Optical frequency/wavelength references

Hollberg, L.; Oates, C. W.; Wilpers, G.; Hoyt, Chad; Barber, Zeb W.; Diddams, Scott A.; Oskay, W. H.; Bergquist, J. C.

doi:10.1088/0953-4075/38/9/003

Cited by 67 publications

(44 citation statements)

References 178 publications

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“…It has made possible Bose-Einstein condensation [2], while laser-cooled atoms are used, for instance, in atomic clocks [3] and as frequency standards [4], and have been proposed for parity violation measurements [5] and quantum information processing [6].…”

Section: Introductionmentioning

confidence: 99%

Time dependence of laser cooling in optical lattices

et al. 2005

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We study the dynamics of the cooling of a gas of caesium atoms in an optical lattice, both experimentally and with 1D full-quantum Monte Carlo simulations. We find that, contrary to the standard interpretation of the Sisyphus model, the cooling process does not work by a continuous decrease of the average kinetic energy of the atoms in the lattice. Instead, we show that the momentum of the atoms follows a bimodal distribution, the atoms being gradually transferred from a hot to a cold mode. We suggest that the cooling mechanism should be depicted in terms of a rate model, describing the transfer between the two modes along with the processes occurring within each mode.

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Section: Introductionmentioning

confidence: 99%

Time dependence of laser cooling in optical lattices

et al. 2005

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“…Dk, 32.60.+i, 06.20.fb,44.40.+a An atom immersed in an electric field E a becomes polarized -the electronic wave-function is stretched into alignment with the field. Generally, energies of the lowest-lying electronic quantum states |i are reduced by − cold alkaline-earth atoms tightly confined in an optical standing wave potential so their intrinsically narrow, largely imperturbable,may establish stable and accurate frequency and time references [4,5]. In analogy to a pendulum's oscillation slowing due to thermal expansion, a ytterbium lattice clock slows when electrically stretched, or polarized, by thermal blackbody radiation (BBR) fields [6,7].…”

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confidence: 99%

“…may establish stable and accurate frequency and time references [4,5]. In analogy to a pendulum's oscillation slowing due to thermal expansion, a ytterbium lattice clock slows when electrically stretched, or polarized, by thermal blackbody radiation (BBR) fields [6,7].…”

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High-Accuracy Measurement of Atomic Polarizability in an Optical Lattice Clock

et al. 2012

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Despite being a canonical example of quantum mechanical perturbation theory, as well as one of the earliest observed spectroscopic shifts, the Stark effect contributes the largest source of uncertainty in a modern optical atomic clock through blackbody radiation. By employing an ultracold, trapped atomic ensemble and high stability optical clock, we characterize the quadratic Stark effect with unprecedented precision. We report the ytterbium optical clock's sensitivity to electric fields (such as blackbody radiation) as the differential static polarizability of the ground and excited clock levels α clock = 36.2612(7) kHz (kV/cm) −2 . The clock's fractional uncertainty due to room temperature blackbody radiation is reduced an order of magnitude to 3 × 10 −17 .PACS numbers: 32.10. Dk, 32.60.+i, 06.20.fb,44.40.+a An atom immersed in an electric field E a becomes polarized -the electronic wave-function is stretched into alignment with the field. Generally, energies of the lowest-lying electronic quantum states |i are reduced by − cold alkaline-earth atoms tightly confined in an optical standing wave potential so their intrinsically narrow, largely imperturbable,may establish stable and accurate frequency and time references [4,5]. In analogy to a pendulum's oscillation slowing due to thermal expansion, a ytterbium lattice clock slows when electrically stretched, or polarized, by thermal blackbody radiation (BBR) fields [6,7]. This phenomenon has been measured in the cesium fountain primary standard [8,9] and other optical transitions [1,10,11].No shield at finite temperature protects a clock atom from the time varying electric field of BBR, the electromagnetic energy absorbed and re-emitted by all matter in thermal equilibrium according to the Stefan-Boltzmann law [12]. Inside a hollow shell of opaque matter (a blackbody), the time-averaged electric field intensity depends strongly on temperature:where α ≈ 1/137 is the fine-structure constant, k B is Boltzmann's constant, and T is the blackbody's absolute temperature [13]. Near room temperature, the spectrum of radiation is peaked strongly near 9.6 µm-invisible to the eye and also far detuned from strong electronic transitions in ytterbium.The ytterbium clock frequency (ν ≈ 518 THz) is shifted by the net BBR Stark effect of the two clock states, which can be expressed aswhere αg,e are the static polarizabilities of ground and excited states ( 1 S 0 and 3 P 0 , respectively), and η clock (T ) [7] arXiv:1112.2766v1 [physics.atom-ph]

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“…Ft,42.50.Hz,42.62.Fi Recent advances in the field of optical frequency metrology make measurements with a fractional accuracy of 10 −17 or better a realistic short term goal [1]. Among other possible applications (e.g.…”

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Accurate Optical Lattice Clock withSr87Atoms

et al. 2006

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We report a frequency measurement of the 1 S0 − 3 P0 transition of 87 Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879 (5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall. Two previous measurements of this transition were found to disagree by about 2 × 10 −13 , i.e. almost four times the combined error bar, instilling doubt on the potential of optical lattice clocks to perform at a high accuracy level. In perfect agreement with one of these two values, our measurement essentially dissipates this doubt.PACS numbers: 06.30. Ft,42.50.Hz,42.62.Fi Recent advances in the field of optical frequency metrology make measurements with a fractional accuracy of 10 −17 or better a realistic short term goal [1]. Among other possible applications (e.g. a redefinition of the S.I. second, optical very long baseline interferometry in space, direct mapping of the earth gravitational using the Einstein effect,...), a very interesting prospect with measurements at that level is a reproducible test of Einstein Equivalence Principle by the repeated determination of the frequency ratio of different atomic and molecular transitions [2,3,4,5,6,7]. The topicality of such a test has recently been renewed by measurements at the cosmological scale which seem to indicate a slow variation of the electron to proton mass ratio [8]. The richness of the test directly depends on the performance of the clocks that are used but also on the variety of clock transitions and atomic species on which high accuracy frequency standards are based.In that context, optical lattice clocks are expected to play a central role in the future of this field. They use a large number of atoms confined in the Lamb-Dicke regime by an optical lattice in which the first order perturbation of the clock transition cancels [9]. Due to the lattice confinement motional effects, which set a severe limitation to standards with neutral atoms in free fall [10,11], essentially vanish [12]. This gives hope for a ultimate fractional accuracy better than 10 −17 . On the other hand, the large number of atoms in an optical lattice clock in principle opens the way to a short term fractional frequency stability significantly better than 10 −15 τ −1/2 with τ the averaging time in seconds. In this regime the coherence time of the laser frequency locked to the clock transition would be several seconds, possibly tens of seconds [25]. Such a long coherence time could for instance be used to reduce the width of the optical resonances in single ion clocks down to or below the 0.1 Hz range opening new prospects for these devices also. Finally, the optical lattice clock scheme is in principle applicable to a large number of atomic species (Sr, Yb, Hg, Ca, Mg,...) which is a key feature for the fundamental test discussed above. It is then particularly problematic that the frequency delivered by the first two evaluated optical lattice clocks, which both use 87 Sr, disagree by about 2 × ...

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Optical frequency/wavelength references

Cited by 67 publications

References 178 publications

Time dependence of laser cooling in optical lattices

Time dependence of laser cooling in optical lattices

High-Accuracy Measurement of Atomic Polarizability in an Optical Lattice Clock

Accurate Optical Lattice Clock withSr87Atoms

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