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Sample records for additional sex combs

  1. Male- and female-specific variants of doublesex gene products have different roles to play towards regulation of Sex combs reduced expression and sex comb morphogenesis in Drosophila

    Thangjam Ranjita Devi; B V Shyamala

    2013-09-01

    Sexually dimorphic characters have two-fold complexities in pattern formation as they have to get input fromboth somatic sex determination as well as the positional determining regulators. Sex comb development in Drosophila requires functions of the somatic sex-determining gene doublesex and the homeotic gene Sex combs reduced. Attempts have not been made to decipher the role of dsx in imparting sexually dimorphic expression of SCR and the differential function of sex-specific variants of dsx products in sex comb development. Our results in this study indicate that male-like pattern of SCR expression is independent of dsx function, and dsxF must be responsible for bringing about dimorphism in SCR expression, whereas dsxM function is required with Scr for the morphogenesis of sex comb.

  2. Analysis of the Sequence and Phenotype of Drosophila Sex combs reduced Alleles Reveals Potential Functions of Conserved Protein Motifs of the Sex combs reduced Protein

    Sivanantharajah, Lovesha; Percival-Smith, Anthony

    2009-01-01

    The Drosophila Hox gene, Sex combs reduced (Scr), is required for patterning the larval and adult, labial and prothoracic segments. Fifteen Scr alleles were sequenced and the phenotypes analyzed in detail. Six null alleles were nonsense mutations (Scr2, Scr4, Scr11, Scr13, Scr13A, and Scr16) and one was an intragenic deletion (Scr17). Five hypomorphic alleles were missense mutations (Scr1, Scr3, Scr5, Scr6, and Scr8) and one was a small protein deletion (Scr15). Protein sequence changes were ...

  3. Participation of Polycomb group gene extra sex combs in hedgehog signaling pathway

    Polycomb group (PcG) genes are required for stable inheritance of epigenetic states across cell divisions, a phenomenon termed cellular memory. PcG proteins form multimeric nuclear complex which modifies the chromatin structure of target site. Drosophila PcG gene extra sex combs (esc) and its vertebrate orthologs constitute a member of ESC-E(Z) complex, which possesses histone methyltransferase activity. Here we report isolation and characterization of medaka esc homolog, termed oleed. Hypomorphic knock-down of oleed using morpholino antisense oligonucleotides resulted in the fusion of eyes, termed cyclopia. Prechordal plate formation was not substantially impaired, but expression of hedgehog target genes was dependent on oleed, suggesting some link with hedgehog signaling. In support of this implication, histone methylation, which requires the activity of esc gene product, is increased in hedgehog stimulated mouse NIH-3T3 cells. Our data argue for the novel role of esc in hedgehog signaling and provide fundamental insight into the epigenetic mechanisms in general

  4. Drosophila O-GlcNAc transferase (OGT) is encoded by the Polycomb group (PcG) gene, super sex combs (sxc).

    Sinclair, Donald A R; Syrzycka, Monika; Macauley, Matthew S; Rastgardani, Tara; Komljenovic, Ivana; Vocadlo, David J; Brock, Hugh W; Honda, Barry M

    2009-08-11

    O-linked N-acetylglucosamine transferase (OGT) reversibly modifies serine and threonine residues of many intracellular proteins with a single beta-O-linked N-acetylglucosamine residue (O-GlcNAc), and has been implicated in insulin signaling, neurodegenerative disease, cellular stress response, and other important processes in mammals. OGT also glycosylates RNA polymerase II and various transcription factors, which suggests that it might be directly involved in transcriptional regulation. We report here that the Drosophila OGT is encoded by the Polycomb group (PcG) gene, super sex combs (sxc). Furthermore, major sites of O-GlcNAc modification on polytene chromosomes correspond to PcG protein binding sites. Our results thus suggest a direct role for O-linked glycosylation by OGT in PcG-mediated epigenetic gene silencing, which is important in developmental regulation, stem cell maintenance, genomic imprinting, and cancer. In addition, we observe rescue of sxc lethality by a human Ogt cDNA transgene; thus Drosophila may provide an ideal model to study important functional roles of OGT in mammals. PMID:19666537

  5. The gap gene Krüppel of Rhodnius prolixus is required for segmentation and for repression of the homeotic gene sex comb-reduced.

    Lavore, Andrés; Esponda-Behrens, Natalia; Pagola, Lucía; Rivera-Pomar, Rolando

    2014-03-01

    The establishment of the anterior-posterior segmentation in insects requires the concerted action of a hierarchical gene network. Here, we study the orthologue of Krüppel gap gene in the hemipteran Rhodnius prolixus (Rp-Kr). We characterized its structure, expression pattern and function. The genomic sequence upstream of the Rp-Kr transcriptional unit shows a putative regulatory region conserved in the orthologue genes from Drosophila melanogaster and Tribolium castaneum. Rp-Kr expression is zygotic and it is expressed in the anterior half of the embryo (the posterior half of the egg) during the blastoderm stage and germ band formation; later, during germ band extension, it is expressed in a central domain, from T2 to A3. The Rp-Kr loss of function phenotypes shows disrupted thoracic and abdominal segmentation. Embryos with weak segmentation phenotypes show homeotic transformations, in which an ectopic tibial comb, typical of T1 leg, appears in T2, which correlates with the ectopic expression of Rp-sex-comb reduced in this leg. PMID:24406318

  6. Multi-dimensional laser mode combs (mode hyper-combs)

    Schwartz, Alon

    2012-01-01

    Laser frequency combs, as most lasers, are one-dimensional. Here we present a realization of d-dimensional laser mode lattices (mode hyper-combs) with unique properties. They are constructed from regular 1-dimensional combs by multi-frequency modulation in active mode-locking (AML). The hyper-comb, with near neighbor mode interaction and noise functioning as temperature, is mapped to interacting magnetic spin-lattices in the spherical-model, which is one of the few statistical-mechanics systems soluble in all dimensions. The important result is that such systems have, in d>2 dimensions, a phase-transition to a global mode-phase-ordered hyper-comb. It changes the nature of AML lasers, giving ultimately short and robust pulses which can capture very broad frequency bandwidths. Additionally, the hyper-combs can serve as a rare physical realization of the spherical-model in any dimension.

  7. Wing defects in Drosophila xenicid mutant clones are caused by C-terminal deletion of additional sex combs (Asx.

    Kara Bischoff

    Full Text Available BACKGROUND: The coordinated action of genes that control patterning, cell fate determination, cell size, and cell adhesion is required for proper wing formation in Drosophila. Defects in any of these basic processes can lead to wing aberrations, including blisters. The xenicid mutation was originally identified in a screen designed to uncover regulators of adhesion between wing surfaces [1]. PRINCIPAL FINDINGS: Here, we demonstrate that expression of the betaPS integrin or the patterning protein Engrailed are not affected in developing wing imaginal discs in xenicid mutants. Instead, expression of the homeotic protein Ultrabithorax (Ubx is strongly increased in xenicid mutant cells. CONCLUSION: Our results suggest that upregulation of Ubx transforms cells from a wing blade fate to a haltere fate, and that the presence of haltere cells within the wing blade is the primary defect leading to the adult wing phenotypes observed.

  8. Scaling of Yb-Fiber Frequency Combs

    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).

  9. Modeling Frequency Comb Sources

    Li Feng

    2016-06-01

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

  10. Random walks on combs

    Durhuus, B; Wheater, J; Durhuus, Bergfinnur; Jonsson, Thordur; Wheater, John

    2006-01-01

    We develop techniques to obtain rigorous bounds on the behaviour of random walks on combs. Using these bounds we calculate exactly the spectral dimension of random combs with infinite teeth at random positions or teeth with random but finite length. We also calculate exactly the spectral dimension of some fixed non-translationally invariant combs. We relate the spectral dimension to the critical exponent of the mass of the two-point function for random walks on random combs, and compute mean displacements as a function of walk duration. We prove that the mean first passage time is generally infinite for combs with anomalous spectral dimension.

  11. Combing the Globe

    2010-01-01

    China’s top comb maker aims to sell its high-end hand-crafted products to overseas customers while improving its brand image For some, woodcarving and small carpentry work are hobbies. But for Tan Chuanhua and his Carpenter Tan comb brand, the woodworking craft has become a deep-rooted moneymaker. The Chongqing-based handcraft wood comb maker raised HK$140 million ($18 mil-

  12. Smooth Combs Inside Hedgehogs

    Biswas, Kingshook

    2009-01-01

    We use techniques of tube-log Riemann surfaces due to R.Perez-Marco to construct a hedgehog containing smooth $C^{\\infty}$ combs. The hedgehog is a common hedgehog for a family of commuting non-linearisable holomorphic maps with a common indifferent fixed point. The comb is made up of smooth curves, and is transversally bi-H\\"older regular.

  13. Dynamics of comb-of-comb networks

    Liu, Hongxiao; Lin, Yuan; Dolgushev, Maxim; Zhang, Zhongzhi

    2016-03-01

    The dynamics of complex networks, a current hot topic in many scientific fields, is often coded through the corresponding Laplacian matrix. The spectrum of this matrix carries the main features of the networks' dynamics. Here we consider the deterministic networks which can be viewed as "comb-of-comb" iterative structures. For their Laplacian spectra we find analytical equations involving Chebyshev polynomials whose properties allow one to analyze the spectra in deep. Here, in particular, we find that in the infinite size limit the corresponding spectral dimension goes as ds→2 . The ds leaves its fingerprint on many dynamical processes, as we exemplarily show by considering the dynamical properties of polymer networks, including single monomer displacement under a constant force, mechanical relaxation, and fluorescence depolarization.

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

    Hansson Tobias

    2016-06-01

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

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

    Hansson, Tobias; Wabnitz, Stefan

    2016-06-01

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

  16. Concentration addition, independent action and generalized concentration addition models for mixture effect prediction of sex hormone synthesis in vitro

    Hadrup, Niels; Taxvig, Camilla; Pedersen, Mikael;

    2013-01-01

    of the concentration addition (CA), independent action (IA) and generalized concentration addition (GCA) models. First we measured effects of single chemicals and mixtures thereof on steroid synthesis in H295R cells. Then single chemical data were applied to the models; predictions of mixture effects were calculated...... and compared to the experimental mixture data. Mixture 1 contained environmental chemicals adjusted in ratio according to human exposure levels. Mixture 2 was a potency adjusted mixture containing five pesticides. Prediction of testosterone effects coincided with the experimental Mixture 1 data. In contrast...

  17. Biological and Biomimetic Comb Polyelectrolytes

    Aristeidis Papagiannopoulos

    2010-05-01

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

  18. Molecular Comb Development

    Ferrell, T.L.; Thundat, G.T.; Witkowski, C.E., III (Protein Discovery, Inc.)

    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.

  19. Measurement of microresonator frequency comb stability by spectral interferometry

    Webb, Karen E; Anthony, Jessienta; Coen, Stephane; Erkintalo, Miro; Murdoch, Stuart G

    2015-01-01

    We demonstrate a new technique for the experimental measurement of the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the complex degree of first order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs, and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses.

  20. Measurement of microresonator frequency comb coherence by spectral interferometry.

    Webb, K E; Jang, J K; Anthony, J; Coen, S; Erkintalo, M; Murdoch, S G

    2016-01-15

    We experimentally investigate the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the magnitude of the complex degree of first-order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses. PMID:26766693

  1. Raman-assisted coherent, mid-infrared frequency combs in silicon microresonators

    Griffith, Austin G; Okawachi, Yoshitomo; Cardenas, Jaime; Mohanty, Aseema; Gaeta, Alexander L; Lipson, Michal

    2016-01-01

    We demonstrate the first low-noise mid-IR frequency comb source using a silicon microresonator. Our observation of strong Raman scattering lines in the generated comb suggests that Raman and four-wave mixing interactions play a role in assisting the transition to the low-noise state. In addition, we characterize, the intracavity comb generation dynamics using an integrated PIN diode, which takes advantage of the inherent three-photon absorption process in silicon.

  2. Sub-lethal effects of pesticide residues in brood comb on worker honey bee (Apis mellifera development and longevity.

    Judy Y Wu

    Full Text Available BACKGROUND: Numerous surveys reveal high levels of pesticide residue contamination in honey bee comb. We conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan. METHODOLOGY/PRINCIPAL FINDINGS: Worker bees were reared in brood comb containing high levels of known pesticide residues (treatment or in relatively uncontaminated brood comb (control. Delayed development was observed in bees reared in treatment combs containing high levels of pesticides particularly in the early stages (day 4 and 8 of worker bee development. Adult longevity was reduced by 4 days in bees exposed to pesticide residues in contaminated brood comb during development. Pesticide residue migration from comb containing high pesticide residues caused contamination of control comb after multiple brood cycles and provided insight on how quickly residues move through wax. Higher brood mortality and delayed adult emergence occurred after multiple brood cycles in contaminated control combs. In contrast, survivability increased in bees reared in treatment comb after multiple brood cycles when pesticide residues had been reduced in treatment combs due to residue migration into uncontaminated control combs, supporting comb replacement efforts. Chemical analysis after the experiment confirmed the migration of pesticide residues from treatment combs into previously uncontaminated control comb. CONCLUSIONS/SIGNIFICANCE: This study is the first to demonstrate sub-lethal effects on worker honey bees from pesticide residue exposure from contaminated brood comb. Sub-lethal effects, including delayed larval development and adult emergence or shortened adult longevity, can have indirect effects on the colony such as premature shifts in hive roles and foraging activity. In addition, longer development time for bees may provide a reproductive advantage for parasitic Varroa destructor

  3. Optical frequency combs generated mechanically

    Sumetsky, M

    2016-01-01

    It is shown that a highly equidistant optical frequency comb can be generated by the parametric excitation of an optical bottle microresonator with nanoscale effective radius variation by its natural mechanical vibrations.

  4. Mid-infrared frequency combs

    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.

  5. Scientific Opinion on Rooster Combs Extract

    EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA

    2013-06-01

    Full Text Available Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA was asked to carry out the additional assessment for ‘Rooster Combs Extract’ (RCE as a food ingredient in the context of Regulation (EC No 258/97, taking into account the comments and objections of a scientific nature raised by Member States. Rooster combs extract results from a production process involving enzymatic hydrolysis of rooster combs and subsequent filtration, concentration and precipitation steps. The principle constituents of RCE are the glycosaminoglycans hyaluronic acid, chondroitin sulphate A and dermatan sulphate. The applicant intends to add RCE to a number of dairy products with a recommended maximum intake of 80 mg RCE per portion and per day. The target population is the general population, with the exception of pregnant women, children and people with adverse reactions to sodium hyaluronate and/or avian protein. In the high intake scenario for “consumers only”, the highest daily intake would occur in adults in Belgium (0.788 g. The highest intake scenario for “all subjects” was estimated for adolescents in Denmark (0.427 g/day. The Panel notes that no adverse effects were observed at the highest tested dose of 600 mg/kg bw per day in a 90-day oral toxicity study in rats. Considering the nature, the natural occurrence and previous consumption of RCE constituents, the Panel is of the opinion that the margin between the intended as well as the estimated maximum possible intake of RCE in relation to the highest dose administered to rats without adverse effects in a subchronic oral toxicity study is sufficient. The Panel concludes that the novel food ingredient, Rooster Comb Extract, is safe under the proposed uses and use levels.

  6. Schizocordulia gen. nov. related to Aeschnosom Selys with description of the female and additional data on the male of Schizocordulia rustica (Selys comb. nov. (Odonata, Corduliidae Schizocordulia gen. nov. relacionado a Aeschnosoma Selys com descrição da fêmea e dados adicionais sobre o macho de Schizocordulia rustica (Selys comb. nov. (Odonata, Corduliidae

    Angelo B.M. Machado

    2005-09-01

    Full Text Available The monotypical genus Schizocordulia is created for Schizocordulia rustica (Selys, 1871 comb. nov. known from a single male from Bahia, Brazil lacking the anal appendages. The female is described and the redescription of the male made by GEIJKES (1970 is completed by the description and illustration of the penis, the anal appendages and the pilose plate. The main characters separating the new genus from the closely related Aeschnosoma Selys, 1870 are the bifid male inferior appendage, the very long internal branch of the hamulus, the presence of a pilose plate on the male 7th abdominal segment, and the large and complex valvula vulvae of the female. The study was based on 33 males and 2 females, which allowed an evaluation of the intraspecific variations in Schizocordulia rustica.Cria-se o gênero monotípico Schizocordulia para Schizocordulia rustica (Selys, 1871 comb. nov. espécie conhecida de um único exemplar macho sem os apêndices anais. Descreve-se a fêmea e a redescrição do macho feita por GEIJKES (1970 é completada pela descrição e ilustração do pênis, da placa pilosa e dos apêndices anais. Os principais caracteres utilizados para separar Schizocordulia do gênero afim Aeschnosoma Selys, 1870 são o apêndice inferior do macho bífido, o ramo interno do hâmulo muito longo, a presença de uma placa pilosa no 7º segmento abdominal e a válvula da vulva da fêmea grande e complexa. Este estudo foi baseado em 33 machos e 2 fêmeas, o que permitiu uma avaliação das variações intraespecíficas em Schizocordulia rustica.

  7. Quantum Cascade Laser Frequency Combs

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

    2016-06-01

    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 100mW and frequency coverage of 100 cm-1 in the mid-infrared region. In the THz range, 10mW 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 first dual-comb spectroscopy measurements. The capability of the structure to integrate monothically nonlinear optical elements as well as to operate as a detector shows great promise for future chip integration of dual-comb systems.

  8. [The skull of Combe Capelle].

    Hoffmann, Almut; Wegner, Dietrich

    2002-12-01

    Since the end of World War II two of the most important anthropological artefacts of the Museum für Vor- und Frühgeschichte in Berlin, the skulls and skeletons of Le Moustier and Combe Capelle, were believed to be missing or destroyed, respectively. The postcrania were severely damaged during a fire after the museum was bombed in February 1945, while the skulls were brought to the Soviet Union in 1945. In 1965, the skull of the Neanderthal man from Le Moustier and the chain of the grave of Combe Capelle were found amongst the art objects returned by the Soviet Union into the German Democratic Republic in 1958. However, the Combe Capelle skull was still missing. In the end of 2001 this skull could be found and identified in a store-house of the museum. Now, one the oldest known representatives of Homo sapiens sapiens is again available for scientific research and public exhibitions. PMID:12529957

  9. Quantum Cascade Laser Frequency Combs

    Faist, Jérôme; Villares, Gustavo; 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 th...

  10. Monolithically integrated absolute frequency comb laser system

    Wanke, Michael C.

    2016-07-12

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

  11. On Frequency Combs in Monolithic Resonators

    Savchenkov A. A.

    2016-06-01

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

  12. Ultrafast electrooptic dual-comb interferometry

    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.

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

    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.

  14. Seasonal production and spatial distribution of Melipona bicolor schencki (Apidae; Meliponini) castes in brood combs in southern Brazil

    Jr, Ney; Blochtein, Betina; Serrão, José

    2013-01-01

    Melipona bicolor schencki is currently considered a threatened stingless bee in southern Brazil, and studies about its ecology may provide new insights to enable its conservation. This study evaluated the seasonal variability in the sex/caste proportion, numbers of combs and brood cells, and spatial distribution of the individuals present in emerging combs in five polygynous colonies of M. bicolor schencki for 1 year. Throughout the year, the colonies showed similar variations. Individual com...

  15. Support for same-sex marriage in the US Senate is growing, but additional gains will be difficult to achieve

    Theriault, Sean; Thomas , Herschel

    2014-01-01

    In the last few years, state after state and senator after senator have declared their support for full marriage equality. Such momentum suggests that the goals of same-sex marriage advocates will be realized sooner rather than later. In new research, Sean Theriault and Herschel Thomas analyze when senators announce their support for same-sex marriage. Contrary to the popularly held belief that their decisions will quickly snowball into filibuster-proof numbers, they find that most of the ...

  16. Flexible radio-frequency photonics: Optoelectronic frequency combs and integrated pulse shaping

    Metcalf, Andrew J.

    Microwave photonics is a discipline which leverages optoelectronics to enhance the generation, transport, and processing of high-frequency electrical signals. At the heart of many emerging techniques is the optical frequency comb. A comb is a lightwave source whose spectrum is made up of discrete equally spaced spectral components that share a fixed phase relationship. These discrete coherent oscillators --known as comb lines-- collectively form a Fourier basis that describe a periodic optical waveform. Within the last two decades frequency-stabilized broadband combs produced from mode-locked lasers have led to revolutionary advancements in precision optical frequency synthesis and metrology. Meanwhile, Fourier-transform optical pulse shaping, which provides a means to control a comb's Fourier basis in both amplitude and phase, has emerged as an integral tool in optical communications, broadband waveform generation, and microwave photonic filtering. However, traditional comb and pulse shaping architectures are often plagued by complex and bulky setups, rendering robust and cost effective implementation outside of the laboratory a challenge. In addition, traditional comb sources based on short-pulse lasers do not possess qualities which are ideally suited for this new application regime. Motivated by the shortcomings in current architectures, and empowered by recent advancements in optoelectronic technology, this dissertation focuses on developing novel and robust schemes in optical frequency comb generation and line-by-line pulse shaping. Our results include: the invention and low-noise characterization of a broadband flat-top comb source; the realization of an optoelectronic-based time cloak; and finally, the development of an integrated pulse shaper, which we use in conjunction with our flat-top comb source to demonstrate a rapidly reconfigurable microwave photonic filter.

  17. Quantum Cascade Laser Frequency Combs

    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...

  18. On-chip dual-comb based on quantum cascade laser frequency combs

    Dual-comb spectroscopy is emerging as an appealing application of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs. Here, we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs. 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 centered at 1330 cm−1 (7.52 μm), demonstrating that this device represents a critical step towards compact dual-comb systems

  19. On-chip dual-comb based on quantum cascade laser frequency combs

    Villares, G.; Wolf, J.; Kazakov, D.; Süess, M. J.; Hugi, A.; Beck, M.; Faist, J.

    2015-12-01

    Dual-comb spectroscopy is emerging as an appealing application of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs. Here, we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs. 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 centered at 1330 cm-1 (7.52 μm), demonstrating that this device represents a critical step towards compact dual-comb systems.

  20. On-chip dual-comb based on quantum cascade laser frequency combs

    Villares, G., E-mail: gustavo.villares@phys.ethz.ch; Wolf, J.; Kazakov, D.; Süess, M. J.; Beck, M.; Faist, J., E-mail: jfaist@phys.ethz.ch [Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich (Switzerland); Hugi, A. [IRsweep GmbH, CH-8093 Zürich (Switzerland)

    2015-12-21

    Dual-comb spectroscopy is emerging as an appealing application of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs. Here, we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs. 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{sup −1} centered at 1330 cm{sup −1} (7.52 μm), demonstrating that this device represents a critical step towards compact dual-comb systems.

  1. Octave Spanning Frequency Comb on a Chip

    Del'Haye, P; Gavartin, E; Holzwarth, R; Kippenberg, T J

    2009-01-01

    Optical frequency combs have revolutionized the field of frequency metrology within the last decade and have become enabling tools for atomic clocks, gas sensing and astrophysical spectrometer calibration. The rapidly increasing number of applications has heightened interest in more compact comb generators. Optical microresonator based comb generators bear promise in this regard. Critical to their future use as 'frequency markers', is however the absolute frequency stabilization of the optical comb spectrum. A powerful technique for this stabilization is self-referencing, which requires a spectrum that spans a full octave, i.e. a factor of two in frequency. In the case of mode locked lasers, overcoming the limited bandwidth has become possible only with the advent of photonic crystal fibres for supercontinuum generation. Here, we report for the first time the generation of an octave-spanning frequency comb directly from a toroidal microresonator on a silicon chip. The comb spectrum covers the wavelength range...

  2. Ultrafast electrooptic dual-comb interferometry.

    Durán, Vicente; Tainta, Santiago; Torres-Company, Victor

    2015-11-16

    Dual-comb interferometry is a particularly compelling technique that relies on the phase coherence of two laser frequency combs for measuring broadband complex spectra. 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 dual-comb interferometer that is based on electrooptic frequency combs and measures consecutive complex spectra at an ultra-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. PMID:26698533

  3. Normal-dispersion microresonator Kerr frequency combs

    Xue Xiaoxiao

    2016-06-01

    Full Text Available Optical microresonator-based Kerr frequency comb generation has developed into a hot research area in the past decade. Microresonator combs are promising for portable applications due to their potential for chip-level integration and low power consumption. According to the group velocity dispersion of the microresonator employed, research in this field may be classified into two categories: the anomalous dispersion regime and the normal dispersion regime. In this paper, we discuss the physics of Kerr comb generation in the normal dispersion regime and review recent experimental advances. The potential advantages and future directions of normal dispersion combs are also discussed.

  4. Combing gravitational hair in 2 + 1 dimensions

    Donnelly, William; Marolf, Donald; Mintun, Eric

    2016-01-01

    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 AdS3 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 [-α ,α ]. At linear order in source strength the energy is independent of the combing parameter α, but nonlinearities cause the full energy to diverge as α \\to 0. In general, solutions with combed gravitational flux also suffer from what we call displacement from their naive location. For weak sources and large α one may set the displacement to zero by further increasing the energy, though for strong sources and small α we find no preferred notion of a zero-displacement solution. In the latter case we conclude that naively expected gravitational Wilson lines do not exist. In the zero-displacement case, taking the AdS scale ℓ to infinity gives finite-energy flux-directed solutions that may be called asymptotically flat.

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

    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.

  6. Microresonator Soliton Dual-Comb Spectroscopy

    Suh, Myoung-Gyun; Yang, Ki Youl; Yi, Xu; Vahala, Kerry

    2016-01-01

    Rapid characterization of optical and vibrational spectra with high resolution can identify species in cluttered environments and is important for assays and early alerts. In this regard, dual-comb spectroscopy has emerged as a powerful approach to acquire nearly instantaneous Raman and optical spectra with unprecedented resolution. Spectra are generated directly in the electrical domain and avoid bulky mechanical spectrometers. Recently, a miniature soliton-based comb has emerged that can potentially transfer the dual-comb method to a chip platform. Unlike earlier microcombs, these new devices achieve high-coherence, pulsed mode locking. They generate broad, reproducible spectral envelopes, which is essential for dual-comb spectroscopy. Here, dual-comb spectroscopy is demonstrated using these devices. This work shows the potential for integrated, high signal-to-noise spectroscopy with fast acquisition rates.

  7. Frequency comb transferred by surface plasmon resonance

    Geng, Xiao Tao; Chun, Byung Jae; Seo, Ji Hoon; Seo, Kwanyong; Yoon, Hana; Kim, Dong-Eon; Kim, Young-Jin; Kim, Seungchul

    2016-01-01

    Frequency combs, millions of narrow-linewidth optical modes referenced to an atomic clock, have shown remarkable potential in time/frequency metrology, atomic/molecular spectroscopy and precision LIDARs. Applications have extended to coherent nonlinear Raman spectroscopy of molecules and quantum metrology for entangled atomic qubits. Frequency combs will create novel possibilities in nano-photonics and plasmonics; however, its interrelation with surface plasmons is unexplored despite the important role that plasmonics plays in nonlinear spectroscopy and quantum optics through the manipulation of light on a subwavelength scale. Here, we demonstrate that a frequency comb can be transformed to a plasmonic comb in plasmonic nanostructures and reverted to the original frequency comb without noticeable degradation of quantum metrology and subwavelength photonic circuits. PMID:26898307

  8. Ultrabroadband coherent supercontinuum frequency comb

    Ruehl, Axel; McKay, Hugh; Thomas, Brian; Dong, Liang; Fermann, Martin E.; Hartl, Ingmar [IMRA America Inc., 1044 Woodridge Avenue, Ann Arbor, Michigan 48105 (United States); Martin, Michael J.; Cossel, Kevin C.; Chen Lisheng; Benko, Craig; Ye Jun [JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, 440 UCB, Boulder, Colorado 80309 (United States); Dudley, John M. [Institute FEMTO-ST, CNRS-University of Franche-Comte UMR 6174, Besancon (France)

    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.

  9. Cantharellus gallaecicus (Blanco-Dios Olariaga, comb. & stat. nov (Cantharellaceae

    Olariaga, Ibai

    2007-12-01

    Full Text Available Cantharellus gallaecicus comb. & stat. nov. is proposed, after the examination of its holotype and additional material. Based on the characters observed in all the studied material (i.e., thinwalled hyphae of the pileipelis, minute basidiomata with white to grey pileus, and surface that turns yellow when bruised it is considered that C. gallaecicus is more closely related to C. romagnesianus than to C. cibarius.Se propone Cantharellus gallaecicus comb. & stat. nov. tras revisar su holótipo y material adicional disponible. Dado que todo el material examinado posee hifas del pileipelis de pared delgada, basidiomas pequeños con píleo de blanco a gris, y superficie que vira a amarillo al roce, se considera que C. gallaecicus es una especie más estrechamente relacionada con C. romagnesianus que con C. cibarius.

  10. Direct frequency comb spectroscopy of trapped ions

    Wolf, A L; Ubachs, W; Eikema, K S E

    2008-01-01

    Direct frequency comb spectroscopy of trapped ions is demonstated for the first time. It is shown that the 4s^2S_(1/2)-4p^2P_(3/2) transition in calcium ions can be excited directly with a frequency comb laser that is upconverted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress background signal from non-resonant comb modes. The measured transition frequency of f=761 905 012.7(0.5) MHz presents an improvement in accuracy of more than two orders of magnitude.

  11. Fluctuations for internal DLA on the Comb

    Asselah, Amine; Rahmani, Houda

    2013-01-01

    We study internal diffusion limited aggregation (DLA) on the two dimensional comb lattice. The comb lattice is a spanning tree of the euclidean lattice, and internal DLA is a random growth model, where simple random walks, starting one at a time at the origin of the comb, stop when reaching the first unoccupied site. An asymptotic shape is suggested by a lower bound of Huss and Sava. We show that fluctuations with respect to this shape are gaussian as in the one-dimensional lattice.

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

    Ideguchi, Takuro; Kobayashi, Yohei; Goda, Keisuke

    2015-01-01

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

  13. Dual-Comb Spectroscopy based on Mid-IR Quantum-Cascade-Lasers Frequency-combs

    Full text: Optical frequency combs act as rulers in the frequency domain and have revolutionised many fields such as high-resolution spectroscopy. To wide their applications, realizing a compact mid-IR spectrometer using frequency combs is of paramount importance, as the fundamental roto-vibrational bands of most light molecules lie on this spectral region. We have recently demonstrated a mid-IR, all-solid-state frequency comb based on a quantum cascade laser. Here a compact dual-comb spectrometer is realised. The dual-comb spectrometer covers 60 cm-1 with individual tooth linewidth of 150 kHz by using mid-IR QCL based frequency combs centered at 1430. (author)

  14. Combing gravitational hair in 2+1 dimensions

    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. Comb-Net: a high-density WDM network with centralized wavelength combs

    Gerla, Mario; Chiaretti, Guido; Rotolo, Salvatore

    1993-11-01

    In this paper, we propose Comb-Net, a tree PON architecture in which several laser combs at the root of the tree supply wavelengths to all stations in the PON. Namely, each station receives several wavelengths from comb laser sources located at the root of the PON, via a Comb Distribution network. It then selects (by fixed or tunable filters) some predefined or agreed upon wavelengths, and uses these as sources; i.e., it modulates them (in amplitude or phase) using an external modulator. The modulated wavelengths are then transmitted on the Multiaccess Communications network, which is separate from the Comb Distribution network. The novelty of Comb-Net is to replace the individual (fixed or tunable) lasers at the station with a set of centralized comb generators. The advantages are better stability control, lower noise and potentially lower cost since each station does not require a dedicated source. In the paper, we describe an example of Comb-Net architecture in which the Multiaccess Data network is based on a physical tree topology and on two separate virtual topologies embedded within the physical topology using WDM: a single hop topology used for circuit switched connections; and a multihop topology used for packet switched traffic. We illustrate the Comb-Net architecture with a simple case study.

  16. Optical frequency comb generation in optical fibres

    Zajnulina, Marina

    2015-01-01

    Optical frequency combs (OFC) constitute an array of phase-correlated equidistant spectral lines with nearly equal intensities over a broad spectral range. The adaptations of combs generated in mode-locked lasers proved to be highly efficient for the calibration of high-resolution (resolving power > 50000) astronomical spectrographs. The observation of different galaxy structures or the studies of the Milky Way are done using instruments in the low- and medium resolution range. To such instru...

  17. Quantum cascade laser Kerr frequency comb

    Lecaplain, Caroline; Javerzac-Galy, Clément; 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 ...

  18. Optical Frequency Comb Generation based on Erbium Fiber Lasers

    Droste, Stefan; Ycas, Gabriel; Washburn, Brian R.; Coddington, Ian; Newbury, Nathan R.

    2016-06-01

    Optical frequency combs have revolutionized optical frequency metrology and are being actively investigated in a number of applications outside of pure optical frequency metrology. For reasons of cost, robustness, performance, and flexibility, the erbium fiber laser frequency comb has emerged as the most commonly used frequency comb system and many different designs of erbium fiber frequency combs have been demonstrated. We review the different approaches taken in the design of erbium fiber frequency combs, including the major building blocks of the underlying mode-locked laser, amplifier, supercontinuum generation and actuators for stabilization of the frequency comb.

  19. Optical Frequency Comb Generation based on Erbium Fiber Lasers

    Droste Stefan

    2016-06-01

    Full Text Available Optical frequency combs have revolutionized optical frequency metrology and are being actively investigated in a number of applications outside of pure optical frequency metrology. For reasons of cost, robustness, performance, and flexibility, the erbium fiber laser frequency comb has emerged as the most commonly used frequency comb system and many different designs of erbium fiber frequency combs have been demonstrated. We review the different approaches taken in the design of erbium fiber frequency combs, including the major building blocks of the underlying mode-locked laser, amplifier, supercontinuum generation and actuators for stabilization of the frequency comb.

  20. Sonic Hedgehog-signalling patterns the developing chicken comb as revealed by exploration of the pea-comb mutation.

    Henrik Boije

    Full Text Available The genetic basis and mechanisms behind the morphological variation observed throughout the animal kingdom is still relatively unknown. In the present work we have focused on the establishment of the chicken comb-morphology by exploring the Pea-comb mutant. The wild-type single-comb is reduced in size and distorted in the Pea-comb mutant. Pea-comb is formed by a lateral expansion of the central comb anlage into three ridges and is caused by a mutation in SOX5, which induces ectopic expression of the SOX5 transcription factor in mesenchyme under the developing comb. Analysis of differential gene expression identified decreased Sonic hedgehog (SHH receptor expression in Pea-comb mesenchyme. By experimentally blocking SHH with cyclopamine, the wild-type single-comb was transformed into a Pea-comb-like phenotype. The results show that the patterning of the chicken comb is under the control of SHH and suggest that ectopic SOX5 expression in the Pea-comb change the response of mesenchyme to SHH signalling with altered comb morphogenesis as a result. A role for the mesenchyme during comb morphogenesis is further supported by the recent finding that another comb-mutant (Rose-comb, is caused by ectopic expression of a transcription factor in comb mesenchyme. The present study does not only give knowledge about how the chicken comb is formed, it also adds to our understanding how mutations or genetic polymorphisms may contribute to inherited variations in the human face.

  1. Low noise electro-optic comb generation by fully stabilizing to a mode-locked fiber comb.

    Kuse, Naoya; Schibli, Thomas R; Fermann, Martin E

    2016-07-25

    A fully stabilized EO comb is demonstrated by phase locking the two degrees of freedom of an EO comb to a low noise mode-locked fiber comb. Division/magnification of residual phase noise of locked beats is observed by measuring an out-of-loop beat. By phase locking the 200 th harmonics of the EO comb and a driving cw frequency to a fiber comb, a record low phase noise EO comb across +/- 200 harmonics (from 1544.8 nm to 1577.3 nm) is demonstrated. PMID:27464140

  2. Ultrasonic comb transducer for smart materials

    Rose, J. L.

    1998-04-01

    Installation of a small multi-element comb type ultrasonic transducer is proposed as a component of a smart structure. It can be used in either an active or passive mode in carrying out ultrasonic bulk or guided wave nondestructive evaluation. Theoretical methods are developed and experimental results are presented for guided wave generation and mode control with this very efficient and versatile novel comb type ultrasonic transducer. Excitation and probe design is crucial in mode selection. The comb transducer generates waves that are influenced by such parameters as number of elements, spacing between elements, dimension, pulsing sequence, and pressure distribution. The excited elastic field depends on the excitation frequency, plate thickness, and elastic properties. Techniques are studied to optimize the applied loading and the comb transducer design parameters so that only modes that are most sensitive to particular material characteristics can be generated. Complete understanding of the comb transducer parameters and their impact on the elastic field allows us to efficiently generate higher order modes as well as low phase velocity modes which are valuable in composite material characterization. Sample experiments are presented for various plate and tube like structures.

  3. Gapless dual-comb spectroscopy in terahertz region

    Yasui, Takeshi; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu

    2014-01-01

    We demonstrated combination of gapless terahertz (THz) comb with dual-comb spectroscopy, namely gapless dual-THz-comb spectroscopy, to achieve the spectral resolution equal to width of the THz comb tooth. The gapless THz comb was realized by interpolating frequency gaps between the comb teeth with sweeping of a laser mode-locked frequency. The demonstration of low-pressure gas spectroscopy with gapless dual-THz-comb spectroscopy clearly indicated that the spectral resolution was decreased down to 2.5-MHz width of the comb tooth and the spectral accuracy was enhanced to 10-6 within the spectral range of 1THz. The proposed method will be a powerful tool to simultaneously achieve high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.

  4. Direct frequency comb laser cooling and trapping

    Jayich, A M; Campbell, W C

    2016-01-01

    Continuous wave (CW) lasers are the enabling technology for producing ultracold atoms and molecules through laser cooling and trapping. The resulting pristine samples of slow moving particles are the de facto starting point for both fundamental and applied science when a highly-controlled quantum system is required. Laser cooled atoms have recently led to major advances in quantum information, the search to understand dark energy, quantum chemistry, and quantum sensors. However, CW laser technology currently limits laser cooling and trapping to special types of elements that do not include highly abundant and chemically relevant atoms such as hydrogen, carbon, oxygen, and nitrogen. Here, we demonstrate that Doppler cooling and trapping by optical frequency combs may provide a route to trapped, ultracold atoms whose spectra are not amenable to CW lasers. We laser cool a gas of atoms by driving a two-photon transition with an optical frequency comb, an efficient process to which every comb tooth coherently cont...

  5. Frequency-agile dual-comb spectroscopy

    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.

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

    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...

  7. Optical Frequency Combs From Semiconductor Lasers and Applications in Ultrawideband Signal Processing and Communications

    Delfyett, Peter J.; Gee, Sangyoun; Choi, Myoung-Taek; Izadpanah, Hossein; Lee, Wangkuen; Ozharar, Sarper; Quinlan, Franklyn; Yilmaz, Tolga

    2006-07-01

    Modelocked semiconductor lasers are used to generate a set of phase-locked optical frequencies on a periodic grid. The periodic and phase coherent nature of the optical frequency combs makes it possible for the realization of high-performance optical and RF arbitrary-waveform synthesis. In addition, the resulting optical frequency components can be used for communication applications relying on direct detection, dense wavelength division multiplexing (WDM), coherent-detection WDM, optical time-division multiplexing, and optical code division multiple access. This paper highlights the recent results in the use of optical frequency combs generated from semiconductors for ultrawideband signal processing and communication applications.

  8. Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

    Liu, Ya; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

    2016-01-01

    Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses wit...

  9. Inter-comb synchronization by mode-to-mode locking

    Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo

    2016-08-01

    Two combs of fiber femtosecond lasers are synchronized through the optical frequency reference created by injection-locking of a diode laser to a single comb mode. Maintaining a mHz-level narrow linewidth, the optical frequency reference permits two combs to be stabilized by mode-to-mode locking with a relative stability of 1.52  ×  10‑16 at 10 s with a frequency slip of 2.46 mHz. This inter-comb synchronization can be utilized for applications such as dual-comb spectroscopy or ultra-short pulse synthesis without extra narrow-linewidth lasers.

  10. Time sequence photography of Roosters Comb

    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...

  11. Quantum cascade laser Kerr frequency comb

    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...

  12. Phase separation of comb polymer nanocomposite melts.

    Xu, Qinzhi; Feng, Yancong; Chen, Lan

    2016-02-01

    In this work, the spinodal phase demixing of branched comb polymer nanocomposite (PNC) melts is systematically investigated using the polymer reference interaction site model (PRISM) theory. To verify the reliability of the present method in characterizing the phase behavior of comb PNCs, the intermolecular correlation functions of the system for nonzero particle volume fractions are compared with our molecular dynamics simulation data. After verifying the model and discussing the structure of the comb PNCs in the dilute nanoparticle limit, the interference among the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions between the comb polymer and nanoparticles in spinodal demixing curves is analyzed and discussed in detail. The results predict two kinds of distinct phase separation behaviors. One is called classic fluid phase boundary, which is mediated by the entropic depletion attraction and contact aggregation of nanoparticles at relatively low nanoparticle-monomer attraction strength. The second demixing transition occurs at relatively high attraction strength and involves the formation of an equilibrium physical network phase with local bridging of nanoparticles. The phase boundaries are found to be sensitive to the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions. As the side chain length is fixed, the side chain number has a large effect on the phase behavior of comb PNCs; with increasing side chain number, the miscibility window first widens and then shrinks. When the side chain number is lower than a threshold value, the phase boundaries undergo a process from enlarging the miscibility window to narrowing as side chain length increases. Once the side chain number overtakes this threshold value, the phase boundary shifts towards less miscibility. With increasing nanoparticle-monomer size ratio, a crossover of particle size occurs, above which the phase separation

  13. Modelocked mid-infrared frequency combs in a silicon microresonator

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

    2016-01-01

    Mid-infrared (mid-IR) frequency combs have broad applications in molecular spectroscopy and chemical/biological sensing. Recently developed microresonator-based combs in this wavelength regime could enable portable and robust devices using a single-frequency pump field. Here, we report the first demonstration of a modelocked microresonator-based frequency comb in the mid-IR spanning 2.4 {\\mu}m to 4.3 {\\mu}m. We observe high pump-to-comb conversion efficiency, in which 40% of the pump power is converted to the output comb power. Utilizing an integrated PIN structure allows for tuning the silicon microresonator and controling modelocking and cavity soliton formation, simplifying the generation, monitoring and stabilization of mid-IR frequency combs via free-carrier detection and control. Our results significantly advance microresonator-based comb technology towards a portable and robust mid-IR spectroscopic device that operates at low pump powers.

  14. Dispersion engineering of Quantum Cascade Lasers frequency combs

    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.

  15. Broadband high-resolution x-ray frequency combs

    Cavaletto, Stefano M; Ott, Christian; Buth, Christian; Pfeifer, Thomas; Keitel, Christoph H

    2014-01-01

    Optical frequency combs have had a remarkable impact on precision spectroscopy. Enabling this technology in the x-ray domain is expected to result in wide-ranging applications, such as stringent tests of astrophysical models and quantum electrodynamics, a more sensitive search for the variability of fundamental constants, and precision studies of nuclear structure. Ultraprecise x-ray atomic clocks may also be envisaged. In this work, an x-ray pulse-shaping method is put forward to generate a comb in the absorption spectrum of an ultrashort high-frequency pulse. The method employs an optical-frequency-comb laser, manipulating the system's dipole response to imprint a comb on an excited transition with a high photon energy. The described scheme provides higher comb frequencies and requires lower optical-comb peak intensities than currently explored methods, preserves the overall width of the optical comb, and may be implemented by presently available x-ray technology.

  16. Broadband high-resolution X-ray frequency combs

    Cavaletto, Stefano M.; Harman, Zoltán; Ott, Christian; Buth, Christian; Pfeifer, Thomas; Keitel, Christoph H.

    2014-07-01

    Optical frequency combs have had a remarkable impact on precision spectroscopy. Enabling this technology in the X-ray domain is expected to result in wide-ranging applications, such as stringent tests of astrophysical models and quantum electrodynamics, a more sensitive search for the variability of fundamental constants, and precision studies of nuclear structure. Ultraprecise X-ray atomic clocks may also be envisaged. In this work, an X-ray pulse-shaping method is proposed to generate a comb in the absorption spectrum of an ultrashort high-frequency pulse. The method employs an optical-frequency-comb laser, manipulating the system's dipole response to imprint a comb on an excited transition with a high photon energy. The described scheme provides higher comb frequencies and requires lower optical-comb peak intensities than currently explored methods, preserves the overall width of the optical comb, and may be implemented using currently available X-ray technology.

  17. Air Damping Analysis in Comb Microaccelerometer

    Wu Zhou; Yu Chen; Bei Peng; Hui Yang; Huijun Yu; Heng Liu; Xiaoping He

    2014-01-01

    Air damping significantly influences the dynamical characteristics of MEMS accelerometers. Its effects at micro-scale level sharply depend on the structure layouts and size of MEMS devices. The damping phenomenon of comb microaccelerometers is investigated. The air between fixed plate electrodes and movable plate electrodes cannot flow freely and is compressed. The air damping, therefore, exhibits both viscous effects and stiffness effects. The former generates a drag force like that in macro...

  18. Time-Delay Interferometry with optical frequency comb

    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.

  19. A microresonator frequency comb optical clock

    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.

  20. Radiation comb generation with extended Josephson junctions

    We propose the implementation of a Josephson radiation comb generator based on an extended Josephson junction subject to a time dependent magnetic field. The junction critical current shows known diffraction patterns and determines the position of the critical nodes when it vanishes. When the magnetic flux passes through one of such critical nodes, the superconducting phase must undergo a π-jump to minimize the Josephson energy. Correspondingly, a voltage pulse is generated at the extremes of the junction. Under periodic driving, this allows us to produce a comb-like voltage pulses sequence. In the frequency domain, it is possible to generate up to hundreds of harmonics of the fundamental driving frequency, thus mimicking the frequency comb used in optics and metrology. We discuss several implementations through a rectangular, cylindrical, and annular junction geometries, allowing us to generate different radiation spectra and to produce an output power up to 10 pW at 50 GHz for a driving frequency of 100 MHz

  1. Coherent data transmission with microresonator Kerr frequency combs

    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 (...

  2. Silicon-Chip Mid-Infrared Frequency Comb Generation

    Griffith, Austin G; Cardenas, Jaime; Okawachi, Yoshitomo; Mohanty, Aseema; Fain, Romy; Lee, Yoon Ho Daniel; Yu, Mengjie; Phare, Christopher T; Poitras, Carl B; Gaeta, Alexander L; Lipson, Michal

    2014-01-01

    Optical frequency combs represent a revolutionary technology for high precision spectroscopy due to their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared (IR) spectral region (2-20 um) is of great interest due to the presence of a large number of gas absorption lines in this wavelength regime. Recently, frequency combs have been demonstrated in the MIR in several platforms, including fiber combs, mode-locked lasers, optical parametric oscillators, and quantum cascade lasers. However, these platforms are either relatively bulky or challenging to integrate on-chip. An alternative approach using parametric mixing in microresonators is highly promising since the platform is extremely compact and can operate with relatively low powers. However, material and dispersion engineering limitations have prevented the realization of a microresonator comb source past 2.55 um. Although silicon could in principle provide a CMOS compatible platform for on-chip comb generation deep...

  3. Thermally Controlled Comb Generation and Soliton Modelocking in Microresonators

    Joshi, Chaitanya; Luke, Kevin; Ji, Xingchen; Miller, Steven A; Klenner, Alexander; Okawachi, Yoshitomo; Lipson, Michal; Gaeta, Alexander L

    2016-01-01

    We report the first demonstration of thermally controlled soliton modelocked frequency comb generation in microresonators. By controlling the electric current through heaters integrated with silicon nitride microresonators, we demonstrate a systematic and repeatable pathway to single- and multi-soliton modelocked states without adjusting the pump laser wavelength. Such an approach could greatly simplify the generation of modelocked frequency combs and facilitate applications such as chip-based dual-comb spectroscopy.

  4. Thermally controlled comb generation and soliton modelocking in microresonators

    Joshi, Chaitanya; Jang, Jae K.; Luke, Kevin; Ji, Xingchen; Miller, Steven A.; Klenner, Alexander; Okawachi, Yoshitomo; Lipson, Michal; Gaeta, Alexander L.

    2016-06-01

    We report the first demonstration of thermally controlled soliton modelocked frequency comb generation in microresonators. By controlling the electric current through heaters integrated with silicon nitride microresonators, we demonstrate a systematic and repeatable pathway to single- and multi-soliton modelocked states without adjusting the pump laser wavelength. Such an approach could greatly simplify the generation of modelocked frequency combs and facilitate applications such as chip-based dual-comb spectroscopy.

  5. Designing maleic anhydride-{alpha}-olifin copolymeric combs as wax crystal growth nucleators

    Soni, Hemant P. [Department of Chemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara-390 002 (India); Kiranbala; Bharambe, D.P. [Department of Applied Chemistry, Faculty of Technology and Engineering, The Maharaja Sayajirao University of Baroda, Vadodara-390 001 (India); Agrawal, K.S. [Department of Petrochemical Technology, Polytechnic, The Maharaja Sayajirao University of Baroda, Vadodara-390 002 (India); Nagar, A. [MH ASSET, ONGC, Mumbai (India)

    2010-09-15

    Modification of the wax crystal habit is of great practical interest during transportation and processing of crude oil at low temperature. Various pour point depressant (PPD) additives can facilitate this modification by different mechanisms. Comb shaped polymer additives are known to depress the pour point of crude oil by providing different nucleation sites for the precipitation of wax. This paper describes performance based design, synthesis, characterization and evaluation of comb shaped polymeric diesters. Copolymers of maleic anhydride with different unsaturated C{sub 22} esters were synthesized and copolymers then reacted with two unsaturated fatty alcohols. All products were characterized by Fourier Transform Infra Red (FTIR) spectroscopy and Gel Permeation Chromatography (GPC). Rheological properties of crude (with and without additive) were studied by Advance Rheometer AR-500. In this study the additive based on oleic acid was evaluated as good PPD and rheology modifier. (author)

  6. Intrinsic linewidth of quantum cascade laser frequency combs

    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.

  7. Single-molecule studies of DNA by molecular combing

    Liu Yuying; Wang Pengye; Dou Shuoxing

    2007-01-01

    Molecular combing is a powerful method for aligning a large array of DNA molecules onto a surface. It is a process whereby DNA molecules are stretched and aligned on a glass surface by the force via fluid flow. The ability to comb up to several hundred DNAs on a single cover slip allows for a statistically significant number of measurements to be made. These features make molecular combing an attractive tool for genomic studies, such as DNA replication, DNA transcription, DNA-protein interaction and so on. In this review article, we discuss the molecular combing principle, method and its applications.

  8. Tunable frequency combs based on dual microring resonators

    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...

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

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

    2014-12-01

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

  10. Sharpening of the multistage modified comb filters

    Nikolić Marko

    2011-01-01

    Full Text Available This paper describes the application of filter sharpening method to the modified comb filter (MCF in the case of decimation factor, which is product of two or more positive integers. It is shown that in the case of multistage decimation with MCF, filters in each stage are also MCF. Applying the sharpening to the decimation filter in the last stage provides very good results, with savings in the number of operations comparing to the case of sharpening of the complete filter. Direct-form FIR polyphase filter structure is proposed for the filters in each stage.

  11. Difference-frequency combs in cold atom physics

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

    2016-01-01

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

  12. Microresonator-Based Comb Generation without an External Laser Source

    Johnson, Adrea R; Lamont, Michael R E; Levy, Jacob S; Lipson, Michal; Gaeta, Alexander L

    2013-01-01

    Recent developments demonstrate that parametric four-wave mixing (FWM) in high-Q microresonators is a highly promising and effective approach for optical frequency comb generation, with applications including spectroscopy, optical clocks, arbitrary waveform generation, frequency metrology, and astronomical spectrograph calibration. Each of these microresonator platforms utilizes a scheme in which the system is pumped by a single-frequency laser at a cavity resonance. This scheme requires tuning of the pump wavelength into resonance and the generated comb is susceptible to fluctuations in pump power or frequency which can disrupt the soft thermal lock and comb generation. We demonstrate a novel fiber-microresonator dual-cavity architecture that preferentially oscillates at modes of the microresonator due to its high density of states and generates robust and broadband combs (> 900 nm) without an external pump laser. Such a scheme could greatly simplify the comb generation process and allow for a fully-integrat...

  13. Gas Damping Coefficient Research for MEMS Comb Linear Vibration Gyroscope

    Qiufen, G; Feng, S; Fuqiang, L

    2008-01-01

    Silicon-MEMS gyroscope is an important part of MEMS (Micro Electrical Mechanical System). There are some disturb ignored in traditional gyroscope that must be evaluated newly because of its smaller size (reach the level of micron). In these disturb, the air pressure largely influences the performance of MEMS gyroscope. Different air pressure causes different gas damping coefficient for the MEMS comb linear vibration gyroscope and different gas damping coefficient influences the quality factor of the gyroscope directive. The quality factor influences the dynamic working bandwidth of the MEMS comb linear vibration gyroscope, so it is influences the output characteristic of the MEMS comb linear vibration gyroscope. The paper shows the relationship between the air pressure and the output amplified and phase of the detecting axis through analyzing the air pressure influence on the MEMS comb linear vibration gyroscope. It discusses the influence on the frequency distribute and quality factor of the MEMS comb linear...

  14. Adaptive real-time dual-comb spectroscopy

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

    2012-01-01

    With the advent of laser frequency combs, coherent light sources that offer equally-spaced sharp lines over a broad spectral bandwidth have become available. One decade after revolutionizing optical frequency metrology, frequency combs hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite its intriguing potential for the measurement of molecular spectra spanning tens of nanometers within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the extremely demanding high-bandwidth servo-control conditions of the laser combs. Here we overcome this difficulty. We experimentally demonstrate a straightforward concept of real-time dual-comb spectroscopy, which only uses free-running mode-locked lasers without any phase-lock electronics, a posteriori data-processing, or the need for expertise in frequency metrology. The resulting simplicity and versatility of our new technique of adaptive dual-com...

  15. Comb-locked Lamb-dip spectrometer

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10‑11 cm‑1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10‑23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  16. Ka-band microwave frequency comb Doppler reflectometer system for the Large Helical Device

    A ka-band multi-channel Doppler reflectometer system was constructed for the Large Helical Device (LHD) using a comb frequency generator as a source. A filter bank system is utilized for precise quadrature phase detection, and preliminary back-scattered waves were obtained in LHD plasma experiments. In addition, a direct digital signal acquisition system was successfully demonstrated for providing a greater number of multi-channel measurements. (author)

  17. A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

    Ruan Juan; Zhang Wei-Gang; Zhang Hao; Geng Peng-Cheng; Bai Zhi-Yong

    2013-01-01

    A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated.The filter tunability is achieved by rotating the polarization controller.The spectral shift is dependent on rotation direction and the position of the polarization controller.In addition,the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.

  18. Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism

    The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of ∼2x10-11 at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3x10-12 for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths.

  19. Optical frequency comb-based local oscillator phase noise cancellation in time-delay-interferometer for gravitational wave detection

    Yu, Nan

    Time-delay-interferometer (TDI) is well established as an effective technique to mitigate laser phase noises in laser interferometer gravitational wave detection (GWD). Just as important in the TDI scheme is the ability to suppress the rf local oscillator noise (LO) in the optical heterodyne measurements. We show that LO noises can be effectively and elegantly cancelled by employing optical frequency combs in which the rf signal phases are coherent with the optical phases. In addition, the deployment of optical combs eliminates the need for separate ultra-stable oscillators. This is a simpler and more reliable approach than the modulation scheme, and it can be applied to the most generalized TDI combinations. In this proposed effort, we will investigate the application of optical combs in TDI and demonstrate in a test bed simultaneous noise cancellations in both ranging lasers and rf LOs in a generalized TDI configuration.

  20. Chipscale optical frequency combs: from soliton physics to coherent communication (Conference Presentation)

    Brasch, Victor; Geiselmann, Michael; Herr, Tobias; Lihachev, Grigoriy; Pfeiffer, Martin H. P.; Gorodetsky, Michael L.; Kippenberg, Tobias J.

    2016-04-01

    In our experiment we use silicon nitride waveguides embedded in silicon dioxide on a silicon chip. The cross section of the waveguide is approximately 1.8µm width by 0.8µm height and the ring resonator has a radius of 120µm. This resonator is coupled to a bus waveguide that is used to couple the continuous wave pump light into the resonator and the light from the resonator out again. The pump laser is an amplified diode laser which provides around 2W of pump power in the bus waveguide on the photonic chip. If the pump light is in resonance with one of the resonances of the resonator we can generate a frequency comb from the pump light via the Kerr nonlinearity of the material. The spacing in between the lines of the frequency comb is close to the free spectral range of the resonator, which is 190 GHz for the resonator used. By tuning the pump laser through the resonance and modulating the power of the pump light we can achieve a stable state with a pulsed-shape waveform circulating inside the microresonator. These states are known as dissipative Kerr soliton states and they are solutions to the Lugiato-Lefever equation, which describes the nonlinear physics of the system. So far they had been experimentally demonstrated in fiber-ring cavities as well as crystalline microresonators. The main benefits of these states for Kerr frequency combs is that they allow for low-noise but broadband frequency combs with low modulation in the spectrum. In our case we report a 3-dB bandwidth of 10THz which is equivalent to sub-30fs pulses inside the resonator. Because of the chosen geometry of the waveguide cross section we also observe an effect which is caused by higher-order dispersion. Higher-order dispersion are terms that describe the dispersion beyond the quadratic group velocity dispersion. In order for dissipative Kerr solitons to form, anomalous group velocity dispersion is required. If higher-order terms are present as well, the soliton can still exist but additional

  1. Frequency comb metrology with an optical parametric oscillator.

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

    2016-04-18

    We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-µm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the 87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb = 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-µm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser. PMID:27137274

  2. From "Dirac combs" to Fourier-positivity

    Giraud, Bertrand G

    2015-01-01

    Motivated by various problems in physics and applied mathematics, we look for constraints and properties of real Fourier-positive functions, i.e. with positive Fourier transforms. Properties of the "Dirac comb" distribution and of its tensor products in higher dimensions lead to Poisson resummation, allowing for a useful approximation formula of a Fourier transform in terms of a limited number of terms. A connection with the Bochner theorem on positive definiteness of Fourier-positive functions is discussed. As a practical application, we find simple and rapid analytic algorithms for checking Fourier-positivity in 1- and (radial) 2-dimensions among a large variety of real positive functions. This may provide a step towards a classification of positive positive-definite functions.

  3. Ultra-Broadband Coherent Supercontinuum Frequency Comb

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

    2011-01-01

    We present detailed studies of the coherence properties of an ultra-broadband super-continuum, enabled by a new 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 the first 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 super-continuum coherence on the fiber fractional Raman gain.

  4. Internal Aggregation Models on the Comb Lattice

    Huss, Wilfried

    2011-01-01

    The comb C is a natural spanning tree of the Euclidean lattice Z^2. We study three related cluster growth models on C: internal diffusion limited aggregation (IDLA), in which random walkers move on the vertices of C until reaching an unoccupied site where they stop; rotor-router aggregation in which particles perform deterministic walks, and stop when reaching a site previously unoccupied; and the divisible sandpile model where at each vertex there is a pile of sand, for which, at each step, the mass exceeding 1 is distributed equally among the neighbours. We describe the shape of the divisible sandpile cluster on C, which is then used to give inner bounds for IDLA and rotor-router aggregation.

  5. Stabilization of an optical frequency comb to an external cavity

    Rydberg, Olof

    2014-01-01

    The subject of this master's thesis is stabilizing a frequency comb laser to an external cavity using a couple of servo controllers. The aim of the project was to build a pair of servo controllers, replacing parts of the existing commercial and proprietary solution already in use. The system under control is an optical frequency comb, which is locked to an external cavity and is used for trace gas detection and spectroscopy. The comb is a broadband light source and needs to be locked to the e...

  6. Intrinsic linewidth of quantum cascade laser frequency combs

    Cappelli, Francesco; Villares, Gustavo; 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 in...

  7. Safe sex

    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 ...

  8. Generation of Optical Combs in a WGM Resonator from a Bichromatic Pump

    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

  9. Micro--structured crystalline resonators for optical frequency comb generation

    Grudinin, Ivan S

    2014-01-01

    Optical frequency combs have recently been demonstrated in micro--resonators through nonlinear Kerr processes. Investigations in the past few years provided better understanding of micro--combs and showed that spectral span and mode locking are governed by cavity spectrum and dispersion. While various cavities provide unique advantages, dispersion engineering has been reported only for planar waveguides. In this Letter, we report a resonator design that combines dispersion control, mode crossing free spectrum, and ultra--high quality factor. We experimentally show that as the dispersion of a MgF2 resonator is flattened, the comb span increases reaching 700 nm with as low as 60 mW pump power at 1560 nm wavelength, corresponding to nearly 2000 lines separated by 46 GHz. The new resonator design may enable efficient low repetition rate coherent octave spanning frequency combs without the need for external broadening, ideal for applications in optical frequency synthesis, metrology, spectroscopy, and communicatio...

  10. Wax combs mediate nestmate recognition by guard honeybees

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

    2006-01-01

    context of bees at colony entrances. Wax combs constructed by each experimental colony were swapped between hives and the acceptance of nestmate and non-nestmate forager workers was recorded before and after the swap, and in relation to a control hive not involved in the swap. We conducted the experiment......Research has shown that the wax combs are important in the acquisition of colony odour in the honeybee, Apis mellifera. However, many of these studies were conducted in the laboratory or under artificial conditions. We investigated the role of the wax combs in nestmate recognition in the natural...... in the first year, and from 8 to 47% in the second year. This effect wore off within 3 weeks. Chemical analyses showed that the cuticular profile of non-nestmates involved in the experimental comb swap became more similar to each other after the swap, and that acceptance by guards of bees from...

  11. A Compact, Waveguide Based Programmable Optical Comb Generator Project

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

  12. Terahertz multi-heterodyne spectroscopy using laser frequency combs

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

    2016-01-01

    Frequency combs based on terahertz quantum cascade lasers feature broadband coverage and high output powers in a compact package, making them an attractive option for broadband spectroscopy. Here, we demonstrate the first multi-heterodyne spectroscopy using two terahertz quantum cascade laser combs. With just 100 $\\mu$s of integration time, we achieve peak signal-to-noise ratios exceeding 60 dB and a spectral coverage greater than 250 GHz centered at 2.8 THz. Even with room-temperature detectors we are able to achieve peak signal-to-noise ratios of 50 dB, and as a proof-of-principle we use these combs to measure the broadband transmission spectrum of etalon samples. Finally, we show that with proper signal processing, it is possible to extend the multi-heterodyne spectroscopy to quantum cascade laser combs operating in pulsed mode, greatly expanding the range of quantum cascade lasers that could be suitable for these techniques.

  13. Transfer of optical frequency combs over optical fibre links

    Marra, Giuseppe

    2013-01-01

    In just over a decade the optical frequency comb technique has completely transformed the field of frequency metrology. These devices have made the measurement of the frequency of light a much easier and affordable task when compared to with earlier techniques. With both research and technology development on these devices becoming more mature, optical frequency combs have been affecting other science areas. Applications are already found in spectroscopy, attosecond physics and astrophysics a...

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

    Chembo, Yanne K.

    2016-06-01

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

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

    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...

  16. Radiative properties tailoring of grating by comb-drive microactuator

    Micro-scale grating structures are widely researched in recent years. Although micro-scale fabrication technology is highly advanced today, with grating aspect ratio greater than 25:1 being achievable some fabrication requirements, such as fine groove processing, are still challenging. Comb-drive microactuator is proposed in this paper to be utilized on simple binary grating structures for tailoring or modulating spectral radiation properties by active adjustment. The rigorous coupled-wave analysis (RCWA) is used to calculate the absorptance of proposed structures and to investigate the impacts brought by the geometry and displacement of comb-drive microactuator. The results show that the utilization of comb-drive microactuator on grating improves the absorptance of simple binary grating while avoiding the difficulty fine groove processing. Spectral radiation property tailoring after gratings are fabricated becomes possible with the comb-drive microactuator structure. - Highlights: • A microscale grating structure with comb-driven microactuator is proposed. • The movement of microactuator changes peak absorptance resonance wavelength. • Geometric and displacement effects of comb finger on absorptance are investigated. • Both RCWA and LC circuit models are developed to predict the resonance wavelength. • Resonance frequency equations of LC circuits allow quick design analysis

  17. Treatment of head lice (Pediculus humanus capitis) infestation: is regular combing alone with a special detection comb effective at all levels?

    Kurt, Özgür; Balcıoğlu, I Cüneyt; Limoncu, M Emin; Girginkardeşler, Nogay; Arserim, Süha K; Görgün, Serhan; Oyur, Tuba; Karakuş, Mehmet; Düzyol, Didem; Gökmen, Aysegül Aksoy; Kitapçıoğlu, Gül; Özbel, Yusuf

    2015-04-01

    Head lice infestation (HLI) caused by Pediculus humanus capitis has been a public health problem worldwide. Specially designed combs are used to identify head lice, while anti-lice products are applied on the scalp for treatment. In the present study, we aimed to test whether combing only by precision detection comb (PDC) or metal pin comb (MPC) could be effective alternatives to the use of anti-lice products in children. A total of 560 children from two rural schools in Turkey were screened. In the PDC trial, children were combed every second day for 14 days, while in the MPC trial, combing was performed once in every four days for 15 days. Children were divided into two groups (dry combing and wet combing) for both trials and results were compared. The results showed no significant differences between dry and wet combing strategies for both combs for the removal of head lice (p > 0.05). The number of adult head lice declined significantly on each subsequent combing day in both approaches, except on day 15 in the MPC trial. In the end, no louse was found in 54.1 and 48.9% of children in the PDC and MPC trials, respectively. Since family members of infested children were not available, they were not checked for HLI. Four times combing within 2 weeks with MPC combs was found effective for both treatment of low HLI and prevention of heavy HLI. In conclusion, regular combing by special combs decreases HLI level in children and is safely applicable as long-term treatment. PMID:25604670

  18. Long-path atmospheric measurements using dual frequency comb measurements

    Waxman, Eleanor; Cossel, Kevin; Truong, Gar-Wing; Giorgetta, Fabrizio; Swann, William; Coddington, Ian; Newbury, Nathan

    2016-04-01

    The dual frequency comb spectrometer is a new tool for performing atmospheric trace gas measurements. This instrument is capable of measuring carbon dioxide, methane, and water with extremely high resolution in the region between 1.5 and 2.1 microns in the near-IR. It combines the high resolution of a laboratory-based FTIR instrument with the portability of a long-path DOAS system. We operate this instrument at path lengths of a few kilometers, thus bridging the spatial resolution of in-situ point sensors and the tens of square kilometer footprints of satellites. This spatial resolution is ideal for measuring greenhouse gas emissions from cities. Here we present initial long-path integrated column measurements of the greenhouse gases water, carbon dioxide, and methane in an urban environment. We present a time series with 5 minute time resolution over a 2 kilometer path in Boulder, Colorado at the urban-rural interface. We validate this data via a comparison with an in-situ greenhouse gas monitor co-located along the measurement path and show that we agree well on the baseline concentration but that we are significantly less sensitive to local point source emission that have high temporal variability, making this instrument ideal for measurements of average city-wide emissions. We additionally present progress towards measurements over an 11 kilometer path over downtown Boulder to measure the diurnal flux of greenhouse gases across the city.

  19. The effect of drone comb on a honey bee colony's production of honey

    Seeley, Thomas

    2002-01-01

    This study examined the impact on a colony's honey production of providing it with a natural amount (20%) of drone comb. Over 3 summers, for the period mid May to late August, I measured the weight gains of 10 colonies, 5 with drone comb and 5 without it. Colonies with drone comb gained only 25.2 $\\pm$ 16.0 kg whereas those without drone comb gained 48.8 $\\pm$ 14.8 kg. Colonies with drone comb also had a higher mean rate of drone flights and a lower incidence of drone comb building. The lower...

  20. Sex ratio variation and sex determination in Urtica dioica

    Glawe, Grit Anja

    2006-01-01

    This thesis will first document on variation in progeny sex ratios among individual female plants of Urtica dioica at our field site in Meijendel (Chapter 2). Next, we show that there is also considerable sex ratio variation among male and female flowering shoots in 26 natural populations studied (Chapter 3). Additionally, we studied life history traits of male and female clones to detect sex-specific differences that might have contributed to the sex ratio bias observed in the field. Our res...

  1. Sex Stereotype

    倪媛

    2014-01-01

    This paper analyzes the social phenomenon—sex stereotype.The paper illustrates the characteristics of stereotype and discusses about the factors which influence sex stereotypes and the reasons of its existence.And it also found the positive role that sex stereotype plays in the communication.

  2. Self-referencing of an on-chip soliton Kerr frequency comb without external broadening

    Brasch, Victor; Jost, John D; Geiselmann, Michael; Kippenberg, Tobias J

    2016-01-01

    Self-referencing turns pulsed laser systems into self-referenced frequency combs. Such frequency combs allow counting of optical frequencies and have a wide range of applications. The required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical fibers. Recent advances in the field of Kerr frequency combs have provided a path towards the development of compact frequency comb sources that provide broadband frequency combs, exhibit microwave repetition rates and that are compatible with on-chip photonic integration. These devices have the potential to significantly expand the use of frequency combs. Yet to date self-referencing of such Kerr frequency combs has only been attained by applying conventional, fiber based broadening techniques. Here we demonstrate external broadening-free self-referencing of a Kerr frequency comb. An optical spectrum that spans two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride micro...

  3. Enabling Arbitrary Wavelength Optical Frequency Combs on Chip

    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.

  4. Brillouin filtering of optical combs for narrow linewidth frequency synthesis

    Galindo-Santos, Juan; Velasco, Aitor V.; Carrasco-Sanz, Ana; Corredera, Pedro

    2016-05-01

    We report a tunable monochromatic source generation scheme, based on Brillouin filtering of a self-referenced optical frequency comb. The system benefits from the high stability and mode linewidth of the frequency comb, significantly improving the performance of the original laser source used as Brillouin pump. A synthesized frequency with stability under 4×10-11 and a linewidth under 75 kHz was experimentally demonstrated for two separate pump lasers in the C-band. The proposed monochromatic source can be tuned with high precision in a very broad band by combining a coarse control with the pumping source and a fine control with the optical frequency comb references. In our experimental setup, coarse and fine tuning resolutions were 4 MHz and 20 Hz, respectively. Influence of Brillouin pump fluctuations in the synthesized signal stability were also analyzed for observation times up to 104 s.

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

    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. Laser frequency comb techniques for precise astronomical spectroscopy

    Murphy, Michael T; Light, Philip S; Luiten, Andre N; Lawrence, Jon S

    2012-01-01

    Precise astronomical spectroscopic analyses routinely assume that individual pixels in charge-coupled devices (CCDs) have uniform sensitivity to photons. Intra-pixel sensitivity (IPS) variations may already cause small systematic errors in, for example, studies of extra-solar planets via stellar radial velocities and cosmological variability in fundamental constants via quasar spectroscopy, but future experiments requiring velocity precisions approaching ~1 cm/s will be more strongly affected. Laser frequency combs have been shown to provide highly precise wavelength calibration for astronomical spectrographs, but here we show that they can also be used to measure IPS variations in astronomical CCDs in situ. We successfully tested a laser frequency comb system on the Ultra-High Resolution Facility spectrograph at the Anglo-Australian Telescope. By modelling the 2-dimensional comb signal recorded in a single CCD exposure, we find that the average IPS deviates by <8 per cent if it is assumed to vary symmetri...

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

    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...

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

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

    2015-09-01

    The authors present the performance and noise properties of a software reconfigurable, FSR and wavelength tunable gain switched optical frequency comb source. This source, based on the external injection of a temperature tuned Fabry-Pérot laser diode, offers quasi-continuous wavelength tunability over the C-band (30nm) and FSR tunability ranging from 6 to 14GHz. The results achieved demonstrate the excellent spectral quality of the comb tones (RIN ~-130dB/Hz and low phase noise of 300kHz) and its outstanding stability (with fluctuations of the individual comb tones of less than 0.5dB in power and 5pm in wavelength, characterized over 24hours) highlighting its suitability for employment in next generation flexible optical transmission networks. PMID:26368425

  9. A quadratic-shaped-finger comb parametric resonator

    A large-stroke (8 µm) parametric resonator excited by an in-plane ‘shaped-finger’ electrostatic comb drive is fabricated using a 15 µm thick silicon-on-insulator microelectromechanical systems (SOI-MEMS) process. A quadratic capacitance-engagement response is synthesized by engineering a custom-shaped comb finger profile. A folded-flexure suspension allows lateral motion while constraining rotational modes. The excitation of the nonlinear parametric resonance is realized by selecting an appropriate combination of the linear and cubic electrostatic stiffness coefficients through a specific varying-gap comb-finger design. The large-amplitude parametric resonance promotes high signal-to-noise ratio for potential use in sensitive chemical gravimetric sensors, strain gauges, and mode-matched gyroscope applications. (paper)

  10. How to sell safer sex.

    Overs, C

    1991-09-01

    Social and economic factors determine the extent of the sex industry in societies. Despite AIDS, the sex industry will continue to thrive. Accordingly, health promotion strategies aimed at sex workers and their clients should not stem from the belief that the industry should cease to exist. This paper offers advice in developing and implementing programs to promote safer sex among sex workers. The social context is 1 element to consider in planning successful campaigns. Interventions must be combined with well-planned prevention campaigns aimed at entire populations. The opinions and participation of those involved in the industry should also be sought, while worker discussion and action upon other community issues should not be discouraged. Care should be given to target the numerous and diverse sex worker audiences in addition to other persons related to and involved in the industry. Programs should address the main obstacles to practicing safer sex, and attention should be given to ensure the provision of an adequate and regular supply of cheap or free condoms through varied distribution channels. In the area of service provision, sex workers need easy access to social support and health care services from which they are often excluded. Activities conducted around the world include the marketing of safer sex, distributing printed information on HIV and AIDS to clients, training sex workers to pass designated constructive ideas to others involved in the sex industry, referring sex workers to sex businesses supportive of safer sex practices, and developing street theater and cabaret shows in bars. PMID:12284682

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

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

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

    Klenner, Alexander; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

    2014-01-01

    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...

  13. Device Characterization of High Performance Quantum Dot Comb Laser

    Rafi, Kazi

    2012-02-01

    The cost effective comb based laser sources are considered to be one of the prominent emitters used in optical communication (OC) and photonic integrated circuits (PIC). With the rising demand for delivering triple-play services (voice, data and video) in FTTH and FTTP-based WDM-PON networks, metropolitan area network (MAN), and short-reach rack-to-rack optical computer communications, a versatile and cost effective WDM transmitter design is required, where several DFB lasers can be replaced by a cost effective broadband comb laser to support on-chip optical signaling. Therefore, high performance quantum dot (Q.Dot) comb lasers need to satisfy several challenges before real system implementations. These challenges include a high uniform broadband gain spectrum from the active layer, small relative intensity noise with lower bit error rate (BER) and better temperature stability. Thus, such short wavelength comb lasers offering higher bandwidth can be a feasible solution to address these challenges. However, they still require thorough characterization before implementation. In this project, we briefly characterized the novel quantum dot comb laser using duty cycle based electrical injection and temperature variations where we have observed the presence of reduced thermal conductivity in the active layer. This phenomenon is responsible for the degradation of device performance. Hence, different performance trends, such as broadband emission and spectrum stability were studied with pulse and continuous electrical pumping. The tested comb laser is found to be an attractive solution for several applications but requires further experiments in order to be considered for photonic intergraded circuits and to support next generation computer-communications.

  14. Frequency Comb Assisted Broadband Precision Spectroscopy with Cascaded Diode Lasers

    Liu, Junqiu; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    2016-01-01

    Frequency comb assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this letter we present a novel method using cascaded frequency agile diode lasers, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of integrated microresonators up to the fourth order.

  15. The generation of continuous-variable entanglement frequency comb.

    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

  16. 80 W, 120 fs Yb-fiber frequency comb.

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

    2010-09-15

    We report on a high-power fiber frequency comb exhibiting linear chirped-pulse amplification up to 80 W and generating 120 fs pulses. By proper matching of the group delay between the fiber stretcher and compressor, a compression ratio of 3100 could be achieved. Carrier envelope offset self-referencing and long-term phase locking to an rf reference is demonstrated, exemplifying the suitability of this system for generating vacuum and extreme-UV frequency combs via enhancement in passive cavities and high harmonic generation. PMID:20847763

  17. Walk-off-induced modulation instability, temporal pattern formation, and frequency comb generation in cavity-enhanced second-harmonic generation

    Leo, F; Ricciardi, I; De Rosa, M; Coen, S; Wabnitz, S; Erkintalo, M

    2016-01-01

    We derive a time-domain mean-field equation to model the full temporal and spectral dynamics of light in singly resonant cavity-enhanced second-harmonic generation systems. We show that the temporal walk-off between the fundamental and the second-harmonic fields plays a decisive role under realistic conditions, giving rise to rich, previously unidentified nonlinear behaviour. Through linear stability analysis and numerical simulations, we discover a new kind of quadratic modulation instability which leads to the formation of optical frequency combs and associated time-domain dissipative structures. Our numerical simulations show excellent agreement with recent experimental observations of frequency combs in quadratic nonlinear media [Phys. Rev. A 91, 063839 (2015)]. Thus, in addition to unveiling a new, experimentally accessible regime of nonlinear dynamics, our work enables predictive modeling of frequency comb generation in cavity-enhanced second-harmonic generation systems.

  18. On-chip, self-detected THz dual-comb spectrometer

    Rösch, Markus; Villares, Gustavo; Bosco, Lorenzo; Beck, Mattias; Faist, Jérôme

    2016-01-01

    We present a directly generated on-chip dual-comb source at THz frequencies. The multi-heterodyne beating signal of two free-running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting the unique characteristics of quantum cascade active regions. Up to 30 modes can be detected corresponding to a spectral bandwidth of 630 GHz, being the available bandwidth of the dual comb configuration. The multi-heterodyne signal is used to investigate the equidistance of the comb modes showing an accuracy of $10^{-12}$ at the carrier frequency of 2.5 THz.

  19. Direct Frequency Comb Spectroscopy in the Extreme Ultraviolet

    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...

  20. Coherent cavity-enhanced dual-comb spectroscopy

    Fleisher, Adam J; Reed, Zachary D; Hodges, Joseph T; Plusquellic, David F

    2016-01-01

    Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers, or via sophisticated signal processing algorithms, and therefore long integration times are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The combs of > 250 teeth and 203 MHz spacing were generated by driving the phase modulators with step-recovery diodes, passive devices that provided low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO$_2$, CO, HDO, and H$_2$O at a maximum acquisition rate of 150 kHz. Robus...

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

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

    2015-08-01

    We describe the design, fabrication, and performance of a self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, saturable absorbers for mode-locking, high signal-to-noise ratio (SNR) detection of the control signals, and digital feedback control for frequency stabilization. The output is phase-coherent over a 1-2 μm octave-spanning spectrum with a pulse repetition rate of ˜200 MHz and a residual pulse-to-pulse timing jitter 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.

  2. Uniform asymptotic estimates of transition probabilities on combs

    Bertacchi, Daniela; Zucca, Fabio

    2000-01-01

    We investigate the asymptotical behaviour of the transition probabilities of the simple random walk on the 2-comb. In particular we obtain space-time uniform asymptotical estimates which show the lack of symmetry of this walk better than local limit estimates. Our results also point out the impossibility of getting Jones-type non-Gaussian estimates.

  3. Stabilized chip-scale Kerr frequency comb via a high-Q reference photonic microresonator

    Lim, Jinkang; Huang, Shu-Wei; Vinod, Abhinav K.; Mortazavian, Parastou; Yu, Mingbin; Kwong, Dim-Lee; Savchenkov, Anatoliy A.; Matsko, Andrey B.; Maleki, Lute; Wong, Chee Wei

    2016-08-01

    We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term.

  4. A stabilized chip-scale Kerr frequency comb via a high-Q reference photonic microresonator

    Lim, Jinkang; Vinod, Abhinav K; Mortazavian, Parastou; Yu, Mingbin; Kwong, Dim-Lee; Savchenkov, Anatoliy A; Matsko, Andrey B; Maleki, Lute; Wong, Chee Wei

    2016-01-01

    We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term.

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

    Duran, Vicente; Torres-Company, Victor

    2016-01-01

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

  6. Conflict over condition-dependent sex allocation can lead to mixed sex-determination systems

    Kuijper, B.; Pen, I.

    2014-01-01

    Theory suggests that genetic conflicts drive turnovers between sex-determining mechanisms, yet these studies only apply to cases where sex allocation is independent of environment or condition. Here, we model parent–offspring conflict in the presence of condition-dependent sex allocation, where the environment has sex-specific fitness consequences. Additionally, one sex is assumed to be more costly to produce than the other, which leads offspring to favor a sex ratio less biased toward the ch...

  7. Multi-octave frequency comb generation by χ(3)-nonlinear optical processes in CVD diamond at low temperatures

    We study stimulated Raman scattering (SRS) and Raman four-wave mixing (RFWM) processes in chemical vapour deposition (CVD) diamond crystals. The strong interaction of picosecond laser pulses at 1.064 and 0.532 µm wavelength with the dominant Raman-active F2g mode results in a more than two-octave-spanning frequency comb, ranging from the UV to the NIR spectral region. In addition to spectroscopic analysis of the χ(3)-nonlinear emission at room temperature, comparative measurements have been carried out at cryogenic temperature of 10 K. The Raman shift and the Raman gain are found to change only weakly. Moreover, the potential of SRS frequency comb generation in CVD diamond for ultra-short pulse synthesis is discussed. (letter)

  8. Nested folded-beam suspensions with low longitudinal stiffness for comb-drive actuators

    Nested folded-beam suspensions with a low longitudinal spring constant and a high lateral spring constant have been used in comb-drive actuators. In the new design, every two flexible beams and two stiff members form a parallelogram flexure, which is considered as an ‘element’ of the nested folded-beam suspension. A set of these flexures of increasing size were placed one outside another to compose a nested structure. In this way, a serial mechanical connection between adjacent parallelogram flexures was formed; thus, a longer output stroke was obtained by combining the stroke displacements of all flexures in an additive fashion. The designed suspensions were theoretically analyzed and numerically simulated. Furthermore, comb-drive actuators with conventional and new suspensions were fabricated and tested to verify the predicted function. In the testing cases, the longitudinal spring constants of suspensions with two (conventional), three and four parallelogram flexures on each side were measured as 2.77, 1.75 and 1.36 N m−1. The ratio among these three values was approximately 6:4:3, which is consistent with the theoretical predictions and simulation results. Microfabricated folded beams in series were achieved. (paper)

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

    Neycheva T.

    2009-12-01

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

  10. Comb-assisted coherence transfer between laser fields

    Sala, Tommaso; Burkart, Johannes; Marangoni, Marco; Romanini, Daniele

    2014-01-01

    Single mode laser fields oscillate at frequencies well outside the realm of electronics, but their phase/frequency fluctuations fall into the radio frequency domain, where direct manipulation is possible. Electro-optic devices have sufficient bandwidth for controlling and tailoring the dynamics of a laser field down to sub-nanosecond time scales. Thus, a laser field can be arbitrarily reshaped and in particular its phase/frequency fluctuations can be in principle removed. In practice, the time evolution of a reference laser field can be cloned to replace the fluctuations of another laser field, at a close-by frequency. In fact, it is possible to exploit a partially stabilized optical comb to perform the cloning across a large frequency gap. We realize this long-haul phase transfer by using a fibered Mach-Zehnder single-sideband modulator driven by an appropriate mix of the beat notes of the master and the slave laser with the comb.

  11. Envelope, group and phase velocities in a nested frequency comb

    Masuda, Koji; Hendrie, James; Diels, Jean-Claude; Arissian, Ladan

    2016-05-01

    Fabry–Pérot etalons have been traditionally used in a laser cavity to tune the optical frequency. In this work we present the generation of interwoven frequency combs with insertion of an intracavity Fabry–Pérot in a mode-locked laser. A high frequency comb is generated by insertion of an uncoated (low finesse) Fabry–Pérot inside the laser cavity. The intracavity Fabry–Pérot acquires a high finesse from the laser cavity and the velocity of the pulses in the Fabry–Pérot is affected by the laser cavity length, gain and losses, with the dielectric group velocity dk/dΩ playing only a minor role. The output characteristics are explained by the condition that the radiation is simultaneously resonant with the etalon and the laser cavity.

  12. High density THz frequency comb produced by coherent synchrotron radiation

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

    2014-01-01

    Frequency combs (FC) have radically changed the landscape of frequency metrology and high-resolution spectroscopy investigations extending tremendously the achievable resolution while increasing signal to noise ratio. Initially developed in the visible and near-IR spectral regions, the use of FC has been expanded to mid-IR, extreme ultra-violet and X-ray. Significant effort is presently dedicated to the generation of FC at THz frequencies. One solution based on converting a stabilized optical frequency comb using a photoconductive terahertz emitter, remains hampered by the low available THz power. Another approach is based on active mode locked THz quantum-cascade-lasers providing intense FC over a relatively limited spectral extension. Alternatively, here we show that dense powerful THz FC is generated over one decade of frequency by coherent synchrotron radiation (CSR). In this mode, the entire ring behaves in a similar fashion to a THz resonator wherein electron bunches emit powerful THz pulses quasi-synch...

  13. Micro-Doppler Frequency Comb Generation by Axially Rotating Scatterers

    Kozlov, Vitali; Yankelevich, Yefim; Ginzburg, Pavel

    2016-01-01

    Electromagnetic scattering in accelerating reference frames inspires a variety of phenomena, requiring employment of general relativity for their description. While the quasi-stationary field analysis could be applied to slowly-accelerating bodies as a first-order approximation, the scattering problem remains fundamentally nonlinear in boundary conditions, giving rise to multiple frequency generation (micro-Doppler shifts). Here a frequency comb, generated by an axially rotating subwavelength (cm-range) wire and split ring resonator (SRR), is analyzed theoretically and observed experimentally by illuminating the system with a 2GHz carrier wave. Highly accurate lock in detection scheme enables factorization of the carrier and observation of more than ten peaks in a comb. The Hallen integral equation is employed for deriving the currents induced on the scatterer at rest and a set of coordinate transformations, connecting laboratory and rotating frames, is applied in order to predict the spectral positions and a...

  14. Frequency comb formation in doubly resonant second-harmonic generation

    Leo, F; Ricciardi, I; De Rosa, M; Coen, S; Wabnitz, S; Erkintalo, M

    2016-01-01

    We theoretically study the generation of optical frequency combs and corresponding pulse trains in doubly resonant intracavity second-harmonic generation (SHG). We find that, despite the large temporal walk-off characteristic of realistic cavity systems, the nonlinear dynamics can be accurately and efficiently modelled using a pair of coupled mean-field equations. Through rigorous stability analysis of the system's steady-state continuous wave solutions, we demonstrate that walk-off can give rise to a new, previously unexplored regime of temporal modulation instability (MI). Numerical simulations performed in this regime reveal rich dynamical behaviours, including the emergence of temporal patterns that correspond to coherent optical frequency combs. We also demonstrate that the two coupled equations that govern the doubly resonant cavity behaviour can, under typical conditions, be reduced to a single mean-field equation akin to that describing the dynamics of singly resonant cavity SHG [F. Leo et al., Phys. ...

  15. Computation of Capacitance for MEMS Comb-Drive Structures

    LI Ming-hui; GAO Shi-qiao; LIU Hai-peng; LIANG Xin-jian

    2009-01-01

    According to the characteristics of comb-drive structures,the electrical potential field is analyzed;the model based on corner capacitor is presented and solved with the capacitance characteristic formula of nonlinear capacitor.Compared with the results of finite element method simulation,the model based on corner capacitor is more accurate than the models based on infinite parallel plate capacitor and parallel plate capacitor with edge effects,

  16. Infrared frequency combs and supercontinua for multiplex high sensitivity spectroscopy

    Mandon, Julien; Sorokina, Irina T; Guelachvili, Guy; Picqué, Nathalie

    2007-01-01

    An infrared high-brightness light source based on supercontinuum generation through a SF6 photonic crystal fiber seeded by a Cr^4+:YAG femtosecond oscillator is developed for high resolution multiplex spectroscopy in the 1.5 $\\mu$m region. Moreover, a multiplex high resolution approach based on a Cr^4+:YAG frequency comb enables to probe large spectral domains, with simultaneous sensitive measurement of the absorption and the dispersion associated with all individual spectral features.

  17. Frequency combs with weakly lasing exciton-polariton condensates

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

    2015-01-01

    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 inter- action 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 dis- tributions ap...

  18. Application of the Molecular Combing Technique to Starch Granules

    Zhong-Dong Liu; Liu Boxiang; Jian-Hui Chen; You-Ning Sun; Xiao-Ling Lv; Ze-Sheng Zhang; Pin Sun; Pin Zhang; Yang-Li Wang; Hua Li

    2009-01-01

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

  19. Experimental and theoretical investigation of direct frequency comb spectroscopy

    Peters, Elisabeth

    2011-01-01

    This thesis reports on theoretical and experimental examination of two-photon direct frequency comb spectroscopy (DFCS) using atomic two-level systems. This method is a very promising tool to extend optical spectroscopy into the short wavelength region where only few cw laser sources exist. The high peak intensities of pulsed lasers facilitate efficient nonlinear conversion into frequency regions which are so far unexplored, for example by high harmonic generation (HHG). DFCS is based on...

  20. Comb-e-Chem: an e-science research project

    Frey, Jeremy G.

    2003-01-01

    The background to the Comb-e-Chem e-Science pilot project funded under the UK -Science Programme is presented and the areas being addresses within chemistry and more specifically combinatorial chemistry are disucssed. The ways in which the ideas underlying the application of computer technology can improve the production, analysis and dissemination of chemical information and knowledge in a collaborative environment are discussed.

  1. Generation of a frequency comb and applications thereof

    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.

  2. "Nail" and "comb" effects of cholesterol modified NIPAm oligomers on cancer targeting liposomes

    Li, Wengang

    2014-01-01

    Thermosensitive liposomes are a promising approach to controlled release and reduced drug cytotoxicity. Low molecular weight N-isopropylacrylamide (NIPAm) oligomers (NOs) with different architectures (main chain NOs (MCNOs) and side chain NOs (SCNOs)) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and radical polymerization and then separately used to prepare thermosensitive liposomes. A more controlled and enhanced release was observed for both NO liposomes compared to pristine ones. Two release mechanisms depending on the oligomer architecture, namely "nail" for MCNOs and "comb" for SCNOs, are proposed. In addition to thermosensitivity, the cancer targeting property of NO liposomes was achieved by further biotinylation of the delivery system. © The Royal Society of Chemistry.

  3. Why Sex?

    Nielsen, Rasmus

    2006-01-01

    It is assumed that most organisms have sex because the resulting genetic recombination allows Darwinian selection to work better. It is now shown that in water fleas, recombination does lead to fewer deleterious mutations.......It is assumed that most organisms have sex because the resulting genetic recombination allows Darwinian selection to work better. It is now shown that in water fleas, recombination does lead to fewer deleterious mutations....

  4. Bottle microresonator broadband and low repetition rate frequency comb generator

    Dvoyrin, V

    2016-01-01

    We propose a new type of broadband and low repetition rate frequency comb generator which has the shape of an elongated and nanoscale-shallow optical bottle microresonator created at the surface of an optical fiber. The free spectral range (FSR) of the broadband azimuthal eigenfrequency series of this resonator is the exact multiple of the FSR of the dense and narrowband axial series. The effective radius variation of the microresonator is close to a parabola with a nanoscale height which is greater or equal to lambda/2pi*n0 (here lambda is the characteristic radiation wavelength and n0 is the refractive index of the microresonator material). Overall, the microresonator possesses a broadband, small FSR, and accurately equidistant spectrum convenient for the generation of a broadband and low repetition rate optical frequency comb. It is shown that this comb can be generated by pumping with a cw laser, which radiation frequency matches a single axial eigenfrequency of the microresonator, or, alternatively, by p...

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

    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

  6. Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

    Gao-ming Hu; Yu Lin; Shi-yong Ran; Yan-wei Wang; Guang-can Yang

    2012-01-01

    We investigated the interaction between DNA and hexammine cobalt Ⅲ [Co(NH3)6]3+ by a simple molecular combing method and dynamic light scattering.The average extension of λ-DNA-YOYO-1 complex is found to be 20.9 μm,about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris,1 mmol/L EDTA,pH=8.0),due to bis-intercalation of YOYO-1.A multivalent cation,hexammine cobalt,is used for DNA condensation.We find that the length of DNA-[Co(NH3)6]3+ complexes decrease from 20.9 μm to 5.9 μm as the concentration of the [Co(NH3)6]3+ vary from 0 to 3 μmol/L.This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt.The results from the molecular combing studies are supported by dynamic light scattering investigation,where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions.It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.

  7. Second-harmonic mode coupling in microresonator-based optical frequency comb generation

    Xue, Xiaoxiao; Xuan, Yi; Jaramillo-Villegas, Jose A; Wang, Pei-Hsun; Leaird, Daniel E; Erkintalo, Miro; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Microresonator-based optical frequency comb (microcomb) generation can potentially achieve ultra-compact volume and low power consumption for portable applications. The comb formation is a consequence of cascaded four-wave-mixing due to the third-order Kerr nonlinearity. Mode coupling can affect the comb self-starting and mode-locking behaviors, resulting in complex dynamics that is far from well understood. Understanding the mechanism of mode coupling in comb generation proves highly important to achieve stable and robust microcomb sources. Here, we report a nonlinear mode coupling mechanism in microresonators with simultaneous second- and third-order nonlinearities. The nonlinear dynamics governed by the third-order nonlinearity is altered by second-harmonic mode coupling. As a demonstration of this effect, second-harmonic assisted coherent comb generation is achieved in the normal dispersion region, where comb creation is prohibited in the absence of mode coupling. Since second-order nonlinearity has been ...

  8. Index Balearicum (II): An Annotated check-list of the vascular plants described from the balearic islands. Additions (2002-2007) and corrections

    Roselló Picornell, Josep Antoni; Sáez, Llorenç

    2008-01-01

    Se presentan adiciones y correcciones al listado de plantas vasculares cuyo tipo nomenclatural es originario de las islas Baleares. Se propone una nueva combinación nomenclatural: Sonchus willkommii (Burnat & Barbey) comb. nov. Additions and corrections to the check-list of vascular plants described from the Balearic Islands are presented. A nomenclatural change is proposed: Sonchus willkommii (Burnat & Barbey) comb. nov.

  9. Application of Comb-Type RF-Shield to Bellows Chambers and Gate Valves

    Suetsugu, Yusuke; Ohuchi, Norihito; Shibata, Kyo; Shirai, Mitsuru

    2005-01-01

    A comb-type RF-shield, which was recently proposed for high current accelerators, was experimentally applied to bellows chambers and gate valves. The comb-type RF-shield has a structure of nested comb teeth, and has higher thermal strength and lower impedance than usual finger-type RF shields. The shield is suitable for future high intensity accelerators, such as particle factories aiming a luminosity of 1·1035

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

    Probst, R A; Wang, L.; 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 meas...

  11. Wide and stable optical frequency comb in an intensity-modulated continuous wave pumped optical fiber

    This paper investigates how to obtain a wide and stable optical frequency comb in an intensity-modulated continuous-wave pumped optical fiber by straightforwardly characterizing the signal-to-noise ratio and analyzing the optimal fiber length. The stability of the obtained optical frequency comb is analyzed by a method which is similar to the eye pattern. The prospect for obtaining wider and more stable optical frequency combs is discussed. (paper)

  12. Vertical comb drive microscanners for beam steering, linear scanning, and laser projection applications

    Jung D.; Sandner T.; Kallweit D.; Schenk H.

    2012-01-01

    This paper describes in detail our concept of quasi-static micro scanning mirrors enabling large static deflections and linearized scanning using vertical out-of-plane comb drives. The vertical comb configuration is realized from a planar scanner substrate by wafer bonding. The device concept is highly flexible by design; different kinds of vertical combs (e.g. staggered and angular) can be realized without changing the technological process flow but by design modifications, only. First demon...

  13. Occurrence of fungi in combs of fungus-growing termites (Isoptera: Termitidae, Macrotermitinae)

    Guedegbe, Herbert; Miambi, Edouard; Pando, Anne; Roman, Jocelyne; Houngnandan, P.; Rouland Lefèvre, Corinne

    2009-01-01

    Fungus-growing termites cultivate their mutualistic basidiomycete Termitomyces species on a substrate called a fungal comb. Here, the Suicide Polymerase Endonuclease Restriction (SuPER) method was adapted for the first time to a fungal study to determine the entire fungal community of fungal combs and to test whether fungi other than the symbiotic cultivar interact with termite hosts. Our molecular analyses show that although active combs are dominated by Termitomyces fungi isolated with dire...

  14. Optical frequency comb technology for ultra-broadband radio-frequency photonics

    Torres-Company, Victor; Weiner, Andrew M.

    2014-01-01

    The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with opti...

  15. Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb

    Fortier, T. M.; Coq, Y Le; Stalnaker, J. E.; Ortega, D.; Diddams, S. A.; Oates, C. W.; Hollberg, L.

    2006-01-01

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrat...

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

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

    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...

  17. Moral Pluralism and Sex Education

    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…

  18. Effect of a breather soliton in Kerr frequency combs on optical communication systems.

    Bao, Changjing; Liao, Peicheng; Zhang, Lin; Yan, Yan; Cao, Yinwen; Xie, Guodong; Mohajerin-Ariaei, Amirhossein; Li, Long; Ziyadi, Morteza; Almaiman, Ahmed; Kimerling, Lionel C; Michel, Jurgen; Willner, Alan E

    2016-04-15

    In this study, we numerically investigate the effect of Kerr-comb-generated breather soliton pulses on optical communication systems. The breather soliton pulse amplitude and spectrum envelope oscillate periodically in time. Simulations show that the spectrum of each comb line in the breather soliton state has multiple sub-teeth due to the periodic oscillation of the comb spectrum. In the simulation, the comb output is modulated with different formats. We find that the sub-teeth distort quadrature phase-shift-keyed signals but have less of an effect on on-off-keyed signals. PMID:27082339

  19. Mid-infrared dual-comb spectroscopy with electro-optic modulators

    Yan, Ming; Iwakuni, Kana; Millot, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2016-01-01

    We demonstrate dual-comb spectroscopy based on difference frequency generation of frequency-agile near-infrared frequency combs, produced with the help of electro-optic modulators. The combs have a remarkably flat intensity distribution and their positions and line spacings can be selected freely by simply dialing a knob. We record, in the 3-micron region, Doppler-limited absorption spectra with resolved comb lines within milliseconds. Precise molecular line parameters are retrieved. Our technique holds promise for fast and sensitive time-resolved studies e.g. of trace gases.

  20. Damping effects of capacitive comb fingers on biomimetic MEMS directional microphone

    Roth, John; Touse, Michael; Sinibaldi, Jose; Karunasiri, Gamani

    2011-03-01

    MEMS directional sound sensors that use two coupled wings moving in air are subjected to viscous damping. The amplitude of oscillation of the sensors is read out by measuring the capacitance of interdigitated comb fingers along the edges of the wings. In this presentation, effects of damping on MEMS sensors with and without comb fingers will be described. It was found that the sensors with comb fingers have a significantly larger damping indicating that the longer perimeter due to combs is responsible for the observed increase. However, the increase in damping reduces the quality factor which improves the response time of the device. This work is supported by NSF.

  1. A preliminary investigation of the potential mechanical sensitivity of vertical comb drives

    This article describes a preliminary step taken in investigating the potential of vertical comb drives to be used as force-compensation mechanisms in interfacial force microscopes, by exploring the lower limit of the stiffness of the springs the comb drives can be fabricated with. The stiffness of their springs will affect the sensitivity of the microscope. Six vertical comb drives were fabricated for this study; the dimensions of their spring beams were chosen with the intention of giving them stiffnesses of three different orders of magnitude. During fabrication it was found that etching the tops of some of the teeth down to create the vertical offset between the combs can be done using only photoresist to mask the rest of the teeth. The stiffnesses of the fabricated springs were estimated by applying loads to them and measuring their resulting deflections. Weights were applied to the two comb drives with the stiffest springs. Voltages were also applied to them so as to determine the force-voltage relationship for their comb design. Since the other four comb drives had the same comb design, the stiffnesses of their springs could be estimated from the displacements of their movable combs when voltages were applied to them. (paper)

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

    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

  3. Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb

    Fortier, T M; Stalnaker, J E; Ortega, D; Diddams, S A; Oates, C W; Hollberg, L

    2006-01-01

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.

  4. Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb.

    Fortier, T M; Coq, Y Le; Stalnaker, J E; Ortega, D; Diddams, S A; Oates, C W; Hollberg, L

    2006-10-20

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity. PMID:17155398

  5. Extra sex combs, chromatin, and cancer: Exploring epigenetic regulation and tumorigenesis in Drosophila

    Can Zhang; Bo Liu; Guangyao Li; Lei Zhou

    2011-01-01

    Developmental genetic studies in Drosophila unraveled the importance of Polycomb group (PcG) and Trithorax group (TrxG) genes in controlling cellular identity.PcG and TrxG proteins form histone modifying complexes that catalyze repressive or activating histone modifications,respectively,and thus maintaining the expression status of homeotic genes.Human orthologs of PcG and TrxG genes are implicated in tumorigenesis as well as in determining the prognosis of individual cancers.Recent whole genome analyses of cancers also highlighted the importance of histone modifying proteins in controlling tumorigenesis.Comprehensive understanding of the mechanistic relationship between histone regulation and tumorigenesis holds the promise of significantly advancing our understanding and management of cancer.It is anticipated that Drosophila melanogaster,the model organism that contributed significantly to our understanding of the functional role of histone regulation in development,could also provide unique insight for our understanding of how histone dysregulation can lead to cancer.In this review,we will discuss several recent advances in this regard.

  6. Sex differences in the brain-an interplay of sex steroid hormones and sex chromosomes.

    Grgurevic, Neza; Majdic, Gregor

    2016-09-01

    Although considerable progress has been made in our understanding of brain function, many questions remain unanswered. The ultimate goal of studying the brain is to understand the connection between brain structure and function and behavioural outcomes. Since sex differences in brain morphology were first observed, subsequent studies suggest different functional organization of the male and female brains in humans. Sex and gender have been identified as being a significant factor in understanding human physiology, health and disease, and the biological differences between the sexes is not limited to the gonads and secondary sexual characteristics, but also affects the structure and, more crucially, the function of the brain and other organs. Significant variability in brain structures between individuals, in addition to between the sexes, is factor that complicates the study of sex differences in the brain. In this review, we explore the current understanding of sex differences in the brain, mostly focusing on preclinical animal studies. PMID:27433022

  7. A new Generation of Spectrometer Calibration Techniques based on Optical Frequency Combs

    Schmidt, Piet O; Kimeswenger, Stefan

    2007-01-01

    Typical astronomical spectrographs have a resolution ranging between a few hundred to 200.000. Deconvolution and correlation techniques are being employed with a significance down to 1/1000 th of a pixel. HeAr and ThAr lamps are usually used for calibration in low and high resolution spectroscopy, respectively. Unfortunately, the emitted lines typically cover only a small fraction of the spectrometer's spectral range. Furthermore, their exact position depends strongly on environmental conditions. A problem is the strong intensity variation between different (intensity ratios {>300). In addition, the brightness of the lamps is insufficient to illuminate a spectrograph via an integrating sphere, which in turn is important to calibrate a long-slit spectrograph, as this is the only way to assure a uniform illumination of the spectrograph pupil. Laboratory precision laser spectroscopy has experienced a major advance with the development of optical frequency combs generated by pulsed femto-second lasers. These lase...

  8. Bottlebrush and comb-like elastomers as ultra-soft electrical and acoustically active materials

    Daniel, William; Vatankhah-Varnosfaderani, Mohammad; Pandya, Ashish; Burdynska, Joanna; Morgan, Benjamin; Everhart, Matthew; Matyjaszewski, Krzysztof; Dobrynin, Andrey; Rubinstein, Michael; Sheiko, Sergei; UNC MIRT Team

    Without swelling in a solvent, it is challenging to obtain materials with a modulus below 105 Pa, which is dictated by chain entanglements. We show that macromolecules can be disentangled by dense grafting of side chains to long polymer chains. The bottlebrush and comb-like architectures demonstrate a unique combination of flexibility and network dilution, leading to significant decrease of the entanglement modulus (Ge) and increase of extensibility. Following theoretical predictions, it has been shown that the Ge is controlled by the polymerization degrees of sidechains (nsc) and grafting spacer (ng) as Ge ~ (ng /nsc) 1 . 5 . Using the reduced entanglement density, we developed solvent-free elastomers with moduli on the order of 100 Pa and excellent extensibility. Using bottlebrush architectures we have developed PDMS dielectric actuators with high deformation at low electric field strength. Additionally strong acoustic adsorption leads to materials showing shape and volume control in light opaque environments. NSF (DMR 1409710, DMR 1122483, DMR 1407645, and DMR 1436201).

  9. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    Snijkers, F.

    2016-03-31

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

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

    Augustine, S.; Jaspers, C.; Kooijman, S. A. L. M.; F. Carlotti; Poggiale, J.-C.; Freitas, V.; H. W. van der Veer; van Walraven, L.

    2014-01-01

    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 ...

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

    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 cognitive radio, and next-generation radar systems. PMID:26512477

  12. Application of the Molecular Combing Technique to Starch Granules

    Zhong-Dong Liu

    2009-10-01

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

  13. Comb-Line Filter with Coupling Capacitor in Ground Plane

    Toshiaki Kitamura

    2011-01-01

    Full Text Available A comb-line filter with a coupling capacitor in the ground plane is proposed. The filter consists of two quarter-wavelength microstrip resonators. A coupling capacitor is inserted into the ground plane in order to build strong coupling locally along the resonators. The filtering characteristics are investigated through numerical simulations as well as experiments. Filtering characteristics that have attenuation poles at both sides of the passband are obtained. The input susceptances of even and odd modes and coupling coefficients are discussed. The filters using stepped impedance resonators (SIRs are also discussed, and the effects of the coupling capacitor for an SIR structure are shown.

  14. Repetition rate multiplication of a femtosecond frequency comb

    Lešundák, Adam; Šmíd, Radek; Voigt, D.; Čížek, Martin; van den Berg, S.; Číp, Ondřej

    Bellingham: SPIE, 2015, 94501L: 1-9. ISBN 9781628415667. ISSN 0277-786X. [Photonics, Devices, and Systems /6./. Prague (CZ), 27.08.2014-29.08.2014] R&D Projects: GA ČR GAP102/10/1813; GA ČR(CZ) GPP102/12/P962; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : Fabry-Perot cavity * laser frequency comb * repetition rate multiplication Subject RIV: BH - Optics, Masers, Lasers

  15. Dual-frequency comb generation with differing GHz repetition rates by parallel Fabry–Perot cavity filtering of a single broadband frequency comb source

    Mildner, Jutta; Meiners-Hagen, Karl; Pollinger, Florian

    2016-07-01

    We present a dual-comb-generator based on a coupled Fabry–Perot filtering cavity doublet and a single seed laser source. By filtering a commercial erbium-doped fiber-based optical frequency comb with CEO-stabilisation and 250 MHz repetition rate, two broadband coherent combs of different repetition rates in the GHz range are generated. The filtering doublet consists of two Fabry–Perot cavities with a tunable spacing and Pound–Drever–Hall stabilisation scheme. As a prerequisite for the development of such a filtering unit, we present a method to determine the actual free spectral range and transmission bandwidth of a Fabry–Perot cavity in situ. The transmitted beat signal of two diode lasers is measured as a function of their tunable frequency difference. Finally, the filtering performance and resulting beat signals of the heterodyned combs are discussed as well as the optimisation measures of the whole system.

  16. Optimally Coherent Kerr Combs Generated with Crystalline Whispering Gallery Mode Resonators for Ultrahigh Capacity Fiber Communications

    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 ˜109 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.

  17. Gaussian-shaped Optical Frequency Comb Generation for Microwave Photonic Filtering

    Wu, Rui; Hamidi, Ehsan; Supradeepa, V R; Song, Min Hyup; Leaird, Daniel E; Weiner, Andrew M

    2011-01-01

    Using only electro-optic modulators, we generate a 41-line 10-GHz Gaussian-shaped optical frequency comb. We use this comb to demonstrate apodized microwave photonic filters with greater than 43-dB sidelobe suppression without the need for a pulse shaper.

  18. Broadband Kerr frequency combs and intracavity soliton dynamics influenced by high-order cavity dispersion

    Wang, Shaofei; Guo, Hairun; Bai, Xuekun;

    2014-01-01

    We numerically investigate the influence of high-order dispersion (HOD) on temporal and spectral characteristics of microresonator-based optical frequency combs. Theoretical analysis based on the moment method associated with numerical simulations are utilized to study the comb evolution dynamics...

  19. MICROBIOLOGICAL COMPARISON BETWEEN HONEY IN JAR AND HONEY IN COMB FOR HUMAN CONSUMPTION

    G. Formato

    2013-02-01

    Full Text Available The Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, during August-July 2007 analyzed, for the microbial aspects, 37 samples of jar honey and 53 samples of honey in comb obtained from 37 farms of Latium Region. In the jar honey there weren’t values up to 1*103 colony-forming unit (CFU/g of bacteria mesophiles, while in the honey in comb it was not up to 2*103 CFU/g. Bacillus cereus was found in 22 samples (41,5% of honey in comb and in 18 samples (48,6% of jar honey; Clostridium perfringens was found in 6 (11,3% samples of honey in comb and in 6 samples (16,2% of jar honey; Clostridium baratii was found in 1 (1,9% sample of honey in comb and in 1 sample (2,7% of jar honey; coagulase-positive staphylococci were found in 4 (11,3% samples of honey in comb and in 4 samples (10,8% of jar honey; Clostridium sordelli was found in 2 samples (3,8% of honey in comb and in 1 sample (2,7% of jar honey. Only 2 samples of honey in comb and 1 sample of jar honey had yeasts up to 1000 CFU/g. Finally, 9 samples (24,3% of jar honey and 16 samples (30,2% of honey in jar were positives for moulds.

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

    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.

  1. Picometer-resolution dual-comb spectroscopy with a free-running fibre laser

    Zhao, Xin; Zhao, Bofeng; Li, Cui; Pan, Yingling; Liu, Ya; Yasui, Takeshi; Zheng, Zheng

    2016-01-01

    Dual-comb spectroscopy utilizes two sets of comb lines with slightly different comb-tooth-spacings, and optical spectral information is acquired by measuring the radio-frequency beat notes between the sets of comb lines. It holds the promise as a real-time, high-resolution analytical spectroscopy tool for a range of important applications. However, the stringent requirement on the coherence between comb lines from two separate lasers and the sophisticated control system to achieve that have confined the technology to the top metrology laboratories. By replacing electronics with the law of physics in lasers, a much simpler, dual-comb spectroscopy scheme is demonstrated here using just one dual-wavelength, passively mode-locked fiber laser. Dual-comb pulses with a repetition-frequency difference determined by the intracavity dispersion are shown to be robust against common-mode cavity drifts and noises. As sufficiently low relative linewidth is maintained between two sets of comb lines, capability to resolve pi...

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

    Pu, Minhao; Ottaviano, Luisa; Semenova, Elizaveta;

    2016-01-01

    The combination of nonlinear and integrated photonics enables Kerr frequency comb generation in stable chip-based microresonators. Such a comb system will revolutionize applications, including multi-wavelength lasers, metrology, and spectroscopy. Aluminum gallium arsenide (AlGaAs) exhibits very h...

  3. Nonlinear Doppler - Free comb-spectroscopy in counter-propagating fields

    Pulkin, S A; Arnautov, V; Uvarova, S V; Savel'eva, S

    2014-01-01

    The method of Doppler - free comb - spectroscopy for dipole transitions was proposed. The calculations for susceptibility spectrum for moving two-level atoms driving by strong counter propagating combs have been done. The used theoretical method based on the Fourier expansion of the components of density matrix on two rows on kv (v-velocity of group of atoms, k-projection of wave vector) and {\\Omega} (frequency between comb components). For testing of validity of this method the direct numerical integration was done. The narrow peaks with homogeneous width arise on the background of Doppler counter. The contrast of these peaks is large for largest amplitudes of comb-components. Power broadening is increasing with increase of field amplitudes. The spectral range of absorption spectrum is determined by the spectral range of comb generator and all homogeneous lines arise simultaneously. The spectral resolution is determined by the width of homogeneously-broadening lines. The physical nature of narrow peaks is in...

  4. Characterization of a DFG comb showing quadratic scaling of the phase noise with frequency.

    Puppe, Thomas; Sell, Alexander; Kliese, Russell; Hoghooghi, Nazanin; Zach, Armin; Kaenders, Wilhelm

    2016-04-15

    We characterize an Er:fiber laser frequency comb that is passively carrier envelope phase-stabilized via difference frequency generation at a wavelength of 1550 nm. A generic method to measure the comb linewidth at different wavelengths is demonstrated. By transferring the properties of a comb line to a cw external cavity diode laser, the phase noise is subsequently measured by tracking the delayed self-heterodyne beat note. This relatively simple characterization method is suitable for a broad range of optical frequencies. Here, it is used to characterize our difference frequency generation (DFG) comb over nearly an optical octave. With repetition-rate stabilization, a radiofrequency reference oscillator limited linewidth is achieved. A lock to an optical reference shows out-of-loop linewidths of the comb at the hertz level. The phase noise measurements are in excellent agreement with the elastic tape model with a fix point at zero frequency. PMID:27082368

  5. Operation of an optically coherent frequency comb outside the metrology lab

    Sinclair, Laura C; Swann, William C; Rieker, Greg B; Hati, Archita; Iwakuni, Kana; Newbury, Nathan R

    2013-01-01

    We demonstrate a self-referenced fiber frequency comb that can operate outside the well-controlled optical laboratory. The frequency comb has residual optical linewidths of < 1 Hz, sub-radian residual optical phase noise, and residual pulse-to-pulse timing jitter of 2.4 - 5 fs, when locked to an optical reference. This fully phase-locked frequency comb has been successfully operated in a moving vehicle with 0.5 g peak accelerations and on a shaker table with a sustained 0.5 g rms integrated acceleration, while retaining its optical coherence and 5-fs-level timing jitter. This frequency comb should enable metrological measurements outside the laboratory with the precision and accuracy that are the hallmarks of comb-based systems. Work of the U.S. government, not subject to copyright

  6. Sex work among men who have sex with men and transgender women in Bogotá.

    Bianchi, Fernanda T; Reisen, Carol A; Zea, Maria Cecilia; Vidal-Ortiz, Salvador; Gonzales, Felisa A; Betancourt, Fabián; Aguilar, Marcela; Poppen, Paul J

    2014-11-01

    This qualitative study examined sex work among internally displaced male and transgender female sex workers in Bogotá, Colombia. Internal displacement has occurred in Colombia as a result of decades of conflict among armed groups and has created large-scale migration from rural to urban areas. Informed by the polymorphous model of sex work, which posits that contextual conditions shape the experience of sex work, we examined three main research questions. The first dealt with how internal displacement was related to the initiation of sex work; the second concerned the effect of agency on sex worker satisfaction; and the third examined how sex work in this context was related to HIV and other risks. Life history interviews were conducted with 26 displaced individuals who had done sex work: 14 were men who have sex with men and 12 were transgender women (natal males). Findings revealed that many participants began doing sex work in the period immediately after displacement, because of a lack of money, housing, and social support. HIV risk was greater during this time due to limited knowledge of HIV and inexperience negotiating safer sex with clients. Other findings indicated that sex workers who exerted more control and choice in the circumstances of their work reported greater satisfaction. In addition, we found that although many sex workers insisted on condom use with clients, several noted that they would sometimes have unprotected sex for additional money. Specific characteristics affecting the experience of sex work among the transgender women were also discussed. PMID:24464550

  7. Balance of the Sexes: Addressing Sex Differences in Preclinical Research

    Zakiniaeiz, Yasmin; Cosgrove, Kelly P.; Potenza, Marc N.; Mazure, Carolyn M.

    2016-01-01

    Preclinical research is fundamental for the advancement of biomedical sciences and enhancing healthcare. Considering sex differences in all studies throughout the entire biomedical research pipeline is necessary to adequately inform clinical research and improve health outcomes. However, there is a paucity of information to date on sex differences in preclinical work. As of 2009, most (about 80 percent) rodent studies across 10 fields of biology were still conducted with only male animals. In 2016, the National Institutes of Health implemented a policy aimed to address this concern by requiring the consideration of sex as a biological variable in preclinical research grant applications. This perspective piece aims to (1) provide a brief history of female inclusion in biomedical research, (2) describe the importance of studying sex differences, (3) explain possible reasons for opposition of female inclusion, and (4) present potential additional solutions to reduce sex bias in preclinical research. PMID:27354851

  8. When Sex Is Painful

    ... AQ FREQUENTLY ASKED QUESTIONS GYNECOLOGIC PROBLEMS FAQ020 When Sex Is Painful • How common is painful sex? • What causes pain during sex? • Where is pain during sex felt? • When should ...

  9. Sex during Pregnancy

    ... Story" 5 Things to Know About Zika & Pregnancy Sex During Pregnancy KidsHealth > For Parents > Sex During Pregnancy ... satisfying and safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during ...

  10. Lévy processes on a generalized fractal comb

    Sandev, Trifce; Iomin, Alexander; Méndez, Vicenç

    2016-09-01

    Comb geometry, constituted of a backbone and fingers, is one of the most simple paradigm of a two-dimensional structure, where anomalous diffusion can be realized in the framework of Markov processes. However, the intrinsic properties of the structure can destroy this Markovian transport. These effects can be described by the memory and spatial kernels. In particular, the fractal structure of the fingers, which is controlled by the spatial kernel in both the real and the Fourier spaces, leads to the Lévy processes (Lévy flights) and superdiffusion. This generalization of the fractional diffusion is described by the Riesz space fractional derivative. In the framework of this generalized fractal comb model, Lévy processes are considered, and exact solutions for the probability distribution functions are obtained in terms of the Fox H-function for a variety of the memory kernels, and the rate of the superdiffusive spreading is studied by calculating the fractional moments. For a special form of the memory kernels, we also observed a competition between long rests and long jumps. Finally, we considered the fractal structure of the fingers controlled by a Weierstrass function, which leads to the power-law kernel in the Fourier space. This is a special case, when the second moment exists for superdiffusion in this competition between long rests and long jumps.

  11. Scanning micro-resonator direct-comb absolute spectroscopy

    Gambetta, Alessio; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-01-01

    Direct optical frequency Comb Spectroscopy (DCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DCS approach based on a scanning Fabry-Perot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from XUV to THz. An application to high-precision spectroscopy of acetylene at 1.54 um is presented, demonstrating frequency resolution as low as 20 MHz with a single-scan optical bandwidth up to 1 THz in 20-ms measurement time and a noise-equ...

  12. Comb-referenced laser distance interferometer for industrial nanotechnology.

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

    2016-01-01

    A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10(-10). The uncertainty is estimated to be in a 10(-8) level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10(-10) level in vacuum. PMID:27558016

  13. Development of femtosecond optical frequency comb laser tracker

    Yang, Ju-qing; Zhou, Wei-hu; Dong, Deng-feng; Zhang, Zi-li; Lao, Da-bao; Ji, Rong-yi; Wang, Da-yong

    2016-01-01

    A new type femtosecond laser tracker is one high precision measurement instrument with urgent need in science research region and industrial manufacture field. This paper focuses on the operational principle and the structure development of the femtosecond laser tracer, and the method of error compensation as well. The system modules were studied and constructed. The femtosecond frequency comb module was firstly analyzed and developed. The femtosecond laser frequency comb performed perfectly high precise distance measurement for laser tracker. The experimental result showed that the stability of repetition rate reached 3.0×10-12@1s and the stability of carrier envelop offset reached 1.0×10-10@1s. The initial experiment showed that measurement error was less than 1ppm. Later the error compensation module was introduced, and the optoelectronic aiming and tracking control module was built. The actual test result showed that the stability of miss distance was better than 2.0 μm, the tracking speed could reach 2m/s.

  14. Comb-referenced laser distance interferometer for industrial nanotechnology

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

    2016-01-01

    A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10−10. The uncertainty is estimated to be in a 10−8 level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10−10 level in vacuum. PMID:27558016

  15. A Study of the Effect of the Fringe Fields on the Electrostatic Force in Vertical Comb Drives

    Else Gallagher

    2014-10-01

    Full Text Available The equation that describes the relationship between the applied voltage and the resulting electrostatic force within comb drives is often used to assist in choosing the dimensions for their design. This paper re-examines how some of these dimensions—particularly the cross-sectional dimensions of the comb teeth—affect this relationship in vertical comb drives. The electrostatic forces in several vertical comb drives fabricated for this study were measured and compared to predictions made with four different mathematical models in order to explore the amount of complexity required within a model to accurately predict the electrostatic forces in the comb drives.

  16. Damages to the Black Sea, Caspian Sea and Baltic Sea by the invader comb jelly Mnemiopsis leidyi

    Elif Eker Develi

    2011-10-01

    Full Text Available In the present study changes in ecosystems of the Black Sea, Caspian Sea and Baltic Sea after the invasion of ctenophore Mnemiopsis leidyi were investigated. Excessive increase in plant plankton as a result of antrophogenic eutrophication leads to a shift in mesozooplankton com¬position, which is the main food item of these comb jellies. For instance, while some mesozoo¬plankton species disappeared from the environment or substantially decreased in number, some others increased in quantity. These changes in food chain may promote the rise of jellyfishes rather than fish in the environment. In addition, decrease in planktivorous fish abundance as a consequence of overfishing also triggers the increase of newly introduced comb jellies, which were possibly introduced via ballast waters of ships, in the ecosystem. Increase in abundance of M. leidyi, which compete with planktivorous fishes (anchovy, Engraulis encrasicolus ponticus in the Black Sea, kilka, Clupeonella spp. in the Caspian Sea for their food, causes to decrease of planktivorous fish stocks which have already been vulnerable due to overfishing. Another reason for successfully adaption of M. leidyi to its new ecosystems could be linked to global warming which provides favourable temperature ranges for reproduction and growth of this ctenophore. Although there are still many debates related to possible negative effects, one of the ways to reduce harmful impacts of invaders might be the transport of natural predators of these invaders to the new ecosystems of invaders. For example, it was reported that the abun¬dance of Mnemiopsis leidyi decreased to very low levels during 1999-2004 in the Black Sea following the introduction of another comb jelly, Beroe ovata, which feed on this ctenophore.

  17. Steering optical comb frequency by rotating polarization state

    Zhang, Y; Zhang, X F; Zhang, L; Han, W; Guo, W; Jiang, H; Zhang, S

    2016-01-01

    Optical frequency combs, with precise control of repetition rate and carrier-envelope-offset frequency, have revolutionized many fields, such as fine optical spectroscopy, optical frequency standards, ultra-fast science research, ultra-stable microwave generation and precise ranging measurement. However, existing high bandwidth frequency control methods have small dynamic range, requiring complex hybrid control techniques. To overcome this limitation, we develop a new approach, where a home-made intra-cavity electro-optic modulator tunes polarization state of laser signal rather than only optical length of the cavity, to steer frequencies of a nonlinear-polarization-rotation mode-locked laser. By taking advantage of birefringence of the whole cavity, this approach results in not only broadband but also relative large-dynamic frequency control. Experimental results show that frequency control dynamic range increase at least one order in comparison with the traditional intra-cavity electro-optic modulator techn...

  18. Direct frequency comb two-photon laser cooling and trapping

    Jayich, Andrew; Long, Xueping; Campbell, Wesley C.

    2016-05-01

    Generating and manipulating high energy photons for spectroscopy on electric dipole transitions of atoms and molecules with deeply bound valence electrons is difficult. Further, laser cooling of such species is even more challenging for lack of laser power. A possible solution is to drive two-photon transitions. This may alleviate the photon energy problem and open the door to cold, trapped samples of highly desirable species with tightly bound electrons. We perform a proof of principle experiment with rubidium by driving a two-photon transition with an optical frequency comb. We perform optical cooling and extend this technique to trapping, where we are able to make a magneto-optical trap in one dimension. This work is supported by the National Science Foundation CAREER program.

  19. A Coherent Raman Oscillator Pumped by a Frequency Comb

    Pe'er, Avi

    2014-01-01

    Free induction decay is the coherent emission of light that follows the excitation of a medium by a short pulse. During the coherence time of the medium ($T_2$), all atoms/molecules oscillate 'in unison', forming a macroscopic dipole that emits light as a large coherent antenna, 'broadcasting' information on the quantum state of the atoms/molecules and its dynamical evolution. We present an optical oscillator, where the coherent dipole emission from a dynamical wave-packet, is amplified beyond the lasing threshold. By placing a molecular medium in an optical cavity that is synchronously pumped by a frequency comb laser, emission from the excitation of one pump pulse can return to the medium with subsequent pump pulses, allowing stimulated amplification. When threshold is crossed, a broadband coherent oscillation is achieved, bearing information on the coherent wave-packet dynamics inside the medium. We analyze theoretically this coherent Raman oscillator and simulate thoroughly it's dynamics under most realis...

  20. Examination of Replication Dynamics in Fragile Sites Through Molecular Combing

    Chumki, Shahana Ahmed

    2015-08-01

    Full Text Available Chromosomal fragile sites are specific loci that exhibit instability visible as gaps and breaks on the chromosome following inhibition of DNA synthesis and are generally categorized into two main classes: rare fragile sites (RFSs and common fragile sites (CFSs. Under standard conditions, CFSs are typically stable but are prone to breakage in cells subjected to replication stress. In recent years, their role in the generation of gross chromosome rearrangements has become increasingly evident, and fragile sites have now connected to chromosome instability in cancer cells. The connection between CFSs and cancer thus highlights the importance of the regulation of DNA replication to prevent cancer development. The study of fragile sites in the yeast model organism has provided insight into the mechanisms that lead to breakage and genome instability. Through the process of molecular combing, replication dynamics can be observed at fragile sites to further understand the consequence of replication stress on DNA damage.

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

    Augustine, Starrlight; Jaspers, Cornelia; Kooijman, Sebastiaan A. L.M.;

    2014-01-01

    Mnemiopsis leidyi is an invasive comb jellywhich has successfully established itself in European seas. The species is known to produce spectacular blooms yet it is holoplanktonic and not much is known about its population dynamics in between. One way to gain insight on how M. leidyi might survive...... between blooms and how it can bloom so fast is to study how the metabolism of this species actually responds to environmental changes in food and temperature over its different life-stages. To this end we combined modelling and data analysis to study the energy budget of M. leidyi over its full life....... Intriguingly, the onset of the acceleration appears to be delayed and the data do not yet exist which allows determining what actually triggers it. It is hypothesised that this delay confers a lot of metabolic flexibility by controlling generation time. We compared the DEB model parameters for this species...

  2. Charge-optimized many-body (COMB) potential for zirconium

    Noordhoek, Mark J.; Liang, Tao; Lu, Zizhe; Shan, Tzu-Ray; Sinnott, Susan B.; Phillpot, Simon R.

    2013-10-01

    An interatomic potential for zirconium is developed within the charge-optimized many-body (COMB) formalism. The potential correctly predicts the hexagonal close-packed (HCP) structure as the ground state with cohesive energy, lattice parameters, and elastic constants matching experiment well. The most stable interstitial position is the basal octahedral followed by basal split, in agreement with recent first principles calculations. Stacking fault energies within the prism and basal planes satisfactorily match first principles calculations. A tensile test using nanocrystalline zirconium exhibits both prismatic {1 0 1bar 0} slip and pyramidal {1 1 2bar 2} slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

  3. High-Resolution Displacement Measurement using a Femtosecond Frequency Comb

    Číp, Ondřej; Šmíd, Radek; Čížek, Martin; Mikel, Břetislav; Buchta, Zdeněk; Lazar, Josef

    Düsseldorf: VDI Verlag GmbH, 2011, s. 313-319. ISBN 978-3-18-092156-3. ISSN 0083-5560. [IMEKO Symposium - Laser Metrology for Precision Measurement and Inspection in Industry 2011 /10./. Braunschweig (DE), 12.09.2011-14.09.2011] R&D Projects: GA ČR GP102/09/P293; GA ČR GPP102/11/P819; GA ČR GAP102/10/1813; GA MŠk ED0017/01/01; GA MŠk(CZ) LC06007; GA ČR GP102/09/P630 Institutional research plan: CEZ:AV0Z20650511 Keywords : Fabry-Perot cavity * femtosecond frequency comb Subject RIV: BH - Optics, Masers, Lasers

  4. Direct Frequency Comb Measurement of OD + CO -> DOCO Kinetics

    Bjork, Bryce J; Heckl, Oliver H; Changala, P Bryan; Spaun, Ben; Heu, Paula; Follman, David; Deutsch, Christoph; Cole, Garrett D; Aspelmeyer, Markus; Okumura, Mitchio; Ye, Jun

    2016-01-01

    The kinetics of the OH + CO reaction, fundamental to both atmospheric and combustion chemistry, are complex due to the formation of the HOCO intermediate. Despite extensive studies on this reaction, HOCO has not been observed at thermal reaction conditions. Exploiting the sensitive, broadband, and high-resolution capabilities of time-resolved cavity-enhanced direct frequency comb spectroscopy, we observe OD + CO reaction kinetics with the detection of stabilized trans-DOCO, the deuterated analogue of trans-HOCO, and its yield. By simultaneously measuring the time-dependent concentrations of both trans-DOCO and OD species, we observe unambiguous low-pressure termolecular dependence on the reaction rate coefficients for both N2 and CO bath gases. These results confirm the HOCO formation mechanism and quantify its yield.

  5. Ptychographic hyperspectral spectromicroscopy with an extreme ultraviolet high harmonic comb

    Zhang, Bosheng; Seaberg, Matthew H; Shanblatt, Elisabeth R; Porter, Christina L; Karl,, Robert; Mancuso, Christopher A; Kapteyn, Henry C; Murnane, Margaret M; Adams, Daniel E

    2016-01-01

    We demonstrate a new scheme of spectromicroscopy in the extreme ultraviolet (EUV) spectral range, where the spectral response of the sample at different wavelengths is imaged simultaneously. It is enabled by applying ptychographical information multiplexing (PIM) to a tabletop EUV source based on high harmonic generation, where four spectrally narrow harmonics near 30 nm form a spectral comb structure. Extending PIM from previously demonstrated visible wavelengths to the EUV/X-ray wavelengths promises much higher spatial resolution and more powerful spectral contrast mechanism, making PIM an attractive spectromicroscopy method in both the microscopy and the spectroscopy aspects. Besides the sample, the multicolor EUV beam is also imaged in situ, making our method a powerful beam characterization technique. No hardware is used to separate or narrow down the wavelengths, leading to efficient use of the EUV radiation.

  6. Coherent Raman spectro-imaging with laser frequency combs

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

    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.

  8. Origin and stability of dark pulse Kerr combs in normal dispersion resonators.

    Parra-Rivas, Pedro; Gomila, Damià; Knobloch, Edgar; Coen, Stéphane; Gelens, Lendert

    2016-06-01

    We analyze dark pulse Kerr frequency combs in optical resonators with normal group-velocity dispersion using the Lugiato-Lefever model. We show that in the time domain the combs correspond to interlocked switching waves between the upper and lower homogeneous states, and explain how this fact accounts for many of their experimentally observed properties. Modulational instability does not play any role in their existence. We provide a detailed map indicating for which parameters stable dark pulse Kerr combs can be found, and how they are destabilized for increasing values of frequency detuning. PMID:27244374

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

    Phillips, D.F.; Glenday, A. G.; Sasselov, D.; Szentgyorgyi, A.; Walsworth, R.L.; Li, C. -H.; Cramer, C; Furesz, G.; Chang, G; Benedick, A. J.; Chen, L.-J.; Kärtner, F. X.; Korzennik, S.

    2012-01-01

    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 v...

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

    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

  11. A direct frequency comb for two-photon transition spectroscopy in a cesium vapor

    Zhang Yi-Chi; Wu Ji-Zhou; Li Yu-Qing; Jin Li; Ma Jie; Wang Li-Rong; Zhao Yan-Ting; Xiao Lian-Tuan; Jia Suo-Tang

    2012-01-01

    A phase-stabilized femtosecond frequency comb is used to measure high-resolution spectra of two-photon transition 62S1/2-62P1/2,3/2-82S1/2 in a cesium vapor.The broadband laser output from a femtosecond frequency comb is split into counter-propagating parts,shaped in an original way,and focused into a room-temperature cesium vapor.We obtain high-resolution two-photon spectroscopy by scanning the repetition rate of femtosecond frequency comb,and through absolute frequency measurements.

  12. Mid-Infrared Optical Frequency Combs based on Difference Frequency Generation for Molecular Spectroscopy

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

    2015-01-01

    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.

  13. Combing non-epitaxially grown nanowires for large-area electronic devices

    A facile route for aligning randomly oriented nanowires synthesized by a vapor–liquid–solid method for the fabrication of nanoelectronic devices was achieved using a polymer combing technique. By controlling the Young’s modulus of the polymer combs, van der Waals interactions and shearing forces between the combs and nanowires can be manipulated and thus the nanowire density and alignment can be controlled. Using the proposed method, field-effect transistors were directly fabricated on as-grown substrates after aligning the nanowires, thereby demonstrating the feasibility of the scheme for the production of nanoelectronic devices. (paper)

  14. Resonance interaction between cold Rb atoms and a frequency comb

    Full text: A long life time of atoms in a magneto-optical trap (MOT) makes it a powerful tool to study interactions with optical fields processing small cross sections. Since the life time in MOT can reach a few seconds, even processes with characteristic rates of 1 -s1 can be easily analyzed if they result in losses of trapped atoms. We have investigated the interaction of laser-cooled 87Rb atoms in a MOT with a femtosecond (fs) laser radiation in the spectral region 760-820 nm. We show that in a wide range of average intensities of the fs laser field (2) the dominating process is the cascade ionization. In this case the femtosecond radiation interacts with the atomic ensemble both as spectrally-narrow components (a frequency comb) and as a powerful ionizing laser field. Atoms excited by a single mode of a frequency comb from the 5P3/2(F = 3) to the 5D5/2(F = 2, 3, 4) hyperfine sublevels are consequently ionized by a full power of the fs laser from the 5D level to the continuum. By tuning the repetition rate frep of the fs laser we observe the periodic spectrum in the MOT luminescence at 780 nm (the cooling transition) reproducing the hyperfine structure of the 5D level. We have quantitatively analyzed the ionization of the 5D5/2 level by monitoring the loading rate of the MOT at different powers of the fs laser radiation using an auxiliary cw laser locked to the 5P3/2(F = 3) → 5D5/2(F = 4) at 776 nm. A sensitive method allowing accurate determination of the 5/2 5D level population is developed. (author)

  15. Same sex families and children

    Mršević Zorica

    2009-01-01

    Full Text Available Introduction comprises the information on two main forms of same sex families, civic partnership (same sex partnership and same sex marriage. Countries and various status modalities of legal regulations are mentioned. The main part of the text is dedicated to presentation of the findings of the most recent research on various aspects regarding children of same sex partnerships. It comprises presentations grouped in four main chapters: acceptance of same sex partnerships, acceptance of legal recognition of the same sex partnerships, family plans of homosexual teenagers, and raising children within and by the same sex partners. Also the real life cases mirroring legal changes through their life destinies are presented, such is e.g. the Irish way to legalization of the same sex partnerships. In addition, a love story of two women crowned by giving birth of their four children is mentioned. Reasons against and negative reactions the author puts under the title Homophobia. In the Concluding remarks, the author presents the most recent examples of legal changes happened in Norway, Ecuador, and in the American states of California and Connecticut. It was also stated that in European countries of low birth rate, the same sex families are inevitably identified as one of demographically valuable source of creating and raising children, which is worthy to be supported, rather than being hindered without reason and discriminated. Although different than a model of heterosexual family, same sex partnerships neither are harrowing to traditional family values, nor reflex of any kind of promiscuous, antisocial behavior, avoidance of parenthood, and negation of family. Quite opposite, these families are an outcome of endeavors of homosexuals not to be deprived of family, parenthood and all of other values of stabile, monogamous, emotional/sexual socially accepted and legally recognized and regulated conventional family. .

  16. Origin of Sex Revisited

    Santos, Mauro; Zintzaras, Elias; Szathmáry, Eörs

    2003-10-01

    Why did sex ever arise in the first place? Why it does not disappear in view of the greater efficiency of asexuals? These are clearly two different questions, and we suggest here that the solution for the origin of sex does not necessarily come from theoretical considerations based on currently existing genetic systems. Thus, while we agree with a number of authors in that the emergence of sex (understood as the exchange of genetic material between genomes) is deeply rooted in the origin of life and happened during the very early stages in the transition from individual genes (`replicators') to bacteria-like cells (`reproducers'), we challenge the idea that recombinational repair was the major selective force for the emergence of sex. Taking the stochastic corrector model as a starting point, we provide arguments that question the putative costs of redundancy in primitive protocells. In addition, if genes that cause intragenomic conflict (i.e., parasites) are taken into account, it is certainly wrong to suggest that cellular fusion would be beneficial at the population level (although this strong claim needs some qualifications). However, when a continuous input of deleterious mutations that impair the fitness of the protocell as a whole is considered in the model (in the realistic range in which stable mutant distributions of quasi-species within compartments are established), there are circumstances when sex could be beneficial as a side effect of the dynamic equilibrium between cellular fusion-mutation-selection. The scenario we have explored numerically is fully consistent with the idea that the universal ancestor was not a discrete entity but an ensemble of proto-organisms that exchanged much genetic information.

  17. TREATMENT OF 50 CASES OF MIGRAINE BY SCALP ACUPUNCTURE COMBINED WITH ELECTRO-COMB STIMULATION

    CAO Renjun; SHI Qing

    2002-01-01

    @@ The authors of the present paper treated 50cases of migraine by scalp acupuncture plus electro-comb stimulation from 1995 to 1999 and achieved satisfactory therapeutic effects. It is reported as follows.

  18. Photonic chip based optical frequency comb using soliton induced Cherenkov radiation

    Brasch, Victor; Geiselmann, Michael; Lihachev, Grigoriy; Pfeiffer, Martin H P; Gorodetsky, Michael L; Kippenberg, Tobias J

    2014-01-01

    By continuous wave pumping of a dispersion engineered, planar silicon nitride microresonator, continuously circulating, sub-30fs short temporal dissipative solitons are generated, that correspond to pulses of 6 optical cycles and constitute a coherent optical frequency comb in the spectral domain. Emission of soliton induced Cherenkov radiation caused by higher order dispersion broadens the spectral bandwidth to 2/3 of an octave, sufficient for self referencing, in excellent agreement with recent theoretical predictions and the broadest coherent microresonator frequency comb generated to date. The ability to preserve coherence over a broad spectral bandwidth using soliton induced Cherenkov radiation marks a critical milestone in the development of planar optical frequency combs, enabling on one hand application in e.g. coherent communications, broadband dual comb spectroscopy and Raman spectral imaging, while on the other hand significantly relaxing dispersion requirements for broadband microresonator frequen...

  19. Microwave and RF Applications for Micro-resonator based Frequency Combs

    Nguyen, Thach G; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

    2015-01-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contr...

  20. Intracavity characterization of micro-comb generation in the single-soliton regime

    Wang, Pei-Hsun; Xuan, Yi; Xue, Xiaoxiao; Bao, Chengying; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Soliton formation in on-chip micro-comb generation balances cavity dispersion and nonlinearity and allows coherent, low-noise comb operation. We study the intracavity waveform of an on-chip microcavity soliton in a silicon nitride microresonator configured with a drop port. Whereas combs measured at the through port are accompanied by a very strong pump line which accounts for >99% of the output power, our experiments reveal that inside the microcavity, most of the power is in the soliton. Time-domain measurements performed at the drop port provide information that directly reflects the intracavity field. Data confirm a train of bright, close to bandwidth-limited pulses, accompanied by a weak continuous wave (CW) background with a small phase shift relative to the comb.

  1. Quantum Correlations, Entanglement, and Squeezed States of Light in Kerr Optical Frequency Combs

    Chembo, Yanne K

    2014-01-01

    The dynamical behavior of Kerr optical frequency combs is very well understood today from the perspective of the semi-classical approximation. In this article, we provide a theoretical understanding of the phenomena of quantum correlations, multimode entanglement and squeezed states of light that can occur in these frequency combs when quantum noise is accounted for. We prove that for all stationary spatio-temporal patterns, the side-modes that are symmetrical relatively to the central (pumped) mode in the frequency domain display quantum correlations that can lead to squeezed states of light under some optimal conditions that are analytically determined. We show that these quantum correlations can persist regardless the dynamical state of the system (rolls or solitons), regardless of the spectral extension of the comb (number sidemodes), and regardless of the dispersion regime (normal or anomalous). We study with particular emphasis the two principal architectures for Kerr comb generation, namely the add-thr...

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

    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.

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

    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.

  4. Generation of high-frequency combs locked to atomic resonances by quantum phase modulation

    Liu, Zuoye; Cavaletto, Stefano M; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas

    2013-01-01

    A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.

  5. Closed-form solutions and scaling laws for Kerr frequency combs.

    Renninger, William H; Rakich, Peter T

    2016-01-01

    A single closed-form analytical solution of the driven nonlinear Schrödinger equation is developed, reproducing a large class of the behaviors in Kerr-comb systems, including bright-solitons, dark-solitons, and a large class of periodic wavetrains. From this analytical framework, a Kerr-comb area theorem and a pump-detuning relation are developed, providing new insights into soliton- and wavetrain-based combs along with concrete design guidelines for both. This new area theorem reveals significant deviation from the conventional soliton area theorem, which is crucial to understanding cavity solitons in certain limits. Moreover, these closed-form solutions represent the first step towards an analytical framework for wavetrain formation, and reveal new parameter regimes for enhanced Kerr-comb performance. PMID:27108810

  6. Supercontinuum Comb Generation Using Optical Pulse Synthesizer and Highly Nonlinear Dispersion-Shifted Fiber

    Choi, Samuel; Tamura, Naoyuki; Kashiwagi, Ken; Shioda, Tatsutoshi; Tanaka, Yosuke; Kurokawa, Takashi

    2009-09-01

    We propose a novel supercontinuum (SC) generation technology using an optical pulse synthesizer and highly nonlinear dispersion-shifted fiber. The optical pulse synthesizer enables us to reshape seed pulses optimized for broadband SC generation. 25.0 and 12.5 GHz SC combs were successfully generated by propagating synthesized seed pulses in the highly nonlinear fiber. We investigated how seed pulse conditions including shape, peak power, repetition rate, and center wavelength affect SC spectral bandwidth. We also evaluated interferometric signal waveforms from a Michelson interferometer using the generated SC comb as the light source. Interferometric peak width improved to 35.5 µm when peak power reached 7.9 W for the Gaussian pulse-based SC comb. Numerical simulation results almost agreed with experimental results. The difference between SC combs generated from Gaussian and sech2 pulses was confirmed by the simulations.

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

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

    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 coe...

  8. Evaluation and modelling of integral capacitors produced by interdigitated comb electrodes

    Leandro Alfredo Ramajo; Damian Enrique Ramajo; María Marta Reboredo; Diego Hernan Santiago; Miriam Susana Castro

    2008-01-01

    Integral capacitors (IC) of one or two-layer printed wiring board (PWB) circuits were produced using comb electrodes fixtures and dielectric composites as the inter-electrode material. ICs were fabricated at laboratory scale, using copper comb electrodes and BaTiO3-epoxy composite materials deposited on a glass-Epoxy FR4 board. They were experimentally tested in order to obtain their electrical response. Furthermore, ICs behaviour was modelled through 2-dimensional models applying finite elem...

  9. On the Polyphase Decomposition for Design of Generalized Comb Decimation Filters

    Laddomada, Massimiliano

    2007-01-01

    Generalized comb filters (GCFs) are efficient anti-aliasing decimation filters with improved selectivity and quantization noise (QN) rejection performance around the so called folding bands with respect to classical comb filters. In this paper, we address the design of GCF filters by proposing an efficient partial polyphase architecture with the aim to reduce the data rate as much as possible after the Sigma-Delta A/D conversion. We propose a mathematical framework in order to completely char...

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

    Mohannad Y. Elsayed; Frederic Nabki; 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 ...

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

    Pang, Xiaodan; Beltrán, Marta; Sánchez, José;

    2013-01-01

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

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

    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

  13. Flexible Optical-Comb-Based Multi-Wavelength Conversion for Optical Switching and Multicast

    Vilar Mateo, Ruth; Ramos Pascual, Francisco; Marques, C.; Nogueira, Regina Isabel; Teixeira, A; Llorente Sáez, Roberto; RAMOS, FRAN JOSE

    2011-01-01

    Experimental results on multi-wavelength conversion based on optical comb generation for optical switching and multicast applications are presented. All the newly generated channels showed good performance with clear and open eye diagrams. FP7-ICT- 2009-4-249142 FP7-ICT-2007-1- 216863 Vilar Mateo, R.; Ramos Pascual, F.; Marques, C.; Nogueira, RI.; Teixeira, A.; Llorente Sáez, R.; Ramos, FJ. (2011). Flexible Optical-Comb-Based Multi-Wavelength Conversion for Optical Switch...

  14. Sex-linked dominant

    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 ...

  15. Sex-linked dominant

    Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant ... can be either an autosomal chromosome or a sex chromosome. It also depends on whether the trait ...

  16. Sex-differences in heritability of BMI

    Schousboe, K; Willemsen, G; Kyvik, Kirsten Ohm;

    2003-01-01

    pairs (including opposite sex pairs) aged 20-29 and 30-39 from eight different twin registries participating in the GenomEUtwin project. Quantitative genetic analyses were conducted and sex differences were explored. Variation in BMI was greater for women than for men, and in both sexes was primarily...... explained by additive genetic variance in all countries. Sex differences in the variance components were consistently significant. Results from analyses of opposite sex pairs also showed evidence of sex-specific genetic effects suggesting there may be some differences between men and women in the genetic...... factors that influence variation in BMI. These results encourage the continued search for genes of importance to the body composition and the development of obesity. Furthermore, they suggest that strategies to identify predisposing genes may benefit from taking into account potential sex specific effects....

  17. A stable multi-wavelength PM-EDF laser based on a nonlinear amplifying loop mirror and a TCF comb filter

    Zou, Hui; Lou, Shuqin; Su, Wei; Han, Bolin

    2014-01-01

    A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) ring cavity laser employing a twin-core fiber (TCF) comb filter and a nonlinear amplifying loop mirror (NALM) is proposed and demonstrated. By appropriately adjusting the polarization controllers, the NALM as an amplitude equalizer can effectively reduce the mode competition caused by the homogeneous broadening gain medium in the PM-EDF. Under 150 mW pump power, up to 26 wavelength outputs within a 3 dB bandwidth are achieved and their signal-to-noise ratio (SNR) is 39.5 dB. Besides, the TCF comb filter is experimentally fabricated using a length of 0.78 m TCF spliced between two segments of the single-mode fiber. The transmission spectra of the filter in experimental measurements are in accord with the results of theoretical analysis, and its wavelength spacing is 0.29 nm. Meanwhile, the power fluctuation and wavelength shift are within 0.1 dB and 0.02 nm, respectively. The experimental results indicate that the proposed multi-wavelength fiber laser performs with high stability at room temperature. In addition, the multi-wavelength laser with the TCF comb filter can offer more wavelengths in a 3 dB spectral range and higher SNR than one using a Sagnac loop filter, and the length of the filter is also reduced by more than six times.

  18. A stable multi-wavelength PM-EDF laser based on a nonlinear amplifying loop mirror and a TCF comb filter

    A stable multi-wavelength polarization-maintaining erbium-doped fiber (PM-EDF) ring cavity laser employing a twin-core fiber (TCF) comb filter and a nonlinear amplifying loop mirror (NALM) is proposed and demonstrated. By appropriately adjusting the polarization controllers, the NALM as an amplitude equalizer can effectively reduce the mode competition caused by the homogeneous broadening gain medium in the PM-EDF. Under 150 mW pump power, up to 26 wavelength outputs within a 3 dB bandwidth are achieved and their signal-to-noise ratio (SNR) is 39.5 dB. Besides, the TCF comb filter is experimentally fabricated using a length of 0.78 m TCF spliced between two segments of the single-mode fiber. The transmission spectra of the filter in experimental measurements are in accord with the results of theoretical analysis, and its wavelength spacing is 0.29 nm. Meanwhile, the power fluctuation and wavelength shift are within 0.1 dB and 0.02 nm, respectively. The experimental results indicate that the proposed multi-wavelength fiber laser performs with high stability at room temperature. In addition, the multi-wavelength laser with the TCF comb filter can offer more wavelengths in a 3 dB spectral range and higher SNR than one using a Sagnac loop filter, and the length of the filter is also reduced by more than six times. (paper)

  19. Walk-Off-Induced Modulation Instability, Temporal Pattern Formation, and Frequency Comb Generation in Cavity-Enhanced Second-Harmonic Generation

    Leo, F.; Hansson, T.; Ricciardi, I.; De Rosa, M.; Coen, S.; Wabnitz, S.; Erkintalo, M.

    2016-01-01

    We derive a time-domain mean-field equation to model the full temporal and spectral dynamics of light in singly resonant cavity-enhanced second-harmonic generation systems. We show that the temporal walk-off between the fundamental and the second-harmonic fields plays a decisive role under realistic conditions, giving rise to rich, previously unidentified nonlinear behavior. Through linear stability analysis and numerical simulations, we discover a new kind of quadratic modulation instability which leads to the formation of optical frequency combs and associated time-domain dissipative structures. Our numerical simulations show excellent agreement with recent experimental observations of frequency combs in quadratic nonlinear media [Phys. Rev. A 91, 063839 (2015)]. Thus, in addition to unveiling a new, experimentally accessible regime of nonlinear dynamics, our work enables predictive modeling of frequency comb generation in cavity-enhanced second-harmonic generation systems. We expect our findings to have wide impact on the study of temporal and spectral dynamics in a diverse range of dispersive, quadratically nonlinear resonators.

  20. Influence of Wheat-Milled Products and Their Additive Blends on Pasta Dough Rheological, Microstructure, and Product Quality Characteristics

    B. Dhiraj

    2013-01-01

    Full Text Available This study is aimed to assess the suitability of T. aestivum wheat milled products and its combinations with T. durum semolina with additives such as ascorbic acid, vital gluten and HPMC (Hydroxypropyl methyl cellulose for pasta processing quality characteristics such as pasta dough rheology, microstructure, cooking quality, and sensory evaluation. Rheological studies showed maximum dough stability in Comb1 (T. aestivum wheat flour and semolina. Colour and cooking quality of Comb2 (T. durum semolina and T. aestivum wheat flour and Comb3 (T. aestivum wheat semolina and T. durum semolina were comparable with control. Pasting results indicated that T. aestivum semolina gave the lowest onset gelatinization temperature (66.9°C but the highest peak viscosity (1.053 BU. Starch release was maximum in Comb1 (53.45% when compared with control (44.9% as also proved by microstructure studies. Firmness was seen to be slightly high in Comb3 (2.430 N when compared with control (2.304 N, and sensory evaluations were also in the acceptable range for the same. The present study concludes that Comb3 comprising 50% T. durum semolina and 50% T. aestivum refined wheat flour with additives would be optimal alternate for 100% T. durum semolina for production of financially viable pasta.

  1. Precision spectroscopy with a frequency-comb-calibrated solar spectrograph

    Doerr, H.-P.

    2015-06-01

    The measurement of the velocity field of the plasma at the solar surface is a standard diagnostic tool in observational solar physics. Detailed information about the energy transport as well as on the stratification of temperature, pressure and magnetic fields in the solar atmosphere are encoded in Doppler shifts and in the precise shape of the spectral lines. The available instruments deliver data of excellent quality and precision. However, absolute wavelength calibration in solar spectroscopy was so far mostly limited to indirect methods and in general suffers from large systematic uncertainties of the order of 100 m/s. During the course of this thesis, a novel wavelength calibration system based on a laser frequency comb was deployed to the solar Vacuum Tower Telescope (VTT), Tenerife, with the goal of enabling highly accurate solar wavelength measurements at the level of 1 m/s on an absolute scale. The frequency comb was developed in a collaboration between the Kiepenheuer-Institute for Solar Physics, Freiburg, Germany and the Max Planck Institute for Quantum Optics, Garching, Germany. The efforts cumulated in the new prototype instrument LARS (Lars is an Absolute Reference Spectrograph) for solar precision spectroscopy which is in preliminary scientific operation since~2013. The instrument is based on the high-resolution echelle spectrograph of the VTT for which feed optics based on single-mode optical fibres were developed for this project. The setup routinely achieves an absolute calibration accuracy of 60 cm/s and a repeatability of 2.5 cm/s. An unprecedented repeatability of only 0.32 cm/s could be demonstrated with a differential calibration scheme. In combination with the high spectral resolving power of the spectrograph of 7x10^5 and virtually absent internal scattered light, LARS provides a spectral purity and fidelity that previously was the domain of Fourier-transform spectrometers only. The instrument therefore provides unique capabilities for

  2. On-chip frequency comb generation at visible wavelengths via simultaneous second- and third-order optical nonlinearities.

    Miller, Steven; Luke, Kevin; Okawachi, Yoshitomo; Cardenas, Jaime; Gaeta, Alexander L; Lipson, Michal

    2014-11-01

    Microresonator-based frequency comb generation at or near visible wavelengths would enable applications in precise optical clocks, frequency metrology, and biomedical imaging. Comb generation in the visible has been limited by strong material dispersion and loss at short wavelengths, and only very narrowband comb generation has reached below 800 nm. We use the second-order optical nonlinearity in an integrated high-Q silicon nitride ring resonator cavity to convert a near-infrared frequency comb into the visible range. We simultaneously demonstrate parametric frequency comb generation in the near-infrared, second-harmonic generation, and sum-frequency generation. We measure 17 comb lines converted to visible wavelengths extending to 765 nm. PMID:25401803

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

    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

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

    Otani, Saria; Hansen, Lars H.; Sørensen, Søren Johannes; Thomas-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 b...

  5. The Assembly of Nanorods in Comb Polymer Supramolecules

    Mastroianni, Alexander; Thorkelsson, Kari; Luther, Joseph; Alivisatos, Paul; Xu, Ting

    2010-03-01

    Inorganic nanoparticles exhibit a wide range of size-dependent properties and present great promise in technological applications. Fully harnessing this potential requires developing bottom-up strategies to assemble nanoparticles over multiple length scales simultaneously. Nanoparticles have been co-assembled with block copolymers (BCPs). Often this approach requires delicate balance between particle-polymer interactions and entropic penalty associated with polymer chain deformation upon particle incorporation. Recently, we showed that a coil-comb supramolecule formed by non- covalent attachment of small molecule amphiphiles to one block of a BCP can be used to direct nanoparticle assemblies with high precision. The alkyl tail of the small molecules chosen interacts favorably with the native alkyl ligands of a wide variety of inorganic nanoparticles and eliminates the need for particle surface modification. Upon attaching small molecule to one BCP block, the polymer chain stiffens, providing entropic driving force to further direct nanoparticle organization within BCP microdomains. Here, the co-assembly of these supramolecules with nanorods was systematically investigated as a function of small molecule loading, supramolecular morphology, nanorod diameter, and aspect ratio. The presented fundamental studies pave a path toward nanorod-based device fabrication.

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

    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.

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

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

    2015-01-01

    Quantum entanglement is a fundamental resource for secure information processing and communications, where hyperentanglement or high-dimensional entanglement has been separately proposed towards 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 energy and time domain. The long-postulated Hong-Ou-Mandel quantum revival is exhibited, with up to 19 time-bins, 96.5% visibilities. We further witness the high-dimensional energy-time entanglement through Franson revivals, which is 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 deviations while observing recurrent Clauser-Horne-Shimony-Holt S-parameters up to...

  8. Background-free electric field-induced second harmonic generation with interdigitated combs of electrodes.

    Jašinskas, Vidmantas; Gedvilas, Mindaugas; Račiukaitis, Gediminas; Gulbinas, Vidmantas

    2016-06-15

    The electric field-induced second harmonic (EFISH) generation is a powerful tool for the investigation of optical nonlinearities, material polarization, internal electric fields, and other properties of photonic materials and devices. A conventional generation of the second harmonics (SH) in materials with the disturbed centrosymmetry causes a field-independent background to EFISH and limits its applications. Here we suggest and analyze the application of the interdigitated combs of electrodes for EFISH generation in thin films. Interdigitated electrodes form an optical transmission amplitude diffraction grating. Phase matching of the EFISH radiation creates unusual diffraction fringes with the zero intensity along the zeroth order direction and with the diffraction angles different from diffraction angles of incident fundamental laser radiation and its second harmonics. It enables a simple geometrical separation of the EFISH signal from a conventional SH background, simplifies the sample preparation, and provides additional experimental possibilities. We demonstrate applicability of the suggested technique for characterization of submicrometer thickness organic films of transparent and resonantly interacting polymers and of their mixtures. PMID:27304282

  9. Octave-wide frequency comb centered at 4 μm based on a subharmonic OPO with Hz-level relative comb linewidth

    Smolski, V. O.; Xu, J.; Schunemann, P. G.; Vodopyanov, K. L.

    2016-03-01

    We study coherence properties of a more-than-octave-wide (2.6-7.5 μm) mid-IR frequency comb based on a 2-μm Tmfiber- laser-pumped degenerate (subharmonic) optical parametric oscillator (OPO) that uses orientation-patterned gallium arsenide (OP-GaAs) as gain element. By varying intracavity dispersion, we observed a 'phase' transition from a singlecomb state (at exactly OPO degeneracy) to a two-comb state (near-degenerate operation), characterized by two spectrally overlapping combs (signal and idler) with distinct carrier-envelope offset frequencies. We achieve this by generating a supercontinuum (SC) from the mode-locked Tm laser that spans most of the near-IR range, and observing RF beats between the SC and parasitic sum-frequency light (pump + OPO) that also falls into the near-IR. We found RF linewidth to be average power and high (up to 90%) pump depletion make this comb source very attractive for numerous applications including trace molecular detection and chemical sensing with massively parallel spectral data acquisition.

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

    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.

  11. The Riddle of Sex.

    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)

  12. Morphology and phylogenies of two hypotrichous brackish-water ciliates from China, Neourostylopsis orientalis n. sp. and Protogastrostyla sterkii (Wallengren, 1900) n. comb., with establishment of a new genus Neourostylopsis n. gen. (Protista, Ciliophora, Hypotrichia).

    Chen, Xiangrui; Shao, Chen; Liu, Xihan; Huang, Jie; Al-Rasheid, Khaled A S

    2013-03-01

    This paper investigates the morphology, infraciliature and small-subunit (SSU) rRNA gene sequences of two hypotrichous ciliates, Neourostylopsis orientalis n. sp., and Protogastrostyla sterkii (Wallengren, 1900) n. comb. (basionym Gastrostyla sterkii), collected from coastal waters in southern China. Neourostylopsis orientalis n. sp. is diagnosed mainly by the arrangement of brownish cortical granules, the numbers of adoral membranelles and frontal and transverse cirri and the characteristics of its midventral cirral pairs. The SSU rRNA gene phylogeny strongly supports the establishment of the new genus Neourostylopsis n. gen., which is characterized mainly by the following features: frontal and transverse cirri clearly differentiated, buccal cirri present, two frontoterminal cirri, midventral complex composed of midventral pairs only and not exceeding the halfway point of the cell, more than one row of marginal cirri on each side which derive from individual anlagen within each parental row, caudal cirri lacking. Thus, two new combinations are required: Neourostylopsis songi (Lei et al., 2005) n. comb., and Neourostylopsis flavicana (Wang et al., 2011) n. comb. Additionally, improved diagnoses for both Metaurostylopsis and Apourostylopsis are supplied in this study. Protogastrostyla sterkii (Wallengren, 1900) n. comb. differs from the similar congener Protogastrostyla pulchra mainly in body shape, ratio of buccal field to body length in vivo and molecular data. Based on the present studies, we conclude that the estuarine population of P. pulchra collected by J. Gong and others [Gong et al., J Eukaryot Microbiol (2007) 54, 468-478] is a population of P. sterkii. PMID:23355699

  13. Food additives

    ... this page: //medlineplus.gov/ency/article/002435.htm Food additives To use the sharing features on this page, please enable JavaScript. Food additives are substances that become part of a food ...

  14. Spotlight on Sex Equity: A Filmography.

    Shaffer, Susan Morris, Comp.

    This catalog contains a list of films, slide-tape presentations, and filmstrips presented at a 2-day film festival sponsored by the Mid-Atlantic Center for Sex Equity and other resources. The guide represents new media resources in addition to classics that meet the requirements of Title IX provisions on sex equity. The filmography is divided into…

  15. Sex Education for Patients

    Zitner, David

    1985-01-01

    Sex education evokes a wide variety of responses in the community and from teachers. Consequently, physicians have a responsibility to present sex education material in a factual, objective way. Many people are misinformed about sexual behavior. Physicians can help patients and the community by being aware of appropriate sex education for each age group. A curriculum for sex education, and opportunities to provide sex information for patients of different ages and stages in the lifecycle, are...

  16. Microwave and RF applications for micro-resonator based frequency combs

    Nguyen, Thach G.; Shoeiby, Mehrdad; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T.; Little, Brent E.; Morandotti, Roberto; Mitchell, Arnan; Moss, David J.

    2016-02-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is 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.

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

    Chang, Guoqing; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X

    2010-01-01

    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 \\approx100,000; 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. Spann...

  18. A novel vertical comb-drive electrostatic actuator using a one layer process

    This paper presents the design, fabrication and testing of a new residual stress gradient based vertical comb-drive actuator. Conventional vertical comb-drive actuators need two structural layers, i.e. one for the moving fingers and a second for the fixed fingers. A vertical comb-drive actuator based on a single structural layer micromachining process, using the residual stress gradient along the thickness of the nickel of the MetalMUMPs (Metal Multi-User MEMS process) fabrication process, is developed. The MetalMUMPs provides a 20 μm thick nickel film and is subject to residual stress gradients along its thickness. Two curve-up beams are devised to curve out of plane after release. The curve-up beams raise a plate with comb fingers above the substrate to form the moving fingers. The fixed comb fingers are connected to the substrate via anchors. When a voltage is applied across the moving and the fixed fingers, the moving fingers move down towards the fixed fingers. Experimental measurements on prototypes have verified the design principle. A vertical displacement of 4.81 µm at 150 V was measured. (paper)

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

    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...

  20. Cutaneous hyalohyphomycosis due to Parengyodontium album gen. et comb. nov.

    Tsang, Chi-Ching; Chan, Jasper F W; Pong, Wai-Mei; Chen, Jonathan H K; Ngan, Antonio H Y; Cheung, Mei; Lai, Christopher K C; Tsang, Dominic N C; Lau, Susanna K P; Woo, Patrick C Y

    2016-10-01

    "Engyodontium album" is an environmental saprobic mould and an emerging opportunistic pathogen able to cause both superficial and systemic infections. In this study, we isolated a mould from the skin lesion biopsy specimen of the right shin in a patient who received renal transplantation for end-stage renal failure with prednisolone, tacrolimus, and azathioprine immunosuppressant therapy. Histology of the skin biopsy showed mild squamous hyperplasia and neutrophilic infiltrate in the epidermis, active chronic inflammation in the dermis, and fat necrosis in the subcutis, with numerous fungal elements within the serum crusts. On Sabouraud glucose agar, the fungus grew as white, cobweb-like, floccose colonies. Microscopically, conidiogenous cells were arranged in whorls of one to seven at wide angles, with zigzag-shaped terminal fertile regions and smooth, hyaline, oval, apiculate conidia. DNA sequencing showed the mould isolate belonged to "E. album" but matrix-assisted laser desorption ionisation-time of flight mass spectrometry (MALDI-TOF MS) failed to identify the isolate. Phylogenetic analyses based on the internal transcribed spacer region, 28S nuclear ribosomal DNA, and β-tubulin gene and MALDI-TOF MS coupled with hierarchical cluster analysis showed that "E. album" is distantly related to other Engyodontium species and should be transferred to a novel genus within the family Cordycipitaceae, for which the name Parengyodontium album gen. et comb. nov. is proposed. Three potential cryptic species within this species complex were also revealed. Antifungal susceptibility testing showed posaconazole and voriconazole had high activities against all clinical P. album isolates and may be better drug options for treating P. album infections. PMID:27161787

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

    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...

  2. Evaluating the performance of the NPL femtosecond frequency combs: Agreement at the $10^{-21}$ level

    Johnson, L A M; Margolis, H S

    2014-01-01

    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 x $10^{-18}$ when measuring an optical frequency against a common microwave reference. When simultaneously measuring the ratio of two optical frequencies, agreement at the 3 x $10^{-21}$ 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 x $10^{-16}$. The technical details presented underpin recent absolute frequency measurements of the $^{88}$Sr$^+$ and $^{171}$Yb$^+$ optical clock transitions at NPL, as well as a frequency ratio measurement between the two optical clock...

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

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

  4. Optical frequency comb technology for ultra-broadband radio-frequency photonics

    Torres-Company, Victor

    2014-01-01

    The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with optical communication equipment are covered. Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation.

  5. Dual optical frequency comb architecture with capabilities from visible to mid-infrared.

    Jerez, Borja; Martín-Mateos, Pedro; Prior, Estefanía; de Dios, Cristina; Acedo, Pablo

    2016-06-27

    In this paper, a new approach to dual comb generation based on well-known optical techniques (Gain-Switching and Optical Injection Locking) is presented. The architecture can be implemented using virtually every kind of continuous-wave semiconductor laser source (DFB, VCSEL, QCL) and without the necessity of electro-optic modulators. This way, a frequency-agile and adaptive dual-comb architecture is provided with potential implementation capabilities from mid-infrared to near ultraviolet. With a RF comb comprising around 70 teeth, the system is validated in the 1.5 μm region measuring the absorption feature of H13CN at 1538.523 nm with a minimum integration time of 10 μs. PMID:27410649

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

    Mohannad Y. Elsayed

    2013-12-01

    Full Text Available 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 μV/°/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.

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

    Xia, Wei; Chen, Xuzong

    2016-04-01

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

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

    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

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

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

    2015-01-01

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

  10. Solar radial velocity variations and the search for Venus enabled by a laser frequency comb

    Phillips, David F.; Dumusque, Xavier; Li, Chih-Hao; Glenday, Alexander; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

    2016-05-01

    We have recently demonstrated 50 cm/s sensitivity in measuring the radial velocity (RV) between the Earth and Sun using a simple, compact 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 have been operating the solar telescope to detect the RV signal of the Sun as a star for the past year both to study RV jitter associated with stellar (solar) fluctuations and to demonstrate sensitivity of these instruments to detect terrestrial exoplanets. In this talk I will present results from calibrating the HARPS-N exoplanet searcher spectrograph, solar RV stability, and the current status of our search for the signature of Venus.

  11. A stabilized 18 GHz chip-scale optical frequency comb at 2.8x10-16 relative inaccuracy

    Huang, S -W; Yu, M; McGuyer, B H; Kwong, D -L; Zelevinsky, T; Wong, C W

    2015-01-01

    Optical frequency combs, coherent light sources that connect optical frequencies with microwave oscillations, have become the enabling tool for precision spectroscopy, optical clockwork and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but four-wave-mixing in high-Q resonators have emerged as alternative platforms. Here we report the generation and full stabilization of CMOS-compatible optical frequency combs. The spiral microcomb's two degrees-of-freedom, one of the comb line and the native 18 GHz comb spacing, are first simultaneously phase-locked to known optical and microwave references. Second, with pump power control, active comb spacing stabilization improves the long-term stability by six orders-of-magnitude, reaching an instrument-limited 3.6 mHz/sqrt(t) residual instability. Third, referencing thirty-three of the nitride frequency comb lines against a fiber comb, we demonstrate the comb tooth-to-tooth frequency relative inaccu...

  12. Observation of Rb Two-Photon Absorption Directly Excited by an Erbium-Fiber-Laser-Based Optical Frequency Comb via Spectral Control

    Wu, Jiutao; Hou, Dong; Dai, Xiaoliang; Qin, Zhengyu; Zhang, Zhigang; Zhao, Jianye

    2013-01-01

    We demonstrated the observation of Rb two-photon absorption directly excided by an optical frequency comb at fiber communication bands. A chain of comb spectral control is elaborately implemented to increase the power of the second harmonic optical frequency comb generation and the two-photon transition strength. A two-photon transition spectrum is obtained with clearly resolved transition lines. It provides a potential approach to realize the optical frequency comb or optical clock at ~1.5{\\...

  13. Length and refractive index measurement by Fourier transform interferometry and frequency comb spectroscopy

    In this paper we describe the progress we have made in our simultaneous length measurement and the femtosecond comb interferometric spectroscopy in a conventional arrangement with a moving mirror. Scanning and detection over an interval longer than the distance between two consecutive pulses of the frequency comb allow for a spectral resolution of the individual frequency modes of the comb. Precise knowledge of comb mode frequency leads to a precise estimation of the spectral characteristics of inspected phenomena. Using the pulse train of the frequency comb allows for measurement with highly unbalanced lengths of interferometer arms, i.e. an absolute long distance measurement. Further, we present a non-contact (double sided) method of measurement of the length/thickness of plane-parallel objects (gauge blocks, glass samples) by combining the fs comb (white light) with single frequency laser interferometry. The position of a fringe packet is evaluated by estimating the stationary phase position for any wavelength in the spectral band used. The repeatability of this position estimation is a few nanometres regardless of whether dispersion of the arms is compensated (transform limited fringe packet ∼10 fringes FWHM) or highly different (fringe packet stretched to >200 fringes FWHM). The measurement of steel gauge block by this method was compared with the standard method, and deviation (+13 ± 12) nm for gauge blocks (2 to 100) mm was found. The measurement of low reflecting ceramic gauges or clear glass samples was also tested. In the case of glass, it becomes possible to measure simultaneously both the thickness and the refractive index (and dispersion) of flat samples. (paper)

  14. Why we should consider sex (and study sex differences) in addiction research.

    Sanchis-Segura, Carla; Becker, Jill B

    2016-09-01

    Among mammals, every cell has a biological sex, and the sex of an individual pervades its body and brain. In this review, we describe the processes through which mammals become phenotypically male or female by organizational and activational influences of genes and hormones throughout development. We emphasized that the molecular and cellular changes triggered by sex chromosomes and steroid hormones may generate sex differences in overt physiological functions and behavior, but they may alternatively promote end-point convergences between males and females. Clinical and pre-clinical evidences suggest that sex and gender differences modulate drug consumption as well as of the transition towards drug-promoted pathological states such as dependence and addiction. Additionally, sex differences in drug pharmacokinetics and pharmacodynamics will also influence dependence and addiction as well as side effects of drugs. These effects will further interact with socially gendered factors to result in sex differences in the access to, engagement in and efficacy of any therapeutic attempt. Finally, we maintain that 'sex sameness' is as important as 'sex differences' when building a complete understanding of biology for both males and females and provide a framework with which to classify and guide investigation into the mechanisms mediating sex differences and sex sameness. PMID:27029841

  15. Animal models of absence epilepsies: What do they model and do sex and sex hormones matter?

    van Luijtelaar, Gilles; Onat, Filiz Yilmaz; Gallagher, Martin J.

    2014-01-01

    While epidemiological data suggest a female prevalence in human childhood- and adolescence-onset typical absence epilepsy syndromes, the sex difference is less clear in adult-onset syndromes. In addition, although there are more females than males diagnosed with typical absence epilepsy syndromes, there is a paucity of studies on sex differences in seizure frequency and semiology in patients diagnosed with any absence epilepsy syndrome. Moreover, it is unknown if there are sex ...

  16. Nutritional bias as a new mode of adjusting sex allocation

    Magrath, MJL; van Lieshout, E; Visser, GH; Komdeur, J

    2004-01-01

    Sex biases in the allocation of resources to offspring occur in a broad range of taxa. Parents have been shown to achieve such biases either by producing numerically more of one sex or by providing the individuals of one sex with a greater quantity of resources. In addition, skews in allocation coul

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

    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.

  18. Synthesis and Properties of Star-Comb Polymers and Their Doxorubicin Conjugates

    Chen, Bo; van der Poll, Derek G.; Jerger, Katherine; Floyd, William C.; Fréchet, Jean M.J.; Szoka, Francis C.

    2011-01-01

    We describe a six step synthesis to water soluble doxorubicin (DOX)-loaded biodegradable PEGylated star-comb polymers with favorable pharmaceutical properties by atom transfer radical polymerization (ATRP) starting with a commercially available tripentaerythritol carrying eight reactive sites. The low polydispersity polymers degrade in a stepwise manner into lower molecular weight (MW) fragments by 15 days at 37 °C at either pH 5.0 or pH 7.4. The half-life of the star-comb polymers in blood i...

  19. Origin and stability of dark pulse Kerr combs in normal dispersion resonators

    Parra-Rivas, Pedro; Knobloch, Edgar; Coen, Stéphane; Gelens, Lendert

    2016-01-01

    We analyze dark pulse Kerr frequency combs in optical resonators with normal group-velocity dispersion using the Lugiato-Lefever model. We show that in the time domain these correspond to interlocked switching waves between the upper and lower homogeneous states, and explain how this fact accounts for many of their experimentally observed properties. Modulational instability does not play any role in their existence. Furthermore, we provide a detailed map indicating where stable dark pulse Kerr combs can be found in parameter space, and how they are destabilized for increasing values of frequency detuning.

  20. Origin and stability of dark pulse Kerr combs in normal dispersion resonators

    Parra-Rivas, Pedro; Gomila, Damià; Knobloch, Edgar; Coen, Stéphane; Gelens, Lendert

    2016-06-01

    We analyze dark pulse Kerr frequency combs in optical resonators with normal group-velocity dispersion using the Lugiato-Lefever model. We show that in the time domain these correspond to interlocked switching waves between the upper and lower homogeneous states, and explain how this fact accounts for many of their experimentally observed properties. Modulational instability does not play any role in their existence. Furthermore, we provide a detailed map indicating where stable dark pulse Kerr combs can be found in parameter space, and how they are destabilized for increasing values of frequency detuning.

  1. Parallel fiber amplifiers with carrier–envelope drift control for coherent combination of optical frequency combs

    We demonstrated an active feed-forward method for compensating the relative phase drifts of fiber optical amplifiers. The frequency drifts of relative phase noise were well controlled in a variation range from ± 15 Hz of free-running, to approximately ± 1.5 Hz between the amplifier input and output. Coherent combination of two femtosecond fiber chirped-pulse amplifiers seeded by a Ti:S comb oscillator was achieved, which would benefit frequency comb combination to achieve high accuracy and high power. (paper)

  2. Synthesis and characterization of star-comb polybutadiene and poly(ethylene-co-butene)

    2010-01-01

    A novel star-comb polybutadiene(SC-PB) was synthesized with n-butyllithium(n-BuLi) as initiator,epoxidized star liquid polybutadiene(ESPB) as coupling agent,cyclohexane as solvent by living anionic polymerization and grafting-onto technology. The SC-PB was subsequently hydrogenated by homogeneous catalysis(catalytic hydrogenation using nickel naphthenate/ triisobutyl aluminum),to transform the SC-PB into the corresponding star-comb poly(ethylene-co-butene)(SC-PEB).The SC-PB was characterized by SEC-TALLS...

  3. Coherent frequency combs produced by self frequency modulation in quantum cascade lasers

    Khurgin, J. B.; Dikmelik, Y. [Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Hugi, A.; Faist, J. [Institute for Quantum Electronics, ETH Zurich, Wolfgang-Pauli-Strasse 16, 8093 Zurich (Switzerland)

    2014-02-24

    One salient characteristic of Quantum Cascade Laser (QCL) is its very short τ ∼ 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.

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

    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.

  5. Integrated frequency comb source based Hilbert transformer for wideband microwave photonic phase analysis.

    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

  6. Coherent combs of anti-matter from nonlinear electron-positron pair creation

    Krajewska, K

    2014-01-01

    Electron-positron pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse. Thus, resembling the Young-double slit experiment for anti-matter (matter) waves.

  7. Coherent combs of antimatter from nonlinear electron-positron-pair creation

    Krajewska, K.; Kamiński, J. Z.

    2014-11-01

    Electron-positron-pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to the appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse, thus resembling the Young-type double-slit experiment for antimatter (matter) waves.

  8. Comb/serpentine/cross-bridge test structure for fabrication process evaluation

    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.

  9. Application of Laser Frequency Combs and Nitrogen Vacancy Diamond Magnetometers to Searches for New Physics

    Phillips, D. F.; Walsworth, R. L.

    2014-01-01

    Searches for new physics often benefit from improved technologies. Here we discuss possible applications of two emerging technologies to searches for physics beyond the Standard Model. First, laser frequency combs enable broad spectral coverage and coherent conversion between optical and RF signals. We are investigating tests of the nonminimal Standard-Model Extension using frequency combs coupled to broadband optical cavities. Second, nitrogen vacancy centers in diamond enable precision nanoscale magnetometry with applications from imaging to quantum science. We are investigating their use in searches for short-range spin-spin couplings.

  10. Bactericide Effect of Atmospheric Plasma of Flat and Comb Electrodes on Escherichia coli

    A. Hosseinzadeh Colagar; F. Sohbatzadeh; S. Mirzanejhad; N. Asadian

    2008-01-01

    Objective: The current study was undertaken to examine the bactericide effects of atmospheric plasma produced by flat and comb electrodes on E.coli.Materials and Methods: DC (20 W) and AC (500 W) power supplies, flat and comb electrodes, insulator and oxygen gas were used to produce atmospheric plasma. Bactericide effects of the atmospheric plasma were studied on E.coli on sterilized plate placed on ice powder, at 3 McFarland concentration.Results: Flow of the atmospheric plasma produced by f...

  11. Experimental observation of coherent cavity soliton frequency combs in silica microspheres

    Webb, Karen E; Coen, Stéphane; Murdoch, Stuart G

    2016-01-01

    We report on the experimental observation of coherent cavity soliton frequency combs in silica microspheres. Specifically, we demonstrate that careful alignment of the microsphere relative to the coupling fiber taper allows for the suppression of higher-order spatial modes, reducing mode interactions and enabling soliton formation. Our measurements show that the temporal cavity solitons have sub-100-fs durations, exhibit considerable Raman self-frequency shift, and generally come in groups of three or four, occasionally with equidistant spacing in the time domain. RF amplitude noise measurements and spectral interferometry confirm the high coherence of the observed soliton frequency combs, and numerical simulations show good agreement with experiments.

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

    Zhang, Liang; Lu, Ping; Chen, Li;

    2012-01-01

    A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber...... of the fiber ring resonator can be measured with the transmission spectrum. A good linearity is obtained between displacement and the inverse of wavelength spacing with an R2 of 0.9989, and high sensitivities better than 40  pm/με within the range of 0 to 10  με are achieved. The sensitivity can be...

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

    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.

  14. Green, red and IR frequency comb line generation from single IR pump in AlN microring resonator

    Jung, Hojoong; Guo, Xiang; Fischer, Debra; Tang, Hong X

    2014-01-01

    On-chip frequency comb generations enable compact broadband sources for spectroscopic sensing and precision spectroscopy. Recent microcomb studies focus on infrared spectral regime and have difficulty in accessing visible regime. Here, we demonstrate comb-like visible frequency line generation through second, third harmonic, and sum frequency conversion of a Kerr comb within a high Q aluminum nitride microring resonator pumped by a single telecom laser. The strong power enhancement, in conjunction with the unique combination of Pockels and Kerr optical nonlinearity of aluminum nitride, leads to cascaded frequency conversions in the visible spectrum. High-resolution spectroscopic study of the visible frequency lines indicates matched free spectrum range over all the bands. This frequency doubling and tripling effect in a single microcomb structure offers great potential for comb spectroscopy and self-referencing comb.

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

    Otani, Saria; Hansen, Lars Hestbjerg; Sørensen, Søren J;

    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...

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

    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

  17. Sex Education: Another View

    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)

  18. Same sex, no sex, and unaware sex in neurotoxicology.

    Weiss, Bernard

    2011-10-01

    Males and females of virtually all species differ in how they respond to their environment. Because such differences exist in almost all biological realms, including disease patterns and therapeutic outcomes, they have evoked calls by various bodies to incorporate their assessment in research. Neurobehavioral indices pose special questions because, unlike outwardly visible markers, they are described by complex functional outcomes or subtle alterations in brain structure. These divergent responses arise because they are inscribed in the genome itself and then by endocrine mechanisms that govern sexual differentiation of the brain during development and operate throughout life. Other organ systems that exhibit sex differences include the liver, an important consideration for neurotoxicology because it may process many toxic chemicals differentially in males and females. Despite the scope and pervasiveness of sex differences, however, they are disregarded by much of neurotoxicology research. Males predominate in behavioral experiments, few such experiments study both sexes, some investigators fail to even describe the sex of their subjects, and in vitro studies tend to wholly ignore sex, even for model systems aimed at neurological disorders that display marked sex differences. The public is acutely aware of sex differences in behavior, as attested by its appetite for books on the topic. It closely follows debates about the proportion of women in professions that feature science and mathematics. Neurotoxicology, especially in the domain of laboratory research, will be hindered in its ability to translate its findings into human health measures if it assigns sex differences to a minor role. It must also be sensitive to how such debates are framed. Often, the differences evoking the most discussion are subtle in scope. They do not lend themselves to the typical analyses conducted by experimenters; that is, reliance on mean differences and null hypothesis testing. PMID

  19. Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs

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

    2016-06-01

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

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

    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

  1. Sex Education in Croatia

    Bijelić, Nataša

    2008-01-01

    Abstract This article explores the influence of the Catholic church on educational policy, more specifically on sex education, in Croatia. It explores tensions between secular and religious discourses regarding the introduction of a sex education programme supported by the Catholic church into Croatian schools. The presence of the Catholic doctrine in the educational system provided the basis for the introduction of sex education with a religious framework, namely the GROZD sex edu...

  2. Sex Differences in Cognition

    Fairweather, Hugh

    1976-01-01

    Sex differences in cognitive skills, grouped into motor, spatial and linguistic areas, are assessed in relation to current theories of cerebral lateralization. Few convincing sex differences exist, either overall, or in interactions with functional localization. Qualifying criteria include age, birth order, culture, sex of experimenter and sex…

  3. Practice Safer Sex

    ... of a long-term, faithful sexual relationship. Use protection for all kinds of sexual contact. Remember that you don't only get HIV from penile-vaginal sex. Use a condom during oral sex and during anal sex. Dental dams also ...

  4. Additivity dominance

    Paul Rozin

    2009-10-01

    Full Text Available Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned. In support of this, skim milk (with major subtraction of fat is rated as more natural than whole milk with a small amount of natural vitamin D added. It is also noted that ``additives'' is a common word, with a synonym reported by a native speaker in 17 of 18 languages, whereas ``subtractive'' is lexicalized in only 1 of the 18 languages. We consider reasons for additivity dominance, relating it to omission bias, feature positive bias, and notions of purity.

  5. Comb-shaped single ion conductors based on polyacrylate ethers and lithium alkyl sulfonate

    Comb-shaped single ion conductors have been synthesized by (1) sulfonation of small molecule chloroethyleneglycols, which, after ion exchange to the Li+ salt were then converted to the acrylate by reaction with acryloyl chloride and copolymerized with polyethylene glycol monomethyl ether acrylate (Mn = 454, n = 8) (PAE8-co-E3SO3Li); (2) sulfonation of chloride end groups grafted on to prepolymers of polyacrylate ethers (PAE8-g-EnSO3Li, n = 2, 3). The highest conductivity at 25 deg. C of 2.0 x 10-7 S cm-1 was obtained for the PAE8-co-E3SO3Li with a salt concentration of EO/Li = 40. The conductivity of PAE8-g-E3SO3Li is lower than that of PAE8-co-E3SO3Li at similar salt concentrations, which is related to the incomplete sulfonation of the grafted polymer that leads to a lower concentration of Li+. The addition of 50 wt.% of plasticizer, PC/EMC (1/1, v/v), to PAE8-g-E2SO3Li increases the ambient conductivity by three orders of magnitude, which is due to the increased ion mobility in a micro-liquid environment and an increase concentration of free ions as a result of the higher dielectric constant of the solvent. A symmetrical Li/Li cell with an electrolyte membrane consisting of 75 wt.% PC/EMC (1/1, v/v) was cycled at a current density of 100 μA cm-2 at 85 deg. C. The cycling profile showed no concentration polarization after a break-in period during the first few cycles, which was apparently due to reaction of the solvent at the lithium metal surface that reacted with lithium metal to form a stable SEI layer

  6. Sex-specific nestling body mass in relation to brood sex composition in the Eurasian Sparrowhawk Accipiter nisus

    Vedder, O; Dijkstra, C; Dekker, AL; Waasdorp, S; Visser, GH

    2005-01-01

    The trade-off between brood size and offspring quality as predicted by life history theory, has been extensively studied in birds. However, in sexually size-dimorphic birds, where the larger sex requires more investment from the parents, the potential additional trade-off between brood sex ratio and offspring quality has received less attention. Effects of brood sex composition on nestling fitness can have implications for optimal sex allocation strategies. A harmful effect of a higher propor...

  7. Controlled deposition and combing of DNA across lithographically defined patterns on silicon

    Nazari, Zeniab Esmail; Gurevich, Leonid

    2013-01-01

    We have developed a new procedure for efficient combing of DNA on a silicon substrate, which allows reproducible deposition and alignment of DNA molecules across lithographically defined patterns. The technique involves surface modification of Si/SiO2 substrates with a hydrophobic silane by using...

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

    Zhao, Ying; Pang, Xiaodan; Deng, Lei; Yu, Xianbin; Zheng, Xiaoping; Monroy, Idelfonso Tafur

    2012-01-01

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

  9. Conformational Properties of Comb-Like Polyelectrolytes: A Coarse-Grained MD Study.

    Ghelichi, Mahdi; Eikerling, Michael H

    2016-03-17

    This article presents a coarse-grained molecular dynamics study of single comb-like polyelectrolyte or ionomer chains in aqueous solution. The model polymer is comprised of a hydrophobic backbone chain with grafted side chains that terminate in anionic headgroups. The comb-polymer is modeled at a coarse-grained level with implicit treatment of the solvent. The computational study rationalizes conformational properties of the backbone chain and localization of counterions as functions of side chain length, grafting density of side chains, backbone stiffness, and counterion valence. The main interplay that determines the ionomer properties unfolds between electrostatic interactions among charged groups, hydrophobic backbone interactions, and steric effects induced by the pendant side chains. Depending on the density of branching sites, we have found two opposing effects of side chain length on the backbone gyration radius and local persistence length. Variation in comb-polyelectrolyte architecture is shown to have nontrivial effects on the localization of mobile counterions. Changes in Bjerrum length and counterion valence are also shown to alter the strength of Coulomb interactions and emphasize the role of excluded-volume effects on controlling the backbone conformational behavior. The results of simulations are in qualitative agreement with existing experimental and theoretical studies. The comprehensive conformational picture provides a framework for future studies of comb-polyelectrolyte systems. PMID:26910617

  10. Hybrid Optical Comb Filter with Multi-Port Fiber Coupler for DWDM Optical Network

    2003-01-01

    Optical comb filters based on multi-port fused fiber couplers are proposed and numerically analyzed, 3-arm MZI composed by 1×7 fiber splitter and 3×3 fiber coupler, and 2-stage cascaded FIR type MZI interleave filter.

  11. Optical Comb Generation for Streak Camera Calibration for Inertial Confinement Fusion Experiments

    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

  12. Reclassification of Thermoanaerobium acetigenum as Caldicellulosiruptor acetigenus comb. nov and emendation of the genus description

    Onyenwoke, R.U.; Lee, Y.J.; Dabrowski, Slawomir; Ahring, Birgitte Kiær; Wiegel, J.

    2006-01-01

    physiological properties of the type strain, X6B(T) (= DSM 7040(T) = ATCC BAA-11149(T)), we propose that Thermoanaerobium acetigenum should be reclassified as Caldicellulosiruptor acetigenus comb. nov. Strain X6B(T) contains two separate 16S rRNA genes bracketing another species in the phylogenetic 16S r...

  13. Theoretical calculation of the rotational excitation probability of the lithium chloride molecule in terahertz frequency combs

    We investigated how the pulse parameters of optical frequency combs affect the rotational excitation probability of the lithium chloride (7Li37Cl) molecule. Time evolution of the rotational population distribution was calculated by the close-coupling method. It was confirmed that the rotational excitation is restricted owing to the centrifugal distortion of the rotating molecule. (author)

  14. Generation of platicons and frequency combs in optical microresonators with normal GVD by modulated pump

    Lobanov, Valery E; Gorodetsky, Michael L

    2015-01-01

    We demonstrate that flat-topped dissipative solitonic pulses, platicons, and corresponding frequency combs can be excited in optical microresonators with normal group velocity dispersion using either amplitude modulation of the pump or bichromatic pump. Soft excitation may occur in particular frequency range if modulation depth is large enough and modulation frequency is close to the free spectral range of the microresonator.

  15. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

    Rutkowski, Lucile

    2016-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique and we present the corresponding formalism for quantitative broadband spectroscopy. We achieve high sensitivity and broadband performance by acquiring spectra covering more than 2000 cm$^{-1}$ around 12600 cm$^{-1}$ (800 nm), resolving the 3$\

  16. Oscillatory Shear Flow-Induced Alignment of Lamellar Melts of Hydrogen-Bonded Comb Copolymer Supramolecules

    Moel, Karin de; Mäki-Ontto, Riikka; Stamm, Manfred; Ikkala, Olli; Brinke, Gerrit ten; M„ki-Ontto, R.; Maki-Ontto, R

    2001-01-01

    In this work we present the orientational behavior of comb copolymer-like supramolecules P4VP(PDP)1.0, obtained by hydrogen bonding between poly(4-vinylpyridine) and pentadecylphenol, during large-amplitude oscillatory shear flow experiments over a broad range of frequencies (0.001-10 Hz). The align

  17. Influence of deep RIE tolerances on comb-drive actuator performance

    This paper analyses the various etching tolerances and profiles of comb-drive microstructures by using deep reactive ion etching (RIE) and studies their influence on the actuator's performance. The comb-drive actuators studied in this paper are fabricated with the silicon-on-glass (SOG) wafer process using deep RIE and wafer bonding, which present very high-aspect-ratio and high-strength microstructures. However, the deep RIE process generates some tolerances and varies the dimension and profile of comb fingers and flexures due to the process limitations. We have analysed the different etching tolerances and studied their influence on the actuator's performance, in terms of the electrostatic force, flexure stiffness, actuator's displacement, air damping and quality factor of the actuator. The analysis shows that the comb fingers with a positive slope profile generated a larger electrostatic force, and the flexures with a negative profile induced the loss of the actuator's stiffness. The combination of these two profiles leads to a great increase in the actuator's displacement and decrease in the quality factor. The measured results of the SOG fabricated actuators have demonstrated the influence of deep RIE tolerance on the actuator's performance

  18. Osho - Insights on sex.

    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

  19. Additivity dominance

    Paul Rozin; Claude Fischler; Christy Shields-Argeles

    2009-01-01

    Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA) that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned....

  20. A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration

    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 ∼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.

  1. Scalable and reconfigurable generation of flat optical comb for WDM-based next-generation broadband optical access networks

    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.

  2. Generation of Kerr combs centered at 4.5{\\mu}m in crystalline microresonators pumped by quantum cascade lasers

    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$^8$.

  3. Generation of Kerr combs centered at 45 μm in crystalline microresonators pumped with quantum-cascade lasers

    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 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$^8$.

  4. Generation of a 650 nm - 2000 nm Laser Frequency Comb based on an Erbium-Doped Fiber Laser

    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.

  5. 性别、医疗与消费文化——明清时期梳篦的文化史%Gender, medicine and consumer culture: the cultural history of comb in the Ming and Qing Dynasties

    陈思言

    2014-01-01

    In the Ming and Qing Dynasties,in addition to combing the hair,the comb also gradually played a role in people' s daily life for disease treatment and keeping people' s health.In short,during this period,the characteristic of comb reveal,as a whole,its reinforcing practicability and weakening of its ornamentality.During its application,people' s behavioral activities endowed the comb with definite cultural connotation,which,thanks to the presence of gender and personality,became the symbol for expressing love between man and woman.By analogizing people's thought,since the comb could dredge something.Therefore,it can be used to cure diseases.Thus,it could be seen that,based on consumer's cultural description,the comb,tiny as it may be,did reflect the aesthetic ideas and interests and daily life-preservation habit of the literati due to the flourishing of book market in the Ming and Qing Dynasties.%明清时期梳篦除了被用以栉发外,还渐渐以养生治病的角色走入了人们的日常生活,梳篦在当时总体呈实用性增强、装饰性减淡的态势.在使用过程中,人的行为活动赋予了梳篦一定的文化意涵,由于身份及性别化叙述的存在,梳篦化约为男女之情的象征符号.同时,明清医方遵循以意解药的原则,故时人取梳篦的疏通性以期达到治病的效果.梳篦虽小,通过它却可窥见明清时期的消费风气背后反映的文人化论述和当时的审美旨趣,以及书籍市场繁荣带来的日常养生风习的兴盛.

  6. Plant sex chromosome evolution.

    Charlesworth, Deborah

    2013-01-01

    It is now well established that plants have an important place in studies of sex chromosome evolution because of the repeated independent evolution of separate sexes and sex chromosomes. There has been considerable recent progress in studying plant sex chromosomes. In this review, I focus on how these recent studies have helped clarify or answer several important questions about sex chromosome evolution, and I shall also try to clarify some common misconceptions. I also outline future work that will be needed to make further progress, including testing some important ideas by genetic, molecular, and developmental approaches. Systems with different ages can clearly help show the time course of events during changes from an ancestral co-sexual state (hermaphroditism or monoecy), and I will also explain how different questions can be studied in lineages whose dioecy or sex chromosomes evolved at different times in the past. PMID:23125359

  7. Sex Differences in Lifespan.

    Austad, Steven N; Fischer, Kathleen E

    2016-06-14

    Sex differences in longevity can provide insights into novel mechanisms of aging, yet they have been little studied. Surprisingly, sex-specific longevity patterns are best known in wild animals. Evolutionary hypotheses accounting for longevity patterns in natural populations include differential vulnerability to environmental hazards, differential intensity of sexual selection, and distinct patterns of parental care. Mechanistic hypotheses focus on hormones, asymmetric inheritance of sex chromosomes and mitochondria. Virtually all intensively studied species show conditional sex differences in longevity. Humans are the only species in which one sex is known to have a ubiquitous survival advantage. Paradoxically, although women live longer, they suffer greater morbidity particularly late in life. This mortality-morbidity paradox may be a consequence of greater connective tissue responsiveness to sex hormones in women. Human females' longevity advantage may result from hormonal influences on inflammatory and immunological responses, or greater resistance to oxidative damage; current support for these mechanisms is weak. PMID:27304504

  8. Sex in Fungi

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

    2011-01-01

    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 d...

  9. Sex determination in salmonids

    Yano, Ayaka; Guyomard, René; Jouanno, Elodie; Fostier, Alexis; Quillet, Edwige; Guiguen, Yann

    2012-01-01

    Members of the salmonid family are present worldwide and many of them are species of major importance for aquaculture, wild stock fisheries or recreational sport fisheries. Sex determination has been well studied in this fish family, because of the importance of a better sex control in aquaculture and also because salmonids can be excellent research models. All salmonid species in which sex determination has been studied in details thus far belong to the Salmoninae subfamily (mainly salmons, ...

  10. Sex differences in anxiety and emotional behavior

    Donner, Nina C.; Lowry, Christopher A.

    2013-01-01

    Research has elucidated causal links between stress exposure and the development of anxiety disorders, but due to the limited use of female or sex-comparative animal models, little is known about the mechanisms underlying sex differences in those disorders. This is despite an overwhelming wealth of evidence from the clinical literature that the prevalence of anxiety disorders is about twice as high in women compared to men, in addition to gender differences in severity and treatment efficacy....

  11. Frequency Comb-Referenced Spectroscopy in the ν1 + ν3 Region of Acetylene

    Cich, Matthew J.; Forthomme, Damien; Hall, Gregory E.; Mcraven, Christopher P.; Sears, Trevor J.; Twagirayezu, Sylvestre

    2014-06-01

    class="MsoNormal">By using saturation dip absorption spectroscopy with an extended cavity diode laser locked to a frequency comb, we have measured the rest frequencies of transitions in the ν4 = 1 and ν5 = 1 hot bands in the ν1 + ν3 combination band of acetylene. The measured line frequencies are accurate to approximately 20 kHz i.e. approximately one part in 1011. Positions of the hot-band lines quoted in the HITRAN database, which are derived from the analysis of high-resolution FTIR spectra, are of the order of 10's of MHz in error. These measurements were undertaken because pressure broadened lineshape measurements of rotational lines in the combination band indicated that weak underlying hot band features were not correctly accounted for on the basis of their previously reported positions. As a result, measured line profiles in the band could not be accurately fit leading to errors of up to 1% in acetylene concentrations derived from the measurements. In addition, the pressure broadened P(11) line in the ν1 + ν3 combination band has been studied as a function of varying concentration of the absorber in nitrogen. Mixture concentrations of 1, 5 and 10% at 296 K and pressures between a few Torr and one atmosphere were made and the measurements analyzed using two different speeddependent broadening models. These experiments are designed to test the additivity of contributions to pressure broadening and shift in speed-dependent line-shape modeling, i.e. whether the lineshape parameters follow partial pressure weighting in the binary mixtures. P(11) is relatively isolated with respect to underlying hot band transitions and neighboring transitions of the same band, but it was found that the accurate positions of underlying hot-band transitions were crucial to the successful modeling of the observed line shapes, even though these lines are typically 100-1000 times weaker than P(11) itself and are many Doppler line widths removed from the line center

  12. Osho - Insights on sex

    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...

  13. Analysis of the Offspring Sex Ratio of Chicken by Using Molecular Sexing

    FENG Yan-ping; GONG Yan-zhang; Nabeel Ahmed Affara; PENG Xiu-li; YUAN Jin-feng; ZHAO Rui-xia; Mohammed Yusuf; Osman Jeffer; ZHANG Shu-jun

    2006-01-01

    The overall sex ratio of offspring (dead embryos and hatch chicks) from all the fertilized eggs of 140 hens collected for30 days was studied using duplex PCR of certain fragments of sex chromosomes. Additional 894 dead embryos over a period of 21 days of incubation were also investigated to verify the sex ratio of the dead embryos. The sex of the early dead embryos was identified using this molecular sexing technique. The sex ratio of the hatch chicks and the total offspring of the hens investigated in this experiment did not differ from the expected sex ratio (i.e., 1:1). However, the number of female dead embryos was significantly more than that of males. The data indicated that the different physiologic function of males and females contributed to female-biased mortality during incubation. It was also found by further analysis that the sex ratios of the offspring of some hens were significantly biased to female or male over the period investigated, which suggested that the sex ratio of offspring might be influenced by the maternal condition to some degrees.

  14. Neurogenin 3 Mediates Sex Chromosome Effects on the Generation of Sex Differences in Hypothalamic Neuronal Development

    Maria Julia Scerbo

    2014-07-01

    Full Text Available The organizational action of testosterone during critical periods of development is the cause of numerous sex differences in the brain. However, sex differences in neuritogenesis have been detected in primary neuronal hypothalamic cultures prepared before the peak of testosterone production by fetal testis. In the present study we assessed the hypothesis of that cell-autonomous action of sex chromosomes can differentially regulate the expression of the neuritogenic gene neurogenin 3 (Ngn3 in male and female hypothalamic neurons, generating sex differences in neuronal development. Neuronal cultures were prepared from male and female E14 mouse hypothalami, before the fetal peak of testosterone. Female neurons showed enhanced neuritogenesis and higher expression of Ngn3 than male neurons. The silencing of Ngn3 abolished sex differences in neuritogenesis, decreasing the differentiation of female neurons. The sex difference in Ngn3 expression was determined by sex chromosomes, as demonstrated using the four core genotypes mouse model, in which a spontaneous deletion of the testis-determining gene Sry from the Y chromosome was combined with the insertion of the Sry gene onto an autosome. In addition, the expression of Ngn3, which is also known to mediate the neuritogenic actions of estradiol, was increased in the cultures treated with the hormone, but only in those from male embryos. Furthermore, the hormone reversed the sex differences in neuritogenesis promoting the differentiation of male neurons. These findings indicate that Ngn3 mediates both cell-autonomous actions of sex chromosomes and hormonal effects on neuritogenesis.

  15. A 23.75-GHz frequency comb with two low-finesse filtering cavities in series for high resolution spectroscopy

    侯磊; 韩海年; 王薇; 张龙; 庞利辉; 李德华; 魏志义

    2015-01-01

    A laser frequency comb with several tens GHz level is demonstrated, based on an Yb-doped femtosecond fiber laser and two low-finesse Fabry–P´erot cavities (FPCs) in series. The original 250-MHz mode-line-spacing of the source comb is filtered to 4.75 GHz and 23.75 GHz, respectively. According to the multi-beam interferences theory of FPC, the side-mode suppression rate of FPC schemes is in good agreement with our own theoretical results from 27 dB of a single FPC to 43 dB of paired FPCs. To maintain long-term stable operation and determine the absolute frequency mode number in the 23.75-GHz comb, the Pound–Drever–Hall (PDH) locking technology is utilized. Such stable tens GHz frequency combs have important applications in calibrating astronomical spectrographs with high resolution.

  16. Single envelope equation modelling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearity

    Hansson, T; Erkintalo, M; Anthony, J; Coen, S; Ricciardi, I; De Rosa, M; Wabnitz, S

    2016-01-01

    We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator (WGR). We examine both separate and co-existing intra-cavity doubly resonant second-harmonic generation and parametric oscillation processes, and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains, or isolated pulses.

  17. An Analysis of Near Field and Application of a New Comb-shaped Antenna for Radio Frequency Identification

    2001-01-01

    A new comb-shaped antenna for radio frequency identification is proposed. The kind of antenna can replace some antenna array. So it is very convenient for omnidirectional identification. The test result proves this antenna is viable.

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

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

    2016-01-01

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

  19. Tuneable dual-comb spectrometer based on commercial femtosecond lasers and reference cell for optical frequency calibration

    Portuondo-Campa, E.; Bennès, J.; Balet, L.; Kundermann, S.; Merenda, F.; Boer, G.; Lecomte, S.

    2016-07-01

    Two commercial femtosecond laser sources have been used to implement a dual-comb spectrometer tuneable across a spectral range from 1.5 to 2.2 μm. The optical linewidth of the comb modes was characterized for different time scales in order to estimate the achievable spectral resolution for an optimal acquisition time. The transmission spectra of three different gas samples were recorded, demonstrating good agreement with reference data. Frequency axis calibration was provided via the parallel monitoring of a reference sample. This technique allows an accurate calibration of the frequency axis of the spectrometer, with no need for stabilization or optical referencing of the frequency combs. Our set-up represents a good compromise for a compact and versatile dual-comb spectrometer based on commercially available parts with possible applications in trace-gas monitoring, remote sensing and spectroscopy of short-lived processes.

  20. A 23.75-GHz frequency comb with two low-finesse filtering cavities in series for high resolution spectroscopy

    A laser frequency comb with several tens GHz level is demonstrated, based on a Yb-doped femtosecond fiber laser and two low-finesse Fabry–Pérot cavities (FPCs) in series. The original 250-MHz mode-line-spacing of the source comb is filtered to 4.75 GHz and 23.75 GHz, respectively. According to the multi-beam interferences theory of FPC, the side-mode suppression rate of FPC schemes is in good agreement with our own theoretical results from 27 dB of a single FPC to 43 dB of paired FPCs. To maintain long-term stable operation and determine the absolute frequency mode number in the 23.75-GHz comb, the Pound–Drever–Hall (PDH) locking technology is utilized. Such stable tens GHz frequency combs have important applications in calibrating astronomical spectrographs with high resolution. (paper)

  1. Synthesis and characterization of an exact comb polyisoprene with three branches having the middle branch twice the molecular weight of the other two identical external branches

    Ratkanthwar, Kedar

    2013-01-01

    An exact comb polyisoprene (PI) with three branches, with the middle branch having twice the molecular weight of the two other identical external branches, was synthesized by using anionic polymerization high vacuum techniques and appropriate chlorosilane chemistry. The synthetic approach involves (a) the selective replacement of the two chlorines of 4-(dichloromethylsilyl) diphenylethylene (DCMSDPE, key molecule) with identical PI chains by titration with PILi, (b) the addition of sec-BuLi to the double bond of DPE followed by the polymerization of isoprene from the newly created anionic site to form a 3-arm living star PI, (c) the selective replacement of the two chlorines of trichloromethylsilane with 3-arm star PI to form an H-shape intermediate, and (d) the replacement of the remaining chlorine of trichloromethylsilane by linear PI chains with double the molecular weight. All intermediate and final products were characterized via size exclusion chromatography, temperature gradient interaction chromatography and 1H-NMR spectroscopy. As expected, due to the inability to control the exact stoichiometry of the linking reactants, the main product (exact comb PI) is contaminated by a few by-products, despite the fact that anionic polymerization is the most efficient way to produce well-defined polymers. © 2013 The Royal Society of Chemistry.

  2. Sex tourism in Thailand.

    Van Kerkwijk, C

    1992-01-01

    Many foreigners visit Thailand in search of sex. While long-distance tourism was long enjoyed by members of more privileged social classes, even the lower economical classes of Japan, Malaysia, Europe, America, and Australia can now afford to travel over long distances. This relatively new breed of tourist is more likely to be of lower socioeconomic and educational status and less likely to use condoms when having sex. An estimated 30,000 sex workers are active in Bangkok, of whom 7000/10,000 are females who work specifically in the tourism sector. 1/2-1/3 of the 600 commercial sex establishments in the city are visited by foreigners. Phuket, Pattaya, Koh Samui, and Chiangmai are also well-frequented by sex tourists. Overall, a large, diverse, inexpensive, and accessible commercial sex market exists in Thailand. One may meet sex workers quasi-ubiquitously and be assured to find someone capable of meeting one's sexual needs. With these attributes, Thailand strongly attracts tourists in search of sex. A certain degree of recklessness also prevails among those on vacation. Away from the peers and social mores of their native lands, tourists may engage in sexually activities without criticism. Likewise, Thai sex workers who cater to foreigners, especially females, enjoy more freedom and control in sexual relations than their peers who work among nationals. Neither single nor married women in Thailand are allowed much sexual freedom and are traditionally expected to be obliging docile, and submissive. The greater than normal personal latitude enjoyed by both sex worker and foreigner lead to more negotiation on condom use and overall lower use. As such, Thailand's commercial sex market with foreigners' involvement therein threatens to spread HIV to many other countries throughout the world. PMID:12286018

  3. Color bar coding the BRCA1 gene on combed DNA: a useful strategy for detecting large gene rearrangements.

    Gad, S; Aurias, A; Puget, N; Mairal, A; Schurra, C; Montagna, M; Pages, S; Caux, V; Mazoyer, S; Bensimon, A; Stoppa-Lyonnet, D

    2001-05-01

    Genetic linkage data have shown that alterations of the BRCA1 gene are responsible for the majority of hereditary breast and ovarian cancers. BRCA1 germline mutations, however, are found less frequently than expected. Mutation detection strategies, which are generally based on the polymerase chain reaction, therefore focus on point and small gene alterations. These approaches do not allow for the detection of large gene rearrangements, which also can be involved in BRCA1 alterations. Indeed, a few of them, spread over the entire BRCA1 gene, have been detected recently by Southern blotting or transcript analysis. We have developed an alternative strategy allowing a panoramic view of the BRCA1 gene, based on dynamic molecular combing and the design of a full four-color bar code of the BRCA1 region. The strategy was tested with the study of four large BRCA1 rearrangements previously reported. In addition, when screening a series of 10 breast and ovarian cancer families negatively tested for point mutation in BRCA1/2, we found an unreported 17-kb BRCA1 duplication encompassing exons 3 to 8. The detection of rearrangements as small as 2 to 6 kb with respect to the normal size of the studied fragment is achieved when the BRCA1 region is divided into 10 fragments. In addition, as the BRCA1 bar code is a morphologic approach, the direct observation of complex and likely underreported rearrangements, such as inversions and insertions, becomes possible. PMID:11284038

  4. A stabilized 18 GHz chip-scale optical frequency comb at 2.8x10-16 relative inaccuracy

    Huang, S.-W.; Yang, J.; Yu, M.; McGuyer, B. H.; Kwong, D. -L.; Zelevinsky, T.; Wong, C. W.

    2015-01-01

    Optical frequency combs, coherent light sources that connect optical frequencies with microwave oscillations, have become the enabling tool for precision spectroscopy, optical clockwork and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but four-wave-mixing in high-Q resonators have emerged as alternative platforms. Here we report the generation and full stabilization of CMOS-compatible optical frequency combs. The spira...

  5. Sex Determination in Papaya

    Sex determination is an intriguing system in trioecious papaya. Over the past seven decades various hypotheses, based on the knowledge and information available at the time, have been proposed to explain the genetics of the papaya's sex determination. These include a single gene with three alleles...

  6. Sex Away from Home

    Greenwald, Harold

    1971-01-01

    The reasons why people who are normally truthful to their spouses engage in sex away from home are discussed. These reasons can include loneliness, ego building or the opportunity to have homosexual relations. Sex away from home is likely to increase since the number of people traveling is increasing. (Author/CG)

  7. Single-Sex Classrooms

    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…

  8. Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy

    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.

  9. Dual-pump Kerr Micro-cavity Optical Frequency Comb with varying FSR spacing

    Wang, Weiqiang; Chu, Sai T.; Little, Brent E.; Pasquazi, Alessia; Wang, Yishan; Wang, Leiran; Zhang, Wenfu; Wang, Lei; Hu, Xiaohong; Wang, Guoxi; Hu, Hui; Su, Yulong; Li, Feitao; Liu, Yuanshan; Zhao, Wei

    2016-01-01

    In this paper, we demonstrate a novel dual-pump approach to generate robust optical frequency comb with varying free spectral range (FSR) spacing in a CMOS-compatible high-Q micro-ring resonator (MRR). The frequency spacing of the comb can be tuned by an integer number FSR of the MRR freely in our dual-pump scheme. The dual pumps are self-oscillated in the laser cavity loop and their wavelengths can be tuned flexibly by programming the tunable filter embedded in the cavity. By tuning the pump wavelength, broadband OFC with the bandwidth of >180 nm and the frequency-spacing varying from 6 to 46-fold FSRs is realized at a low pump power. This approach could find potential and practical applications in many areas, such as optical metrology, optical communication, and signal processing systems, for its excellent flexibility and robustness. PMID:27338250

  10. Phase noise analysis of injected gain switched comb source for coherent communications.

    Zhou, Rui; Huynh, Tam N; Vujicic, Vidak; Anandarajah, Prince M; Barry, Liam P

    2014-04-01

    We present experimentally and analytically the phase noise characterization of an externally injected gain switched comb source. The results reveal the residual high frequency FM noise in the comb lines, which stays unnoticed in the optical linewidth value but leads to an increased phase-error variance. The potential impact of the residual phase noise is investigated in a 10.7 GBaud optical DQPSK system where a 2 dB power penalty is recorded at BER of 10(-9). In a 10.7 GBaud digital coherent QPSK system no penalty is observed but with 5 GBaud 16-QAM format a 3 dBpenalty exists at the FEC limit of 4.4e-3. PMID:24718188

  11. Dimensional metrology using the optical comb of a mode-locked laser

    Jin, Jonghan

    2016-02-01

    In the field of dimensional metrology, significant technical challenges have been encountered with regard to large-scale object assembly, satellite positioning, control of the long-distance precision stage, and inspections of large steps or deep holes on semiconductor devices and multi-layered display panels. The key elements required are high speeds, a long dynamic measurable range, and good precision of measurements, and conventional methods can scarcely meet such requirements simultaneously. Promisingly, the advent of the optical comb has opened up numerous possibilities to break through practical limits by exploiting several of its unique features. These include inter-mode interference, a wide spectral bandwidth with a long coherence length and well-defined longitudinal modes. In this review, various dimensional metrological methods using the optical comb are introduced, describing their basic principles and applications in scientific as well as industrial areas.

  12. Evaluation and modelling of integral capacitors produced by interdigitated comb electrodes

    Leandro Alfredo Ramajo

    2008-12-01

    Full Text Available Integral capacitors (IC of one or two-layer printed wiring board (PWB circuits were produced using comb electrodes fixtures and dielectric composites as the inter-electrode material. ICs were fabricated at laboratory scale, using copper comb electrodes and BaTiO3-epoxy composite materials deposited on a glass-Epoxy FR4 board. They were experimentally tested in order to obtain their electrical response. Furthermore, ICs behaviour was modelled through 2-dimensional models applying finite element method (FEM. Results showed that by this laboratory technique it was possible to obtained integral capacitors with low dielectric losses. Moreover, acceptable agreement was found between numerical and experimental capacitance results for all the different analysed ICs. In conclusion, 2D FEM models are a suitable tool to predict electric response of IC devices.

  13. The Impact of Dispersion on Amplitude and Frequency Noise in a Yb-fiber Laser Comb

    Nugent-Glandorf, Lora; Kobayashi, Yohei; Diddams, Scott A

    2011-01-01

    We describe a Yb-fiber based laser comb, with a focus on the relationship between net-cavity dispersion and the frequency noise on the comb. While tuning the net cavity dispersion from anomalous to normal, we measure the amplitude noise (RIN), offset frequency (f_CEO) linewidth, and the resulting frequency noise spectrum on f_CEO. We find that the laser operating at zero net-cavity dispersion has many advantages, including an approximately 100x reduction in free-running f_CEO linewidth and frequency noise power spectral density between laser operation at normal and zero dispersion. In this latter regime, we demonstrate a phase-locked f_CEO beat with low residual noise.

  14. On the Polyphase Decomposition for Design of Generalized Comb Decimation Filters

    Laddomada, Massimiliano

    2007-01-01

    Generalized comb filters (GCFs) are efficient anti-aliasing decimation filters with improved selectivity and quantization noise (QN) rejection performance around the so called folding bands with respect to classical comb filters. In this paper, we address the design of GCF filters by proposing an efficient partial polyphase architecture with the aim to reduce the data rate as much as possible after the Sigma-Delta A/D conversion. We propose a mathematical framework in order to completely characterize the dependence of the frequency response of GCFs on the quantization of the multipliers embedded in the proposed filter architecture. This analysis paves the way to the design of multiplier-less decimation architectures. We also derive the impulse response of a sample 3rd order GCF filter used as a reference scheme throughout the paper.

  15. Fixed-Point Design of Generalized Comb Filters: A Statistical Approach

    Laddomada, Massimiliano

    2008-01-01

    This paper is concerned with the problem of designing computationally efficient Generalized Comb Filters (GCF). Basically, GCF filters are anti-aliasing filters that guarantee superior performance in terms of selectivity and quantization noise rejection compared to classical comb filters, when used as decimation filters in multistage architectures. Upon employing a partial polyphase (PP) architecture proposed in a companion paper, we develop a sensitivity analysis in order to investigate the effects of the coefficients' quantization on the frequency response of the designed filters. We show that the sensitivity of the filter response to errors in the coefficients is dependent on the particular split of the decimation factor between the two sub-filters constituting the PP architecture. The sensitivity analysis is then used for developing a fixed-point implementation of a sample filter from the class of GCF filters, used as reference filter throughout the paper. Finally, we present computer simulations in order...

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

    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.

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

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

    2012-01-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut f\\"ur Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\\"ur 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.

  18. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    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.

  19. WDM-CAP-PON integration with VLLC system based on optical frequency comb

    He, Jing; Dong, Huan; Deng, Rui; Shi, Jin; Chen, Lin

    2016-09-01

    In this paper, a wavelength division multiplexing carrier-less amplitude phase modulation passive optical network (WDM-CAP-PON) integration with visible laser light communication (VLLC) system is proposed and experimentally demonstrated. To reduce the cost of WDM system, the optical frequency comb scheme using one Mach-Zehnder modulator (MZM) is utilized and five flat optical combs can be generated. Meanwhile, a blue laser diode (LD) as a VLLC optical source can provide high data rate and long transmission distance. Utilizing overlap frequency domain equalization (OFDE) and negative chirp of MZM, the system performance in both Q-factor and receiver sensitivity can be improved. After 20 km standard single mode fiber (SSMF) and 4.5 m free space transmission, the experimental results show that 10 Gb/s CAP signal can be achieved under 7% forward error correction (FEC) limit of 3 . 8 × 10-3.

  20. Mid-infrared Fourier transform spectroscopy with a broadband frequency comb.

    Adler, Florian; Masłowski, Piotr; Foltynowicz, Aleksandra; Cossel, Kevin C; Briles, Travis C; Hartl, Ingmar; Ye, Jun

    2010-10-11

    We present a first implementation of optical-frequency-comb-based rapid trace gas detection in the molecular fingerprint region in the mid-infrared. Near-real-time acquisition of broadband absorption spectra with 0.0056 cm(-1) maximum resolution is demonstrated using a frequency comb Fourier transform spectrometer which operates in the 2100-to-3700-cm(-1) spectral region. We achieve part-per-billion detection limits in 30 seconds of integration time for several important molecules including methane, ethane, isoprene, and nitrous oxide. Our system enables precise concentration measurements even in gas mixtures that exhibit continuous absorption bands, and it allows detection of molecules at levels below the noise floor via simultaneous analysis of multiple spectral features. PMID:20941086

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

    Françoise Benz

    2002-01-01

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

  2. Transmission comb of a distributed Bragg reflector with two surface dielectric gratings

    Zhao, Xiaobo; Zhang, Yongyou; Zhang, Qingyun; Zou, Bingsuo; Schwingenschlogl, Udo

    2016-02-01

    The transmission behaviour of a distributed Bragg reector (DBR) with surface dielectric gratings on top and bottom is studied. The transmission shows a comb-like spectrum in the DBR band gap, which is explained in the Fano picture. The number density of the transmission peaks increases with increasing number of cells of the DBR, while the ratio of the average full width at half maximum to the corresponding average free spectral range, being only few percent for both transversal electric and magnetic waves, is almost invariant. The transmission peaks can be narrower than 0.1 nm and are fully separated from each other in certain wavebands. We further prove that the transmission combs are robust against randomness in the heights of the DBR layers. Therefore, the proposed structure is a candidate for an ultra-narrow-band multichannel filter or polarizer.

  3. Continuous probe of cold complex molecules with infrared frequency comb spectroscopy

    Spaun, Ben; Patterson, David; Bjork, Bryce J; Heckl, Oliver H; Doyle, John M; Ye, Jun

    2016-01-01

    Cavity-enhanced frequency comb spectroscopy for molecule detection in the mid-infrared powerfully combines high resolution, high sensitivity, and broad spectral coverage. However, this technique, and essentially all spectroscopic methods, is limited in application to relatively small, simple molecules. Here we integrate comb spectroscopy with continuous, cold samples of molecules produced via buffer gas cooling, thus enabling the study of significantly more complex molecules. We report simultaneous gains in resolution, sensitivity, and bandwidth and demonstrate this combined capability with the first rotationally resolved direct absorption spectra in the CH stretch region of several complex molecules. These include nitromethane (CH$_3$NO$_2$), a model system that presents challenging questions to the understanding of large amplitude vibrational motion, as well as several large organic molecules with fundamental spectroscopic and astrochemical relevance, including naphthalene (C$_{10}$H$_8$), adamantane (C$_{1...

  4. Study on Evaluating Damage of CFRP Using the PVDF Comb Transducer

    Recently, fiber reinforced plastic (FRP) materials become to be used more in producing airplanes because of high specific strength and low weight. However, there can be delamination caused from unexpected impact during the service flight. Since strength reduce comes with these delamination defects, defects in the composite materials should be monitored for safety of the airplane. A PVDF transducer can be used for on-line health monitoring economically. In this study, comb type of PVDF transducer was fabricated for generating and receiving of the guided wave at specific wavelength and was applied to evaluate natural delamination defect with the guided wave. Natural delamination in CFRP was produced with free dropping weight on CFRP surface between the transmitter and the receiver transducers. At every impacts, guided wave was generated and received in the pitch-catch way with the PVDF(Polyvinylidene fluoride) comb transducer and variation of the guided wave signal was compared according to accumulation of impact damage.

  5. Dispersing multi-component and unstable powders in aqueous media using comb-type anionic polymers

    Laarz, E.; Kauppi, A.; Andersson, K.M.;

    2006-01-01

    We have investigated the effect of polymeric dispersants on the rheological properties and consolidation behavior of concentrated cemented carbide (WC-Co) and magnesia (MgO) suspensions. The relatively novel types of comb-type anionic polymers with grafted non-ionic side chains are effective...... dispersants also in multi-component powder mixtures with a complex solution and surface chemistry and result in more robust suspensions at significantly higher solids loading compared with e.g., a traditional cationic polyelectrolyte. Direct force measurements on comb-type dispersants with different lengths...... of the grafted ethylene oxide side chains showed that the dispersants adsorb onto a MgO surface and infer a repulsion where the range scales with the length of the poly ethylene oxide side chains. The compressibility and the consolidation behavior of MgO particle networks in response to a centrifugal...

  6. Photonic chip-based optical frequency comb using soliton Cherenkov radiation.

    Brasch, V; Geiselmann, M; Herr, T; Lihachev, G; Pfeiffer, M H P; Gorodetsky, M L; Kippenberg, T J

    2016-01-22

    Optical solitons are propagating pulses of light that retain their shape because nonlinearity and dispersion balance each other. In the presence of higher-order dispersion, optical solitons can emit dispersive waves via the process of soliton Cherenkov radiation. This process underlies supercontinuum generation and is of critical importance in frequency metrology. Using a continuous wave-pumped, dispersion-engineered, integrated silicon nitride microresonator, we generated continuously circulating temporal dissipative Kerr solitons. The presence of higher-order dispersion led to the emission of red-shifted soliton Cherenkov radiation. The output corresponds to a fully coherent optical frequency comb that spans two-thirds of an octave and whose phase we were able to stabilize to the sub-Hertz level. By preserving coherence over a broad spectral bandwidth, our device offers the opportunity to develop compact on-chip frequency combs for frequency metrology or spectroscopy. PMID:26721682

  7. Frequency-stabilized Yb:fiber comb with a tapered single-mode fiber

    Yang, Xie; Hai-Nian, Han; Long, Zhang; Zi-Jiao, Yu; Zheng, Zhu; Lei, Hou; Li-Hui, Pang; Zhi-Yi, Wei

    2016-04-01

    We demonstrate a stable Yb:fiber frequency comb with supercontinuum generation by using a specially designed tapered single-mode fiber, in which a spectrum spanning from 500 nm to 1500 nm is produced. The carrier-envelope offset signal of the Yb:fiber comb is measured with a signal-to-noise ratio of more than 40 dB and a linewidth narrower than 120 kHz. The repetition rate and carrier-envelope offset signals are simultaneously phase locked to a microwave reference frequency. Project supported by the National Basic Research Program of China (973 Program) (Grant No. 2012CB821304) and the National Natural Science Foundation of China (Grant No. 61378040).

  8. Study on high coupling efficiency Er-doped fiber laser for femtosecond optical frequency comb

    Pang, Lihui; Liu, Wenjun; Han, Hainian; Wei, Zhiyi

    2016-09-01

    The femtosecond laser is crucial to the operation of the femtosecond optical frequency comb. In this paper, a passively mode-locked erbium-doped fiber laser is presented with 91.4 fs pulse width and 100.8 MHz repetition rate, making use of the nonlinear polarized evolution effect. Using a 976 nm pump laser diode, the average output power is 16 mW from the coupler and 27 mW from the polarization beam splitter at the pump power of 700 mW. The proposed fiber laser can offer excellent temporal purity in generated pulses with high power, and provide a robust source for fiber-based frequency combs and supercontinuum generation well suited for industrial applications.

  9. Generation of multiphoton entangled quantum states by means of integrated frequency combs.

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

    2016-03-11

    Complex optical photon states with entanglement shared among several modes are critical to improving our fundamental understanding of quantum mechanics and have applications for quantum information processing, imaging, and microscopy. We demonstrate that optical integrated Kerr frequency combs can be used to generate several bi- and multiphoton entangled qubits, with direct applications for quantum communication and computation. Our method is compatible with contemporary fiber and quantum memory infrastructures and with chip-scale semiconductor technology, enabling compact, low-cost, and scalable implementations. The exploitation of integrated Kerr frequency combs, with their ability to generate multiple, customizable, and complex quantum states, can provide a scalable, practical, and compact platform for quantum technologies. PMID:26965623

  10. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    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

  11. Unified approach to cascaded stimulated Brillouin scattering and frequency-comb generation

    Dong, Mark; Winful, Herbert G.

    2016-04-01

    We present a unified approach to cascaded stimulated Brillouin scattering and frequency-comb generation in which the multitude of interacting pump, Stokes, and anti-Stokes optical fields is described by a single forward wave and a single backward wave at a single carrier frequency. The envelopes of these two waves are modulated through coupling to a single acoustic oscillation and through four-wave mixing. Starting from a single pump field, we observe the emergence of a comb of frequencies as the intensity is increased. The set of three differential equations derived here is sufficient to describe the generation of any number of Brillouin sidebands in oscillator systems that would have required hundreds of coupled equations in the standard approach. We test this approach on some published experiments and find excellent agreement with the results.

  12. Spectroscopy of the methane ν3 band with an accurate midinfrared coherent dual-comb spectrometer

    We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 μm. The amplitude and phase spectra of the P, Q, and partial R branches of the methane ν3 band are measured at 25 to 100 MHz point spacing with resolution under 10 kHz and a signal-to-noise ratio of up to 3500. A fit of the absorbance and phase spectra yields the center frequency of 132 rovibrational lines. The systematic uncertainty is estimated to be 300 kHz, which is 10-3 of the Doppler width and a 10-fold improvement over Fourier transform spectroscopy. These data quantify the accuracy and resolution achievable with direct comb spectroscopy in the midinfrared.

  13. Transmission comb of a distributed Bragg reflector with two surface dielectric gratings

    Zhao, Xiaobo

    2016-02-19

    The transmission behaviour of a distributed Bragg reector (DBR) with surface dielectric gratings on top and bottom is studied. The transmission shows a comb-like spectrum in the DBR band gap, which is explained in the Fano picture. The number density of the transmission peaks increases with increasing number of cells of the DBR, while the ratio of the average full width at half maximum to the corresponding average free spectral range, being only few percent for both transversal electric and magnetic waves, is almost invariant. The transmission peaks can be narrower than 0.1 nm and are fully separated from each other in certain wavebands. We further prove that the transmission combs are robust against randomness in the heights of the DBR layers. Therefore, the proposed structure is a candidate for an ultra-narrow-band multichannel filter or polarizer.

  14. Sex Determination, Sex Ratios, and Genetic Conflict

    Werren, John H.; Beukeboom, Leo W.

    1998-01-01

    Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in oppo

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

    Optical frequency comb technology has been used in this work for the first time to investigate the nuclear structure of light radioactive isotopes. Therefore, three laser systems were stabilized with different techniques to accurately known optical frequencies and used in two specialized experiments. Absolute transition frequency measurements of lithium and beryllium isotopes were performed with accuracy on the order of 10-10. Such a high accuracy is required for the light elements since the nuclear volume effect has only a 10-9 contribution to the total transition frequency. For beryllium, the isotope shift was determined with an accuracy that is sufficient to extract information about the proton distribution inside the nucleus. A Doppler-free two-photon spectroscopy on the stable lithium isotopes 6,7Li was performed in order to determine the absolute frequency of the 2S → 3S transition. The achieved relative accuracy of 2 x 10-10 is improved by one order of magnitude compared to previous measurements. The results provide an opportunity to determine the nuclear charge radius of the stable and short-lived isotopes in a pure optical way but this requires an improvement of the theoretical calculations by two orders of magnitude. The second experiment presented here was performed at ISOLDE/CERN, where the absolute transition frequencies of the D1 and D2 lines in beryllium ions for the isotopes 7,9,10,11Be were measured with an accuracy of about 1 MHz. Therefore, an advanced collinear laser spectroscopy technique involving two counter-propagating frequency-stabilized laser beams with a known absolute frequency was developed. The extracted isotope shifts were combined with recent accurate mass shift calculations and the root-mean square nuclear charge radii of 7,10Be and the one-neutron halo nucleus 11Be were determined. Obtained charge radii are decreasing from 7Be to 10Be and increasing again for 11Be. While the monotone decrease can be explained by a nucleon

  16. Small displacement evaluation by a highly-coherent tunable laser referenced to stabilized femtosecond comb

    Číp, Ondřej; Šmíd, Radek; Hrabina, Jan; Čížek, Martin; Hucl, Václav; Lešundák, Adam; Holá, Miroslava; Lazar, Josef; Růžička, Bohdan

    Budva: University of Montenegro, 2013. s. 51. [ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva] R&D Projects: GA ČR GAP102/10/1813; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : passive optical resonator * highly-coherent tunable laser * femtosecond comb Subject RIV: BH - Optics, Masers, Lasers

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

    Saha, Kasturi; Okawachi, Yoshitomo; Shim, Bonggu; Levy, Jacob S.; Salem, Reza; Johnson, Adrea R.; Foster, Mark A.; 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 ...

  18. Collective control of the timing and type of comb construction by honey bees (Apis mellifera)

    Pratt, Stephen

    2004-01-01

    This review considers how a honey bee colony optimally controls the timing and type of new comb construction. Optimal timing requires bees to balance the energy costs of construction with the opportunity costs of lacking storage space during nectar flows. They do so by conditioning the start of building on (1) the attainment of a fullness threshold, and (2) the availability of nectar. A dynamic optimization model has suggested that this rule is slightly suboptimal, but may compensate for this...

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

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

    2012-01-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut f\\"ur Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\\"ur 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 ...

  20. Small displacement evaluation by a highly-coherent tunable laser referenced to stabilized femtosecond comb

    Číp, Ondřej; Šmíd, Radek; Hrabina, Jan; Čížek, Martin; Hucl, Václav; Lešundák, Adam; Holá, Miroslava; Růžička, Bohdan; Lazar, Josef

    Budva : University of Montenegro, 2013. s. 51. [ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva] R&D Projects: GA ČR GAP102/10/1813; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : passive optical resonator * highly-coherent tunable laser * femtosecond comb Subject RIV: BH - Optics, Masers, Lasers

  1. Data review leading to a conceptual model of the hydrogeology of the Combe Down area, Bath

    Macdonald, D. M. J.; Whitehead, E J; Butcher, A.S.

    2000-01-01

    Bath and North East Somerset Council (B&NES) has obtained funds from the Department of Environment, Transport and the Regions to carry-out stabilisation of stone mines located in the Combe Down area to the south-east of the city of Bath. There are potentially significant engineering geology and hydrogeology implications associated with the project. The British Geological Survey (BGS) has been appointed by B&NES to provide independent geological advice. In this role, BGS has undert...

  2. CombeChem: semantic support for the chemical information life cycle

    Frey, Jeremy G.

    2006-01-01

    CombeChem” provided experience of e-science semantic support for the chemical data lifecycle, from inception in the laboratory to dissemination of data, showing how laboratory data should be recorded, using electronic laboratory notebooks, enriched with appropriate metadata, to ensure information can be correctly understood when subsequently accessed, (“Annotation@Source”). Chemical information results from a chain of analysis & data integration. Current chemical data storage methodologies p...

  3. Laser frequency combs and ultracold neutrons to probe braneworlds through induced matter swapping between branes

    Sarrazin, Michael; Petit, Fabrice

    2008-01-01

    This paper investigates a new experimental framework to test the braneworld hypothesis. Recent theoretical results have shown the possibility of matter exchange between branes under the influence of suitable magnetic vector potentials. It is shown that the required conditions might be achieved with present-day technology. The experiment uses a source of pulsed and coherent electromagnetic radiation and relies on the Hansch frequency comb technique well-known in ultrahigh-precision spectroscop...

  4. Brazilian species of Gadila (Mollusca: Scaphopoda: Gadilidae): rediscovery of Gadila elongata comb. nov. and shell morphometrics

    Carlos H. S. Caetano; Victor Scarabino; Ricardo S. Absalão

    2010-01-01

    Gadila elongata comb. nov. was described in 1920 from the northern Gulf of Mexico. Until recently, it was only known from the type locality. Herein we present the first record of G. elongata from Brazil (Northeast coast, Ceará state, collected at 177 m) and a morphometrics analysis of the Brazilian species of Gadila. A multivariate Discriminant Function Analysis, based on nine shell morphometric variables (length, maximum diameter, length to maximum diameter ratio, distance of point of maximu...

  5. Asymptotic Capacity of Wireless Ad Hoc Networks with Realistic Links under a Honey Comb Topology

    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.

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

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

    2014-01-01

    We demonstrate an octave-spanning frequency comb with a spectrum covering wavelengths from 1,540 nm up to 3,200 nm. The supercontinuum is generated by pumping a 1-cm long dispersion engineered silicon wire waveguide by 70 fs pulses with an energy of merely 15 pJ. We confirm the phase coherence of the output spectrum by beating the supercontinuum with narrow bandwidth CW lasers. We show that the experimental results are in agreement with numerical simulations.

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

    Bally J.

    2011-07-01

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

  8. Analysis of Trace Impurities in Semiconductor Gas via Cavity-Enhanced Direct Frequency Comb Spectroscopy

    Cossel, Kevin C.; Adler, Florian; 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 -- mea...

  9. Towards highest spectral efficiency: Optical sinc-shaped Nyquist pulses generation from rectangular frequency comb

    Brès, Camille Sophie; Soto, Marcelo A.; Alem, Mehdi; Shoaie, Mohammad Amin; Vedadi, Armand; Schneider, Thomas; Thévenaz, Luc

    2014-01-01

    In this paper, we review a method to produce optical sinc-shaped Nyquist pulses with unprecedented quality. The method is based on the synthesis of a rectangular shaped and phase-locked frequency comb from a combination of intensity modulators. The result is a highly flexible pulse generator that can easily be integrated in already installed communication systems. All-optical pulse shaping methods for highest spectral efficiencies are attractive since high-bitrate spectrally efficient channel...

  10. Conformation of comb liquid crystal polymers by neutron small angle scattering

    A review is made of the direct information obtained by small angle neutron scattering about the anisotropy of the components parallel and perpendicular to the orienting magnetic field of the radius of gyration of comb like liquid crystal polymers. The behaviour of the conformation versus temperature is reported for several samples. Until now all samples show an oblate conformation in the smectic phase and probably the whole range of the nematic phase. The results are compared with the available theoretical predictions

  11. 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.

    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 : 1ω7c 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

  12. Reclassification of [Glaciecola] lipolytica and [Aestuariibacter] litoralis in Aliiglaciecola gen. nov., as Aliiglaciecola lipolytica comb. nov. and Aliiglaciecola litoralis comb. nov., respectively.

    Jean, Wen Dar; Hsu, Cheng Yu; Huang, Ssu-Po; Chen, Jwo-Sheng; Lin, Saulwood; Su, Mong-Huai; Shieh, Wung Yang

    2013-08-01

    Following phylogenetic analysis based on 16S rRNA gene sequences, together with DNA G+C contents and differential chemotaxonomic and physiological characteristics, a new genus with the name Aliiglaciecola gen. nov. is proposed to more appropriately accommodate two recognized species of the genera Glaciecola and Aestuariibacter. Accordingly, [Glaciecola] lipolytica and [Aestuariibacter] litoralis should be reassigned to the novel genus as Aliiglaciecola lipolytica comb. nov. (type strain, E3(T) = JCM 15139(T) = CGMCC 1.7001(T)) and Aliiglaciecola litoralis comb. nov. (type strain, KMM 3894(T) = JCM 15896(T) = NRIC 0754(T)), respectively. Aliiglaciecola lipolytica is proposed as the type species of this new genus. Physiologically, the combined characteristics of positive reactions for nitrate reduction and growth at 4 °C and 36 °C distinguish the new genus from the genera Aestuariibacter and Glaciecola by one to three traits. Moreover, the new genus is also distinguished from the genus Glaciecola by the fatty acid profile and distinguished from the genus Aestuariibacter by the differences of major isoprenoid quinone (MK-7 vs Q-8) and DNA G+C content (40.8-43.0 mol% vs 48.0-54.0 mol%). PMID:23315410

  13. Massively parallel dual-comb molecular detection with subharmonic optical parametric oscillators

    Smolski, Viktor O; Xu, Jia; Vodopyanov, Konstantin L

    2016-01-01

    Mid-infrared (mid-IR) spectroscopy offers unparalleled sensitivity for the detection of trace gases, solids and liquids, which is based on the existence of strong telltale vibrational bands in this part of the spectrum. It was shown more than a decade ago that a dual-comb Fourier spectroscopy could provide superior spectral coverage combined with high resolution and extremely fast data acquisition. Capabilities of this method were limited because of difficulty of producing twins of mutually coherent frequency combs in the mid- IR. Here we report a phase-coherent and broadband dual-comb system that is based on a pair of subharmonic (frequency-divide-by-two) optical parametric oscillators, pumped in turn by two phase-locked thulium fiber lasers at 2-micron wavelength. We demonstrate simultaneous detection of multiple molecular species in the whole band of 3.2-5.3 microns (frequency span 1200 cm^{-1}) augmented by the pump laser band of 1.85-2 microns (span 400 cm^{-1}), with spectral resolution 0.01-0.07 cm^{-1...

  14. COMBS: open source python library for RVE generation - Application to microscale diffusion simulations in cementitious materials

    In the context of radioactive waste storage and disposal, the knowledge of the concrete diffusivity is primordial in the numerical simulations of the long term behavior of these materials. COMBS is an open source python library, it is used to define the shapes of the inclusions, to insert them in the box featuring the representative volume element (RVE) of the cementitious medium, and to assess their diffusive properties. The algorithms developed in COMBS target a fast placement of the inclusions and a fast generation of the RVE shape and mesh. Two application cases are considered: the unaltered material diffusivity and the degraded material diffusivity. The first case of application focuses on the description of the capillary porosity. The second application case focuses on the description of the degradation of cementitious material (mineral and porosity) and the diffusive properties associated. The reliability of the analytical effective medium approximations (MT and SC) is confirmed from 3D finite elements (FE) calculations performed on a matrix-inclusions microstructure obtained by RVE generation with Combs. The results also show the need to take into account the percolation behavior

  15. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals.

    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

  16. Spectral distortion of dual-comb spectrometry due to repetition rate fluctuation

    Hong-Lei, Yang; Hao-Yun, Wei; Yan, Li

    2016-04-01

    Dual-comb spectrometry suffers the fluctuations of parameters in combs. We demonstrate that the repetition rate is more important than any other parameter, since the fluctuation of the repetition rate leads to a change of difference in the repetition rate between both combs, consequently causing the conversion factor variation and spectral frequency misalignment. The measured frequency noise power spectral density of the repetition rate exhibits an integrated residual frequency modulation of 1.4 Hz from 1 Hz to 100 kHz in our system. This value corresponds to the absorption peak fluctuation within a root mean square value of 0.19 cm‑1 that is verified by both simulation and experimental result. Further, we can also simulate spectrum degradation as the fluctuation varies. After modifying misaligned spectra and averaging, the measured result agrees well with the simulated spectrum based on the GEISA database. Project supported by the State Key Laboratory of Precision Measurement Technology & Instruments of Tsinghua University and the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205147).

  17. Frequency-comb formation in doubly resonant second-harmonic generation

    Leo, F.; Hansson, T.; Ricciardi, I.; De Rosa, M.; Coen, S.; Wabnitz, S.; Erkintalo, M.

    2016-04-01

    We theoretically study the generation of optical frequency combs and corresponding pulse trains in doubly resonant intracavity second-harmonic generation (SHG). We find that, despite the large temporal walk-off characteristic of realistic cavity systems, the nonlinear dynamics can be accurately and efficiently modeled using a pair of coupled mean-field equations. Through rigorous stability analysis of the system's steady-state continuous-wave solutions, we demonstrate that walk-off can give rise to an unexplored regime of temporal modulation instability. Numerical simulations performed in this regime reveal rich dynamical behaviors, including the emergence of temporal patterns that correspond to coherent optical frequency combs. We also demonstrate that the two coupled equations that govern the doubly resonant cavity behavior can, under typical conditions, be reduced to a single mean-field equation akin to that describing the dynamics of singly-resonant-cavity SHG [F. Leo et al., Phys. Rev. Lett. 116, 033901 (2016), 10.1103/PhysRevLett.116.033901]. This reduced approach allows us to derive a simple expression for the modulation instability gain, thus permitting us to acquire significant insight into the underlying physics. We anticipate that our work will have a wide impact on the study of frequency combs in emerging doubly resonant cavity SHG platforms, including quadratically nonlinear microresonators.

  18. Sex and Fertility After SCI

    Full Text Available ... women face after a spinal cord injury? How should expectations about sex change after a spinal cord ... people do with a catheter during sex? How should people deal with spasticity during sex? What about ...

  19. Sex and Fertility After SCI

    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 ...

  20. Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy

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

    2016-01-01

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

  1. Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy.

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

    2016-01-01

    An important technique for discovering and characterizing planets beyond our solar system relies upon measurement of weak Doppler shifts in the spectra of host stars induced by the influence of orbiting planets. A recent advance has been the introduction of optical frequency combs as frequency references. Frequency combs produce a series of equally spaced reference frequencies and they offer extreme accuracy and spectral grasp that can potentially revolutionize exoplanet detection. Here we demonstrate a laser frequency comb using an alternate comb generation method based on electro-optical modulation, with the comb centre wavelength stabilized to a molecular or atomic reference. In contrast to mode-locked combs, the line spacing is readily resolvable using typical astronomical grating spectrographs. Built using commercial off-the-shelf components, the instrument is relatively simple and reliable. Proof of concept experiments operated at near-infrared wavelengths were carried out at the NASA Infrared Telescope Facility and the Keck-II telescope. PMID:26813804

  2. Comb polymer architecture and particle size effects on the behavior of biphasic nanoparticle inks for direct-write assembly

    Yoshikawa, Jun

    Biphasic nanoparticle mixtures composed of attractive and repulsive colloidal species enable the direct-write assembly of 3D structures with much finer features than those produced by pure colloidal gels. These mixtures rely on the use of comb polymer dispersants to render one particle population stable, while the other population is attractive. In this thesis, we systematically investigate the effects of comb polymer architecture and particle size ratio on the behavior of biphasic nanoparticle inks with the overarching aim of further advancing the direct-write assembly of 3D colloidal structures. We first investigated the effects of both pure polyelectrolytes, poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA), and comb polymer dispersants composed of a PMAA backbone with methoxy-poly(ethylene oxide) (mPEO) teeth of varying molecular weights on the stability of barium titanate (BaTiO 3) suspensions. While each dispersant imparts stability to BaTiO 3 nanoparticles at low ionic strength (nanoparticle suspensions are studied. Shear elastic modulus, shear yield stress, and compressive yield stress are measured for mixtures of varying total volume fraction, attractive-to-repulsive volume fraction, and particle size ratio between attractive and repulsive species. Our observations indicate that the repulsive particles hinder the formation of the attractive gel network. The time required for shear elastic modulus to approach a steady-state value increases with the fraction of repulsive species. Furthermore, this behavior becomes more significant with increasing the repulsive particle size. Additionally, we find that biphasic suspensions composed of both identical and different mean particle sizes exhibit larger φ-scaling exponents for compressive yield stress than shear yield stress, indicating that such systems become more resistant to compression with increasing φ. This observation suggests that the biphasic suspensions flowing through fine nozzles are more

  3. Beliefs About Sex and Parent-Child-Church Sex Communication Among Church-Based African American Youth.

    Moore, Erin; Berkley-Patton, Jannette; Bohn, Alexandria; Hawes, Starlyn; Bowe-Thompson, Carole

    2015-10-01

    Parent-child sex communication has been shown to be protective against sexual risk among African American youth. The current study sought to use the theory of planned behavior as a framework for focus group discussions (N = 54 youth participants aged 12-19 years) to explore church youths' (a) sex beliefs and values (attitudes), (b) sources and evaluation of sex communication and education (subjective norms), (c) facilitator/barriers to adolescent sexual risk reduction and communication behaviors (perceived behavioral control), and (d) intentions to engage in these behaviors. Additionally, participants identified strategies for consideration in developing tailored parent-child-church sex communication education programs for use in African American churches. Themes suggested both positive and negative attitudes toward premarital sex and parents and churches as key sources of sex education and communication. Strategies to enhance parent-child-church sex communication are discussed in the context of these findings. PMID:25260385

  4. Juvenile Sex Offenders.

    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

  5. Comb-Type Grafted Hydrogels of PNIPAM and PDMAEMA with Reversed Network-Graft Architectures from Controlled Radical Polymerizations

    Sheng-Qi Chen

    2016-02-01

    Full Text Available Dual thermo- and pH-responsive comb-type grafted hydrogels of poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA and poly(N-isopropylacrylamide (PNIPAM with reversed network-graft architectures were synthesized by the combination of atom transfer radical polymerization (ATRP, reversible addition-fragmentation chain transfer (RAFT polymerization and click chemistry. Two kinds of macro-cross-linkers with two azido groups at one chain-end and different chain length [PNIPAM–(N32 and PDMAEMA–(N32] were prepared with N,N-di(β-azidoethyl 2-halocarboxylamide as the ATRP initiator. Through RAFT copolymerization of DMAEMA or NIPAM with propargyl acrylate (ProA using dibenzyltrithiocarbonate as a chain transfer agent, two network precursors with different content of alkynyl side-groups [P(DMAEMA-co-ProA and P(NIPAM-co-ProA] were obtained. The subsequent azido-alkynyl click reaction of macro-cross-linkers and network precursors led to the formation of the network-graft hydrogels. These dual stimulus-sensitive hydrogels exhibited rapid response, high swelling ratio and reproducible swelling/de-swelling cycles under different temperatures and pH values. The influences of cross-linkage density and network-graft architecture on the properties of the hydrogels were investigated. The release of ceftriaxone sodium from these hydrogels showed both thermal- and pH-dependence, suggesting the feasibility of these hydrogels as thermo- and pH-dependent drug release devices.

  6. Brandtodinium gen. nov. and B. nutricula comb. Nov. (Dinophyceae), a dinoflagellate commonly found in symbiosis with polycystine radiolarians.

    Probert, Ian; Siano, Raffaele; Poirier, Camille; Decelle, Johan; Biard, Tristan; Tuji, Akihiro; Suzuki, Noritoshi; Not, Fabrice

    2014-04-01

    Symbiotic interactions between pelagic hosts and microalgae have received little attention, although they are widespread in the photic layer of the world ocean, where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders Spumellaria, Collodaria and Nassellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate Scrippsiella nutricula, a species originally described by Karl Brandt in the late nineteenth century as Zooxanthella nutricula. The free-living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free-living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine-symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free-living stage does not match that of Scrippsiella or related genera, and LSU and SSU rDNA-based molecular phylogenies place these symbionts in a distinct clade within the Peridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name Brandtodinium gen. nov. and the recombination of S. nutricula as B. nutricula comb. nov. PMID:26988195

  7. Impact of particle size on interaction forces between ettringite and dispersing comb-polymers in various electrolyte solutions.

    Ferrari, Lucia; Kaufmann, Josef; Winnefeld, Frank; Plank, Johann

    2014-04-01

    The inter-particle forces play a fundamental role for the flow properties of a particle suspension in response to shear stresses. In concrete applications, cement admixtures based on comb-polymers like polycarboxylate-ether-based superplasticizer (PCE) are used to control the rheological behavior of the fresh mixtures, as it is negatively impacted by certain early hydration products, like the mineral ettringite. In this work, dispersion forces due to PCE were measured directly at the surface of ettringite crystals in different electrolyte solutions by the means of atomic force microscopy (AFM) applying spherical and sharp silicon dioxide tips. Results show an effective repulsion between ettringite surface and AFM tips for solutions above the IEP of ettringite (pH∼12) and significant attraction in solution at lower pH. The addition of polyelectrolytes in solution provides dispersion forces exclusively between the sharp tips (radius ≈ 10 nm) and the ettringite surface, whereas the polymer layer at the ettringite surface results to be unable to disperse large colloidal probes (radius ≈ 10 μm). A simple modeling of the inter-particle forces explains that, for large particles, the steric hindrance of the studied PCE molecules is not high enough to compensate for the Van der Waals and the attractive electrostatic contributions. Therefore, in cement suspensions the impact of ettringite on rheology is probably not only related to the particle charge, but also related to the involved particle sizes. PMID:24491324

  8. Group velocity enhancement for guided lightwave by band-pulling effect in single-mode silicon comb photonic crystal wires

    Photonic crystal waveguides (PCWs), which usually exhibit the slow-light effect near the band edge frequency, may in fact be used to induce higher group velocity (vg). The presence of the band edge, due to periodically carving a strip waveguide (SW) into a PCW of a comb-shape dielectric wire, results in the band-pulling effect. The band-pulling effect, which lifts the fundamental photonic band toward the band gap, not only enhances vg by reducing the effective index but also prevents the band from bending toward the light cone of the core material, leading to additional vg enhancement. The maximum PCW vg (0.43c; c = vacuum light speed) found from numerical modeling was higher than SW vg at all widths and thicknesses, except for extremely low thickness below 80 nm. We found by numerical modeling and experiments that up to 75% enhancement at the 1550 nm wavelength may be achieved in a fabricated single-mode PCW (0.38c) compared with an SW (0.21c) of the same width and thickness. The higher vg was confirmed by measuring the PCW’s group index using ring resonators. The PCW propagation loss of 2.1 dB mm−1 and the bandwidth-distance product of 100 Gb/s-cm were deduced from experimental results. Our findings seemed encouraging for employing PCWs in optical interconnect applications. (paper)

  9. Time-Delay Interferometry with optical frequency comb

    Tinto, Massimo; Yu, Nan

    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 probabili...

  10. Observation of Rb Two-Photon Absorption Directly Excited by an Erbium-Fiber-Laser-Based Optical Frequency Comb via Spectral Control

    Wu, Jiutao; Dai, Xiaoliang; Qin, Zhengyu; Zhang, Zhigang; Zhao, Jianye

    2013-01-01

    We demonstrated the observation of Rb two-photon absorption directly excided by an optical frequency comb at fiber communication bands. A chain of comb spectral control is elaborately implemented to increase the power of the second harmonic optical frequency comb generation and the two-photon transition strength. A two-photon transition spectrum is obtained with clearly resolved transition lines. It provides a potential approach to realize the optical frequency comb or optical clock at ~1.5{\\mu}m with high stability and accuracy.

  11. Steroid signaling activation and intracellular localization of sex steroid receptors

    Giraldi, Tiziana; Giovannelli, Pia; Di Donato, Marzia; Castoria, Gabriella; Migliaccio, Antimo; Auricchio, Ferdinando

    2010-01-01

    In addition to stimulating gene transcription, sex steroids trigger rapid, non-genomic responses in the extra-nuclear compartment of target cells. These events take place within seconds or minutes after hormone administration and do not require transcriptional activity of sex steroid receptors. Depending on cell systems, activation of extra-nuclear signaling pathways by sex steroids fosters cell cycle progression, prevents apoptosis, leads to epigenetic modifications and increases cell migrat...

  12. Juvenile Sex Offenders.

    Ryan, Eileen P; Otonichar, Joseph M

    2016-07-01

    Sexual offending by juveniles accounts for a sizable percentage of sexual offenses, especially against young children. In this article, recent research on female juvenile sex offenders (JSOs), risk factors for offending in juveniles, treatment, and the ways in which these youth may differ from general delinquents will be reviewed. Most JSOs do not go on to develop paraphilic disorders or to commit sex offenses during adulthood, and as a group, they are more similar to nonsexual offending juvenile delinquents than to adult sex offenders. Recent research has elucidated some differences between youth who commit sex offenses and general delinquents in the areas of atypical sexual interests, the use of pornography, and early sexual victimization during childhood. PMID:27222141

  13. Sex, Deportation and Rescue

    Plambech, Sine

    2016-01-01

    This contribution explores the economies interlinked by the migration of Nigerian women sex workers. The literature and politics of sex work migration and human trafficking economies are commonly relegated to the realm that focuses on profits for criminal networks and pimps, in particular...... recirculating the claim that human trafficking is the “third largest” criminal economy after drugs and weapons. Based on ethnographic fieldwork among Nigerian sex worker migrants conducted in Benin City, Nigeria, in 2011 and 2012, this study brings together four otherwise isolated migration economies...... – facilitation, remittances, deportation, and rescue – and suggests that we have to examine multiple sites and relink these in order to more fully understand the complexity of sex work migration. Drawing upon literature within transnational feminist analysis, critical human trafficking studies, and migration...

  14. Safer Sex Guidelines

    ... barriers. Be sure to use water-based lubricants. Oral sex has low risk of transmitting HIV, but it ... you are willing to take. Know how much protection you want to use during different kinds of ...

  15. Sex Differences and Sex Steroids in Lung Health and Disease

    Townsend, Elizabeth A.; Miller, Virginia M.; Prakash, Y. S.

    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 ...

  16. Sex-role and opposite-sex interpersonal attraction.

    Lombardo, J P; Francis, P L; Brown, S

    1988-12-01

    Androgynous, traditional, and undifferentiated male and female subjects indicated their attraction to three opposite-sex strangers who were described as having an androgynous, traditional, and undifferentiated sex-role. Subjects' ability to describe the sex-roles of the strangers was also measured. Androgynous strangers were most preferred, undifferentiated strangers least preferred. The least preferred undifferentiated strangers' sex-role was most accurately described. Subjects were least successful in describing the androgynous sex-role. PMID:3226838

  17. Morphometric sexing of Northwest Atlantic Roseate Terns

    Palestis, Brian G.; Nisbet, Ian C.T.; Hatch, Jeremy J.; Szczys, Patricia; Spendelow, Jeffrey A.

    2012-01-01

    A difficulty in the study of monomorphic species is the inability of observers to visually distinguish females from males. Based on a sample of 745 known-sex birds nesting at Bird Island, MA, USA, a discriminant function analysis (DFA) was used to sex Roseate Terns (Sterna dougallii) of the Northwest Atlantic population using morphological measurements. DFA using only the total length of the head (including the bill) correctly identified the sex of approximately 86% of the terns, which increased to 88% if both members of a pair were measured. Including additional measurements increased these percentages slightly, to 87% and 90%, respectively. These levels of accuracy are generally higher than those reported for other species of terns. Because female-female pairs are frequent in this population, one cannot assume that the member of a pair with the larger head is a male, and additional discriminant functions were developed to help separate female-female from male-female pairs.

  18. Echelle spectrograph calibration with a frequency comb based on a harmonically mode-locked fiber laser: a proposal

    Details for constructing an astronomical frequency comb suitable as a wavelength reference for echelle spectrographs associated with optical telescopes are outlined. The source laser for the frequency comb is a harmonically mode-locked fiber laser with a central wavelength of 1.56 μm. The means of producing a repetition rate greater than 7 GHz and a peak optical power of ∼8 kW are discussed. Conversion of the oscillator light into the visible can occur through a two-step process of (i) nonlinear conversion in periodically poled lithium niobate and (ii) spectral broadening in photonic crystal fiber. While not necessarily octave spanning in spectral range to permit the use of an f -to- 2f interferometer for offset frequency control, the frequency comb can be granted accuracy by linking the mode spacing and a comb tooth to separate frequency references. The design avoids the use of a Fabry-Perot cavity to increase the mode spacing of the frequency comb; however, the level of supermode suppression and sideband asymmetry in the fiber oscillator and in the subsequent frequency conversion stages are aspects that need to be experimentally tested.

  19. Characterization of Perylene in Tropical Environment: Comparison of New and Old Fungus Comb for Identifying Perylene Precursor in Macrotermes gilvus Termite Nests of Peninsular Malaysia

    Alireza Riyahi Bakhtiari

    2010-01-01

    Full Text Available This is the first record on the distribution of perylene in new and old fungus combs of termite nest (Macrotermes gilvus in order to determine perylene source in tropical environment. Twenty four samples of new and old fungus combs, inner and outer nest walls, fresh and decomposed bark, decomposed stem, soil, and soil-wood interface were collected in order to test of two hypotheses; i Perylene is produced in the termite’s hindgut (M. gilvus and ii Perylene is present only in new fungus comb of M. gilvus termite nests. For one Station (Station A the profile of perylene concentration was the following order: fungus comb > outer nest wall ≥ Soil-Wood interface ≥ decomposed stem ≥ decomposed bark ≥ Inner nest wall > Soil. For the other Station (i.e. B the profile was new fungus comb > inner nest wall > old fungus comb ≥ outer nest wall ~ Soil. The perylene concentration was found up to 21-54 times higher in fungus comb as compare to the rest of the samples in Station A. whereas, the perylene concentration was 85-400 times higher in new fungus comb as compare to the remaining samples in Station B, this can be due to the production or accumulation of perylene in these nests. On the other hand, smaller termite nests (Stations C and E no perylene was detected, due to the fact that the new fungus comb was not found in those nests. The results confirmed the following hypotheses; perylene occurs only in new fungus comb and may be attributed to the high concentrations of aromatic rings of lignin in new fungus comb.

  20. Same sex families and children

    Mršević Zorica

    2009-01-01

    Introduction comprises the information on two main forms of same sex families, civic partnership (same sex partnership) and same sex marriage. Countries and various status modalities of legal regulations are mentioned. The main part of the text is dedicated to presentation of the findings of the most recent research on various aspects regarding children of same sex partnerships. It comprises presentations grouped in four main chapters: acceptance of same sex partnerships, acceptance of legal ...

  1. Predictors of Safer Sex Intentions and Protected Sex Among Heterosexual HIV-Negative Methamphetamine Users: An Expanded Model of the Theory of Planned Behavior

    Mausbach, Brent T.; Semple, Shirley J.; Strathdee, Steffanie A.; Thomas L Patterson

    2009-01-01

    The purpose of this study was to test a version of the Theory of Planned Behavior (TPB) for predicting safe sex behavior in a sample of 228 HIV-negative heterosexual methamphetamine users. We hypothesized that, in addition to TPB constructs, participants’ amount of methamphetamine use and desire to stop unsafe sex behaviors would predict intentions to engage in safer sex behaviors. In turn, we predicted that safer sex intentions would be positively correlated with participants’ percentage of ...

  2. Turnover of Sex Chromosomes in Celebensis Group Medaka Fishes.

    Myosho, Taijun; Takehana, Yusuke; Hamaguchi, Satoshi; Sakaizumi, Mitsuru

    2015-12-01

    Sex chromosomes and the sex-determining (SD) gene are variable in vertebrates. In particular, medaka fishes in the genus Oryzias show an extremely large diversity in sex chromosomes and the SD gene, providing a good model to study the evolutionary process by which they turnover. Here, we investigated the sex determination system and sex chromosomes in six celebensis group species. Our sex-linkage analysis demonstrated that all species had an XX-XY sex determination system, and that the Oryzias marmoratus and O. profundicola sex chromosomes were homologous to O. latipes linkage group (LG) 10, while those of the other four species, O. celebensis, O. matanensis, O. wolasi, and O. woworae, were homologous to O. latipes LG 24. The phylogenetic relationship suggested a turnover of the sex chromosomes from O. latipes LG 24 to LG 10 within this group. Six sex-linkage maps showed that the former two and the latter four species shared a common SD locus, respectively, suggesting that the LG 24 acquired the SD function in a common ancestor of the celebensis group, and that the LG 10 SD function appeared in a common ancestor of O. marmoratus and O. profundicola after the divergence of O. matanensis. Additionally, fine mapping and association analysis in the former two species revealed that Sox3 on the Y chromosome is a prime candidate for the SD gene, and that the Y-specific 430-bp insertion might be involved in its SD function. PMID:26497145

  3. Sex differences in schizophrenia.

    Abel, Kathryn M; Drake, Richard; Goldstein, Jill M

    2010-01-01

    Evidence suggests sex differences in schizophrenia reflect differences in both neurodevelopmental processes and social effects on disease risk and course. Male:female incidence approximates 1.4:1 but at older onset women predominate. Prevalence differences appear smaller. Men have poorer premorbid adjustment and present with worse negative and less depressive symptoms than women, which may explain their worse medium term outcome according to a range of measures. Substance abuse is a predominantly male activity in this group, as elsewhere. Findings of sex differences in brain morphology are inconsistent but occur in areas that normally show sexual dimorphism, implying that the same factors are important drivers of sex differences in both normal neurodevelopmental processes and those associated with schizophrenia. There are sex differences in antipsychotic responses but sex-specific endocrine effects on illness and response to antipsychotics are potentially complex. Oestrogen's role as an adjunctive medication is not yet clear due to methodological differences between the few randomized controlled trials. Services that are sensitive to differences in gender can better meet their patients' specific needs and potentially improve outcome. PMID:21047156

  4. Sex Determination and Sexual Organ Differentiation in Flowering Plants

    Hou Yanan; Li Fenglan; Gao Shumin

    2004-01-01

    The research in the genetics of sex determination and the differentiation of reproductive organs in flowering plants has long been a topic in recent years. Understanding the genetic and molecular mechanisms that control sex determination in flowering plants relies on detailed studies of the differentiation of sexual organs. Current theories about sex chromosomes have illuminated the mechanisms of plant sex determination. In addition, recent progress in cloning floral homeotic genes which regulate the identity of the floral organs has generated molecular markers to compare the developmental programs of male, female and hermaphrodite flowers in several species. In this review, the authors focus attention on these recent findings and provide a brief overview of the genetics of plant sex determination and the mechanism of sex determination gene expression and gene programs.

  5. Frequency comb offset dynamics of SESAM modelocked thin disk lasers.

    Emaury, Florian; Diebold, Andreas; Klenner, Alexander; Saraceno, Clara J; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

    2015-08-24

    We present a detailed study of the carrier-envelope offset (CEO) frequency dynamics of SESAM modelocked thin disk lasers (TDLs) pumped by kW-class highly transverse multimode pump diodes with a typical M(2) value of 200-300, and give guidelines for future frequency stabilization of multi-100-W oscillators. We demonstrate CEO frequency detection with > 30 dB signal-to-noise ratio with a resolution bandwidth of 100 kHz from a SESAM modelocked Yb:YAG TDL delivering 140 W average output power with 748-fs pulses at 7-MHz pulse repetition rate. We compare with a low-power CEO frequency stabilized Yb:CALGO TDL delivering 2.1 W with 77-fs pulses at 65 MHz. For both lasers, we perform a complete noise characterization, measure the relevant transfer functions (TFs) and compare them to theoretical models. The measured TFs are used to determine the propagation of the pump noise step-by-step through the system components. From the noise propagation analysis, we identify the relative intensity noise (RIN) of the pump diode as the main contribution to the CEO frequency noise. The resulting noise levels are not excessive and do not prevent CEO frequency stabilization. More importantly, the laser cavity dynamics are shown to play an essential role in the CEO frequency dynamics. The cavity TFs of the two lasers are very different which explains why at this point a tight CEO frequency lock can be obtained with the Yb:CALGO TDL but not with the Yb:YAG TDL. For CEO stabilization laser cavities should exhibit high damping of the relaxation oscillations by nonlinear intra-cavity elements, for example by operating a SESAM in the roll-over regime. Therefore the optimum SESAM operation point is a trade-off between enough damping and avoiding multiple pulsing instabilities. Additional cavity components could be considered for supplementary damping independent of the SESAM operation point. PMID:26368160

  6. Flexible PVDE comb transducers for excitation of axisymmetric guided waves in pipe

    Flexible PVDF pipe comb transducers are easy to install by wrapping around any size pipe. It is possible to mechanically couple these transducers to the pipe thereby eliminating the need to bond electrodes to the film and couple the transducer to the pipe. The simple fabrication process, installation, and affordability of these transducers makes them realistic candidates for condition based monitoring of some critical pipeline applications. These transducers are capable of exciting lower order axisymmetric modes with minimal radial displacement and maximum axial displacement as well as modes with both surface displacement components. This versatility is extremely important since under certain loading conditions modes with significant radial displacement are almost completely attenuated.

  7. Novel architecture for ultra-stable micro-ring resonator based optical frequency combs

    Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Ferrera, Marcello; Razzari, Luca; Duchesne, David; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto

    2014-01-01

    We report a novel geometry for OPOs based on nonlinear microcavity resonators. This approach relies on a self-locked scheme that enables OPO emission without the need for thermal locking of the pump laser to the microcavity resonance. By exploiting a CMOS-compatible microring resonator, we achieve oscillation with a complete absence of shutting down, or self-terminating behavior, a very common occurrence in externally pumped OPOs. Further, this scheme consistently produces very wide bandwidth (>300nm, limited by our experimental set-up) combs that oscillate at a spacing of the FSR of the micro cavity resonance.

  8. Localized frequency comb and formation of embedded solitons in silicon-based slot waveguides

    Roy, Samudra

    2012-01-01

    We explore the possibility to excite the so-called embedded solitons in specially designed slot waveguides based on silicon and silica or silicon nanocrystals. This requires the excitation of the structure with quasi-TM polarized pulses -- for which Raman effect is absent -- and at a specific infrared wavelength for which only the second- and fourth-order group velocity coefficients are non-vanishing. Pulses launched in these conditions will generate a spectrally localized continuum, associated to a frequency comb coming from the spectral interference of many embedded solitons.

  9. Application of digital signal processing in locking of CW lasers on optical frequency combs

    Čížek, Martin; Číp, Ondřej; Šmíd, Radek; Hrabina, Jan; Mikel, Břetislav; Lazar, Josef

    Budva : University of Montenegro, 2013. s. 146. [ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva] R&D Projects: GA ČR GPP102/11/P819; GA ČR GAP102/10/1813; GA TA ČR TA01010995; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : digital signal processing * CW lasers * optical frequency combs Subject RIV: BH - Optics, Masers, Lasers

  10. Multiple trapping on a comb structure as a model of electron transport in disordered nanostructured semiconductors

    Sibatov, R. T., E-mail: ren-sib@bk.ru; Morozova, E. V., E-mail: kat-valezhanina@yandex.ru [Ulyanovsk State University (Russian Federation)

    2015-05-15

    A model of dispersive transport in disordered nanostructured semiconductors has been proposed taking into account the percolation structure of a sample and joint action of several mechanisms. Topological and energy disorders have been simultaneously taken into account within the multiple trapping model on a comb structure modeling the percolation character of trajectories. The joint action of several mechanisms has been described within random walks with a mixture of waiting time distributions. Integral transport equations with fractional derivatives have been obtained for an arbitrary density of localized states. The kinetics of the transient current has been calculated within the proposed new model in order to analyze time-of-flight experiments for nanostructured semiconductors.

  11. Application of digital signal processing in locking of CW lasers on optical frequency combs

    Čížek, Martin; Číp, Ondřej; Šmíd, Radek; Hrabina, Jan; Mikel, Břetislav; Lazar, Josef

    Budva: University of Montenegro, 2013. s. 146. [ALT´13. Annual International Conference on Advanced Laser Technologies /21./. 16.09.2013-20.09.2013, Budva] R&D Projects: GA ČR GPP102/11/P819; GA ČR GAP102/10/1813; GA TA ČR TA01010995; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : digital signal processing * CW lasers * optical frequency combs Subject RIV: BH - Optics, Masers, Lasers

  12. Digital System for Keeping Optical Frequency Comb in Long- Term Stable Operation

    Čížek, Martin; Šmíd, Radek; Hucl, Václav; Lazar, Josef; Číp, Ondřej

    Piscataway: IEEE, 2014, s. 193-195. ISBN 978-1-4799-5252-6. [EFTF 2014. European Frequency and Time Forum /28./. Neuchatel (CH), 23.07.2014-26.07.2014] R&D Projects: GA ČR GAP102/10/1813; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01; GA MŠk EE2.4.31.0016 Institutional support: RVO:68081731 Keywords : optical frequency comb * long-term operation * stabilization * digital signal processing Subject RIV: BH - Optics, Masers, Lasers

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

    Zhao, Ying; Pang, Xiaodan; Deng, Lei; Yu, Xianbin; Zheng, Xiaoping; Tafur Monroy, Idelfonso

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multi-gigabit quadrature phase shift keying (QPSK) signal at 62.5, 82.5 and 102.5GHz carrier frequencies is studied to evaluate the downconversion efficiency. The proposed photonic harmonic mixer can be a candidate for...

  14. Displacement actuator controlled by a femtosecond comb and Fabry-Perot cavity in the feedback

    Číp, Ondřej; Čížek, Martin; Šmíd, Radek; Hucl, Václav; Mikel, Břetislav; Lazar, Josef

    Piscataway: IEEE, 2014, s. 606-607. ISBN 978-1-4799-5205-2. ISSN 0589-1485. [Conference on Precision Electromagnetic Measuerements /29./ CPEM 2014. Rio de Janeiro (BR), 24.08.2014-29.08.2014] R&D Projects: GA ČR GAP102/10/1813; GA ČR(CZ) GPP102/12/P962; GA ČR GB14-36681G; GA MŠk(CZ) LO1212; GA MŠk ED0017/01/01 Institutional support: RVO:68081731 Keywords : sub-nanometer resolution * frequency comb * homodyne interferometer * scale non-linearity * tunable laser Subject RIV: BH - Optics, Masers, Lasers

  15. The femtosecond optical frequency comb based tool for spectral analysis of molecular absorbtion gases

    Lešundák, Adam; Šmíd, Radek; Buchta, Zdeněk; Mikel, Břetislav; Lazar, Josef; Randula, A.; Číp, Ondřej

    Ostrava: TANGER Ltd, 2012, s. 836-840. ISBN 978-80-87294-32-1. [NANOCON 2012. International Conference /4./. Brno (CZ), 23.10.2012-25.10.2012] R&D Projects: GA MPO FR-TI2/705; GA TA ČR TA01010995; GA ČR GAP102/10/1813; GA ČR GPP102/11/P819 Institutional support: RVO:68081731 Keywords : frequency comb * Fourier transform spectroscopy * interferometer * gas absorption Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  16. Caste ontogeny and the distribution of reproductive cells on the combs of Melipona beecheii (Apidae: Meliponini)

    Moo-Valle, Humberto; José Javier G. Quezada-Euán,; Canto-Martín, Julio; Gonzalez-Acereto, Jorge

    2004-01-01

    The duration of the development phases of workers, males and gynes was studied in Melipona beecheii, an economically important stingless bee species in southern Mexico. We also determined if gynes and male cells were distributed in clusters on the combs as in other Melipona where laying workers exist. The results showed that the total length of development for the workers was 52.72 ± 1.28 days. In the case of the gynes and males, it was 50.80 (± 1.52) and 53.43 (± 1.12) days, respectively. We...

  17. Remotely manageable phase-locked loop controller for stabilizing optical frequency combs

    Hucl, Václav; Čížek, Martin; Šmíd, Radek; Lazar, Josef; Číp, Ondřej

    Piscataway: IEEE, 2014. ISBN 978-1-4673-5225-3. [URSI General Assembly and Scientific Symposium (URSI GASS) 2014 /31./. Beijing (CN), 16.08.2014-23.08.2014] R&D Projects: GA ČR GAP102/10/1813; GA ČR GPP102/11/P819; GA MŠk ED3.1.00/12.0232; GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : optical frequency combs * digital signal processing * stabilization Subject RIV: BH - Optics, Masers, Lasers

  18. Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules

    Rose Franck

    2007-01-01

    Full Text Available AbstractMicrotubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed.

  19. SYNTHESIS AND CHARACTERIZATION OF COMB-LIKE POLYMERS BEARING HETEROCYCLIC AZO GROUP AND MESOGENIC GROUP

    Hui-qi Zhang; Wen-qiang Huang; Chen-xi Li; Bing-lin He

    1999-01-01

    The synthesis and characterization of a series of novel comb-like polymethacrylates bearing heterocyclic azo group and mesogenic group are described. The thermal properties of the polymers such as thermal stability and phase transition behavior were investigated by thermogravimetric analysis, differential thermal analysis and polarizing optical microscopy techniques. The experimental results show that all the synthesized polymers do not exhibit liquid crystallinity except the homopolymer of the mesogenic monomer MAPB2 and the glass transition temperatures of the polymers increase with increasing content of azo moiety in polymers linearly.

  20. The two dimensional shapes of simple three and four junction ideal comb polymers

    de Regt, Robin; Bishop, Marvin; Barillas, Adam J.; Borgeson, Tylor; von Ferber, Christian

    2016-09-01

    We redesign and apply a scheme originally proposed by Wei (1995) [2,3] to produce numerical shape parameters with high precision for arbitrary tree-branched polymers based on their Kirchhoff matrix eigenvalue spectrum. This algorithm and a Monte Carlo growth method on square and triangular lattices are employed to investigate the shapes of ideal three and four junction two dimensional comb polymers. We find that the extrapolated values obtained by all of these methods are in excellent agreement with each other and the available theory. We confirm that polymers with a complete set of interior branches display a more circular shape.

  1. IONIC CONDUCTIVITY IN THE COMPLEXES OF COMB-SHAPED POLYETHER WITH LITHIUM AROMATIC SULFONATE

    ZHANG Shengshui; QIU Weihua; XUE Dacui; LIU Qingguo

    1993-01-01

    Complexes of comb-shaped polyether and lithium aromatic sulfonates bearing different negative charge number were prepared by in situ thermal polymerization. Their conductivity depends deeply on salt content, ambient temperature and negative charge number of the added salts. Results show that anions can be partly immobilized by increasing their negative charges at lower temperature.Against discharge time the short circuit current of the battery (Li/complex film/Lix V3O8) is stabilized by increasing the anionic charge number of the complex.

  2. Fiber-comb-stabilized light source at 556 nm for magneto-optical trapping of ytterbium

    Yasuda, Masami; Kohno, Takuya; Inaba, Hajime; Nakajima, Yoshiaki; Hosaka, Kazumoto; Onae, Atsushi; Hong, Feng-Lei

    2010-01-01

    A frequency-stabilized light source emitting at 556 nm is realized by frequency-doubling a 1112-nm laser, which is phase-locked to a fiber-based optical frequency comb. The 1112-nm laser is either an ytterbium (Yb)-doped distributed feedback fiber laser or a master-slave laser system that uses an external cavity diode laser as a master laser. We have achieved the continuous frequency stabilization of the light source over a five-day period. With the light source, we have completed the second-...

  3. Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

    Chandler, David W; Strecker, Kevin E

    2014-04-01

    In an embodiment, a dual-etalon cavity-ring-down frequency-comb spectrometer system is described. A broad band light source is split into two beams. One beam travels through a first etalon and a sample under test, while the other beam travels through a second etalon, and the two beams are recombined onto a single detector. If the free spectral ranges ("FSR") of the two etalons are not identical, the interference pattern at the detector will consist of a series of beat frequencies. By monitoring these beat frequencies, optical frequencies where light is absorbed may be determined.

  4. Combining combing and secondary ion mass spectrometry to study DNA on chips using 13C and 15N labeling

    Cabin-Flaman, Armelle; Monnier, Anne-Francoise; Coffinier, Yannick; Audinot, Jean-Nicolas; Gibouin, David; Wirtz, Tom; Boukherroub, Rabah; Migeon, Henri-Noël; Bensimon, Aaron; Jannière, Laurent; Ripoll, Camille; Norris, Victor

    2016-01-01

    Dynamic secondary ion mass spectrometry ( D-SIMS) imaging of combed DNA – the combing, imaging by SIMS or CIS method – has been developed previously using a standard NanoSIMS 50 to reveal, on the 50 nm scale, individual DNA fibers labeled with different, non-radioactive isotopes in vivo and to quantify these isotopes. This makes CIS especially suitable for determining the times, places and rates of DNA synthesis as well as the detection of the fine-scale re-arrangements of DNA and of molecules associated with combed DNA fibers. Here, we show how CIS may be extended to 13C-labeling via the detection and quantification of the 13C 14N - recombinant ion and the use of the 13C: 12C ratio, we discuss how CIS might permit three successive labels, and we suggest ideas that might be explored using CIS. PMID:27429742

  5. Multi-service small-cell cloud wired/wireless access network based on tunable optical frequency comb

    Xiang, Yu; Zhou, Kun; Yang, Liu; Pan, Lei; Liao, Zhen-wan; Zhang, Qiang

    2015-11-01

    In this paper, we demonstrate a novel multi-service wired/wireless integrated access architecture of cloud radio access network (C-RAN) based on radio-over-fiber passive optical network (RoF-PON) system, which utilizes scalable multiple- frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC). In the baseband unit (BBU) pool, the generated optical comb lines are modulated into wired, RoF and WiFi/WiMAX signals, respectively. The multi-frequency RoF signals are generated by beating the optical comb line pairs in the small cell. The WiFi/WiMAX signals are demodulated after passing through the band pass filter (BPF) and band stop filter (BSF), respectively, whereas the wired signal can be received directly. The feasibility and scalability of the proposed multi-service wired/wireless integrated C-RAN are confirmed by the simulations.

  6. Self-similar pulse evolution in a fiber laser with a comb-like dispersion-decreasing fiber.

    Tang, Yuxing; Liu, Zhanwei; Fu, Walter; Wise, Frank W

    2016-05-15

    We demonstrate an erbium fiber laser with self-similar pulse evolution inside a comb-like dispersion-decreasing fiber. We show numerically and experimentally that the comb-like dispersion-decreasing fiber works as well as an ideal one, and offers major practical advantages. The existence of a nonlinear attractor is verified by the invariant pulse chirp over a wide range of net cavity dispersion in experiments. The laser generates 1.3 nJ pulses with parabolic shapes and linear chirps, which can be dechirped to 37 fs. Comb-like dispersion-decreasing fiber should enable the generation of high-energy few-cycle pulses directly from a fiber oscillator. PMID:27176985

  7. High-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator

    Zhu, Feng; Kolomenskii, Alexandre A; Strohaber, James; Holzwarth, Ronald; Schuessler, Hans A

    2013-01-01

    We report on a high-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator with a stabilized repetition rate at 250 MHz. The mid-infrared frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW with a pulse duration of about 80 fs, and spectrum coverage from 2.9 to 3.6 um. The coherence properties of the produced high-power broadband mid-infrared frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of a ~200 ppm methane-air mixture in a short 20 cm glass cell at ambient atmospheric pressure and temperature was measured.

  8. Comb-like optical transmission spectrum resulting from a four-cornered two-waveguide-connected network

    In this Letter a four-cornered two-waveguide-connected network (FCTWCN) is proposed to generate comb-like optical transmission spectrum, where nearest-neighbor nodes are connected by two segments of one-dimensional waveguides. We investigate the band structure and transmission spectrum of electromagnetic waves propagating through FCTWCNs and find that the transmission through a FCTWCN exhibits periodic comb-like characteristic and the range, number and width of continuous equidistant frequency bands can be controlled by adjusting the lengths of the two types of segments. The comb-like frequency bands may be useful for the designing of optical switches, optical narrowband filters, high capacity telecommunications, and multichannel filters, etc.

  9. Frequency Comb Generation in 300 nm Thick SiN Concentric-Racetrack-Resonators: Overcoming the Material Dispersion Limit

    Kim, Sangsik; Wang, Cong; Jaramillo-Villegas, Jose A; Xue, Xiaoxiao; Bao, Chengying; Xuan, Yi; Leaird, Daniel E; Weiner, Andrew M; Qi, Minghao

    2016-01-01

    Kerr nonlinearity based frequency combs and solitons have been generated from on-chip optical microresonators with high quality factors and global or local anomalous dispersion. However, fabrication of such resonators usually requires materials and/or processes that are not standard in semiconductor manufacturing facilities. Moreover, in certain frequency regimes such as visible and ultra-violet, the large normal material dispersion makes it extremely difficult to achieve anomalous dispersion. Here we present a concentric racetrack-shaped resonator that achieves anomalous dispersion in a 300 nm thick silicon nitride film, suitable for semiconductor manufacturing but previously thought to result only in waveguides with high normal dispersion, a high intrinsic Q of 1.5 million, and a novel mode-selective coupling scheme that allows coherent combs to be generated. We also provide evidence suggestive of soliton-like pulse formation in the generated comb. Our method can achieve anomalous dispersion over moderately...

  10. Absolute distance measurement by dual-comb interferometry with multi-channel digital lock-in phase detection

    We present a dual-comb-based heterodyne multi-wavelength absolute interferometer capable of long distance measurements. The phase information of the various comb modes is extracted in parallel by a multi-channel digital lock-in phase detection scheme. Several synthetic wavelengths of the same order are constructed and the corresponding phases are averaged to deduce the absolute lengths with significantly reduced uncertainty. Comparison experiments with an incremental HeNe reference interferometer show a combined relative measurement uncertainty of 5.3 × 10−7 at a measurement distance of 20 m. Combining the advantage of synthetic wavelength interferometry and dual-comb interferometry, our compact and simple approach provides sufficient precision for many industrial applications. (paper)

  11. The Predominant Relationship Between Sexual Environment Characteristics and HIV-Serodiscordant Condomless Anal Sex Among HIV-Positive Men Who Have Sex with Men (MSM).

    Perry, Nicholas S; Wade Taylor, S; Elsesser, Steven; Safren, Steven A; O'Cleirigh, Conall

    2016-06-01

    In some studies, situational factors have been shown to be stronger predictors of condomless sex than individual risk factors. Cross-sectional relationships between condomless anal sex (CAS) with HIV-serodiscordant partners and risk factors across ecological levels (individual, sexual environment) were examined using a sample (N = 60) of HIV-positive men who have sex with men (MSM) who reported multiple recent episodes of CAS. Negative binomial regressions were used to evaluate the association of contextual risk factors (e.g., substance use during sex, transactional sex, public sex, sex at a sex party) with recent condomless sex, controlling for demographics and mental health. Results demonstrated that sexual environment factors, particularly sex under the influence of drugs or alcohol (B = .019, p < .05), transactional sex (B = .035, p < .01), and public sex (B = .039, p < .01) explained a large proportion of the variance in CAS. Only sex at a sex party was not related to CAS (p = .39). For each additional sexual environment in which men engaged, their rates of CAS increased (B = .39, p < .01). Secondary prevention interventions that are tailored to the proximal sexual environment could be maximally effective, particularly if they address substance use and other challenging sexual situations. PMID:26395194

  12. Corruption and sex

    Milutinović-Bojanić Sanja

    2013-01-01

    Full Text Available Taking into account the difference between the ancient and modern (even postmodern understandings of corruption, I am curious to explore why the bond linking corruption and sex seems so obvious. I have no intention of investigating both phenomena in the context of any moral category. What then did Flaubert have on his mind when he wrote that Rodolphe “treated Emma quite sans façon. He made of her something supple and corrupt.” What underpins the irresistible attraction between corruption and sex? Why is it impossible to eradicate corruption and repress sex and perceive them as solely functional strategies of generation and reproduction? This short outline follows certain philosophical remarks of Luce Irigaray and her thematization of the sexual difference in the demarcation of generation and corruption.

  13. Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators

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

    2016-03-01

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

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

    Zakova, Monika

    2010-02-11

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

  15. Sex Disparities in Stroke

    Dehlendorff, Christian; Andersen, Klaus Kaae; Olsen, Tom Skyhøj

    2015-01-01

    between 2003 and 2012 (N=79 617), and the Danish Register of Causes of Death. Information was available on age, sex, marital status, stroke severity, stroke subtype, socioeconomic status, and cardiovascular risk profile. We studied only deaths due to the index stroke, with the assumption that death.......5%) or 1 month (6.9%), respectively. After the age of 60 years, women had more severe strokes than men. Up to ages in the mid-60s, no difference in the risk of death from stroke was seen between the 2 sexes. For people aged >65 years, however, the risk gradually became greater in men than in women and...

  16. Hilbert Transform based Quadrature Hybrid RF Photonic Coupler via a Micro-Resonator Optical Frequency Comb Source

    Nguyen, Thach G; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

    2015-01-01

    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.

  17. Transferring the stability of iodine-stabilized diode laser at 634 nm to radio frequency by an optical frequency comb

    Lin Yi; Xianghui Qi; Wenlan Chen; Dawei Zhou; Tong Zhou; Xiaoji Zhou; Xuzong Chen

    2009-01-01

    An optical frequency comb phase-locked on an iodine frequency stabilized diode laser at 634 nm is con structed to transfer the accuracy and stability from the optical domain to the radio frequency domain. An external-cavity diode laser is frequency-stabilized on the Doppler-free absorption signals of the hyperfine transition R(80)8-4 using the third-harmonic detection technique. The instability of the ultra-stable op tical oscillator is determined to be 7 x 10-12 by a cesium atomic clock via the optical frequency comb's mass frequency dividing technique.

  18. Mid-IR frequency measurement using an optical frequency comb and a long-distance remote frequency reference

    Chanteau, Bruno; Zhang, Wei; Santarelli, Giorgio; Coq, Yann Le; Auguste, Frédéric; Darquié, Benoît; Chardonnet, Christian; Amy-Klein, Anne

    2012-01-01

    We have built a frequency chain which enables to measure the absolute frequency of a laser emitting in the 28-31 THz frequency range and stabilized onto a molecular absorption line. The set-up uses an optical frequency comb and an ultrastable 1.55 $\\mu$m frequency reference signal, transferred from LNE-SYRTE to LPL through an optical link. We are now progressing towards the stabilization of the mid-IR laser via the frequency comb and the extension of this technique to quantum cascade lasers. Such a development is very challenging for ultrahigh resolution molecular spectroscopy and fundamental tests of physics with molecules.

  19. The CombLayer build of the MCNPX models for the design of the fast neutron ports in the European Spallation Source

    Building MCNPX models is a time consuming process. At ISIS, a modeling architecture called 'CombLayer' has been developed, which allows MCNPX models to be produced rapidly, and in a highly parametric manner. In this work, CombLayer has been used for neutronic studies for the European Spallation Source (ESS). Initially, MCNPX models of the ESS were modified to include the irradiation ports and material test volumes. The computational time required to run each of these models was prohibitive, which precludes running multiple configurations for optimizations. To help mitigate this performance problem, we built the model using the CombLayer coding model. CombLayer is a C++ tool-kit for building geometric models. These models can then be rewritten in various formats, including MCNPX. As the CombLayer program has a working model, it is able to perform simple geometric optimizations (e.g. minimizing the cell literals, removing complementary objects) and some computed variance reduction

  20. Flexibility, persistence, and success in sex therapy.

    Sewell, H H; Abramowitz, S I

    1979-11-01

    The predictive utility of patient flexibility as a moderator of persistence and benefit from sex therapy was examined. In addition to a direct self-report flexibility scale, 21 couples completed psychometric measures of sexual and marital compatibility before undergoing a modified Masters and Johnson sexual retraining regimen. Following treatment the 15 continuing pairs filled out the same satisfaction inventories and, along with their male and female cotherapists, made posttherapy ratings of change on sex-specific personal and marital criteria. Flexibility proved to be a strikingly effective discriminator of remainers from early terminators and demonstrated promise as a predictor of favorable sex therapy outcome. Results are discussed in terms of the need to identify and prepare rigid individuals who cannot easily accommodate the relatively directive and value-laden features of sexual retraining. PMID:518289

  1. Frequency Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths

    Rieker, Gregory B; Swann, William C; Kofler, Jon; Zolot, Alex M; Sinclair, Laura C; Baumann, Esther; Cromer, Christopher; Petron, Gabrielle; Sweeney, Colm; Tans, Pieter P; Coddington, Ian; Newbury, Nathan R

    2014-01-01

    We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in greenhouse gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with <1 kHz frequency accuracy, no instrument lineshape, and a 0.0033-cm^-1 point spacing. The fitted path-averaged concentrations and temperature yield dry-air mole fractions. These are compared with a point sensor under well-mixed conditions to evaluate current absorption models for real atmospheres. In heterogeneous conditions, time-resolved data demonstrate tracking of strong variations in mole fractions. A precision of <1 ppm for CO2 and <3 ppb for CH4 is achieved in 5 minutes in this initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global s...

  2. Generation of An Efficient Digital Watermark Key Based on Honey Comb Polynomial Interpolation Approach

    G.RoslineNesakumari

    2013-03-01

    Full Text Available The present paper provides a new mechanism with two stages for efficient authentication based on Honey Comb Polynomial Interpolation (HCPI and Morphological Border Sorted Pixel Value Difference (MBSPVD scheme. A simple polynomial interpolation technique on new hexagonal structure called Honey Comb structure (HCS is used for generating the key of the digital watermark. The polynomial interpolation gives a high secured key, which is difficult to break. HCS is used in the present paper to select pixel positions for generating the Digital Watermark key (DWK. The significant factor of the present method is, the digital watermark is generated by using DWK. The importance of HCS representation is that it possesses special computational features that are pertinent to the vision process. The HCS has features of higher degree of circular symmetry, uniform connectivity, greater angular resolution, and which leads to reduce storage and computation in image processing operations. The DWK is placed in the image by using MBSPVD method. Its guarantees high authentication, robustness, security and copyright protection. The Lagrange Polynomial interpolation (LPI is used for retrieving the digital watermark from the DWK. The LPI accomplish the aim of image authentication and protection without reducing the image quality. The proposed HCPI-MBSPVD is tested with various attacks and compared with various existing image authentication and copyright protection methods. The comparisons and results indicate the efficacy of the proposed method.

  3. PH- and salt-dependent molecular combing of DNA: experiments and phenomenological model

    Benke, Annegret; Pompe, Wolfgang [Institut fuer Werkstoffwissenschaft and Max-Bergmann-Zentrum fuer Biomaterialien, Technische Universitaet Dresden, D-01062 Dresden (Germany); Mertig, Michael, E-mail: annegret.benke@nano.tu-dresden.de [Physikalische Chemie, Technische Universitaet Dresden, D-01062 Dresden (Germany)

    2011-01-21

    {lambda}-DNA as well as plasmids can be successfully deposited by molecular combing on hydrophobic surfaces, for pH values ranging from 4 to 10. On polydimethylsiloxane (PDMS) substrates, the deposited DNA molecules are overstretched by about 60-100%. There is a significant influence of sodium ions (NaCl) on the surface density of the deposited DNA, with a maximum near to 100 mM NaCl for a DNA solution (28 ng {mu}l{sup -1}) at pH 8. The combing process can be described by a micromechanical model including: (i) the adsorption of free moving coiled DNA at the substrate; (ii) the stretching of the coiled DNA by the preceding meniscus; (iii) the relaxation of the deposited DNA to the final length. The sticky ends of {lambda}-DNA cause an adhesion force in the range of about 400 pN which allows a stable overstretching of the DNA by the preceding meniscus. The exposing of hidden hydrophobic bonds of the overstretched DNA leads to a stable deposition on the hydrophobic substrate. The pH-dependent density of deposited DNA as well as the observed influence of sodium ions can be explained by their screening of the negatively charged DNA backbone and sticky ends, respectively. The final DNA length can be derived from a balance of the stored elastic energy of the overstretched molecules and the energy of adhesion.

  4. Integrated wideband optical frequency combs with high stability and their application in microwave photonic filters

    Sun, Wenhui; Wang, Sunlong; Zhong, Xin; Liu, Jianguo; Wang, Wenting; Tong, Youwan; Chen, Wei; Yuan, Haiqing; Yu, Lijuan; Zhu, Ninghua

    2016-08-01

    An integrated wideband optical frequency comb (OFC) based on a semiconductor quantum dot laser is realized with high stability. The OFC module is packaged in our lab. A circuit which is designed to provide a low-ripple current and control the temperature regards as a servo system to enhance the stability of the OFC. The frequency stability of the OFC is 2.7×10-9 (Allan Variance). The free spectral range (FSR) of the OFC is 40 GHz and the number of comb lines is up to 55. The flatness of the OFC over span of 4 nm can be limited to 0.5 dB. Negative coefficients microwave photonic filters with multiple taps are generated based on the proposed OFC. For the 10 taps microwave photonic filter, the pass-band at 8.74 GHz has a 3 dB bandwidth of 630 MHz with 16.58 dB side-lobe suppression. Compared with the published microwave photonic filters, the proposed system is more stable, of more compact structures, and of less power consumption.

  5. Genomic data do not support comb jellies as the sister group to all other animals.

    Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert

    2015-12-15

    Understanding how complex traits, such as epithelia, nervous systems, muscles, or guts, originated depends on a well-supported hypothesis about the phylogenetic relationships among major animal lineages. Traditionally, sponges (Porifera) have been interpreted as the sister group to the remaining animals, a hypothesis consistent with the conventional view that the last common animal ancestor was relatively simple and more complex body plans arose later in evolution. However, this premise has recently been challenged by analyses of the genomes of comb jellies (Ctenophora), which, instead, found ctenophores as the sister group to the remaining animals (the "Ctenophora-sister" hypothesis). Because ctenophores are morphologically complex predators with true epithelia, nervous systems, muscles, and guts, this scenario implies these traits were either present in the last common ancestor of all animals and were lost secondarily in sponges and placozoans (Trichoplax) or, alternatively, evolved convergently in comb jellies. Here, we analyze representative datasets from recent studies supporting Ctenophora-sister, including genome-scale alignments of concatenated protein sequences, as well as a genomic gene content dataset. We found no support for Ctenophora-sister and conclude it is an artifact resulting from inadequate methodology, especially the use of simplistic evolutionary models and inappropriate choice of species to root the metazoan tree. Our results reinforce a traditional scenario for the evolution of complexity in animals, and indicate that inferences about the evolution of Metazoa based on the Ctenophora-sister hypothesis are not supported by the currently available data. PMID:26621703

  6. Environmental-adaptability analysis of an all polarization-maintaining fiber-based optical frequency comb.

    Feng, Ye; Xu, Xin; Hu, Xiaohong; Liu, Yuanshan; Wang, Yishan; Zhang, Wei; Yang, Zhi; Duan, Lina; Zhao, Wei; Cheng, Zhao

    2015-06-29

    We demonstrate an all polarization-maintaining (PM) fiber-based optical frequency comb and provide the detailed environmental stability analysis results. The frequency comb has been built by commercial available PM fiber completely, and its static uncertainty in optical domain is 350 Hz in 1 s when referenced to a low noise oven controlled crystal oscillator. The acoustic resonant frequencies of the system have been measured. It is proved that acoustic-vibration induced phase noise could be eliminated by low pass vibration-isolation structure. Further, the existence of the optimum working temperature is illustrated. At this temperature (289.6 K), the out-loop integrated phase noise of f(r) and the temperature-drift induced instability of f(CEO) reach the lowest level 31.6 μrad and 0 kHz/(mW∙K) respectively. Finally, the system is proved to be stable under different humidity (18% ~80%) by a 240-day-long record of the f(CEO). PMID:26191762

  7. Smooth and flat phase-locked Kerr frequency comb generation by higher order mode suppression

    Huang, S.-W.; Liu, H.; Yang, J.; Yu, M.; Kwong, D.-L.; Wong, C. W.

    2016-05-01

    High-Q microresonator is perceived as a promising platform for optical frequency comb generation, via dissipative soliton formation. In order to achieve a higher quality factor and obtain the necessary anomalous dispersion, multi-mode waveguides were previously implemented in Si3N4 microresonators. However, coupling between different transverse mode families in multi-mode waveguides results in periodic disruption of dispersion and quality factor, and consequently causes perturbation to dissipative soliton formation and amplitude modulation to the corresponding spectrum. Careful choice of pump wavelength to avoid the mode crossing region is thus critical in conventional Si3N4 microresonators. Here, we report a novel design of Si3N4 microresonator in which single-mode operation, high quality factor, and anomalous dispersion are attained simultaneously. The novel microresonator is consisted of uniform single-mode waveguides in the semi-circle region, to eliminate bending induced mode coupling, and adiabatically tapered waveguides in the straight region, to avoid excitation of higher order modes. The intrinsic quality factor of the microresonator reaches 1.36 × 106 while the group velocity dispersion remains to be anomalous at ‑50 fs2/mm. With this novel microresonator, we demonstrate that broadband phase-locked Kerr frequency combs with flat and smooth spectra can be generated by pumping at any resonances in the optical C-band.

  8. Optical Comb from a Whispering Gallery Mode Resonator for Spectroscopy and Astronomy Instruments Calibration

    Strekalov, Dmitry V.; Yu, Nam; Thompson, Robert J.

    2012-01-01

    The most accurate astronomical data is available from space-based observations that are not impeded by the Earth's atmosphere. Such measurements may require spectral samples taken as long as decades apart, with the 1 cm/s velocity precision integrated over a broad wavelength range. This raises the requirements specifically for instruments used in astrophysics research missions -- their stringent wavelength resolution and accuracy must be maintained over years and possibly decades. Therefore, a stable and broadband optical calibration technique compatible with spaceflights becomes essential. The space-based spectroscopic instruments need to be calibrated in situ, which puts forth specific requirements to the calibration sources, mainly concerned with their mass, power consumption, and reliability. A high-precision, high-resolution reference wavelength comb source for astronomical and astrophysics spectroscopic observations has been developed that is deployable in space. The optical comb will be used for wavelength calibrations of spectrographs and will enable Doppler measurements to better than 10 cm/s precision, one hundred times better than the current state-of-the- art.

  9. Smooth and flat phase-locked Kerr frequency comb generation by higher order mode suppression.

    Huang, S-W; Liu, H; Yang, J; Yu, M; Kwong, D-L; Wong, C W

    2016-01-01

    High-Q microresonator is perceived as a promising platform for optical frequency comb generation, via dissipative soliton formation. In order to achieve a higher quality factor and obtain the necessary anomalous dispersion, multi-mode waveguides were previously implemented in Si3N4 microresonators. However, coupling between different transverse mode families in multi-mode waveguides results in periodic disruption of dispersion and quality factor, and consequently causes perturbation to dissipative soliton formation and amplitude modulation to the corresponding spectrum. Careful choice of pump wavelength to avoid the mode crossing region is thus critical in conventional Si3N4 microresonators. Here, we report a novel design of Si3N4 microresonator in which single-mode operation, high quality factor, and anomalous dispersion are attained simultaneously. The novel microresonator is consisted of uniform single-mode waveguides in the semi-circle region, to eliminate bending induced mode coupling, and adiabatically tapered waveguides in the straight region, to avoid excitation of higher order modes. The intrinsic quality factor of the microresonator reaches 1.36 × 10(6) while the group velocity dispersion remains to be anomalous at -50 fs(2)/mm. With this novel microresonator, we demonstrate that broadband phase-locked Kerr frequency combs with flat and smooth spectra can be generated by pumping at any resonances in the optical C-band. PMID:27181420

  10. Lithium battery with solid polymer electrolyte based on comb-like copolymers

    Daigle, Jean-Christophe; Vijh, Ashok; Hovington, Pierre; Gagnon, Catherine; Hamel-Pâquet, Julie; Verreault, Serge; Turcotte, Nancy; Clément, Daniel; Guerfi, Abdelbast; Zaghib, Karim

    2015-04-01

    In this paper we report on the synthesis of comb-like copolymers as solid polymer electrolytes (SPE). The synthesis involved anionic polymerization of styrene (St) and 4-vinylanisole (VA) as the followed by grafting of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) by Atom Transfer Radical Polymerization (ATRP). The comb-like copolymer's structure was analyzed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The membranes were made by solvent casting and the morphologies were analyzed by atomic forces microscopy (AFM) and scanning electron microscopy (SEM). We observed that a nano and micro phase separation occurs which improves ionic conductivity. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10-5 Scm-1) at room temperature owing to the negligible values (<10 kJ mol-1) of the activation energies for conductivity. The batteries with these polymers exhibit a capacity of 146 mAh g-1 at C/24, and no evidence of degradation after intense cycling was observed. However, poor cycle life was observed at C/6 and C/3, which is a consequence of several factors. We partially explain that behavior by arguing that whereas PEO lightly "solvates" Li+ thus slowing Li-ion mobility, and PEGMA chains "solvate" Li ions too strongly, trapping and inhibiting their mobility.

  11. Large range dual-axis micro-stage driven by electrostatic comb-drive actuators

    This paper presents a micro XY stage that employs electrostatic comb-drive actuators and achieves a bi-directional displacement range greater than 225 µm per motion axis. The proposed XY stage design comprises four rigid stages (ground, motion stage, and two intermediate stages) interconnected via flexure modules. The motion stage, which has two translational degrees of freedom, is connected to two independent single degree of freedom intermediate stages via respective parallelogram (P) transmission flexures. The intermediate stages are connected to the ground via respective clamped paired double parallelogram (C-DP-DP) guidance flexures. The C-DP-DP flexure, unlike conventional flexures such as the paired double parallelogram flexure (DP-DP), provides high bearing direction stiffness (Kb) while maintaining low motion direction stiffness (Km) over a large range of motion direction displacement. This helps delay the onset of sideways instability in the comb-drive actuators that are integrated with the intermediate stages, thereby offering a significantly greater actuation stroke compared to existing designs. The presented work includes closed-form stiffness analysis of the proposed micro-stage, finite elements simulation, and experimental measurements of its static and dynamic behavior. (paper)

  12. Channel Estimation Based in Comb-Type Pilots Arrangement for OFDM System over Time Varying Channel

    Hala M. Mahmoud

    2010-07-01

    Full Text Available Orthogonal Frequency Division Multiplexing (OFDM has been recently applied widely in wireless communication systems, due to its high data rate, transmission capability with high bandwidth, efficiency and its robustness to multipath delay .Channel estimation is an essential problem in OFDM system. Pilot-aided channel estimation has been used; a good choice of the pilot pattern should match the channel behavior both in time and frequency domains. We explored comb pilot arrangements. The advantage for comb type pilots arrangement in channel estimation is the ability to track the variation of the channel caused by doppler frequency, it is observed that the doppler effect can be reduced, and so this will increase the system mobility. Kalman and Least Square (LS estimators have been proposed to estimate the Channel Frequency Response (CFR at the pilots location, then CFR at data sub channels are obtained by mean of interpolation between estimates at pilot locations. Different types of interpolations have been used such as; low pass interpolation; spline cubic interpolation and linear interpolation. Kalman estimation has better performance than LS estimation. The estimators perform about the same for SNR lower than 10 dB. The performances of all schemes have been compared by finding Bit Error Rate (BER, where BPSK modulation scheme was used.

  13. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    Elshurafa, Amro

    2011-08-01

    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression for the electrostatic force generated between the combs of the rotor and the stator is derived and takes into account both the transverse and longitudinal capacitances present. After formulating the problem, the resulting stiff differential equations are solved analytically using the method of multiple scales, and a closed-form solution is obtained. Furthermore, the nonlinear boundary value problem that describes the dynamics of inextensional spring beams is solved using straightforward perturbation to obtain the linear and nonlinear spring constants of the beam. The analytical solution is verified numerically using a Matlab/Simulink environment, and the results from both analyses exhibit excellent agreement. Stability analysis based on phase plane trajectory is also presented and fully explains previously reported empirical results that lacked sufficient theoretical description. Finally, the proposed solutions are, once again, verified with previously published measurement results. The closed-form solutions provided are easy to apply and enable predicting the actual behavior of resonators and gyroscopes with similar structures. © 2011 IEEE.

  14. Prospects for precision measurements of atomic helium using direct frequency comb spectroscopy

    Eyler, E E; Stowe, Matthew C; Thorpe, Michael J; Schibli, T R; Ye, Jun

    2007-01-01

    We analyze several possibilities for precisely measuring electronic transitions in atomic helium by the direct use of phase-stabilized femtosecond frequency combs. Because the comb is self-calibrating and can be shifted into the ultraviolet spectral region via harmonic generation, it offers the prospect of greatly improved accuracy for UV and far-UV transitions. To take advantage of this accuracy an ultracold helium sample is needed. For measurements of the triplet spectrum a magneto-optical trap (MOT) can be used to cool and trap metastable $2 ^3S$ state atoms. We analyze schemes for measuring the two-photon $2 ^3S \\to 4 ^3S$ interval, and for resonant two-photon excitation to high Rydberg states, $2 ^3S \\to 3 ^3P \\to n^3S,D$. We also analyze experiments on the singlet-state spectrum. To accomplish this we propose schemes for producing and trapping ultracold helium in the $1 ^1S$ or $2 ^1S$ state via intercombination transition. A particularly intriguing scenario is the possibility of direct singlet state sp...

  15. Fiber-comb-stabilized light source at 556 nm for magneto-optical trapping of ytterbium

    Yasuda, Masami; Inaba, Hajime; Nakajima, Yoshiaki; Hosaka, Kazumoto; Onae, Atsushi; Hong, Feng-Lei

    2010-01-01

    A frequency-stabilized light source emitting at 556 nm is realized by frequency-doubling a 1112-nm laser, which is phase-locked to a fiber-based optical frequency comb. The 1112-nm laser is either an ytterbium (Yb)-doped distributed feedback fiber laser or a master-slave laser system that uses an external cavity diode laser as a master laser. We have achieved the continuous frequency stabilization of the light source over a five-day period. With the light source, we have completed the second-stage magneto-optical trapping (MOT) of Yb atoms using the 1S0 - 3P1 intercombination transition. The temperature of the ultracold atoms in the MOT was 40 uK when measured using the time-of-flight method, and this is sufficient for loading the atoms into an optical lattice. The fiber-based frequency comb is shown to be a useful tool for controlling the laser frequency in cold-atom experiments.

  16. Independent sex chromosome evolution in lower vertebrates: a molecular cytogenetic overview in the Erythrinidae fish family.

    Cioffi, M B; Liehr, T; Trifonov, V; Molina, W F; Bertollo, L A C

    2013-01-01

    The Erythrinidae fish family is an excellent model for analyzing the evolution of sex chromosomes. Different stages of sex chromosome differentiation from homomorphic to highly differentiated ones can be found among the species of this family. Here, whole chromosome painting, together with the cytogenetic mapping of repetitive DNAs, highlighted the evolutionary relationships of the sex chromosomes among different erythrinid species and genera. It was demonstrated that the sex chromosomes can follow distinct evolutionary pathways inside this family. Reciprocal hybridizations with whole sex chromosome probes revealed that different autosomal pairs have evolved as the sex pair, even among closely related species. In addition, distinct origins and different patterns of differentiation were found for the same type of sex chromosome system. These features expose the high plasticity of the sex chromosome evolution in lower vertebrates, in contrast to that occurring in higher ones. A possible role of this sex chromosome turnover in the speciation processes is also discussed. PMID:23919986

  17. Sex hormones and brain dopamine functions.

    Sotomayor-Zarate, Ramon; Cruz, Gonzalo; Renard, Georgina M; Espinosa, Pedro; Ramirez, Victor D

    2014-01-01

    Sex hormones exert differential effects on a variety of sensitive tissues like the reproductive tract, gonads, liver, bone and adipose tissue, among others. In the brain, sex hormones act as neuroactive steroids regulating the function of neuroendocrine diencephalic structures like the hypothalamus. In addition, steroids can exert physiological effects upon cortical, limbic and midbrain structures, influencing different behaviors such as memory, learning, mood and reward. In the last three decades, the role of sex hormones on monoamine neurotransmitters in extra-hypothalamic areas related to motivated behaviors, learning and locomotion has been the focus of much research. The purpose of this thematic issue is to present the state of art concerning the effects of sex hormones on the neurochemical regulation of dopaminergic midbrain areas involved in neurobiological and pathological processes, such as addiction to drugs of abuse. We also discuss evidence of how neonatal exposure to sex hormones or endocrine disrupting chemicals can produce long-term changes on the neurochemical regulation of dopaminergic neurons in the limbic and midbrain areas. PMID:25540983

  18. How Sex Attitudes Develop

    Arnstein, Helene S.

    1976-01-01

    Excerpt from "The Roots of Love" (Helene S. Arnstein, 1975). Book is concerned with feelings that are part of child's developmental stages. Included in excerpt are: genital self-discovery, masturbation, discovery of sex differences, and birth fantasies. Stresses importance of parent's feelings which are communicated to child.

  19. When Sex Meets Law

    YIN PUMIN

    2010-01-01

    @@ Ma Yaohai,an associate professor of computer science at Nanjing University of Technology in east China's Jiangsu Province,was sentenced to three and a half years in prison on May 20 for organizing group-sex parties,renewing nationwide debate on sexual freedom in China.

  20. The Opposite of Sex

    2011-01-01

    Can women and men truly be friends? Hollywood this year has been in love with the idea of friends"with benefits,"and it seems like people have forgotten that women and men have friendships where sex never enters the equation.But is the idea of a platonic