First Phase-Coherent Frequency Measurement of Visible Radiation

Schnatz, H.; Lipphardt, B.; Helmcke, J.; Riehle, F.; Zinner, G.

doi:10.1103/physrevlett.76.18

Cited by 212 publications

(91 citation statements)

References 16 publications

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“…In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg + and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of |(∂fCa/∂t)/fCa| ≤ 8 × 10 −14 yr −1 , and |(∂fHg/∂t)/fHg| ≤ 30 × 10 −14 yr −1 .Optical standards based on a single ion or a collection of laser-cooled atoms are emerging as the most stable and accurate frequency sources of any sort [1,2,3,4,5]. However, because of their high frequencies (∼ 500 THz), it has proven difficult to count cycles as required for building an optical clock and comparing to the cesium microwave standard.…”

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confidence: 74%

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Absolute Frequency Measurements of theHg+and Ca Optical Clock Transitions with a Femtosecond Laser

et al. 2001

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The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg + and Ca optical standards with respect to the SI second as realized at NIST. We find the transition frequencies to be fHg = 1 064 721 609 899 143(10) Hz and fCa = 455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg + and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of |(∂fCa/∂t)/fCa| ≤ 8 × 10 −14 yr −1 , and |(∂fHg/∂t)/fHg| ≤ 30 × 10 −14 yr −1 .Optical standards based on a single ion or a collection of laser-cooled atoms are emerging as the most stable and accurate frequency sources of any sort [1,2,3,4,5]. However, because of their high frequencies (∼ 500 THz), it has proven difficult to count cycles as required for building an optical clock and comparing to the cesium microwave standard. Only recently, a reliable and convenient optical clockwork fast enough to count optical oscillations has been realized [6,7,8]. Here, we report an optical clockwork based on a single femtosecond laser that phase coherently divides down the visible radiation of the Hg + and Ca optical frequency standards to a countable radio frequency. By this means we determine the absolute frequencies of these optical transitions with unparalleled precision in terms of the SI second as realized at NIST [9]. Indeed, for the Hg + standard, the statistical uncertainty in the measurement is essentially limited by our knowledge of the SI second at ∼ 2 × 10 −15 . The high precision and high demonstrated stability of the standards [1,4] combined with the straightforward femtosecond-laser-based clockwork suggest Hg + and Ca as excellent references for future all-optical clocks. Additionally, the comparison of atomic frequencies over time provides constraints on the possible time variation of fundamental constants. When combined with previous measurements, the current level of precision allows us to place the tightest constraint yet on the possible variation of optical frequencies with respect to the cesium standard.The Hg + and Ca systems have recently been described elsewhere [1,4,10,11], so we summarize only the basic features. The heart of the mercury optical frequency standard is a single, laser-cooled 199 Hg + ion that is stored in a cryogenic, radio frequency spherical Paul trap. The 2 S 1/2 (F = 0, M F = 0) ↔ 2 D 5/2 (F = 2, M F = 0) electric-quadrupole transition at 282 nm [ Fig. 1(a)] provides the reference for the optical standard [1]. We lock the frequency-doubled output of a well-stabilized 563 nm dye laser to the center of the quadrupole resonance by irradiating the Hg + ion alternately at two frequencies near the maximum slope of the resonance signal and on opposite sides of its center. Transitions to the metastable 2 D 5/2 state are detected with near unit ...

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confidence: 74%

“…Optical standards based on a single ion or a collection of laser-cooled atoms are emerging as the most stable and accurate frequency sources of any sort [1,2,3,4,5]. However, because of their high frequencies (∼ 500 THz), it has proven difficult to count cycles as required for building an optical clock and comparing to the cesium microwave standard.…”

mentioning

confidence: 99%

Absolute Frequency Measurements of theHg+and Ca Optical Clock Transitions with a Femtosecond Laser

et al. 2001

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“…In 2008 a first implementation of the laser frequency comb as a calibration tool for the German Vacuum Tower Telescope (VTT) (Schröter et al 1985) has been demonstrated (Steinmetz et al 2008). The very high resolution of the VTT (0.8 GHz) is still too low to resolve individual modes of the erbium fiber laser frequency comb with ω r = 2π × 250 MHz used for its calibration.…”

Section: Frequency Combs For Astrophysicsmentioning

confidence: 99%

“…To extend this accurate technique to higher frequencies, so called harmonic frequency chains have been constructed since the late 1960ies (Hocker et al 1967;Evenson et al 1973). Because of the large number of steps necessary to build a long harmonic frequency chain, it was not before 1995 when visible laser light was first referenced phase coherently to a cesium atomic clock using this method (Schnatz et al 1996).…”

Section: Ultra-short Pulse Lasers and Frequency Combsmentioning

confidence: 99%

Testing the Stability of the Fine Structure Constant in the Laboratory

et al. 2009

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In this review we discuss the progress of the past decade in testing for a possible temporal variation of the fine structure constant α. Advances in atomic sample preparation, laser spectroscopy and optical frequency measurements led to rapid reduction of measurement uncertainties. Eventually laboratory tests became the most sensitive tool to detect a possible variation of α at the present epoch. We explain the methods and technologies that helped to make this possible.

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“…Therefore, high resolution spectroscopy with a time domain atom interferometer suggests the application as a frequency standard. For this purpose, the direct measurement of the transition frequency compared to a primary frequency standard with a so-called frequency chain [19] is considered.…”

Section: Institut F üR Quantenoptik Der Universität Hannover Welfengmentioning

confidence: 99%

Sub-Kilohertz Optical Spectroscopy with a Time Domain Atom Interferometer

et al. 1998

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We report on the sub-kilohertz optical spectroscopy on the 1 S 0 -3 P 1 intercombination transition in magnesium at 457 nm. The spectroscopic signal is probed by a time domain atom interferometer. The realization of this time domain atom interferometer with laser cooled and trapped atoms allows extremely long interaction times and leads to resolutions down to 491 Hz (FWHM). This corresponds to a high line Q factor of 1.3 3 10 12 . Because of the high accuracy in the determination of the line center, applications with respect to an optical frequency standard are possible. [S0031-9007(98) PACS numbers: 03.75. Dg, 39.20. + q, 39.30. + w, In recent years the field of atom interferometry [1] has opened up new areas in fundamental and applied atomic physics. This is based mainly on the small wavelength of atomic de Broglie waves leading to the high sensitivity of atomic interferometers. In parallel the operation of atom interferometers has shown that due to the small de Broglie wavelength the proposed high sensitivity demands a setup of highest mechanical stability. Very recently several atom interferometric measurements have reached or even surpassed the precision of conventional "state of the art methods." Prominent examples are the realization of a highly sensitive atom-based Sagnac gyroscope [2], the measurement of the Earth's gravitational acceleration [3], and the precise determination ofh͞m atom [4].The Ramsey-Bordé atom interferometer, in particular, has proven to have excellent perspectives for applications in high resolution spectroscopy [1]. In this type of atom interferometer, the atomic wave is split and the partial waves are reflected and recombined by nearly resonant laser light. The phase shift between the two interfering matter waves depends strongly on the frequency of the splitting laser beam producing the spectroscopic signal. The transfer of the Ramsey-Bordé scheme from the originally proposed beam experiment [5] to a time domain interferometer [6] increases the sensitivity and reduces systematic line shifts by several orders of magnitude.Different methods for high resolution optical spectroscopy on neutral atoms as well as ions are currently being discussed and evaluated in the context of the next generation of frequency standards and atomic clocks. Especially, cold neutral atoms are also being used in the development of new microwave clocks [7,8]. In this Letter we report for the first time on atom interferometric high resolution measurements of an optical transition with a line Q factor above 10 12 corresponding to a resolved linewidth well below 1 kHz. The results presented here should be compared to recent results from the methods of the two-photon spectroscopy [9] and spectroscopy on single trapped ions [10]. In two-photon spectroscopy the ac Stark shift affects the obtainable accuracy, whereas in single-ion spectroscopy the stability is limited by the small particle numbers. The atom interferometric measurement of optical transitions discussed here offers the combination of a high accuracy...

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First Phase-Coherent Frequency Measurement of Visible Radiation

Cited by 212 publications

References 16 publications

Absolute Frequency Measurements of theHg+and Ca Optical Clock Transitions with a Femtosecond Laser

Absolute Frequency Measurements of theHg+and Ca Optical Clock Transitions with a Femtosecond Laser

Testing the Stability of the Fine Structure Constant in the Laboratory

Sub-Kilohertz Optical Spectroscopy with a Time Domain Atom Interferometer

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