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Joint Conference of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS)

Absolute frequency measurement of the 40Ca+ clock transition using a LD-based clock laser and UTC(NICT)

Kensuke Matsubara, Ying Li, Shigeo Nagano, Hiroyuki Ito, Masatoshi Kajita, Reiko Kojima, Kazuhiro Hayasaka, Yuko Hanado, Mizuhiko Hosokawa

Published Apr 1, 2009• 2 citations
Publisher

Abstract

We developed an optical frequency standard using40Ca+with the 42S1/2-32D5/2electric quadrupole transition. Its absolute transition frequency is 411 042 129 776 390(7) Hz. The uncertainty is limited by the electric quadrupole shift and ambient magnetic field fluctuation. To determine the absolute transition frequency with a better uncertainty, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency which is corrected for the electric quadrupole shift. It will be used to determine the absolute transition frequency with respect to the SI base units of time and length. In addition, we are developing a magnetic-shielded ion-trap chamber to reduce the transition-line broadening caused by the magnetic field fluctuation.

DOI
10.1109/freq.2009.5168285

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Frequency measurement of the40Ca+clock transition using a LD-based clock laser and UTC(NICT)

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Frequency Measurement of the Optical Clock Transition of40Ca+Ions with an Uncertainty of 10-14Level

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Research on the development of the optical frequency standard based on trapped and cold 40 Ca + with the 4s 2 S 1/2 -3d 2 D 5/2 clock transition at 729 nm is reported. A single calcium ion was trapped and laser cooled in the Paul trap and stay in trap for more than 15 days. The linewidth of a 729 nm laser was reduced to less than 10 Hz by locking to a cavity for longer than 50 hours uninterruptedly. The overall systematic uncertainty of the clock transition has been characterized to be better than 6.5×10 −16 . The absolute frequency of the clock transition was measured at 10 −15 level using an optical frequency comb referenced to a Hydrogen maser, which was calibrated to the SI second through the global positioning system (GPS). The frequency value was 411042129776393.0(1.6) Hz after the correction of the systematic shifts.

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The National Institute of Information and Communications Technology in Japan is proceeding with development of an optical frequency standard using an electric quadrupole transition of Ca+ ions in a small radio-frequency trap. The single, trapped 40Ca+ ions are laser cooled to a temperature of <10 mK using extended-cavity diode lasers at 397 nm and 866 nm. In order to measure the electric quadrupole transition, the linewidth of the clock laser diode at 729 nm is reduced to ~66 Hz using an ultra-low-expansion (ULE) cavity. We observed the electric quadrupole transition with a linewidth of ~600 kHz, together with the ionic motional sidebands. We are also developing optical frequency combs without photonic fibers broadening the spectrum. The experimental is now improved in order to observe the narrower linewidth of the quadrupole transition.

•Dec 9, 2006•0 citations

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We report improved frequency measurement of a single40Ca+optical clock towards the 10-15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by the magnetic field fluctuation, the use of a magnetic shield significantly reduced the observed linewidth of its2S1/2-2D5/2clock transition. From frequency comparison between the40Ca+clock and an87Sr lattice clock, an Allan deviation of 7 × 10-16at an averaging time of one thousand seconds was measured. We now measure the absolute frequency of the40Ca+clock transition with respect to the SI definition of the second.

URSI General Assembly and Scientific Symposium•Aug 1, 2011•0 citations

Progress on the 40Ca+ ion optical clock*

Baolin Zhang, Yao Huang, Huaqing Zhang +4 more

Progress of the 40Ca+ ion optical clock based on the 42S1/2 – 3d 2D5/2 electric quadrupole transition is reported. By setting the drive frequency to the “magic” frequency Ω 0, the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10−19 level. By precisely measuring the differential static scalar polarizability Δα 0, the uncertainty due to the blackbody radiation (BBR) shift (coefficient) is reduced to the 10−19 level. With the help of a second-order integrating servo algorithm, the uncertainty due to the servo error is reduced to the 10−18 level. The total fractional uncertainty of the 40Ca+ ion optical clock is then improved to 2.2× 10−17, whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations. The state preparation is introduced together with improvements in the pulse sequence, and furthermore, a better signal to noise ratio (SNR) and less dead time are achieved. The clock stability of a single clock is improved to 4.8 × 10 − 15 / τ ( in seconds ) .

Chinese Physics B•May 19, 2020•18 citations
We developed an optical frequency standard using40Ca+with the 42S1/2-32D5/2electric quadrupole transition. Its absolute transition frequency is 411 042 129 776 390(7) Hz. The uncertainty is limited by the electric quadrupole shift and ambient magnetic field fluctuation. To determine the absolute transition frequency with a better uncertainty, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency which is corrected for the electric quadrupole shift. It will be used to determine the absolute transition frequency with respect to the SI base units of time and length. In addition, we are developing a magnetic-shielded ion-trap chamber to reduce the transition-line broadening caused by the magnetic field fluctuation.
We developed an optical frequency standard with the 4 2S1/2-3 2D5/2 electric quadrupole transition of 40Ca+ ions. Its absolute transition frequency is 411 042 129 776 390(±7) Hz. The accuracy is limited by the electric quadrupole shift and the ambient magnetic field fluctuation. To determine the absolute transition frequency with a better accuracy, we have observed two pairs of the symmetrically-splitting Zeeman components and measured the transition frequency corrected for the electric quadrupole shift. In addition, we are developing a magnetic-shielded ion-trap chamber to suppress the transition-line broadening caused by the magnetic field fluctuation.
Research on the development of the optical frequency standard based on trapped and cold 40 Ca + with the 4s 2 S 1/2 -3d 2 D 5/2 clock transition at 729 nm is reported. A single calcium ion was trapped and laser cooled in the Paul trap and stay in trap for more than 15 days. The linewidth of a 729 nm laser was reduced to less than 10 Hz by locking to a cavity for longer than 50 hours uninterruptedly. The overall systematic uncertainty of the clock transition has been characterized to be better than 6.5×10 −16 . The absolute frequency of the clock transition was measured at 10 −15 level using an optical frequency comb referenced to a Hydrogen maser, which was calibrated to the SI second through the global positioning system (GPS). The frequency value was 411042129776393.0(1.6) Hz after the correction of the systematic shifts.
The National Institute of Information and Communications Technology in Japan is proceeding with development of an optical frequency standard using an electric quadrupole transition of Ca+ ions in a small radio-frequency trap. The single, trapped 40Ca+ ions are laser cooled to a temperature of <10 mK using extended-cavity diode lasers at 397 nm and 866 nm. In order to measure the electric quadrupole transition, the linewidth of the clock laser diode at 729 nm is reduced to ~66 Hz using an ultra-low-expansion (ULE) cavity. We observed the electric quadrupole transition with a linewidth of ~600 kHz, together with the ionic motional sidebands. We are also developing optical frequency combs without photonic fibers broadening the spectrum. The experimental is now improved in order to observe the narrower linewidth of the quadrupole transition.
We report improved frequency measurement of a single40Ca+optical clock towards the 10-15uncertainty level. In contrast with our previous measurement, in which the accuracy was limited by the magnetic field fluctuation, the use of a magnetic shield significantly reduced the observed linewidth of its2S1/2-2D5/2clock transition. From frequency comparison between the40Ca+clock and an87Sr lattice clock, an Allan deviation of 7 × 10-16at an averaging time of one thousand seconds was measured. We now measure the absolute frequency of the40Ca+clock transition with respect to the SI definition of the second.
Progress of the 40Ca+ ion optical clock based on the 42S1/2 – 3d 2D5/2 electric quadrupole transition is reported. By setting the drive frequency to the “magic” frequency Ω 0, the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10−19 level. By precisely measuring the differential static scalar polarizability Δα 0, the uncertainty due to the blackbody radiation (BBR) shift (coefficient) is reduced to the 10−19 level. With the help of a second-order integrating servo algorithm, the uncertainty due to the servo error is reduced to the 10−18 level. The total fractional uncertainty of the 40Ca+ ion optical clock is then improved to 2.2× 10−17, whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations. The state preparation is introduced together with improvements in the pulse sequence, and furthermore, a better signal to noise ratio (SNR) and less dead time are achieved. The clock stability of a single clock is improved to 4.8 × 10 − 15 / τ ( in seconds ) .