Single-Ion Optical Frequency Standards and Measurement of their Absolute Optical Frequency

Madej, A.A.; Bernard, J. E.

doi:10.1007/3-540-44991-4_7

Cited by 36 publications

(48 citation statements)

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“…Since the fractional instability σ y (τ ) is inversely proportional to the transition frequency, greater stability can be attained using transitions at higher frequencies such as those in the optical region of the electromagnetic spec- trum. Only recently have lasers of sufficient spectral purity become available to probe the narrow resonances provided by transitions between long-lived atomic states [6][7][8][9][10][11][12]. The stable laser source of Refs.…”

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confidence: 99%

“…An excellent review of the performance of similar systems can be found in Ref. [12]. Figure 3 shows a typical power-broadened spectrum with consequent Rabi "sidebands," using τ probe = 10 ms and τ servo = 40 ms. A least-squares fit to the data indicates that it is consistent with a pulse area of 2.41(7)π (relative to n ≈ 0) and a mean vibrational quantum num- 3.…”

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Sub-dekahertz Ultraviolet Spectroscopy of199Hg+

et al. 2000

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Using a laser that is frequency-locked to a FabryPérotétalon of high finesse and stability, we probe the 5d 10 6s 2 S 1/2 (F=0)↔5d 9 6s 2 2 D 5/2 (F=2) ∆mF =0 electricquadrupole transition of a single laser-cooled 199 Hg + ion stored in a cryogenic radio-frequency ion trap. We observe Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm (1.06 × 10 15 Hz), yielding a line Q ≈ 1.6 × 10 14 . We perform a preliminary measurement of the 5d 9 6s 2 2 D 5/2 electric-quadrupole shift due to interaction with the static fields of the trap, and discuss the implications for future trapped-ion optical frequency standards. PACS numbers: 06.30. Ft, 32.30.Jc, 32.80.Pj, 42.62.Fi Precision spectroscopy has held an enduring place in physics, particularly in the elucidation of atomic structure and the measurement of fundamental constants, in the development of accurate clocks, and for fundamental tests of physical laws. Two ingredients of paramount importance are high accuracy, that is, the uncertainty in systematic frequency shifts must be small, and high signal-to-noise ratio, since the desired measurement precision must be reached in a practical length of time. In this paper, we report the measurement of an optical absorption line in a single laser-cooled 199 Hg + ion at a frequency ν 0 = 1.06 × 10 15 Hz (wavelength ≈ 282 nm) for which a linewidth ∆ν = 6.7 Hz is observed, yielding the highest Q ≡ ν 0 /∆ν ever achieved for optical (or lower frequency) spectroscopy. We also report a preliminary measurement of the interaction of the upper state electric-quadrupole moment with the static field gradients of the ion trap, which is expected to contribute the largest uncertainty for a frequency standard based on this system.In spectroscopy and for clocks, fluctuations in frequency measurement are usually expressed fractionally: σ y (τ ) = ∆ν meas (τ )/ν 0 , where τ is the total measurement time. When the stability is limited by quantum fluctuations in state detection,2 , where N is the number of atoms, τ probe is the transition probe time (typically limited by the excited-state lifetime or the stability of the local oscillator), and C is a constant of order unity that depends on the method of interrogation. For many decades, the highest accuracies and the greatest stabilities have been achieved by locking a microwave oscillator to a hyperfine transition in an atomic ground state [1][2][3][4][5]. Since the fractional instability σ y (τ ) is inversely proportional to the transition frequency, greater stability can be attained using transitions at higher frequencies such as those in the optical region of the electromagnetic spec-

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Sub-dekahertz Ultraviolet Spectroscopy of199Hg+

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“…In addition, these references underpin the SI system which forms the basis of physical measurement. New experimental systems employing dipole forbidden optical transitions in trapped and laser-cooled ions and neutral atoms have been shown to be excellent nextgeneration realizations of ultra-accurate frequency references [3][4][5][6][7][8][9][10][11][12][13][14]. Such systems now have evaluated accuracies that exceed the current realizations of the definition of the SI second as realized by a microwave transition in Cs atoms [15].…”

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“…A diode pumped fiber laser provides a repump for the 4d 2 D 3=2 À 5p 2 P 1=2 transition at 1092 nm. Laser powers and detunings at 422 nm and 1092 nm were carefully adjusted to optimize the 422 nm fluorescence and laser cooling [18] such that the measured ion kinetic temperature was T ¼ 1:8 AE 0:8 mK (approaching the Doppler limit for this transition of 0.5 mK) [5]. Detected single-ion fluorescence rates of 10 4 counts per second are observed with a signal to background ratio of 70.…”

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“…A diode pumped fiber laser provides a repump for the 4d 2 D 3=2 À 5p 2 P 1=2 transition at 1092 nm. Laser powers and detunings at 422 nm and 1092 nm were carefully adjusted to optimize the 422 nm fluorescence and laser cooling [18] such that the measured ion kinetic temperature was T ¼ 1:8 AE 0:8 mK (approaching the Doppler limit for this transition of 0.5 mK) [5]. Selected for a Viewpoint in Physics P H Y S I C A L R E V I E W L E T T E R S week ending 16 NOVEMBER 2012 quadrupole allowed 5s 2 S 1=2 À 4d 2 D 5=2 transition whose natural line width is 0.4 Hz [16].…”

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Optical Atomic Clocks Could Redefine Unit of Time

Riehle¹

2012

Physics

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We describe experiments and measurements on a trapped and laser-cooled single ion of 88 Sr þ which, when probed on its reference 5s 2 S 1=2 ! 4d 2 D 5=2 transition at 445 THz, provides an optical frequency standard of evaluated accuracy outperforming the current realization of the SI second. Studies are presented showing that micromotion-associated shifts of the standard can be reduced to the 10 À18 level and uncertainties in the blackbody-induced shifts for the current system are at the low 10 À17 level due to the relatively well-known polarizability of the strontium ion system and careful choice of the trap structure. The current evaluated systematic shifts for the ion transition are at a fractional uncertainty of 2 Â 10 À17 . An absolute frequency measurement performed over a two-month period relative to a maser referenced to the SI second via Global Positioning System time transfer has determined the center frequency for the transition at SD ¼ 444 779 044 095 485:5 AE 0:9 Hz (1 ). DOI: 10.1103/PhysRevLett.109.203002 PACS numbers: 06.30.Ft, 32.70.Jz, 37.10.Ty, 42.50.Lc From precision tests of relativity to the increased understanding of atomic physics and fundamental constants, atomic time standards have helped shed light on subtle physical phenomena that underlie fundamental concepts of physics [1][2][3]. In addition, these references underpin the SI system which forms the basis of physical measurement. New experimental systems employing dipole forbidden optical transitions in trapped and laser-cooled ions and neutral atoms have been shown to be excellent nextgeneration realizations of ultra-accurate frequency references [3][4][5][6][7][8][9][10][11][12][13][14]. Such systems now have evaluated accuracies that exceed the current realizations of the definition of the SI second as realized by a microwave transition in Cs atoms [15]. Among the trapped ion systems studied, the 88 Sr þ 5s 2 S 1=2 ! 4d 2 D 5=2 electric dipole forbidden transition at 445 THz (674 nm) has a very high quality factor (Q ¼ 0 =Á ¼ 10 15 ) and possesses a relatively simple electronic energy level scheme that is favorable for use with widely available solid state laser technology [16]. This ion system was the first to be directly measured against the Cs realization of the second [17] and has been established as one of the secondary representations of the SI second. This system has been primarily studied at the Frequency and Time Group, National Research Council of Canada (NRC) and the National Physical Laboratory (NPL) in the United Kingdom [7,11] with additional groups recently providing results [18]. We describe new results and methods by which the systematic shifts for the system have been reduced to the low 10 À17 level via operation of the trap system under conditions which reduce and in some cases null out significant uncertainties which dominate many optical reference systems. The work also provides a new measurement of the transition center frequency relative to the SI second.A single atomic ion of 88 Sr þ is held in an electr...

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Optical Instrumentation

Hoeschen

Mirandé

2004

Digital Encyclopedia of Applied Physics

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Optical instrumentation is based on phenomena caused by optical radiation. In this article, optical radiation is limited to a wavelength range between 200 nm and 50 µm. After a short survey about the historical development of optical instrumentation, phenomena resulting from the various characteristics of optical radiation, as for instance, a wave or a particle, are considered. Based on the wavelength character, optical instrumentation used for interferometry, colorimetry, spectroscopy, diffraction, imaging, and optical frequency standards is treated. The interaction of optical radiation with matter is used in refractometry, in polarimetry, for studying matter with ultrashort pulses of radiation, and for processing matter with radiation of high‐energy density. Finally, the particle character is considered to be used for fields such as radiometry and energy conversion.

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Single-Ion Optical Frequency Standards and Measurement of their Absolute Optical Frequency

Cited by 36 publications

References 120 publications

Sub-dekahertz Ultraviolet Spectroscopy of199Hg+

Sub-dekahertz Ultraviolet Spectroscopy of199Hg+

Optical Atomic Clocks Could Redefine Unit of Time

Optical Instrumentation

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