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We report on precision laser spectroscopy of the 2S1/2(F = 0) 2D3/2 (F = 2, mF = 0) clock transition in a single ion of 171Yb+. The absolute value of the transition frequency, determined using an optical frequency comb referenced to a hydrogen maser, is 688358979309310 ?? 9 Hz. This corresponds to a fractional frequency uncertainty of 1.3 ?? 10-14.
A compact and simplified 13C2H2 optical frequency standard is currently under development at NPL. The standard uses an inexpensive, commercially available 20 mW DFB diode laser, which is stabilized to line P(16) of the nu1 + nu3 band at 1542 nm in an experimental arrangement which dispenses with the need for an enhancement cavity. Preliminary stability and reproducibility data will be presented.
The 1S0-3P0 transition in neutral strontium is being considered as one of the choices for the future redefinition of the SI second. At the National Physical Laboratory we are designing and implementing an optical clock based on this transition, holding the atoms in an optical lattice during the clock interrogation cycle, which greatly increases the potential accuracy of the clock. Our focus is on...
Two 674-nm optical frequency standards based on the 2S1/2 - 2D5/2 transition in 88Sr+ are under development at NPL. Comparison of the standards allows determination of the frequency stability and reproducibility via difference frequency measurements. A relative frequency stability between the traps of ap3times10-15 over a 100 s averaging time has been observed. A compact, transportable system is also...
The 100 MHz repetition rate of a mode-locked erbium-doped fibre laser has been transmitted over 100 km of spooled fibre. With only passive dispersion compensation, short-term frequency instability below 4 times 10-14 has been demonstrated.
Forbidden transitions in single laser-cooled trapped ions provide highly stable and accurate references for optical frequency standards. This paper describes recent progress on strontium and ytterbium ion optical frequency standards under development at NPL.
In preparation for an absolute frequency measurement referenced directly to the NPL caesium frequency fountain, the authors have made a measurement of the quadrupole shift of the 674 nm transition in 88 Sr+. This allows a determination of the quadrupole moment of the 2D5/2 level, which is compared with Cowan code calculations
A second femtosecond optical frequency comb has been implemented at NPL. This higher repetition rate system offers several advantages over our existing comb, and enables the accuracy of the frequency measurement process to be tested. Results of absolute frequency measurements carried out using the two different systems are compared
The frequency of the 2S1/2 (F = 0) - 2 F7/2(F = 3, mF = 0) transition in a single, trapped, laser cooled ion of 171Yb+ has been measured with a femtosecond laser frequency comb generator. The uncertainty is limited by measurement statistics and by the AC Stark shift
A pair of 778 nm rubidium two photon diode laser frequency standards has been developed at NPL. Their systematic sensitivity to various experimental parameters has been investigated and their stability and reproducibility characterized. Absolute frequency measurements have been made for two hyperfine components
Summary form only given. A single laser-cooled ion held in an electrodynamic trap is a near ideal atomic sample for a frequency standard. The quantum jump technique is used to observe a high-Q forbidden transition in the ion. It has been suggested that the ultimate limit to the reproducibility of a standard of this type will lie in the region of one part in 10/sup 18/.
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