Quantum jumps in a coherently driven Raman system

Early results of Agarwal and Jha [Z. Phys. B 35, 391 (1979)] are used to examine the question of quantum jumps in a Raman (Λ) system driven by two coherent fields. We discuss both short-time (γ<SUB>1</SUB>t≲1) and long-time (γ<SUB>2</SUB>t≊1) behavior of the intensity correlations assuming that the Stokes transition is very weak, γ<SUB>2</SUB>≪γ<SUB>1</SUB>. We calculate the counting statistics of the dark periods using the higher-order intensity correlations. The results differ from those obtained using arguments based on population trapping which predict only a very rare "jump" event. The intermittence in fluorescence produced by a coherently driven Λ system is interpreted in terms of an equivalent two-state Markov process