This file was created by the TYPO3 extension bib --- Timezone: CEST Creation date: 2023-06-02 Creation time: 19-58-35 --- Number of references 14 article FalkeSWMVWLGRSL2011 Metrologia 2011 48 399-407 St.Falke H.Schnatz J. S. R. V.Winfried Th.Middelmann St.Vogt S.Weyers B.Lipphardt G.Grosche F.Riehle U.Sterr Ch.Lisdat article Riehle2010 Physical Review A (2010) 2010 We present nonstandard optical Ramsey schemes that use pulses individually tailored in duration, phase, and frequency to cancel spurious frequency shifts related to the excitation itself. In particular, the field shifts and their uncertainties can be radically suppressed (by two to four orders of magnitude) in comparison with the usual Ramsey method (using two equal pulses) as well as with single-pulse Rabi spectroscopy. Atom interferometers and optical clocks based on two-photon transitions, heavily forbidden transitions, ormagnetically induced spectroscopy could significantly benefit from this method. In the latter case, these frequency shifts can be suppressed considerably below a fractional level of 10^-17. Moreover, our approach opens the door for high-precision optical clocks based on direct frequency comb spectroscopy. Melville, NY: AIP Englisch ISSN 1050-2947 (print) ; ISSN 1094-1622 (online) 10.1103/PhysRevA.82.011804 1 V. I.Yudin A. V.Taichenachev C. W.Oates Z. W.Barber N. D.Lemke A. DLudlow UweSterr ChristianLisdat FritzRiehle article TaichenachevYOBLLSLR2009 JETP Letters (2009) 2009 90 11 713 - 717 We have extended Ramsey spectroscopy by stepping the probe frequency during the two Ramsey excitation pulses to compensate frequency shifts induced by the excitation itself. This makes precision Ramsey spectroscopy applicable even for transitions that have Stark and Zeeman shifts comparable to the spectroscopic resolution. The method enables a new way to evaluate and compensate key frequency shifts, which benefits in particular, optical clocks based on magnetic field-induced, spectroscopy, two-photon transitions, or heavily forbidden transitions. Road Town, Tortola: Pleiades Publ. English ISSN 0021-3640 10.1134/S0021364009230052 A. V.Taichenachev V. I.Yudin C. W.Oates Z. W.Barber N. D.Lemke A. D.Ludlow UweSterr ChristianLisdat FritzRiehle article LisdatVMRS2009 Physical Review Letters (2009) 2009 103 9 090801-1 - 090801-4 We have quantified collisional losses, decoherence and the collision shift in a one-dimensional optical lattice clock on the highly forbidden transition ¹S₀-³P₀ at 698 nm with bosonic ⁸⁸Sr. We were able to distinguish two loss channels: inelastic collisions between atoms in the upper and lower clock state and atoms in the upper clock state only. Based on the measured coefficients, we determine the operation parameters at which a 1D-lattice clock with ⁸⁸Sr shows no degradation due to collisions on the fractional uncertainty level of 10^-16. Ridge, NY: APS English SN 0031-9007 10.1103/PhysRevLett.103.090801 ChristianLisdat WinfredVellore ThomasMiddelmann FritzRiehle UweSterr article KraftVARS2009 Physical Review Letters (2009) 2009 103 13 130401-1 - 130401-4 We have achieved Bose-Einstein condensation of ⁴⁰Ca, the first for an alkaline earth element. The influence of elastic and inelastic collisions associated with the large ground-state s-wave scattering length of ⁴⁰Ca was measured. From these findings, an optimized loading and cooling scheme was developed that allowed us to condense about 2×10⁴ atoms after laser cooling in a two-stage magneto-optical trap and subsequent forced evaporation in a crossed dipole trap within less than 3 s. The condensation of an alkaline earth element opens novel opportunities ¹<em>S</em>-³<em>P</em> asymptotes. Ridge, NY: APS English ISSN 0031-9007 10.1103/PhysRevLett.103.130401 SebastianKraft FelixVogt OliverAppel FritzRiehle UweSterr article NazarovaLRS2008 Journal of the Optical Society of America B (2008) 2008 25 10 1632 - 1638 We investigate the influence of fast frequency fluctuations of the interrogation laser on the obtainable signal-to-noise ratio in Ramsey-Bordé atom interferometers. It is shown that the excessive high frequency noise of diode lasers can degrade significantly the signal-to-noise ratio in an atom interferometer. To overcome these limitations, we have devised a low-noise light source by frequency-filtering a diode laser in a high finesse cavity and further amplifying the transmitted power by injection-locking a solitary laser diode. When this laser source was used for atom interferometry with laser cooled calcium atoms, the signal-to-noise ratio could be further improved by a factor of 3.5 compared to the use of the unfiltered 1-Hz-linewidth laser source. Washington, DC: OSA English ISSN 0740-3224 10.1364/JOSAB.25.001632 TatianaNazarova ChristianLisdat FritzRiehle UweSterr article SchillerGNKWGKMMSRPTERKSTLHH2007 Nucl. Phys. B (Proc. Suppl.) 2007 166 300 arXiv: gr-qc/0608081 S.Schiller A.Görlitz A.Nevsky J.C.J.Koelemeij A.Wicht P.Gill H.A.Klein H.S.Margolis G.Mileti U.Sterr F.Riehle E.Peik Chr.Tamm W.Ertmer E.Rasel V.Klein C.Salomon G.M.Tino P.Lemonde R.Holzwarth T.W.Hänsch article VogtGNSRLT2010 European Physical Journal D (2007) 2007 44 73 - 79 Photoassociation spectroscopy was used to determine the s-wave scattering of ⁴⁰Ca atoms in their electronic ground state. Vibrational levels were observed in an extended range of up to 182 GHz below the dissociation limit 4s^{2 1}S₀-4s4p ¹P₁. Thus, the frequency interval was nearly tripled, in which photoassociation was observed compared to previous measurements. The spectra were analyzed by means of quantum mechanical simulations. Orsay [u.a.]: EDP Sciences [u.a.] English ISSN 1434-6060 10.1140/epjd/e2007-00175-8 FelixVogt ChristopheGrain TatianaNazarova UweSterr FritzRiehle ChristianLisdat E.Tiemann article GrainNDVLTSR2007 European Physical Journal D (2007) 2007 We have investigated the influence of narrow-line laser cooling on the loading of Ca atoms into optical dipole traps. To describe the narrow-line cooling of alkaline-earth atoms in combination with optical dipole trapping, we have developed a model that takes into account the light shifts of the cooling transition in three dimensions. The model is compared with two experimental realizations of optical dipole traps for calcium at the wavelengths 514 nm and 10.6 ?m. Heidelberg [u.a.]: Springer English ISSN 1434-6060 10.1140/epjd/e2007-00052-6 ChristopheGrain TatianaNazarova CarstenDegenhardt FelixVogt ChristianLisdat E.Tiemann UweSterr FritzRiehle article NazarovaRS2006 Appl. Phys. B 2006 83 531?536 T.Nazarova F.Riehle U.Sterr article NazarovaRS2006 Applied Physics B (2006) 2006 84 4 531 - 536 We report a novel mounting of the reference cavity used for stabilization of the clock laser in an optical frequency standard. The cavity axis is oriented horizontally and the cavity is supported in its horizontal symmetry plane on four support points. The positions of the points were optimized by finite element analysis. A sensitivity to accelerations of 1.5 kHz/(m/s²) in the vertical and 14 kHz/(m/s²) in the horizontal direction was measured, which is a reduction in the vertical sensitivity by two orders of magnitude compared to the usual support from below. Berlin [u.a.]: Springer English ISSN 0946-2171 (print) ; ISSN 1432-0649 (online) 10.1007/s00340-006-2225-y TatianaNazarova FritzRiehle UweSterr article DegenhardtSLWSLNPSHR2005 Physical Review A (2005) 2005 72 062111-1 - 062111-17 An optical frequency standard based on an ensemble of neutral calcium atoms laser-cooled to 12 ?K has been realized. By using ultracold atoms, one major previous source of uncertainty, the residual Doppler effect, was reduced. We show that cold collisions contribute a negligible amount to the uncertainty. The influence of a temporal evolution of the phase of the laser pulses used to interrogate the clock transition was measured and corrected for. The frequency of the clock transition at 657 nm was referenced to the caesium fountain clock of PTB utilizing a femtosecond comb generator with a fractional uncertainty of 1.2 x 10^-14. The transition frequency was determined to be (455 986 240 494 144 ± 5.3) Hz, making the calcium clock transition one of the most accurately known optical transitions. A frequency stability of 3 x 10^-15 at 100 s averaging time was achieved and the noise contributions that limit to the observed stability were analyzed in detail. Additionally, the natural linewidth of the clock transition has been determined. Melville, NY: AIP English ISSN 1050-2947 10.1103/PhysRevA.72.062111 CarstenDegenhardt HardoStoehr ChristianLisdat GuidoWilpers HaraldSchnatz BurghardLipphardt TatianaNazarova Paul-EricPottie UweSterr JürgenHelmcke FritzRiehle article WilpersBDSHR2002 Phys. Rev. Lett. (2002) 2002 89 23 230801-1 - 230801-4 We demonstrate how to realize an optical clock with neutral atoms that is competitive to the currently best single ion optical clocks in accuracy and superior in stability. Using ultracold atoms in a Ca optical frequency standard, we show how to reduce the relative uncertainty to below ^10-15. We observed atom interferences for stabilization of the laser to the clock transition with a visibility of 0.36, which is 70% of the ultimate limit achievable with atoms at rest. A novel scheme was applied to detect these atom interferences with the prospect to reach the quantum projection noise limit at an exceptional low instability of 4×10^-17 in 1 s http://link.aps.org/doi/10.1103/PhysRevLett.89.230801 Ridge, NY: American Physical Society English ISSN 0031-9007 10.1103/PhysRevLett.89.230801 1 GuidoWilpers TomasBinnewies CarstenDegenhardt UweSterr JürgenHelmcke FritzRiehle article BinnewiesWSRHMRE2001 Physical Review Letters (2001) 2001 87 12 123002-1 - 123002-4 Ultracold atoms at temperature close to the recoil limit have been achieved by extending Doppler cooling to forbidden transitions. A cloud of ⁴⁰Ca atoms has been cooled and trapped to a temperature as low as 6 ?K by operating a magneto-optical trap on the spin-forbidden intercombination transition. Quenching the long-lived excited state with an additional laser enhanced the scattering rate by a factor of 15, while a high selectivity in velocity was preserved. With this method more than 10 % of pre-cooled atoms from a standard magneto-optical trap have been transferred to the ultracoled trap. Monte-Carlo simulations of the cooling process are in good agreement with the experiments. laser cooling atom interferometry ultracold atoms English ISSN 0031-9007 10.1103/PhysRevLett.87.123002 TomasBinnewies GuidoWilpers UweSterr FritzRiehle JürgenHelmcke T. E.Mehlstäubler E. M.Rasel W.Ertmer