The coherent population trapping passive frequency standard [Rb example]

Coherent population trapping in alkali atoms has opened a new avenue in the implementation of atomic frequency standards having promising characteristics for field use. The paper gives a short description of the phenomenon, interprets experimental observations by means of a four-level model, outlines the use of such a phenomenon in the frequency standard field, and gives an evaluation of the achievable frequency stability based on the contrast and line Q realizable in practice.