Practical realization of a passive coherent population trapping frequency standard

The paper outlines the practical realization and characteristics of a small, totally autonomous passive frequency standard based on the coherent population trapping (CPT) phenomenon. The frequency standard, including physical characteristics, block diagrams of the optical control CPT resonance system and of the digital control electronics, is described. The characteristics of the frequency standard relative to general functionality and frequency stability are given, as measured on several units.