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.
Cs cell atomic clock optically pumped by a diode laser
BEVERINI, NICOLO';MACCIONI, ENRICO;MARSILI, PAOLO;
2001-01-01
Abstract
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
