Coherent-population-trapping maser: Noise spectrum and frequency stability (11 pages)

A. Godone, Filippo Levi, Salvatore Micalizio +1 more

Aldo Godone, Filippo Levi, Salvatore Micalizio +1 more

We examine in this paper the spectral characteristics of a coherent population trapping (CPT) maser in order to evaluate the frequency stability achievable by this kind of passive frequency standard. The peculiar features of the coherent microwave emission associated with the coherent population trapping phenomenon are theoretically examined taking into account the impact of the various noise contributions on the physical principle of operation. The theoretical predictions are then compared with the experimental results obtained with a laboratory prototype of $^{87}\mathrm{R}\mathrm{b}$ CPT maser. The measured frequency stability is mainly limited in the short term by the system thermal noise and in the medium term by the thermal drift and turns out to be in agreement with the computations within a factor of 2.

P. N. Butcher

A. Godone, Filippo Levi, Jaques Vanier

Recent studies have shown the feasibility of a Cs maser without population inversion based on the coherent population trapping phenomenon. Among the main advantages of this type of frequency standard are size, simplicity of implementation, virtual absence of first order light shift and the availability of a low noise microwave signal leading to the realization of a standard with an excellent short term frequency stability.

Filippo Levi, A. Godone, Jaques Vanier

The light shift, as observed in the coherent population trapping (CPT) maser, was investigated theoretically and experimentally. It was found that the light shift originates from the various sidebands that are present in the spectrum of the frequency-modulated laser used to observe the CPT phenomenon.

Ning Lu, Claus Benkert