Improved uncertainty budget for optical frequency measurements with microkelvin neutral atoms: Results for a high-stability 40Ca optical frequency standard
Abstract
Using a Ca optical frequency standard at 657 nm, we demonstrate a method that reduces uncertainties in absolute frequency measurements of optical transitions using freely expanding neutral atoms. Working with atoms that have been laser cooled to 10 μK, we have developed and employed a new technique that combines launching of cold atom clouds with atom interferometry to measure and optimise spectroscopy beam parameters. When applied to a frequency standard with laser beams of high spatial quality, this approach can potentially reduce residual Doppler effect uncertainties to well below one part in 1016. With Doppler uncertainties greatly suppressed, we investigate other potential shifts at the 1-Hz level with a multiplexed measurement system that takes advantage of the low instability of the calcium frequency standard (4×10-15 at 1 s). The resultant fractional frequency uncertainty for the standard is 6.6×10-15, the lowest uncertainty reported to date for a neutral atom optical standard.
- Publication:
-
Applied Physics B: Lasers and Optics
- Pub Date:
- October 2006
- DOI:
- 10.1007/s00340-006-2400-1
- Bibcode:
- 2006ApPhB..85...31W
- Keywords:
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- Probe Beam;
- Probe Pulse;
- Frequency Standard;
- Laser Cool;
- Clock Transition