Optical frequency standard trapped atoms

Where does this spectacular development lead concerning frequency standards Traps for neutral atoms unfortunately perturb the atomic energy levels both the magnetic fields used as well as the laser light for cooling. As an example of what can be achieved, mention may be made of a tuneable dye laser, locked to the intercombination line at 657 nm of Ca atoms, either in an atomic beam or in a magneto-optic trap, has an estimated relative uncertainty of below 10 [38]. 

In this section, different and varions geometries nsed for atomic clocks will be presented. It is essential that the efficiencies of these devices be sufficient to yield a pure systan under well-controUed environmental conditions. Different routes have been followed in order to achieve the optimum signal-to-noise ratio, S/N. As mentioned above, two classes of atomic clocks exist these classes are either microwave or optical frequency standards, and the constraints imposed by each upon the trap geometry are different. 

A very interesting application of cold trapped atoms is their use for an optical frequency standard [1210]. They offer two major advantages reduction of the Doppler effect and prolonged interaction times on the order of 1 s or more. Optical frequency standards may be realized either by atoms in optical traps or by atomic fountains [1211]. 

A very interesting application of cold, trapped atoms is their aspect for an optical frequency standard [14.49]. They offer two major advantages ... 

In this Section, we will describe briefly the most recent projects of atomic clocks involving/based on ion traps as described above. The first part concerns micro-wave clocks, while the one following will be dedicated to optical frequency clocks. Performances of atomic standards can be evaluated only by comparison (frequency beatings) with another devices. When a new atomic standard can be presumed to out-perform the norm, it can be evaluated only from the comparison with a second system, which must be build in a similar way. It is worth noting that performances of each scheme depend on the local oscillator a quartz (eventually, cryogenic) oscillator for the microwave range, and a laser for the optical one. 

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