Velocity-selective optical ramsey fringes by optical pumping in a Ca atomic beam

Norio Ito

William G. Tobias, Bryan Hemingway, Steven Peil

We demonstrate an optical clock based on Ramsey-Bordé interferometry in a laser-cooled ^{40}Ca beam. The mean velocity is reduced by an order of magnitude relative to a thermal beam and the transverse temperature approaches the Doppler limit, enabling the measurement of sub-kHz linewidth fringes in a compact interferometer. Using tailored phase and intensity modulation of the spectroscopy laser to add uniform frequency sidebands, we interrogate atoms throughout the transverse velocity distribution, increasing the Ramsey-Bordé fringe amplitude by a factor of 14 and improving the Allan deviation to 3.4×10^{-15} at one second averaging time.

J. J. Snyder, J. Helmcke, M. Gläser +1 more

R. L. Barger

Resolution sufficient to resolve second-order Doppler broadening (3.9 kHz) has been obtained for the Ca (1)S(0)-(3)P(1) transition (657 nm) by using an atomic beam and optical Ramsey fringe techniques. Laser-beam separations up to 21 cm yield Ca linewidths (HWHM) as narrow as 1 kHz. As resolution is increased to approach, then exceed the second-order linewidth, large asymmetries, shifts, and shape changes occur in the Ramsey fringe profile.

M. M. Salour