, combined with the short gain recovery time causes QCL to operate in the self-frequency-modulated regime characterized by a constant power in time domain and stable coherent comb in the frequency domain.Coherent frequency comb may enable many potential applications of QCL in sensing and measurement.

  18. Evidence for frequency comb emission from a Fabry-Pérot terahertz quantum-cascade laser.

    PubMed

    Wienold, M; Röben, B; Schrottke, L; Grahn, H T

    2014-12-15

    We report on a broad-band terahertz quantum-cascade laser (QCL) with a long Fabry-Pérot ridge cavity, for which the tuning range of the individual laser modes exceeds the mode spacing. While a spectral range of approximately 60 GHz (2 cm(-1)) is continuously covered by current and temperature tuning, the total emission range spans more than 270 GHz (9 cm(-1)). Within certain operating ranges, we found evidence for stable frequency comb operation of the QCL. An experimental technique is presented to characterize frequency comb operation, which is based on the self-mixing effect. PMID:25606987

  19. High order SSB modulation and its application for advanced optical comb generation based on RFS

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    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.

  20. Widely-tunable mid-IR frequency comb source based on difference frequency generation

    E-print Network

    Ruehl, Axel; Hartl, Ingmar; Fermann, Martin E; Eikema, Kjeld S E; Marangoni, Marco

    2012-01-01

    We report on a mid-infrared frequency comb source of unprecedented tunability covering the entire 3-10 {\\mu}m molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman shifted solitons generated in a highly nonlinear suspended-core fiber with the same source. Average powers up to 1.5 mW were achieved at 4.7 {\\mu}m wavelength.

  1. Flat frequency comb generation based on efficiently multiple four-wave mixing without polarization control

    NASA Astrophysics Data System (ADS)

    Dong, Qimeng; Sun, Bao; Chen, Fushen; Jiang, Jun

    2015-09-01

    This paper presents a new technique for flat optical frequency comb (OFC) generation, which is based on the nonlinear process of multiple four-wave mixing (FWM) effects. The nonlinear effects are significantly enhanced by using the proposed optical feedback scheme consisting of a single mode fiber (SMF), two highly nonlinear fibers (HNLFs) with different zero dispersion wavelengths (ZDWs) and polarization beam splitters (PBSs). Simulation results illustrate its efficiency and applicability of expanding a comb to 128 coherent lines spaced by only 20 GHz within 6-dB power deviation.

  2. Optical frequency comb generation from aluminum nitride micro-ring resonator

    E-print Network

    Jung, Hojoong; Fong, King Y; Zhang, Xufeng; Tang, Hong X

    2013-01-01

    Aluminum nitride is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high quality factor aluminum nitride micro-ring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single wavelength continuous-wave pump laser. The Kerr coefficient (n2) of aluminum nitride is further extracted from our experimental results.

  3. Optical Nyquist channel generation using a comb-based tunable optical tapped-delay-line.

    PubMed

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

    2014-12-01

    We demonstrate optical Nyquist channel generation based on a comb-based optical tapped-delay-line. The frequency lines of an optical frequency comb are used as the taps of the optical tapped-delay-line to perform a finite-impulse response (FIR) filter function. A single optical nonlinear element is utilized to multiplex the taps and form the Nyquist signal. The tunablity of the approach over the baud rate and modulation format is shown. Optical signal-to-noise ratio penalty of 2.8 dB is measured for the 11-tap Nyquist filtering of 32-Gbaud QPSK signal. PMID:25490627

  4. Radiative effects driven by shock waves in cavity-less four-wave mixing combs.

    PubMed

    Conforti, Matteo; Trillo, Stefano

    2014-10-01

    We investigate the frequency comb spectrum produced in an optical fiber via multiple four-wave mixing pumped in the normal group-velocity region close to the zero-dispersion wavelength. We show that the dynamics are strongly affected by shock formation. In this regime, the resonant radiation emitted by the shock waves correctly explains the enhanced spectral peaks in the comb. The resonant frequencies found by means of perturbation theory accurately fit those observed from the numerical simulation based on the generalized nonlinear Schrödinger equation. PMID:25360978

  5. Improvement of flatness of optical frequency comb based on nonlinear effect of intensity modulator.

    PubMed

    Dou, Yujie; Zhang, Hongming; Yao, Minyu

    2011-07-15

    Optical frequency comb (OFC) generated using cascaded intensity and phase modulators was experimentally demonstrated. Very flat OFC can be achieved by cascading intensity and phase modulators driven directly by sinusoidal waveform, where chirped fiber Bragg grating or specially tailored radio frequency waveforms are not required. It is found that the spectral flatness of OFC is related to direct current (DC) bias of intensity modulator and the optimum ratio of DC bias to half-wave voltage is 0.35. In the experiment, 15 comb lines within 1 dB spectral power variation are obtained at 10 GHz microwave frequency. The experimental results agree well with the simulation. PMID:21765530

  6. Surface acoustic wave opto-mechanical oscillator and frequency comb generator.

    PubMed

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

    2011-09-01

    We report on realization of an efficient triply resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyperparametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb by observing the modulation of the light escaping the resonator. PMID:21886203

  7. Er-doped fiber frequency comb with mHz relative linewidth.

    PubMed

    Kim, Yunseok; Kim, Seungman; Kim, Young-Jin; Hussein, Hatem; Kim, Seung-Woo

    2009-07-01

    A low-noise fiber frequency comb is demonstrated to improve the frequency accuracy and linewidth by suppressing the phase noise caused by the nonlinear self-phase modulation as well as the amplified spontaneous emission within the Er-doped fiber amplifier. The linewidth of the carrier-envelop- offset signal measures less than 1.9 mHz and the frequency stability well follows the reference Rb clock. This achievement will facilitate the use of the fiber frequency comb for industrial applications to precision near-infrared spectroscopy, frequency calibration, optical clocks and length metrology. PMID:19582112

  8. Widely-tunable mid-infrared frequency comb source based on difference frequency generation.

    PubMed

    Ruehl, Axel; Gambetta, Alessio; Hartl, Ingmar; Fermann, Martin E; Eikema, Kjeld S E; Marangoni, Marco

    2012-06-15

    We report on a mid-IR frequency comb source of unprecedented tunability covering the entire 3-10 ?m molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman-shifted solitons generated in a highly nonlinear suspended-core fiber with the same source. Average powers up to 1.5 mW were achieved at the 4.7 ?m wavelength. PMID:22739865

  9. High-resolution terahertz spectroscopy with a single tunable frequency comb.

    PubMed

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

    2014-12-29

    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). PMID:25607192

  10. Spatial frequency combs and supercontinuum generation in one-dimensional photonic lattices.

    PubMed

    Dong, Rong; Rüter, Christian E; Kip, Detlef; Manela, Ofer; Segev, Mordechai; Yang, Chengliang; Xu, Jingjun

    2008-10-31

    We experimentally demonstrate the formation of spatial supercontinuum and of spatial frequency combs in nonlinear photonic lattices. This process results from multiple four-wave mixing initiated by launching two Floquet-Bloch modes into a one-dimensional lattice. The dynamics of the waves is sensitively dependent on the transverse momentum difference between the two initial modes: when this momentum difference is commensurable with the lattice momentum the waves evolve into a frequency comb, whereas when it is incommensurable the waves evolve into a supercontinuum of spatial frequencies. PMID:18999833

  11. Direct link of a mid-infrared QCL to a frequency comb by optical injection.

    PubMed

    Borri, S; Galli, I; Cappelli, F; Bismuto, A; Bartalini, S; Cancio, P; Giusfredi, G; Mazzotti, D; Faist, J; De Natale, P

    2012-03-15

    A narrow-linewidth comb-linked nonlinear source is used as master radiation to injection lock a room-temperature mid-infrared quantum cascade laser (QCL). This process leads to a direct lock of the QCL to the optical frequency comb, providing the unique features of narrow linewidth, absolute frequency, higher output power, and wide mode-hop-free tunability. The QCL reproduces the injected radiation within more than 94%, with a reduction of the frequency-noise spectral density by 3 to 4 orders of magnitude up to about 100 kHz, and a linewidth narrowing from a few MHz to 20 kHz. PMID:22446207

  12. Coherent frequency combs produced by self frequency modulation in quantum cascade lasers

    SciTech Connect

    Khurgin, J. B.; Dikmelik, Y.; Hugi, A.; Faist, J.

    2014-02-24

    One salient characteristic of Quantum Cascade Laser (QCL) is its very short ????1?ps gain recovery time that so far thwarted the attempts to achieve self-mode locking of the device into a train of single pulses. We show theoretically that four wave mixing, combined with the short gain recovery time causes QCL to operate in the self-frequency-modulated regime characterized by a constant power in time domain and stable coherent comb in the frequency domain. Coherent frequency comb may enable many potential applications of QCL's in sensing and measurement.

  13. Comb/serpentine/cross-bridge test structure for fabrication process evaluation

    NASA Technical Reports Server (NTRS)

    Sayah, Hoshyar R.; Buehler, Martin G.

    1988-01-01

    The comb/serpentine/cross-bridge structure was developed to monitor and evaluate same layer shorts and step coverage problems (open and high-resistance wire over steps) for integrated circuit fabrication processes. The cross-bridge provides local measurements of wire sheet resistance and wirewidth. These local parametric measurements are used in the analysis of the serpentine wire, which identifies step coverage problems. The comb/serpentine/cross-bridge structure was fabricated with 3 microns CMOS/bulk p-well process and tested using a computer-controlled parametric test system.

  14. Pair-by-pair pulse shaping for optical arbitrary waveform generation by dual-comb heterodyne.

    PubMed

    Zhou, Xin; Zheng, Xiaoping; Wen, He; Zhang, Hanyi; Zhou, Bingkun

    2013-12-15

    We present a novel optical arbitrary waveform generation approach based on pair-by-pair pulse shaping. Based on the heterodyne between a pair of optical frequency combs with different repetition rates, the repetition rate of the generated signals can be flexibly tuned from MHz to GHz without changing the setup. The restriction of the spectral resolution of the optical spectrum processor is overcome by the pair-by-pair approach while the spectral resolution of the system can be improved to MHz by dual-comb heterodyne. Hyperfine control of a higher resolution spectrum at MHz is achieved, which benefits the generation of the ultrawideband signals. PMID:24322250

  15. Control of Four-Level Quantum Coherence via Discrete Spectral Shaping of an Optical Frequency Comb

    SciTech Connect

    Stowe, Matthew C.; Peer, Avi; Ye Jun

    2008-05-23

    We present experiments demonstrating high-resolution and wide-bandwidth coherent control of a four-level atomic system in a diamond configuration. A femtosecond frequency comb is used to excite a specific pair of two-photon transitions in cold {sup 87}Rb. The optical-phase-sensitive response of the closed-loop diamond system is studied by controlling the phase of the comb modes with a pulse shaper. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.

  16. High-bandwidth transfer of phase stability through a fiber frequency comb.

    PubMed

    Scharnhorst, Nils; Wübbena, Jannes B; Hannig, Stephan; Jakobsen, Kornelius; Kramer, Johannes; Leroux, Ian D; Schmidt, Piet O

    2015-07-27

    We demonstrate phase locking of a 729 nm diode laser to a 1542 nm master laser via an erbium-doped-fiber frequency comb, using a transfer-oscillator feedforward scheme which suppresses the effect of comb noise in an unprecedented 1.8 MHz bandwidth. We illustrate its performance by carrying out coherent manipulations of a trapped calcium ion with 99 % fidelity even at few-?s timescales. We thus demonstrate that transfer-oscillator locking can provide sufficient phase stability for high-fidelity quantum logic manipulation even without pre-stabilization of the slave diode laser. PMID:26367634

  17. Optical properties of the iridescent organ of the comb-jellyfish Beroë cucumis (Ctenophora)

    NASA Astrophysics Data System (ADS)

    Welch, Victoria; Vigneron, Jean Pol; Lousse, Virginie; Parker, Andrew

    2006-04-01

    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.

  18. Integrated frequency comb source based Hilbert transformer for wideband microwave photonic phase analysis.

    PubMed

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

    2015-08-24

    We demonstrate a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb, generated using a nonlinear microring resonator based on a CMOS compatible, high-index contrast, doped-silica glass platform. The high quality and large frequency spacing of the comb enables filters with up to 20 taps, allowing us to demonstrate a quadrature filter with more than a 5-octave (3 dB) bandwidth and an almost uniform phase response. PMID:26368182

  19. Electromagnetically induced transparency in rubidium vapor prepared by a comb of short optical pulses

    SciTech Connect

    Sautenkov, Vladimir A.; Rostovtsev, Yuri V.; Ye, C.Y.; Welch, George R.; Kocharovskaya, Olga; Scully, Marlan O.

    2005-06-15

    It was shown by Kocharovskaya and Khanin [Sov. Phys. JETP 63, 945 (1986)] that a comb of optical pulses can induce a ground-state atomic coherence and change the optical response of an atomic medium. In our experiment, we studied the propagation of a comb of optical pulses produced by a mode-locked diode laser in rubidium atomic vapor. Electromagnetically induced transparency (EIT) was observed when the pulse repetition rate is a subharmonic of the hyperfine splitting of the ground state. The width of the EIT resonance is determined by the relaxation rate of the ground-state coherence. Possible applications to magnetometery, atomic clocks, and frequency chains are discussed.

  20. Evolution: conflict by the sexes, for the sexes.

    PubMed

    Shuker, David M; Cook, Nicola

    2014-12-01

    A study in spider mites confirms predictions that males and females come into conflict over optimal sex allocation when local mate competition affects sex allocation in haplodiploid species. PMID:25465336

  1. Sex Differences in Influenceability

    ERIC Educational Resources Information Center

    Eagly, Alice H.

    1978-01-01

    Examines the hypothesis that women are more easily influenced than men by reviewing the literature on persuasion and conformity research. Persuasion research and conformity studies not involving group pressure show scant empirical support for sex differences. For group pressure conformity research, a substantial minority of studies support the…

  2. Sex And People.

    ERIC Educational Resources Information Center

    Jones, Kenneth L.; And Others

    This textbook for the college student emphasizes human sexuality as a part of the whole human life experience and contains a balance of biological, psychological, and sociological material. In 16 chapters the following topics are covered: (1) sex and society; (2) historical and cultural perspectives; (3) glandular control of sexual physiology; (4)…

  3. Sex and Cognition.

    ERIC Educational Resources Information Center

    Kimura, Doreen

    This book describes the major differences between men and women in cognitive or problem-solving abilities and discusses the possible biological contributions to such differences. The book argues that sex differences in cognitive patterns and in motor skills arose out of complementary evolutionary histories of men and women and that evidence for…

  4. Disestablishing Sex: The Case for Released-Time Sex Education

    ERIC Educational Resources Information Center

    Glanzer, Perry L.

    2011-01-01

    Allowing nonschool organizations to provide sex education in a released-time format would disestablish state-funded sex education and give families a choice in the sex education that would be provided for their children. Released-time programs, as originally conceived and currently practiced, allow students to be released for a period of time…

  5. A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration

    SciTech Connect

    Quinlan, F.; Diddams, S. A.; Ycas, G.; Osterman, S.

    2010-06-15

    A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380-1820 nm, providing complete coverage over the H-band transmission window of earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is {approx}350 kHz at 1550 nm. The comb frequency uncertainty is bounded by {+-}30 kHz (corresponding to a radial velocity of {+-}5 cm/s), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR.

  6. A 12.5 GHz-Spaced Optical Frequency Comb Spanning >400 nm for near-Infrared Astronomical Spectrograph Calibration

    E-print Network

    Quinlan, F; Osterman, S; Diddams, S

    2010-01-01

    A 12.5 GHz-spaced optical frequency comb locked to a Global Positioning disciplined oscillator for near-IR spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequency nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380 nm to 1820 nm, providing complete coverage over the H-band transmission widow of Earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth and instability of the comb have been examined to estmiate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 db and 45 dB, and the optical linewidth is ~350 kHz at 1550 nm. The comb frequency uncertainty is bounded by +/- 30 kHz (corresponding to a radial velocity of +/- 5 cm/s), limited by the Global Positioning System disciplined oscillator reference. These results indicate this comb can readily support radial velocity measurements below 1 m/s in the near-IR.

  7. A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration.

    PubMed

    Quinlan, F; Ycas, G; Osterman, S; Diddams, S A

    2010-06-01

    A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380-1820 nm, providing complete coverage over the H-band transmission window of earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is approximately 350 kHz at 1550 nm. The comb frequency uncertainty is bounded by +/-30 kHz (corresponding to a radial velocity of +/-5 cm/s), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR. PMID:20590223

  8. Copy Number Variation in Intron 1 of SOX5 Causes the Pea-comb Phenotype in Chickens

    PubMed Central

    Wright, Dominic; Boije, Henrik; Meadows, Jennifer R. S.; Bed'hom, Bertrand; Gourichon, David; Vieaud, Agathe; Tixier-Boichard, Michèle; Rubin, Carl-Johan; Imsland, Freyja; Hallböök, Finn; Andersson, Leif

    2009-01-01

    Pea-comb is a dominant mutation in chickens that drastically reduces the size of the comb and wattles. It is an adaptive trait in cold climates as it reduces heat loss and makes the chicken less susceptible to frost lesions. Here we report that Pea-comb is caused by a massive amplification of a duplicated sequence located near evolutionary conserved non-coding sequences in intron 1 of the gene encoding the SOX5 transcription factor. This must be the causative mutation since all other polymorphisms associated with the Pea-comb allele were excluded by genetic analysis. SOX5 controls cell fate and differentiation and is essential for skeletal development, chondrocyte differentiation, and extracellular matrix production. Immunostaining in early embryos demonstrated that Pea-comb is associated with ectopic expression of SOX5 in mesenchymal cells located just beneath the surface ectoderm where the comb and wattles will subsequently develop. The results imply that the duplication expansion interferes with the regulation of SOX5 expression during the differentiation of cells crucial for the development of comb and wattles. The study provides novel insight into the nature of mutations that contribute to phenotypic evolution and is the first description of a spontaneous and fully viable mutation in this developmentally important gene. PMID:19521496

  9. Scalable and reconfigurable generation of flat optical comb for WDM-based next-generation broadband optical access networks

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Zhang, Chongfu; Zhang, Wei; Jin, Wei; Qiu, Kun

    2014-06-01

    A tunable comb generator (TCG) by cascading a single phase modulator (PM) with two identical intensity modulators (IMs) is proposed for the scalable and reconfigurable generation of flat optical comb. Detailed theoretical analysis is performed to find out the optimized condition for flat optical comb generation using the proposed TCG and the scalability of the generated optical comb is also analyzed under the optimized condition. An experiment is conducted to verify the feasibility of the TCG and the experimental results agree well with the theoretical prediction. The reconfigurability and stability of the obtained optical comb are discussed as well in the experiment. After that, the obtained optical comb is utilized as the optical source for a wavelength-division multiplexed radio-over-fiber (WDM-RoF) system and a hybrid WDM orthogonal frequency-division multiple access passive optical network (WDM-OFDMA-PON). Two corresponding experimental demonstrations are presented to verify the feasibility of employing the obtained flat optical comb as the WDM optical source, respectively. In the WDM-RoF system, 17 WDM channels each carrying 16×5 Gb/s non-return-to-zero (NRZ) data have been up-converted to 10 GHz simultaneously. In the hybrid WDM-OFDMA-PON, 17-channel OFDM-WDM double-sideband (DSB) signal achieving 10.85 Gb/s traffic per channel is successfully transmitted for both wired baseband OFDM access and wireless 10 GHz OFDM access.

  10. The ABCs of Sex Ed.

    ERIC Educational Resources Information Center

    Sroka, Stephen R.

    2002-01-01

    Cites statistics on extent of sexually transmitted diseases and pregnancies among adolescents; describes ideological dispute over how to teach sex education; advocates teaching the ABCs of sex education: Abstinence, Be Monogamous, and Condoms. (PKP)

  11. SHBG (Sex Hormone Binding Globulin)

    MedlinePLUS

    ... Testosterone-estrogen Binding Globulin; TeBG Formal name: Sex Hormone Binding Globulin Related tests: Testosterone , Free Testosterone, Bioavailable ... should know? How is it used? The sex hormone binding globulin (SHBG) test may be used to ...

  12. Abnormal human sex chromosome constitutions

    SciTech Connect

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  13. Same-Sex Relationship Violence

    MedlinePLUS

    ... of violence against women Violence Against Women Same-sex relationship violence Click the red escape button above ... punishments. Return to top More information on Same-sex relationship violence Explore other publications and websites Dating ...

  14. The University of Texas at Austin McCombs School of Business

    E-print Network

    Ghosh, Joydeep

    systemic risk such as those brought dramatically to our attention by the financial crises, precipitated) some major risks. The investment banking industry had inadequate risk recognition and management1 The University of Texas at Austin McCombs School of Business Managing International Risk RM 395

  15. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

    PubMed Central

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  16. Spectral line-by-line pulse shaping of on-chip microresonator frequency combs

    E-print Network

    Purdue University

    with single free-spectral-range spacing, the time-domain data reveal partially coherent behaviour. O ptical. For combs formed as a cascade of sidebands spaced by a single free spectral range that spread from the pump, we are able to compress stably to nearly bandwidth-limited pulses. This indicates high coherence

  17. Optical Fourier transform based in-plane vibration characterization for MEMS comb structure.

    PubMed

    Gao, Yongfeng; Cao, Liangcai; You, Zheng; Zhao, Jiahao; Zhang, Zichen; Yang, Jianzhong

    2013-02-25

    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. PMID:23482039

  18. Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM-

    E-print Network

    Keller, Ursula

    Fully stabilized optical frequency comb with sub-radian CEO phase noise from a SESAM- modelocked 1 mirror (SESAM)-modelocked 1.5-µm DPSSL results in a low-noise CEO-beat, for which a tight phase lock can

  19. Performance Analysis of Block and Comb Type Channel Estimation for Massive MIMO Systems

    E-print Network

    Telek, Miklós

    of the spectral efficiency is derived in the hypothesis of MMSE estimation. In our previous work [10], we type arrangement, is known to play an important role. In this paper we compare the performance of block and comb pilot symbol patterns in terms of uplink mean square error (MSE) and spectral efficiency when

  20. Quantum theory of phase correlations in optical frequency combs generated by stimulated Raman scattering

    SciTech Connect

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

    2010-11-15

    We explore theoretically the phase correlation between multiple generated sidebands in a Raman optical frequency comb under conditions of spontaneous initiation from quantum zero-point noise. We show that there is a near-deterministic correlation between sideband phases in each laser shot which may lead to synthesis of attosecond pulse trains.

  1. Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.

    PubMed

    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

    2012-01-01

    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 (<100 nW) of the radiation emitted from the quantum cascade 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. PMID:22948822

  2. Tunable optical correlator using an optical frequency comb and a nonlinear multiplexer.

    PubMed

    Ziyadi, Morteza; Chitgarha, Mohammad Reza; Khaleghi, Salman; Mohajerin-Ariaei, Amirhossein; Almaiman, Ahmed; Touch, Joe; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

    2014-01-13

    We experimentally demonstrate a tunable optical correlator to search for multiple patterns among QPSK symbols. We utilize an optical frequency comb to generate the coherent signals and multiplex them coherently in a single PPLN waveguide. Multiple patterns with different lengths are successfully searched within QPSK symbols in a 40-Gb/s signal. PMID:24514968

  3. Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process.

    PubMed

    Bauer, Daniel; Bienefeld, Kaspar

    2013-01-01

    The nests of European honeybees (Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on comb-building behaviour have been made in order to understand how bees produce this geometrical structure; however, it still remains a mystery. Direct construction of hexagons by bees was suggested previously, while a recent hypothesis postulated the self-organised construction of hexagonal comb cell arrays; however, infrared and thermographic video observations of comb building in the present study failed to support the self-organisation hypothesis because bees were shown to be engaged in direct construction. Bees used their antennae, mandibles and legs in a regular sequence to manipulate the wax, while some bees supported their work by actively warming the wax. During the construction of hexagonal cells, the wax temperature was between 33.6 and 37.6 °C. This is well below 40 °C, i.e. the temperature at which wax is assumed to exist in the liquid equilibrium that is essential for self-organised building. PMID:23149932

  4. Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process

    NASA Astrophysics Data System (ADS)

    Bauer, Daniel; Bienefeld, Kaspar

    2013-01-01

    The nests of European honeybees ( Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on comb-building behaviour have been made in order to understand how bees produce this geometrical structure; however, it still remains a mystery. Direct construction of hexagons by bees was suggested previously, while a recent hypothesis postulated the self-organised construction of hexagonal comb cell arrays; however, infrared and thermographic video observations of comb building in the present study failed to support the self-organisation hypothesis because bees were shown to be engaged in direct construction. Bees used their antennae, mandibles and legs in a regular sequence to manipulate the wax, while some bees supported their work by actively warming the wax. During the construction of hexagonal cells, the wax temperature was between 33.6 and 37.6 °C. This is well below 40 °C, i.e. the temperature at which wax is assumed to exist in the liquid equilibrium that is essential for self-organised building.

  5. Optical Comb Generation for Streak Camera Calibration for Inertial Confinement Fusion Experiments

    SciTech Connect

    Ronald Justin, Terence Davies, Frans Janson, Bruce Marshall, Perry Bell, Daniel Kalantar, Joseph Kimbrough, Stephen Vernon, Oliver Sweningsen

    2008-09-18

    The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) is coming on-line to support physics experimentation for the U.S. Department of Energy (DOE) programs in Inertial Confinement Fusion (ICF) and Stockpile Stewardship (SS). Optical streak cameras are an integral part of the experimental diagnostics instrumentation at NIF. To accurately reduce streak camera data a highly accurate temporal calibration is required. This article describes a technique for simultaneously generating a precise +/- 2 ps optical marker pulse (fiducial reference) and trains of precisely timed, short-duration optical pulses (so-called “comb” pulse trains) that are suitable for the timing calibrations. These optical pulse generators are used with the LLNL optical streak cameras. They are small, portable light sources that, in the comb mode, produce a series of temporally short, uniformly spaced optical pulses, using a laser diode source. Comb generators have been produced with pulse-train repetition rates up to 10 GHz at 780 nm, and somewhat lower frequencies at 664 nm. Individual pulses can be as short as 25-ps FWHM. Signal output is via a fiber-optic connector on the front panel of the generator box. The optical signal is transported from comb generator to streak camera through multi-mode, graded-index optical fiber.

  6. Power, Prayers, and Protection: Comb Ridge as a Case Study in Navajo Thought

    ERIC Educational Resources Information Center

    McPherson, Robert S.

    2010-01-01

    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…

  7. Adsorption of comb copolymers on weakly attractive solid surfaces A. Strioloa

    E-print Network

    Jayaraman, Arthi

    Adsorption of comb copolymers on weakly attractive solid surfaces A. Strioloa Department In this work continuum and lattice Monte Carlo simulation methods are used to study the adsorption of linear. At infinite dilution the presence of short side chains promotes the adsorption of polymers favoring both

  8. Osmotic pressure and virial coefficients of star and comb polymer solutions: Dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Tzu-Yu; Fang, Che-Ming; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2009-03-01

    The effects of macromolecular architecture on the osmotic pressure ? and virial coefficients (B2 and B3) of star and comb polymers in good solvents are studied by dissipative particle dynamics simulations for both dilute and semiconcentrated regimes. The dependence of the osmotic pressure on polymer concentration is directly calculated by considering two reservoirs separated by a semipermeable, fictitious membrane. Our simulation results show that the ratios An +1?Bn +1/R?g3n are essentially constant and A2 and A3 are arm number (f) dependent, where R?g is zero-density radius of gyration. The value of dimensionless virial ratio g =A3/A22 increases with arm number of stars whereas it is essentially arm number independent for comb polymers. In semiconcentrated regime the scaling relation between osmotic pressure and volume fraction, ? ???, still holds for both star and comb polymers. For comb polymers, the exponent ? is close to ?? (?2.73 for linear chains) and is independent of the arm number. However, for star polymers, the exponent ? deviates from ?? and actually grows with increasing the arm number. This may be attributed to the significant ternary interactions near the star core in the many-arm systems.

  9. Look closer: Time sequence photography of Roosters Comb in the Sheep Creek Range, Nevada

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  10. Effect of partial comb and wattle trim on pullet behavior and thermoregulation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  11. Coherent optical frequency-combs-based wideband signal channelization and analog to digital conversion

    NASA Astrophysics Data System (ADS)

    Yin, Feifei; Dai, Yitang; Li, Jianqiang; Xu, Kun

    2014-11-01

    We demonstrate a photonic-assisted broadband radio frequency (RF) channelization scheme based on dual coherent optical frequency combs (OFCs). The advantages include coarse optical alignment requirement, ideal rectangular frequency response in each channel without any ultra-narrow optical filters, and digitalized output for further processing. Meanwhile, the channel frequency response and crosstalk of the scheme are also evaluated experimentally.

  12. Quantifying single gene copy number by measuring fluorescent probe lengths on combed genomic DNA

    E-print Network

    Michalet, Xavier

    coverslip. It has the advantage that a large number of genomes can be combed per coverslip, which allows. Aneuploidies associated with the development of a variety of malignancies and genetic diseases involve genes by using arrays of cloned DNA on a diagnostic chip, but the ability to reliably quantify subtle

  13. Straining graphene with low-temperature compatible electrostatic comb-drive actuators

    NASA Astrophysics Data System (ADS)

    Khodkov, Tymofiy; Goldsche, Matthias; Reichardt, Sven; Stampfer, Christoph

    2015-03-01

    Graphene holds great promises as an active element in future nano electromechanical systems. Therefore, thorough study of electromechanical properties of this 2D material is a crucial step towards its applications in flexible electronics. We present the fabrication and characterization of silicon-based electrostatic comb-drive actuators made for integrating individual graphene sheets. The micromachined comb-drive actuators are designed such that they can induce significant mechanical forces for straining graphene allowing to systematically investigate mechanical and electromechanical properties of high-quality graphene. By using highly doped silicon the comb-drive actuators become compatible with low temperatures, i.e. cryogenic temperatures allowing for quantum electromechanical experiments. Further device functionality is introduced by a local gate that enables the tunability of the chemical potential of the graphene. This approach makes possible a detailed study of the graphene under controlled high strain allowing simultaneous and independent tuning of other external parameters, i.e temperature, charge density, magnetic field. With Raman spectroscopy we measure and characterize mono and bilayer graphene samples at room temperature under applied strains up to 1%. A detailed analysis of data allows clear separation of strain and doping. It is demonstrated that with this technique graphene sheet reproducibly experiences only strain while operating the comb-drive actuator.

  14. Gravity orientation in social wasp comb cells (Vespinae) and the possible role of embedded minerals

    NASA Astrophysics Data System (ADS)

    Ishay, Jacob S.; Barkay, Zahava; Eliaz, Noam; Plotkin, Marian; Volynchik, Stanislav; Bergman, David J.

    2008-04-01

    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.

  15. A green astro-comb for Earth-like exoplanet searches Chih-Hao Li,1,*

    E-print Network

    Walsworth, Ronald L.

    Chang,2,3 Li-Jin Chen,4 Gabor Furesz,1 Nicholas Langellier,5 Alexander Zibrov,1 Franz Kärtner,2,3 DavidA green astro-comb for Earth-like exoplanet searches Chih-Hao Li,1,* Alexander G. Glenday,1 Guoqing

  16. XUV frequency-comb metrology on the ground state of helium

    SciTech Connect

    Kandula, Dominik Z.; Gohle, Christoph; Pinkert, Tjeerd J.; Ubachs, Wim; Eikema, Kjeld S. E.

    2011-12-15

    The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p {sup 1} P{sub 1} states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p {sup 1} P{sub 1} states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved {sup 4}He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the {sup 4}He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order m{alpha}{sup 6} and m{sup 2}/M{alpha}{sup 5}, but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

  17. Sex Differences and Sex Steroids in Lung Health and Disease

    PubMed Central

    Townsend, Elizabeth A.; Miller, Virginia M.

    2012-01-01

    Sex differences in the biology of different organ systems and the influence of sex hormones in modulating health and disease are increasingly relevant in clinical and research areas. Although work has focused on sex differences and sex hormones in cardiovascular, musculoskeletal, and neuronal systems, there is now increasing clinical evidence for sex differences in incidence, morbidity, and mortality of lung diseases including allergic diseases (such as asthma), chronic obstructive pulmonary disease, pulmonary fibrosis, lung cancer, as well as pulmonary hypertension. Whether such differences are inherent and/or whether sex steroids play a role in modulating these differences is currently under investigation. The purpose of this review is to define sex differences in lung structure/function under normal and specific disease states, with exploration of whether and how sex hormone signaling mechanisms may explain these clinical observations. Focusing on adult age groups, the review addresses the following: 1) inherent sex differences in lung anatomy and physiology; 2) the importance of certain time points in life such as puberty, pregnancy, menopause, and aging; 3) expression and signaling of sex steroid receptors under normal vs. disease states; 4) potential interplay between different sex steroids; 5) the question of whether sex steroids are beneficial or detrimental to the lung; and 6) the potential use of sex steroid signaling as biomarkers and therapeutic avenues in lung diseases. The importance of focusing on sex differences and sex steroids in the lung lies in the increasing incidence of lung diseases in women and the need to address lung diseases across the life span. PMID:22240244

  18. A Community Sex Information Service

    ERIC Educational Resources Information Center

    Welbourne, Ann K.; Carrera, Michael

    1976-01-01

    Describes Community Sex Information, Inc. (CSI), a nonprofit educational organization, staffed by professionals and volunteers in New York City, which provides accurate sex information in a nonjudgmental and supportive manner. One of its major programs is a telephone sex information service. (Author/HMV)

  19. Sex Stereotyping Hurts All Kids.

    ERIC Educational Resources Information Center

    Cutright, Melitta J.

    1991-01-01

    Sex stereotyping (raising boys and girls to be different because of their sex) begins at birth. The article reviews studies detailing sex stereotyping practices and offers suggestions on what parents can do to avoid them. A list of suggestions for raising children in a nonsexist way is included. (SM)

  20. Liberating genetic variance through sex

    E-print Network

    Otto, Sarah

    Liberating genetic variance through sex Andrew D. Peters and Sarah P. Otto* Summary Genetic of reproduction. Indeed, it has long been thought that sex enhances fitness variation and that this explains that sex need not always increase genetic variation in fitness. In particular, if fitness interactions

  1. Sex Stereotyping by Tomorrow's Executives.

    ERIC Educational Resources Information Center

    Kovach, Kenneth A.

    1985-01-01

    Describes a study in which 512 college seniors were surveyed to see if members of one sex would implicitly stereotype by sex to a greater degree than the other. Questions concerned job/home conflicts and selection and promotion. Results indicated that men and women are equally guilty of sex stereotyping, which works against women in the workplace.…

  2. Generation of Kerr combs centered at 4.5 ?m in crystalline microresonators pumped with quantum-cascade lasers.

    PubMed

    Savchenkov, Anatoliy A; Ilchenko, Vladimir S; Di Teodoro, Fabio; Belden, Paul M; Lotshaw, William T; Matsko, Andrey B; Maleki, Lute

    2015-08-01

    We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF2 and MgF2 whispering-gallery-mode resonators pumped with continuous-wave room-temperature quantum cascade lasers. The combs were centered at 4.5 ?m, the longest wavelength to date. A frequency comb wider than one half of an octave was demonstrated when approximately 20 mW of pump power was coupled to an MgF2 resonator characterized with quality factor exceeding 10(8). PMID:26258334

  3. Generation of a 650 nm - 2000 nm Laser Frequency Comb based on an Erbium-Doped Fiber Laser

    E-print Network

    Ycas, Gabriel; Diddams, Scott A

    2012-01-01

    We present a laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 terahertz of bandwidth, from 660 nm to 2000 nm. The system generates 1.2 nJ, 70 fs pulses at 1050 nm by amplifying the 1580 nm laser light in Er:fiber, followed by nonlinear broadening to 1050 nm and amplification in Yb:fiber. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1050 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser.

  4. Generation of Kerr combs centered at 4.5{\\mu}m in crystalline microresonators pumped by quantum cascade lasers

    E-print Network

    Savchenkov, Anatoliy A; Di Teodoro, Fabio; Belden, Paul M; Lotshaw, William T; Matsko, Andrey B; Maleki, Lute

    2015-01-01

    We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF$_2$ and MgF$_2$ whispering-gallery mode resonators pumped with continuous wave room temperature quantum cascade lasers. The combs were centered at 4.5$\\mu$m, the longest wavelength to date. A frequency comb wider than a half of an octave was demonstrated when approximately 20mW of pump power was coupled to an MgF2 resonator characterized with quality factor exceeding 10$^8$.

  5. Selection and amplification of modes of an optical frequency comb using a femtosecond laser injection-locking technique

    SciTech Connect

    Moon, H. S.; Kim, E. B.; Park, S. E.; Park, C. Y.

    2006-10-30

    The authors have demonstrated the selection and the amplification of the components of an optical frequency comb using a femtosecond laser injectionlocking technique. The author used a mode-locked femtosecond Ti:sapphire laser as the master laser and a single-mode diode laser as the slave laser. The femtosecond laser injection-locking technique was applied to a filter for mode selection of the optical frequency comb and an amplifier for amplification of the selected mode. The authors could obtain the laser source selected only the desired mode of the optical frequency comb and amplified the power of the selected modes several thousand times.

  6. All solid state mid-infrared dual-comb spectroscopy platform based on QCL technology

    NASA Astrophysics Data System (ADS)

    Hugi, Andreas; Geiser, Markus; Villares, Gustavo; Cappelli, Francesco; Blaser, Stephane; Faist, Jérôme

    2015-01-01

    We develop a spectroscopy platform for industrial applications based on semiconductor quantum cascade laser (QCL) frequency combs. The platform's key features will be an unmatched combination of bandwidth of 100 cm-1, resolution of 100 kHz, speed of ten to hundreds of ?s as well as size and robustness, opening doors to beforehand unreachable markets. The sensor can be built extremely compact and robust since the laser source is an all-electrically pumped semiconductor optical frequency comb and no mechanical elements are required. However, the parallel acquisition of dual-comb spectrometers comes at the price of enormous data-rates. For system scalability, robustness and optical simplicity we use free-running QCL combs. Therefore no complicated optical locking mechanisms are required. To reach high signal-to-noise ratios, we develop an algorithm, which is based on combination of coherent and non-coherent averaging. This algorithm is specifically optimized for free-running and small footprint, therefore high-repetition rate, comb sources. As a consequence, our system generates data-rates of up to 3.2 GB/sec. These data-rates need to be reduced by several orders of magnitude in real-time in order to be useful for spectral fitting algorithms. We present the development of a data-treatment solution, which reaches a single-channel throughput of 22% using a standard laptop-computer. Using a state-of-the art desktop computer, the throughput is increased to 43%. This is combined with a data-acquisition board to a stand-alone data processing unit, allowing real-time industrial process observation and continuous averaging to achieve highest signal fidelity.

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

    SciTech Connect

    Lai, C.-M.; Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Peng, L.-H.; Yu, N. E.; Boudrioua, A.; Kung, A. H.

    2014-12-01

    Spectrally broad frequency comb generation over 510–555?nm range was reported on chirped quasi-phase-matching (QPM) ?{sup (2)} nonlinear photonic crystals of 12?mm length with periodicity stepwise increased from 5.9??m to 7.1??m. 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.

  8. Threshold conditions, energy spectrum and bands generated by locally periodic Dirac comb potentials

    NASA Astrophysics Data System (ADS)

    Dharani, M.; Shastry, C. S.

    2016-01-01

    We derive expressions for polynomials governing the threshold conditions for different types of locally periodic Dirac comb potentials comprising of attractive and combination of attractive and repulsive delta potential terms confined symmetrically inside a one dimensional box of fixed length. The roots of these polynomials specify the conditions on the potential parameters in order to generate threshold energy bound states. The mathematical and numerical methods used by us were first formulated in our earlier works and it is also very briefly summarized in this paper. We report a number of mathematical results pertaining to the threshold conditions and these are useful in controlling the number of negative energy states as desired. We further demonstrate the correlation between the distribution of roots of these polynomials and negative energy eigenvalues. Using these results as basis, we investigate the energy bands in the positive energy spectrum for the above specified Dirac comb potentials and also for the corresponding repulsive case. In the case of attractive Dirac comb the base energy of the each band excluding the first band coincides with specific eigenvalue of the confining box whereas in the repulsive case it coincides with the band top. We deduce systematic correlation between band gaps, band spreads and box eigenvalues and explain the physical reason for the vanishing of band pattern at higher energies. In the case of Dirac comb comprising of orderly arranged attractive and repulsive delta potentials, specific box eigenvalues occur in the middle of each band excluding the first band. From our study we find that by controlling the number and strength parameters of delta terms in the Dirac comb and the size of confining box it is possible to generate desired types of band formations. We believe the results from our systematic analysis are useful and relevant in the study of various one dimensional systems of physical interest in areas like nanoscience.

  9. The invariant-comb approach and its relation to the balancedness of multipartite entangled states

    NASA Astrophysics Data System (ADS)

    Osterloh, Andreas; Siewert, Jens

    2010-07-01

    The invariant-comb approach is a method to construct entanglement measures for multipartite systems of qubits. The essential step is the construction of an antilinear operator that we call comb in reference to the hairy-ball theorem. An appealing feature of this approach is that, for qubits (or spins 1/2), the combs are automatically invariant under SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex\\kern-.30em C}) , which implies that the obtained invariants are entanglement monotones by construction. By asking which property of a state determines whether or not it is detected by a polynomial SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex \\kern-.30em {C}}) invariant, we find that it is the presence of a balanced part that persists under local unitary transformations. We present a detailed analysis for the maximally entangled states detected by such polynomial invariants, which leads to the concept of irreducibly balanced states. The latter indicates a tight connection with stochastic local operations and classical communication (SLOCC) classifications of qubit entanglement. Combs may also help to define measures for multipartite entanglement of higher-dimensional subsystems. However, for higher spins there are many independent combs, such that it is nontrivial to find an invariant one. By restricting the allowed local operations to rotations of the coordinate system (i.e. again to the SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex \\kern-.30em C}) ), we manage to define a unique extension of the concurrence to general half-integer spin with an analytic convex-roof expression for mixed states.

  10. Generation of green frequency comb from chirped ?(2) nonlinear photonic crystals

    NASA Astrophysics Data System (ADS)

    Lai, C.-M.; Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Yu, N. E.; Boudrioua, A.; Kung, A. H.; Peng, L.-H.

    2014-12-01

    Spectrally broad frequency comb generation over 510-555 nm range was reported on chirped quasi-phase-matching (QPM) ?(2) nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 ?m to 7.1 ?m. 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.

  11. Sex and Women with Cancer -- Overview

    MedlinePLUS

    ... Side Effects » Fertility and Sexual Side Effects in Women » Sex and Women with Cancer » Sex and Women With ... to sex and cancer Next Topic How a woman’s body works Sex and Women With Cancer: Overview This is a ...

  12. Attitudes about Sex Selection and Sex Preference in Iranian Couples Referred for Sex Selection Technology

    PubMed Central

    Ahmadi, Seyedeh Fatemeh; Shirzad, Mahdi; Kamali, Koorosh; Ranjbar, Fahimeh; Behjati-Ardakani, Zohreh; Akhondi, Mohammad Mehdi

    2015-01-01

    Background Gender preference is prevalent in some communities and using medical techniques to choose the baby's sex may cause the gender discrimination and gender imbalance in communities. Therefore, evaluating the gender preferences and attitudes towards using sex selection technologies seems to be necessary. Methods This cross-sectional study was conducted in Avicenna Fertility Center. Participants were 100 women with one child who were referred for sex selection. Data were collected through self-developed questionnaires. The questions were designed by the researchers at the experts’ panel. To determine the validity of the questionnaire, the viewpoints of professors specialized in these issues were obtained. The statistical analysis of the data was performed using SPSS software (Version 11.5), and p < 0.05 was considered significant. Results Tendency toward the male was more than female sex (55.5% male, 15.5% female and 28.5% no tendency). Majority of participants agreed with sex selection with medical reason and sex selection in order to balance the family. Women's level of education had positive effect on agreements to fetal sex selection with medical and non-medical reasons (p < 0.001). Conclusion Although gender preferences were toward the male sex but this preference was not very strong. Most participants agreed with non-medical sex selection for balancing the sex composition of their children. It doesn't seem that non-medical sex selection for family balancing causes severe sex imbalance in Iran. PMID:25717434

  13. "Sex Hormones" in Secondary School Biology Textbooks

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Young, Rebecca

    2008-01-01

    This study explores the extent to which the term "sex hormone" is used in science textbooks, and whether the use of the term "sex hormone" is associated with pre-empirical concepts of sex dualism, in particular the misconceptions that these so-called "sex hormones" are sex specific and restricted to sex-related physiological functioning. We found…

  14. No slave to sex.

    PubMed

    Schön, Isabelle; Martens, Koen

    2003-04-22

    Fully asexual lineages cannot purge accumulating mutations from their genome through recombination. In ancient asexuals that have persisted without sex for millions of years, this should lead to high allelic divergences (the 'Meselson effect') as has been shown for bdelloid rotifers. Homogenizing mechanisms can counter this effect, resulting in low genetic diversity within and between individuals. Here, we show that the ancient asexual ostracod species Darwinula stevensoni has very low nucleotide sequence divergence in three nuclear regions. Differences in genetic diversity between embryos and adults furthermore indicate that up to half of the observed genetic changes in adults can be caused by somatic mutations. Likelihood permutation tests confirm the presence of gene conversion in the multi-copy internal transcribed spacer sequence, but reject rare or cryptic forms of sex as a general explanation for the low genetic diversity in D. stevensoni. Other special mechanisms (such as highly efficient DNA repair) might have been selected for in this ancient asexual to overcome the mutational load and Muller's ratchet. In this case, our data support these hypotheses on the prevalence of sex, even if the two extant ancient asexual groups (bdelloids and darwinulids) seem to follow opposite evolutionary strategies. PMID:12737661

  15. The SW Sex enigma

    E-print Network

    Dhillon, V S; Marsh, T R

    2012-01-01

    The SW Sex stars are a class of cataclysmic variables, originally identified because they shared a number of enigmatic properties - most notably, single-peaked emission lines instead of the double-peaked lines one would expect from their high-inclination accretion discs. We present high time-resolution spectrophotometry of the eclipsing nova-like variables SW Sex and DW UMa, two of the founding members of the SW Sex class. Both systems show single-peaked Balmer and HeII 4686A emission lines that appear to originate from a region in the disc that lies close to, but downstream of, the bright spot. The emission-line light curves are consistent with the finding from X-ray and ultraviolet observations that we predominantly see the flared disc rim and the unobscured back portion of the disc in these systems. In DW UMa, the HeII 4686A emission line originates from close to the white dwarf and exhibits flaring. Such flares have been used to argue for magnetically-channelled accretion, as in the intermediate polars, b...

  16. Sex-role orientation and attachment styles of sex offenders.

    PubMed

    Schneck, Mary M; Bowers, Thomas G; Turkson, Maria A

    2012-04-01

    Given the increase of individuals who have a history of sexual offenses, there has been an increase in research on the etiology of sex-offending behavior. The present purpose was to evaluate the relationship between sex-role orientation and attachment styles of males who were sex offenders. Analysis yielded statistically significant differences between comparison (n = 22) and clinical groups (n = 21) in gender roles, with little sign of the androgynous gender type for sex offenders. The offender group showed significantly lower frequency of androgyny scores and significantly higher scores on feminine and undifferentiated orientations, supporting the theoretical view of sex offenders as being "cross-sex-typed." In addition, the sex offender group had a significantly higher mean score on anxious-avoidant relationship attachment. Based on the present findings, there appears to be a need to help sex offenders explore how their gender roles may relate to their sex-offending behavior and assist sex offenders in the development of adaptive relationships with reduced anxiety and ambivalence. PMID:22662415

  17. Femtosecond spectroscopy of acoustic frequency combs in the 100-GHz frequency range in Al/Si membranes

    NASA Astrophysics Data System (ADS)

    Grossmann, Martin; Klingele, Matthias; Scheel, Patricia; Ristow, Oliver; Hettich, Mike; He, Chuan; Waitz, Reimar; Schubert, Martin; Bruchhausen, Axel; Gusev, Vitalyi; Scheer, Elke; Dekorsy, Thomas

    2013-11-01

    Acoustic frequency combs are optically excited and detected in silicon membranes covered with thin aluminum layers by femtosecond pump-probe spectroscopy. The various frequency combs consist of 11 up to 45 modes ranging in frequency from 10 up to 500 GHz. Evaluating the different modes of the combs allows us to quantify the dynamic properties of this two-layer system with great precision. Deviations of the frequencies of higher modes from a linear relation can be quantitatively understood. The time domain traces show clearly defined pulses which are detected in regular time intervals after each roundtrip in the acoustic cavity formed by the membrane and the metal film. By analyzing the individual reflected pulses and their evolution in time, damping times for the whole frequency range are determined. We analytically derive a deviation of the individual comb modes from integer values of the fundamental frequency which is corroborated by the experiments.

  18. High-power ultra-broadband frequency comb from ultraviolet to infrared by high-power fiber amplifiers.

    PubMed

    Yang, Kangwen; Li, Wenxue; Yan, Ming; Shen, Xuling; Zhao, Jian; Zeng, Heping

    2012-06-01

    A high-power ultra-broadband frequency comb covering the spectral range from ultraviolet to infrared was generated directly by nonlinear frequency conversion of a multi-stage high-power fiber comb amplifier. The 1030-nm infrared spectral fraction of a broadband Ti:sapphire femtosecond frequency comb was power-scaled up to 100 W average power by using a large-mode-area fiber chirped-pulse amplifier. We obtained a frequency-doubled green comb at 515 nm and frequency-quadrupled ultraviolet pulses at 258 nm with the average power of 12.8 and 1.62 W under the input infrared power of 42.2 W, respectively. The carrier envelope phase stabilization was accomplished with an ultra-narrow line-width of 1.86 mHz and a quite low accumulated phase jitter of 0.41 rad, corresponding to a timing jitter of 143 as. PMID:22714317

  19. Measurement of the carrier envelope offset frequency of a femtosecond frequency comb using a Fabry-Perot interferometer

    SciTech Connect

    Basnak, D V; Bikmukhametov, K A; Dmitrieva, N I; Dmitriev, Aleksandr K; Lugovoi, A A; Pokasov, P V; Chepurov, S V

    2010-10-15

    A method for measuring the carrier envelope offset (CEO) frequency of the femtosecond frequency comb with a bandwidth of less than one octave by using a Fabry-Perot interferometer is proposed and experimentally demonstrated. (laser components)

  20. Fottea 10(1): 7582, 2010 75 Phylogenetic position of Ooplanctella planoconvexa, gen. et comb. nova and

    E-print Network

    Fottea 10(1): 75­82, 2010 75 Phylogenetic position of Ooplanctella planoconvexa, gen. et comb. nova. nova, is proposed. Key words: 18S rDNA, Coenochloris, Echinocoleum, molecular phylogeny, Oocystaceae

  1. Patterns of comb row development in young and adult stages of the ctenophores Mnemiopsis leidyi and Pleurobrachia pileus.

    PubMed

    Tamm, Sidney L

    2012-09-01

    The development of comb rows in larval and adult Mnemiopsis leidyi and adult Pleurobrachia pileus is compared to regeneration of comb plates in these ctenophores. Late gastrula embryos and recently hatched cydippid larvae of Mnemiopsis have five comb plates in subsagittal rows and six comb plates in subtentacular rows. Subsagittal rows develop a new (sixth) comb plate and both types of rows add plates at similar rates until larvae reach the transition to the lobate form at ?5 mm size. New plate formation then accelerates in subsagittal rows that later extend on the growing oral lobes to become twice the length of subtentacular rows. Interplate ciliated grooves (ICGs) develop in an aboral-oral direction along comb rows, but ICG formation itself proceeds from oral to aboral between plates. New comb plates in Mnemiopsis larvae are added at both aboral and oral ends of rows. At aboral ends, new plates arise as during regeneration: local widening of a ciliated groove followed by formation of a short split plate that grows longer and wider and joins into a common plate. At oral ends, new plates arise as a single tuft of cilia before an ICG appears. Adult Mnemiopsis continue to make new plates at both ends of rows. The frequency of new aboral plate formation varies in the eight rows of an animal and seems unrelated to body size. In Pleurobrachia that lack ICGs, new comb plates at aboral ends arise between the first and second plates as a single small nonsplit plate, located either on the row midline or off-axis toward the subtentacular plane. As the new (now second) plate grows larger, its distance from the first and third plates increases. Size of the new second plate varies within the eight rows of the same animal, indicating asynchronous formation of plates as in Mnemiopsis. New oral plates arise as in Mnemiopsis. The different modes of comb plate formation in Mnemiopsis versus Pleurobrachia are accounted for by differences in mesogleal firmness and mechanisms of ciliary coordination. In both cases, the body of a growing ctenophore is supplied with additional comb plates centripetally from opposite ends of the comb rows. PMID:22729952

  2. Generation of Optical Combs in a WGM Resonator from a Bichromatic Pump

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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 lasers centered at around 1,560 nanometers. Both laser frequencies were simultaneously scanned around the selected WGMs of the same family. However, they were separated by one, two, three, or ten FSRs. This was achieved by fine-tuning each laser frequency offset until the selected resonances overlap on the oscilloscope screen. The resonator quality factor Q = 7 x 10(exp 7) was relatively low to increase the linewidth and, therefore, the duty cycle of both lasers simultaneously coupled into their WGMs. The optical spectrum analyzer (OSA) connected to the output fiber was continuously acquiring data, asynchronously with the laser scan. The instrument was set to retain the peak power values; therefore, a trace recorded for a sufficiently long period of time reflected the situation with both lasers maximally coupled to the WGMs.

  3. Nonvolitional sex and sexual health.

    PubMed

    Kalmuss, Debra

    2004-06-01

    Nonvolitional sex is sexual behavior that violates a person's right to choose when and with whom to have sex and what sexual behaviors to engage in. The more extreme forms of this behavior include rape, forced sex, childhood sexual abuse, sex trafficking, and violence against people with nonconventional sexual identities. More nuanced forms of nonvolitional sex include engaging in sexual behavior that masks one's nonconventional sexual identity, or that protects one's position with peers, or that represents a quid pro quo for the economic support that one obtains within an intimate relationship. The aim of this essay is to highlight the ways in which nonvolitional sex threatens sexual health and to identify strategies for ameliorating this problem. These strategies will have to be as broad in scope as is the problem that they are designed to address. The essay discusses the following strategies to reduce nonvolitional sex: (1) advocacy for sexual rights, gender equality, and equality for individuals with nonconventional sexual identities; (2) primary prevention programs and interventions that offer comprehensive sexuality education that establishes volitional sex and sexual health as basic human rights; (3) health services that routinely ask clients about their experiences with nonvolitional sex in an open and culturally appropriate manner; and (4) secondary prevention programs to meet the needs of victims of nonvolitional sex identified by the "screening" programs. PMID:15129039

  4. Coherent control of multiphoton resonance dynamics in high-order-harmonic generation driven by two frequency-comb fields

    NASA Astrophysics Data System (ADS)

    Zhao, Di; Jiang, Chen-Wei; Li, Fu-li

    2015-10-01

    We present a theoretical investigation of the multiphoton resonance dynamics in the high-order-harmonic generation (HHG) process driven by two frequency-comb fields with the carrier frequencies of fundamental and second harmonics, respectively. The many-mode Floquet theorem is employed to provide a nonperturbative and exact treatment of the interaction between a quantum system and frequency-comb laser fields. The coupling of the weak second-harmonic control frequency-comb laser field promises more routes to coherently optimize the multiphoton resonance dynamics and HHG power spectra. First, even-order harmonics are generated due to the coupling of the second-harmonic frequency-comb field. Second, the HHG power spectra can be greatly enhanced via multiphoton resonance, which can be achieved by tuning the carrier-envelope-phase (CEP) shifts and the peak intensities of both frequency-comb fields. Furthermore, besides the multiphoton transitions involving only fundamental-harmonic photons, additional multiphoton transitions involving both fundamental- and second-harmonic photons occur, resulting in the generation of combs with frequencies dependent on CEP shifts of both fields. Different multiphoton transition paths can interfere with each other when the two CEP shifts are matching, and the interference of paths allows one to coherently control the HHG power spectra by varying the relative phase between the fields.

  5. Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy

    NASA Astrophysics Data System (ADS)

    Zajnulina, M.; Boggio, J. M. Chavez; Böhm, M.; Rieznik, A. A.; Fremberg, T.; Haynes, R.; Roth, M. M.

    2015-07-01

    We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrödinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.

  6. A two-stage optical frequency comb generator based on polarization modulators and a Mach-Zehnder interferometer

    NASA Astrophysics Data System (ADS)

    Zhang, Fangzheng; Ge, Xiaozhong; Pan, Shilong

    2015-11-01

    A two-stage optical frequency comb (OFC) generator is proposed based on two polarization modulators (PolMs) and a Mach-Zehnder interferometer (MZI). In the first-stage OFC generator, a group of even-order sidebands and a group of odd-order sidebands are generated with similar powers, respectively, based on a single PolM. By tuning the power difference between the two sideband groups using an MZI, a flat OFC with increased comb-lines can be generated. In the experiment, OFCs with up to 11 comb-lines are generated with good flatness, which is better than most of the previous scheme based on a single modulator. To further increase the comb-line number, a second-stage OFC generator is followed using another PolM, which could increase the comb-line number by a factor of up to 5 theoretically. Performance of the proposed two-stage OFC generator is investigated through simulations and experiments. The results can verify the feasibility of the proposed OFC generator, which is a cost-effective way to generate flat OFCs with a large number of comb-lines.

  7. Optical-frequency-comb generation and entanglement with low-power optical input in a photonic molecule

    NASA Astrophysics Data System (ADS)

    Li, Jiahua; Yu, Rong; Ding, Chunling; Wang, Wei; Wu, Ying

    2014-09-01

    Optical-frequency combs consisting of equally spaced sharp lines in frequency space have triggered substantial advances in optical-frequency metrology and precision measurements and in applications such as laser-based gas sensing and molecular fingerprinting. Here, we propose a scheme to generate a type of optical-frequency combs and convert them from one cavity to the other in a hybrid optical system composed of a pair of coupled photonic crystal cavities called a photonic molecule (PM) and a single semiconductor quantum dot (QD) embedded in one cavity of the molecule. Optical-frequency combs are formed by the interaction between a cavity mode and a continuous-wave (CW) two-tone driving laser consisting of a pump field and a seed field via QD-induced strong nonlinearity. In this situation, the initial input pump and seed CW lasers can interact among each other and produce optical higher-order sidebands with equal spacing via parametric frequency conversion provided by QD-induced nonlinear optical effects. Using numerical simulations, it is clearly shown that the beat frequency of the two-tone components plays an important role in determining the comb spacing and matched frequency combs can be formed in the PM. We also demonstrate that the present interacting QD-PM system can serve as a platform to generate large-scale quantum entanglement between two comb modes. The results obtained here may be useful for real experiments in a photonic crystal platform.

  8. Resonant light scattering of a laser frequency comb by a quantum dot

    NASA Astrophysics Data System (ADS)

    Konthasinghe, K.; Peiris, M.; Muller, A.

    2014-08-01

    We investigate the spectral and temporal properties of light scattered near resonantly by a single quantum dot when the incident laser field is a frequency comb consisting of a superposition of monochromatic waves equidistant in frequency. Such fields encompass those generated by, e.g., a periodically pulsed laser. A general theoretical treatment for the calculation of first- and second-order correlation functions is given which takes account of spectral diffusion through a slowly varying detuning from resonance, permitting accurate comparison with experiments. We explore the two distinct regimes in which the frequency-comb separation is either larger or smaller than the radiative decay rate. We verify the validity of our calculations by a comparison with experimental data for the case of a bichromatic field and discuss the manifestation of phase coherence between the incoming field and the scattered single-photon wave packet.

  9. Hierarchical, multilayered cell walls reinforced by recycled silk cocoons enhance the structural integrity of honeybee combs

    PubMed Central

    Zhang, Kai; Duan, Huiling; Karihaloo, Bhushan L.; Wang, Jianxiang

    2010-01-01

    We reveal the sophisticated and hierarchical structure of honeybee combs and measure the elastic properties of fresh and old natural honeycombs at different scales by optical microscope, environmental scanning electron microscope, nano/microindentation, and by tension and shear tests. We demonstrate that the comb walls are continuously strengthened and stiffened without becoming fragile by the addition of thin wax layers reinforced by recycled silk cocoons reminiscent of modern fiber-reinforced composite laminates. This is done to increase its margin of safety against collapse due to a temperature increase. Artificial engineering honeycombs mimic only the macroscopic geometry of natural honeycombs, but have yet to achieve the microstructural sophistication of their natural counterparts. The natural honeycombs serve as a prototype of truly biomimetic cellular materials with hitherto unattainable improvement in stiffness, strength, toughness, and thermal stability. PMID:20439765

  10. Flexible frequency comb generation in a periodically poled lithium niobate waveguide enabling optical multicasting.

    PubMed

    Vercesi, Valeria; Pinna, Sergio; Meloni, Gianluca; Scotti, Filippo; Potì, Luca; Bogoni, Antonella; Scaffardi, Mirco

    2014-10-15

    We propose and demonstrate a technique for the generation of a coherent optical comb, with tunable line spacing in a periodically poled lithium niobate (PPLN) waveguide. A single continuous wave laser is modulated to generate three phase-locked seed lines, which are injected into a PPLN waveguide, to obtain line multiplication. The line spacing is set acting on the frequency of the electrical signal driving the modulator. The quality of the comb is verified measuring the autocorrelation, the phase noise, and the linewidth of the generated lines. With the same scheme, we demonstrate optical multicasting. From a single quadrature phase shift keying signal, modulated at 12.5 and 25 GBaud, five replicas are generated, with spacing 25 and 37.5 GHz. The performance of each signal replica is measured after transmission through 80 km of a single-mode fiber, demonstrating operation with a bit error rate value lower than the forward error correction threshold. PMID:25361135

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

    PubMed

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

    2009-09-28

    We propose a distance meter that utilizes an intermode beat of terahertz frequency in an optical frequency comb to perform high resolution and high dynamic range absolute distance measurements. The proposed system is based on a novel method, called multiheterodyne cross-correlation detection, in which intermode beat frequencies are scaled down to radio frequencies by optical mixing of two detuned optical frequency combs with a nonlinear optical crystal. Using this method, we obtained a 1.056 THz intermode beat and achieved a distance resolution of 0.820 microm from its phase measurement. Absolute distance measurement using 1.056 THz and 8.187 GHz intermode beats was also demonstrated in the range of 10 mm, resulting in a precision of 0.688 microm. PMID:19907518

  12. Analysis of Trace Impurities in Semiconductor Gas via Cavity-Enhanced Direct Frequency Comb Spectroscopy

    E-print Network

    Cossel, Kevin C; Bertness, Kris A; Thorpe, Michael J; Feng, Jun; Raynor, Mark W; Ye, Jun

    2010-01-01

    Cavity-enhanced direct frequency comb spectroscopy (CE-DFCS) has demonstrated powerful potential for trace gas detection based on its unique combination of high bandwidth, rapid data acquisition, high sensitivity, and high resolution, which is unavailable with conventional systems. However, previous demonstrations have been limited to proof-of-principle experiments or studies of fundamental laboratory science. Here we present the development of CE-DFCS towards an industrial application -- measuring impurities in arsine, an important process gas used in III-V semiconductor compound manufacturing. A strongly absorbing background gas with an extremely complex, congested, and broadband spectrum renders trace detection exceptionally difficult, but the capabilities of CE-DFCS overcome this challenge and make it possible to identify and quantify multiple spectral lines associated with water impurities. Further, frequency combs allow easy access to new spectral regions via efficient nonlinear optical processes. Here,...

  13. Frequency-comb-referenced singly-resonant OPO for sub-Doppler spectroscopy.

    PubMed

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

    2012-04-01

    We present a widely-tunable, singly-resonant optical parametric oscillator, emitting more than 1 W between 2.7 and 4.2 ?m, 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?¹²??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 ?1 rovibrational band of CH?I, 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. PMID:22513629

  14. Frequency comb generation at THz frequencies by coherent phonon excitation in Si

    E-print Network

    Hase, Muneaki; Constantinescu, Anca Monia; Petek, Hrvoje; 10.1038/nphoton.2012.35

    2012-01-01

    High-order nonlinear light-matter interactions in gases enable generation of x-ray and attosecond light pulses, metrology, and spectroscopy. Optical nonlinearities in solid-state materials are particularly interesting for combining optical and electronic functions for high-bandwidth information processing. Third-order nonlinear optical processes in silicon have been used to process optical signals with greater than 1 GHz bandwidths. Fundamental physical processes for a Si-based optical modulator in the THz bandwidth range, however, have not yet been explored. Here we demonstrate ultrafast phononic modulation of the optical index of Si by irradiation with intense few-cycle femtosecond pulses. The anisotropic reflectivity modulation by the resonant Raman susceptibility at the fundamental frequency of the longitudinal optical (LO) phonon of Si (15.6 THz) generates a frequency comb up to 7th-order. All optical >100 THz frequency comb generation is realized by harnessing the coherent atomic motion of the Si crysta...

  15. Multi-delay, phase coherent pulse pair generation for precision Ramsey-frequency comb spectroscopy.

    PubMed

    Morgenweg, J; Eikema, K S E

    2013-03-11

    We demonstrate the generation of phase-stable mJ-pulse pairs at programmable inter-pulse delays up to hundreds of nanoseconds. A detailed investigation of potential sources for phase shifts during the parametric amplification of the selected pulses from a Ti:Sapphire frequency comb is presented, both numerically and experimentally. It is shown that within the statistical error of the phase measurement of 10 mrad, there is no dependence of the differential phase shift over the investigated inter-pulse delay range of more than 300 ns. In combination with nonlinear upconversion of the amplified pulses, the presented system will potentially enable short wavelength (<100 nm), multi-transition Ramsey-frequency comb spectroscopy at the kHz-level. PMID:23482099

  16. Fast interrogation of fiber Bragg grating sensors using electro-optic dual optical frequency combs

    NASA Astrophysics Data System (ADS)

    Bonilla-Manrique, O. E.; Garcia-Souto, J. A.; Martin-Mateos, P.; Jerez-Gonzalez, B.; Acedo, P.

    2015-09-01

    In this document, a FBG interrogation system based on a multimode optical source and a direct read-out is proposed for measuring fast phenomena such as vibrations and ultrasounds. The system is based on an electro-optic dual optical frequency-comb. This architecture allows the configuration of the multimode optical source parameters such as the number of modes that are within the reflected spectrum (FWHM) of the FBG. Results are presented for the dual-comb operating under optimized control when mapping these optical modes onto detectable tones of multiples of 100 kHz around a centre radiofrequency tone (40 MHz). Dynamic strain is induced onto the fiber through an actuator, which generates changes in the reflected wavelength of the FBG and in turn the modes within the reflected spectrum. The electrical signals are analyzed using fast Fourier transform algorithms allowing identification of the vibrations.

  17. Implementation of a single femtosecond optical frequency comb for rovibrational cooling

    SciTech Connect

    Shi, W.; Malinovskaya, S.

    2010-07-15

    We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules (e.g., KRb). The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train, providing a controlled population accumulation in the final state. Detuning the pulse train carrier and modulation frequency from one-photon resonances changes the time scale of molecular dynamics but leads to the same complete population transfer to the ultracold state. A standard optical frequency comb with no modulation is shown to induce similar dynamics, leading to rovibrational cooling.

  18. Optical phase-noise dynamics of Titanium:sapphire optical frequency combs

    E-print Network

    Quraishi, Qudsia; Hollberg, Leo

    2014-01-01

    Stabilized optical frequency combs (OFC) can have remarkable levels of coherence across their broad spectral bandwidth. We study the scaling of the optical noise across hundreds of nanometers of optical spectra. We measure the residual phase noise between two OFC's (having offset frequencies $f^{(1)}_0 $ and $f^{(2)}_0$) referenced to a common cavity-stabilized narrow linewidth CW laser. Their relative offset frequency $ \\Delta f_0 = f^{(2)}_0 - f^{(1)}_0 $, which appears across their entire spectra, provides a convenient measure of the phase noise. By comparing $\\Delta f_0$ at different spectral regions, we demonstrate that the observed scaling of the residual phase noise is in very good agreement with the noise predicted from the standard frequency comb equation.

  19. Frequency-comb-assisted precision laser spectroscopy of CHF3 around 8.6 ?m.

    PubMed

    Gambetta, Alessio; Coluccelli, Nicola; Cassinerio, Marco; Fernandez, Toney Teddy; Gatti, Davide; Castrillo, Antonio; Ceausu-Velcescu, Adina; Fasci, Eugenio; Gianfrani, Livio; Santamaria, Luigi; Di Sarno, Valentina; Maddaloni, Pasquale; De Natale, Paolo; Laporta, Paolo; Galzerano, Gianluca

    2015-12-21

    We report a high-precision spectroscopic study of room-temperature trifluoromethane around 8.6 ?m, 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 ?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(-10). Line intensity factors, pressure broadening, and shifting parameters are also provided. PMID:26696053

  20. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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

  1. Destruction of ultra-slow diffusion in a three dimensional cylindrical comb structure

    E-print Network

    A. Iomin; V. Mendez

    2015-08-21

    We present a rigorous result on ultra-slow diffusion by solving a Fokker-Planck equation, which describes anomalous transport in a three dimensional (3D) comb. This 3D cylindrical comb consists of a cylinder of discs threaten on a backbone. It is shown that the ultra-slow contaminant spreading along the backbone is described by the mean squared displacement (MSD) of the order of $\\ln (t)$. This phenomenon takes place only for normal two dimensional diffusion inside the infinite secondary branches (discs). When the secondary branches have finite boundaries, the ultra-slow motion is a transient process and the asymptotic behavior is normal diffusion. In another example, when anomalous diffusion takes place in the secondary branches, a destruction of ultra-slow (logarithmic) diffusion takes place as well. As the result, one observes "enhanced" subdiffusion with the MSD $\\sim t^{1-\\alpha}\\ln t$, where $0<\\alpha<1$.

  2. Adaptive frequency comb illumination for interferometry in the case of nested two-beam cavities

    SciTech Connect

    Harder, Irina; Leuchs, Gerd; Mantel, Klaus; Schwider, Johannes

    2011-09-01

    The homogeneity test of glass plates in a Fizeau interferometer is hampered by the superposition of multiple interference signals coming from the surfaces of the glass plate as well as the empty Fizeau cavity. To evaluate interferograms resulting from such nested cavities, various approaches such as the use of broadband light sources have been applied. In this paper, we propose an adaptive frequency comb interferometer to accomplish the cavity selection. An adjustable Fabry-Perot resonator is used to generate a variable frequency comb that can be matched to the length of the desired cavity. Owing to its flexibility, the number of measurements needed for the homogeneity test can be reduced to four. Furthermore, compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher if a Fabry-Perot filter is applied.

  3. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

    2012-09-01

    Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  5. ComB: SNP Calling and Mapping Analysis for Color and Nucleotide Space Platforms

    PubMed Central

    Souaiaia, Tade; Frazier, Zach

    2011-01-01

    Abstract The determination of single nucleotide polymorphisms (SNPs) has become faster and more cost effective since the advent of short read data from next generation sequencing platforms such as Roche's 454 Sequencer, Illumina's Solexa platform, and Applied Biosystems SOLiD sequencer. The SOLiD sequencing platform, which is capable of producing more than 6?GB of sequence data in a single run, uses a unique encoding scheme where color reads represent transitions between adjacent nucleotides. The determination of SNPs from color reads usually involves the translation of color alignments to likely nucleotide strings to facilitate the use of tools designed for nucleotide reads. This technique results in the loss of significant information in the color read, producing many incorrect SNP calls, especially if regions exist with dense or adjacent polymorphism. Additionally, color reads align ambiguously and incorrectly more often than nucleotide reads making integrated SNP calling a difficult challenge. We have developed ComB, a SNP calling tool which operates directly in color space, using a Bayesian model to incorporate unique and ambiguous reads to iteratively determine SNP identity. ComB is capable of accurately calling short consecutive nucleotide polymorphisms and densely clustered SNPs; both of which other SNP calling tools fail to identify. ComB, which is capable of using billions of short reads to accurately and efficiently perform whole human genome SNP calling in parallel, is also capable of using sequence data or even integrating sequence and color space data sets. We use real and simulated data to demonstrate that ComB's iterative strategy and recalibration of quality scores allow it to discover more true SNPs while calling fewer false positives than tools which use only color alignments as well as tools which translate color reads to nucleotide strings. PMID:21563978

  6. Synthesis of Non-spherical Glycopolymer-Decorated Nanoparticles: Combing Thiol-ene with Catecholic Chemistry.

    PubMed

    Li, Xiao; Zhang, Weidong; Chen, Gaojian

    2016-01-01

    Glycopolymers with carbohydrate side chains are currently being applied in many fields, with much potential for disease treatment. The shape of glycopolymer-bearing nanoparticles has obvious effects on the nanoparticle-cell interaction and is therefore important for the applications of glycopolymers in biological systems. Here a synthetic approach to prepare non-spherical glycopolymer-coated iron oxide nanoparticles is provided, by combing the convenience of inorganic shape control, catecholic chemistry, and thiol-ene reaction. PMID:26537471

  7. Carrier-envelope offset frequency noise analysis in Ti:sapphire frequency combs

    NASA Astrophysics Data System (ADS)

    Sutyrin, Denis V.; Poli, Nicola; Beverini, Nicolò; Tino, Guglielmo M.

    2014-12-01

    We experimentally study two Ti:sapphire optical frequency comb femtosecond regimes, respectively, with a linear and a nonlinear dependence of the carrier-envelope offset frequency (fCEO) on pump intensity. For both regimes, we study the effect of single- and multimode pump lasers on the fCEO phase noise. We demonstrate that the femtosecond regime is playing a more important role on the fCEO phase noise and stability than the pump laser type.

  8. Widely time-dispersion-tuned fiber optical oscillator and frequency comb based on multiple nonlinear processes.

    PubMed

    Chiarello, Fabrizio; Palmieri, Luca; Galtarossa, Andrea; Santagiustina, Marco

    2013-11-15

    An all-fiber optical oscillator based on three nonlinear processes, namely stimulated Raman scattering and broad-band and narrow-band optical parametric amplification, is presented and experimentally characterized. The wavelength tuning is achieved by means of the time-dispersion technique and spans over 160 nm. Through the same technique a fast tunable optical frequency comb has been realized exploiting cascaded four-wave mixing. PMID:24322089

  9. High-resolution broadband terahertz spectroscopy via electronic heterodyne detection of photonically generated terahertz frequency comb.

    PubMed

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

    2014-10-01

    We report an alternative approach to the terahertz frequency-comb spectroscopy (TFCS) based on nonlinear mixing of a photonically generated terahertz pulse train with a continuous wave signal from an electronic synthesizer. A superlattice is used as a nonlinear mixer. Unlike the standard TFCS technique, this approach does not require a complex double-laser system but retains the advantages of TFCS-high spectral resolution and wide bandwidth. PMID:25360955

  10. Asymptotic Capacity of Wireless Ad Hoc Networks with Realistic Links under a Honey Comb Topology

    E-print Network

    Asnani, Himanshu

    2007-01-01

    We consider the effects of Rayleigh fading and lognormal shadowing in the physical interference model for all the successful transmissions of traffic across the network. New bounds are derived for the capacity of a given random ad hoc wireless network that reflect packet drop or capture probability of the transmission links. These bounds are based on a simplified network topology termed as honey-comb topology under a given routing and scheduling scheme.

  11. Application of the interleaved comb chopper to time-of-flight electron spectrometry

    NASA Astrophysics Data System (ADS)

    Jackson, R. H.; LeGore, L. J.; Yang, Z.; Kleban, P.; Frederick, B. G.

    2002-04-01

    We examined the use of the interleaved comb chopper for time-of-flight electron spectrometry. Both static and dynamic behaviors are simulated theoretically and measured experimentally, with very good agreement. The finite penetration of the field beyond the plane of the chopper leads to non-ideal chopper response, which is characterized in terms of an "energy corruption" effect and a lead or lag in the time at which the beam responds to the chopper potential.

  12. J Comb Optim DOI 10.1007/s10878-013-9597-9

    E-print Network

    Xu, Jun-Ming

    J Comb Optim DOI 10.1007/s10878-013-9597-9 On the p-reinforcement and the complexity You Lu · Fu and p be a positive integer. A subset S V is called a p-dominating set if each vertex not in S has. The p-reinforcement number rp(G) is the smallest number of edges whose addition to G results in a graph

  13. Mixed-Sex or Single-Sex Education: How Would Young People Like Their Sex Education and Why?

    ERIC Educational Resources Information Center

    Strange, Vicki; Forrest, Simon; Oakley, Ann

    2003-01-01

    Examined adolescents views about sex education, specifically their views about interaction in single- and mixed-sex groups. Surveys of English secondary school students indicated that most girls, and one-third of boys, want some or all of their sex education to be delivered in single-sex groups. Girls' experiences of sex education with boys…

  14. Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex Ratios of

    E-print Network

    Raftery, Adrian

    Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex past with uncertainty, produced estimates for female-only populations. Here we show how two-sex populations can be similarly reconstructed and probabilistic estimates of various sex ratio quantities

  15. Optical arbitrary waveform processing of more than 100 spectral comb lines

    NASA Astrophysics Data System (ADS)

    Jiang, Zhi; Huang, Chen-Bin; Leaird, Daniel E.; Weiner, Andrew M.

    2007-08-01

    Pulse-shaping techniques, in which user-specified, ultrashort-pulse fields are synthesized by means of parallel manipulation of optical Fourier components, have now been widely adopted. Mode-locked lasers producing combs of frequency-stabilized spectral lines have resulted in revolutionary advances in frequency metrology. However, until recently, pulse shapers addressed spectral lines in groups, at low spectral resolution. Line-by-line pulse shaping, in which spectral lines are resolved and manipulated individually, leads to a fundamentally new regime for optical arbitrary waveform generation, in which the advantages of pulse shaping and of frequency combs are exploited simultaneously. Here we demonstrate programmable line-by-line shaping of more than 100 spectral lines, which constitutes a significant step in scaling towards high waveform complexity. Optical arbitrary waveform generation promises to have an impact both in optical science (allowing, for example, coherent control generalizations of comb-based time-frequency spectroscopies) and in technology (enabling new truly coherent multiwavelength processing concepts for spread-spectrum lightwave communications and light detection and ranging, lidar).

  16. Gigahertz frequency comb from a diode-pumped solid-state laser.

    PubMed

    Klenner, Alexander; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

    2014-12-15

    We present the first stabilization of the frequency comb offset from a diode-pumped gigahertz solid-state laser oscillator. No additional external amplification and/or compression of the output pulses is required. The laser is reliably modelocked using a SESAM and is based on a diode-pumped Yb:CALGO gain crystal. It generates 1.7-W average output power and pulse durations as short as 64 fs at a pulse repetition rate of 1 GHz. We generate an octave-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency fCEO detection method. As a pump source, we use a reliable and cost-efficient commercial diode laser. Its multi-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can be phase-locked by feedback to its current. Using improved electronics, we reached a feedback-loop-bandwidth of up to 300 kHz. A combination of digital and analog electronics is used to achieve a tight phase-lock of fCEO to an external microwave reference with a low in-loop residual integrated phase-noise of 744 mrad in an integration bandwidth of [1 Hz, 5 MHz]. An analysis of the laser noise and response functions is presented which gives detailed insights into the CEO stabilization of this frequency comb. PMID:25607050

  17. Frequency stabilisation of a fibre-laser comb using a novel microstructured fibre.

    PubMed

    Locke, C R; Ivanov, E N; Light, P S; Benabid, F; Luiten, A N

    2009-03-30

    There is great interest in developing high performance optical frequency metrology based around mode-locked fibre lasers because of their low cost, small size and long-term turnkey operation when compared to the solid-state alternative. We present a method for stabilising the offset frequency of a fibre-based laser comb using a 2 f - 3 f technique based around a unique fibre that exhibits strong resonant dispersive wave emission. This fibre requires lower power than conventional highly non-linear fibre to generate a suitable signal for offset frequency stabilisation and this in turn avoids the complexity of additional nonlinear steps. We generate an offset frequency signal from the mixing of a wavelength-shifted second harmonic comb with a third harmonic of the comb. Additionally, we have stabilised the repetition rate of the laser to a level better than 10(-14)/ radicaltau , limited by the measurement system noise floor.We present the means for complete and precise measurement of the transfer function of the laser frequency controls. PMID:19333360

  18. From a discrete to a continuous model for interpulse interference with a frequency-comb laser

    SciTech Connect

    Zeitouny, M. G.; Cui, M.; Bhattacharya, N.; Urbach, H. P.; Berg, S. A. van den; Janssen, A. J. E. M.

    2010-08-15

    We have investigated correlation patterns generated by a frequency-comb laser in a dispersive unbalanced Michelson interferometer and apply the developed formalism to the case of distance metrology. Due to group velocity dispersion, the position of the brightest fringe of the correlation pattern, which is used for distance determination, cannot be derived by simply using the definition of group refractive index of the dispersive medium. It is shown that the discrete spectrum of the optical frequency comb gives rise to correlation functions which can be represented by a series, namely a discrete correlation series. We have developed a general formalism, valid for any pulse train, extending the discrete model to a continuous model of cross-correlation functions using the Poisson summation. Our model is relevant for any offset and repetition frequency of the frequency comb. From the continuous cross-correlation model we show that, even for a homogeneous dispersive medium the position of the brightest fringe varies nonlinearly for small delay distances and stabilizes for longer ones. We have compared the theoretical results to measurements of pulse propagation in air for path-lengths up to 200 m.

  19. Design of optical frequency comb for sky survey astronomical spectrograph calibration

    NASA Astrophysics Data System (ADS)

    Hu, Yao; Wang, Xiang

    2013-12-01

    Sky survey telescope is an important approach to ground-based observation of external galaxies, and further research on large-scale structure of the universe, galaxy formation and evolution. Sky survey spectrograph (SSS) with low resolution is included in such kind of telescope system. The spectral measurement accuracy of SSS will determine the accuracy and scientific value of mass spectral data. Currently iodine absorption cell or Thorium-Argon lamp is adopted as the calibration source for SSS. However, the spectral lines are sparse, with non-uniform spectral interval and intensity, and even instable over long time. The novel astro-comb cannot be applied to SSS directly because the spectral intervals are still too dense to be used in SSS with relatively lower resolution. In this paper, spectral mode filtering method with acceptable energy reduction and accurate spectral line frequency is studied to improve current astro-comb to properly distributed spectral lines and solve the above critical problem. Aiming at calibration for the measuring of the spectral lines in 3700-5900 Å region, we design an improved astro-comb system based on Erbium-doped fiber laser and Fabry-Perot filter series. Feasible systematical parameters are given. It will help develop a novel calibration approach with systematic error reduction to less than 1/10000 of that of the current calibration methods.

  20. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals.

    PubMed

    Peng, Fulai; Liu, Hongyun; Wang, Weidong

    2015-10-01

    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. PMID:26334000

  1. Self-heterodyne interference spectroscopy using a comb generated by pseudo-random modulation.

    PubMed

    Hébert, Nicolas Bourbeau; Michaud-Belleau, Vincent; Anstie, James D; Deschênes, Jean-Daniel; Luiten, Andre N; Genest, Jérôme

    2015-10-19

    We present an original instrument designed to accomplish high-speed spectroscopy of individual optical lines based on a frequency comb generated by pseudo-random phase modulation of a continuous-wave (CW) laser. This approach delivers efficient usage of the laser power as well as independent control over the spectral point spacing, bandwidth and central wavelength of the comb. The comb is mixed with a local oscillator generated from the same CW laser frequency-shifted by an acousto-optic modulator, enabling a self-heterodyne detection scheme. The current configuration offers a calibrated spectrum every 1.12 µs. We demonstrate the capabilities of the spectrometer by producing averaged, as well as time-resolved, spectra of the D1 transition of cesium with a 9.8-MHz point spacing, a 50-kHz resolution and a span of more than 3 GHz. The spectra obtained after 1 ms of averaging are fitted with complex Voigt profiles that return parameters in good agreement with expected values. PMID:26480442

  2. Reclassification of Methanogenium tationis and Methanogenium liminatans as Methanofollis tationis gen. nov., comb. nov. and Methanofollis liminatans comb. nov. and description of a new strain of Methanofollis liminatans

    NASA Technical Reports Server (NTRS)

    Zellner, G.; Boone, D. R.; Keswani, J.; Whitman, W. B.; Woese, C. R.; Hagelstein, A.; Tindall, B. J.; Stackebrandt, E.

    1999-01-01

    Sequencing of 16S rRNA genes and phylogenetic analysis of Methanogenium tationis DSM 2702T (OCM 43T) (T = type strain) and Methanogenium liminatans GKZPZT (= DSM 4140T) as well as other members of the family Methanomicrobiaceae revealed that both species belong to a separate line of descent within this family. In addition, a new strain of Methanogenium liminatans, strain BM1 (= DSM 10196), was isolated from a butyrate-degrading, fluidized bed reactor and characterized. Cells of both species are mesophilic, highly irregular cocci that use H2/CO2 and formate for growth and methanogenesis. In addition, Methanogenium liminatans strains GKZPZT and BM1 used 2-propanol/CO2, 2-butanol/CO2 and cyclopentanol/CO2. Both species contained diether and tetraether lipids. The polar lipids comprised amino-phosphopentanetetrol derivatives, which appear to be characteristic lipids within the family Methanomicrobiaceae. The pattern of glycolipids, phosphoglycolipids and amino-phosphoglycolipids was consistent with the assignment of these two species to a taxon within the family Methanomicrobiaceae, but also permitted them to be distinguished from other higher taxa within this family. The G+C contents of the DNA of Methanogenium tationis and Methanogenium liminatans were 54 and 60 mol% (Tm and HPLC), respectively. On the basis of the data presented, the transfer of Methanogenium tationis and Methanogenium liminatans to the genus Methanofollis gen. nov. as Methanofollis tationis comb. nov. and Methanofollis liminatans comb. nov., respectively, is proposed, with Methanofollis tationis as the type species.

  3. Aliiroseovarius pelagivivens gen. nov., sp. nov., isolated from seawater, and reclassification of three species of the genus Roseovarius as Aliiroseovarius crassostreae comb. nov., Aliiroseovarius halocynthiae comb. nov. and Aliiroseovarius sediminilitoris comb. nov.

    PubMed

    Park, Sooyeon; Park, Ji-Min; Kang, Chul-Hyung; Yoon, Jung-Hoon

    2015-08-01

    A Gram-stain-negative, non-motile, aerobic and ovoid or rod-shaped bacterium, designated GYSW-22T, was isolated from seawater off Geoje Island in the South Sea, South Korea. Strain GYSW-22T grew optimally at 25?°C, at pH?7.0-8.0 and in the presence of 1.0-2.0% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences showed that strain GYSW-22T and the type strains of Roseovarius crassostreae, Roseovarius halocynthiae and Roseovarius sediminilitoris form a coherent cluster, independent of phylogenetic lineages or clusters comprising the type strains of other species of the genus Roseovarius. Strain GYSW-22T exhibited 16S rRNA gene sequence similarities of 97.2, 96.6 and 96.3% to R. halocynthiae MA1-10T, R. crassostreae CV919-312T and R. sediminilitoris M-M10T, respectively, and of 92.6-94.7% to the type strains of other species of the genus Roseovarius. Strain GYSW-22T contained Q-10 as the predominant ubiquinone and C18?:?1?7c as the major fatty acid. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid. The DNA G+C content of strain GYSW-22T was 59.0?mol% and its mean DNA-DNA relatedness value with R. halocynthiae MA1-10T was 15?%. On the basis of the data presented, we propose strain GYSW-22T represents a novel species of a new genus, Aliiroseovarius pelagivivens gen. nov., sp. nov. The type strain of the type species is GYSW-22T (?=?KCTC 42459T?=?CECT 8811T). In this study, it is also proposed that Roseovarius crassostreae, Roseovarius halocynthiae and Roseovarius sediminilitoris be reclassified into the new genus as Aliiroseovarius crassostreae comb. nov. (type strain CV919-312T?=?ATCC BAA-1102T?=?DSM 16950T), Aliiroseovarius halocynthiae comb. nov. (type strain MA1-10T?=?KCTC 23462T?=?CCUG 60745T) and Aliiroseovarius sediminilitoris comb. nov. (type strain M-M10T?=?KCTC 23959T?=?CCUG 62413T), respectively. PMID:25964517

  4. Self-Disclosure: A Function of Sex or Sex Role?

    ERIC Educational Resources Information Center

    Lombardo, John P.; Lavine, Linda O.

    Sex role differences in self disclosure are more clearly defined than are gender differences. Students filled out a Bem Sex Role Inventory (BSRI) as part of an introductory course requirement. Males and females who scored as either androgynous or stereotyped were selected for four targets: mother, father, male best friend, female best friend. Some…

  5. Sense about Sex: Media, Sex Advice, Education and Learning

    ERIC Educational Resources Information Center

    Attwood, Feona; Barker, Meg John; Boynton, Petra; Hancock, Justin

    2015-01-01

    The media are widely acknowledged as important in sex and relationship education, but they are usually associated with "bad" effects on young people in contrast to the "good" knowledge represented by more informational and educational formats. In this paper we look at sex advice giving in newspapers, magazines and television in…

  6. Fungal Sex and Pathogenesis

    PubMed Central

    Butler, Geraldine

    2010-01-01

    Summary: Human fungal pathogens are associated with diseases ranging from dandruff and skin colonization to invasive bloodstream infections. The major human pathogens belong to the Candida, Aspergillus, and Cryptococcus clades, and infections have high and increasing morbidity and mortality. Many human fungal pathogens were originally assumed to be asexual. However, recent advances in genome sequencing, which revealed that many species have retained the genes required for the sexual machinery, have dramatically influenced our understanding of the biology of these organisms. Predictions of a rare or cryptic sexual cycle have been supported experimentally for some species. Here, I examine the evidence that human pathogens reproduce sexually. The evolution of the mating-type locus in ascomycetes (including Candida and Aspergillus species) and basidiomycetes (Malassezia and Cryptococcus) is discussed. I provide an overview of how sex is suppressed in different species and discuss the potential associations with pathogenesis. PMID:20065328

  7. [Sex-linked juvenile retinoschisis].

    PubMed

    François, P; Turut, P; Soltysik, C; Hache, J C

    1976-02-01

    About 13 observations of sexe linked juvenile retinoschisis, the authors describe the ophthalmoscopic, fluorographic and functional aspects of the disease whose caracteristics are:--its sexe linked recessive heredity; --its clinical characterestics associating: a microcystic macular degeneration, peripheral retinal lesions, vitreous body alterations, --an electroretinogram of the negative type. PMID:132916

  8. Sex Differences in Social Behavior.

    ERIC Educational Resources Information Center

    Baker, Therese

    Examining theories from a wide spectrum of disciplines, this paper categorizes research on sex differences in social behavior into four groups and examines the implications of each. The first category of research interprets sex differences as the result of anatomical differences which later affect psychological roles. The implication of this…

  9. Moral Pluralism and Sex Education

    ERIC Educational Resources Information Center

    Corngold, Josh

    2013-01-01

    How should common schools in a liberal pluralist society approach sex education in the face of deep disagreement about sexual morality? Should they eschew sex education altogether? Should they narrow its focus to facts about biology, reproduction, and disease prevention? Should they, in addition to providing a broad palette of information about…

  10. The Consequences of Sex Selection

    ERIC Educational Resources Information Center

    Rothman, Barbara Katz

    2006-01-01

    A group of researchers at Baylor College of Medicine in Houston are set to do a long-term study of families that would permit to select the sex of their babies through genetic testing before implanting the embryo in the mother. Technologies such as in vitro fertilization involved in selecting a baby's sex has societal and psychological…

  11. Types of Juvenile Sex Offenders

    ERIC Educational Resources Information Center

    Bauman, Sheri

    2002-01-01

    Although juvenile sex offenders (JSOs) account for a significant percentage of sex crimes committed in this country, researchers have only recently begun to study this population. One line of inquiry has been to investigate sub-types of offenders, in order to determine whether different types of offenders have different personality profiles and…

  12. Sex Differences in Fetal Habituation

    ERIC Educational Resources Information Center

    Hepper, Peter G.; Dornan, James C.; Lynch, Catherine

    2012-01-01

    There is some evidence for sex differences in habituation in the human fetus, but it is unknown whether this is due to differences in central processing (habituation) or in more peripheral processes, sensory or motor, involved in the response. This study examined whether the sex of the fetus influenced auditory habituation at 33 weeks of…

  13. Sex Equity and Vocational Education.

    ERIC Educational Resources Information Center

    Weinheimer, Suzanne R.

    This publication, compiled as a learning component for persons enrolled in a vocational education teacher education program, provides information on sex equity in vocational education and employment. The content is in nine sections. The first defines sex discrimination, bias, and stereotypes. The next section covers female participation in the…

  14. Teaching Sex Education in Thailand

    ERIC Educational Resources Information Center

    Kay, Noy S.; Jones, Megan R.; Jantaraweragul, Sudgasame

    2010-01-01

    The purposes of this study were to examine the current situation pertaining to the teaching of sex education and identify barriers to teaching sex education among Thai health education teachers. A survey questionnaire was administered to 193 health education teachers who participated in this study. The questionnaire was comprised of three parts:…

  15. The joy of sex pheromones

    PubMed Central

    Gomez-Diaz, Carolina; Benton, Richard

    2013-01-01

    Sex pheromones provide an important means of communication to unite individuals for successful reproduction. Although sex pheromones are highly diverse across animals, these signals fulfil common fundamental roles in enabling identification of a mating partner of the opposite sex, the appropriate species and of optimal fecundity. In this review, we synthesize both classic and recent investigations on sex pheromones in a range of species, spanning nematode worms, insects and mammals. These studies reveal comparable strategies in how these chemical signals are produced, detected and processed in the brain to regulate sexual behaviours. Elucidation of sex pheromone communication mechanisms both defines outstanding models to understand the molecular and neuronal basis of chemosensory behaviours, and reveals how similar evolutionary selection pressures yield convergent solutions in distinct animal nervous systems. EMBO reports advance online publication 13 September 2013; doi:10.1038/embor.2013.140 PMID:24030282

  16. Sex differences in primary hypertension

    PubMed Central

    2012-01-01

    Men have higher blood pressure than women through much of life regardless of race and ethnicity. This is a robust and highly conserved sex difference that it is also observed across species including dogs, rats, mice and chickens and it is found in induced, genetic and transgenic animal models of hypertension. Not only do the differences between the ovarian and testicular hormonal milieu contribute to this sexual dimorphism in blood pressure, the sex chromosomes also play a role in and of themselves. This review primarily focuses on epidemiological studies of blood pressure in men and women and experimental models of hypertension in both sexes. Gaps in current knowledge regarding what underlie male-female differences in blood pressure control are discussed. Elucidating the mechanisms underlying sex differences in hypertension may lead to the development of anti-hypertensives tailored to one's sex and ultimately to improved therapeutic strategies for treating this disease and preventing its devastating consequences. PMID:22417477

  17. Reconstructing the Evolution of Vertebrate Sex Chromosomes

    E-print Network

    Bellott, Daniel W.

    Sex chromosomes and their evolution have captivated researchers since their discovery. For more than 100 years, the dominant model of sex chromosome evolution has held that differentiated sex chromosomes, such as the X and ...

  18. 78 FR 23835 - Sex Offender Registration Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-23

    ...COLUMBIA 28 CFR Part 811 RIN 3225-AA10 Sex Offender Registration Amendments AGENCY...verification of registration information for sex offenders. Furthermore, the rule permits CSOSA to verify addresses of sex offenders by conducting home visits...

  19. Questions and Answers about Sex (For Parents)

    MedlinePLUS

    ... Pregnant? What to Expect Questions and Answers About Sex KidsHealth > Parents > School & Family Life > Tough Topics > Questions ... extent can parents depend on schools to teach sex education? Parents should begin the sex education process ...

  20. Talk to Your Kids about Sex

    MedlinePLUS

    ... Topic En español Talk to Your Kids about Sex Browse Sections The Basics Overview When to Start ... Teach your children the facts about their bodies, sex, and relationships. Talking with your kids about sex ...