Abstract
For ultra-high resolution spectroscopic applications such as optical frequency standards, the value of thermal sources such as atomic beams is currently limited by secondorder Doppler broadening. The use of a longitudinal interaction geometry in which an atomic beam crosses the counter-propagating laser fields at a small angle is able to reduce second-order Doppler broadening to an insignificant level as well as to provide long interaction times without the necessity of large-diameter optical beams. We have analyzed this geometry for the case of the long-lived calcium intercombination line, and conclude that when combined with pulsed (Ramsey) excitation, the longitudinal interaction geometry could be used with a thermal calcium beam to create an optical frequency standard with a reproducibility of the order of 10−14 for a few seconds averaging time. Our initial experimental results have demonstrated the first use of the longitudinal geometry.
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References
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