US EPA

1783842 

Journal Article 

Cs cell atomic clock optically pumped by a diode laser 

Beverini, N; Ortolano, M; Costanzo, GA; De Marchi, A; Maccioni, E; Marsili, P; Ruffini, A; Periale, F; Barychev, V 

2001 

1 

Laser Physics
ISSN: 1054-660X
EISSN: 1531-8494 

11 

10 

1110-1116 

WOS:000171957100012 

In the number of the atomic frequency standards, or atomic
clocks, the devices working by optical pumping of alkali vapor in cell (usually known as Rubidium
frequency standard, because the rubidium atom is traditionally used) are by far the most common.
They are used as a reference for a quartz oscillator in the applications where its long-term
stability is no more adequate. The best commercial device presents a short-term stability only
slightly better than 10(-11) at 1 s, which is, however, almost three order of magnitude larger
than the theoretical limit, when a spectrally narrowed laser diode is used as pumping source. An
accurate analysis of the pumping process and a carefully project of the pumping laser system and
of the microwave interrogation circuits may closer approach the theoretical limit. In this paper
we present an analysis of the interrogation process and the development of a new device, based on
Cs transition at 9192.631 MHz. In this apparatus we control carefully both the spectral purity of
the pumping diode laser, and of the microwave interrogation chain, which are the principal source
of losses for the clock stability. For this purpose, we tested new schemes for locking the diode
laser radiation on the resonance Cs line, new scheme for microwave locking circuit, and a new
microwave resonance cell, where the Cs is directly filled in the metallic cavity for a more
direct control of the cavity mode.