DARK PERIODS IN THE RESONANCE FLUORESCENCE OF A SINGLE LAMBDA-SYSTEM

We use the quantum jump method to study the photon statistics of a sin gle laser-driven atom in the Lambda configuration where both lower lev els are strongly coupled to the common upper level. Under certain cond itions we show that, for almost degenerate lower levels, light and dar k periods occur which are similar to those of the well-known Dehmelt V system. Analytic results for their mean lengths and other statistical properties are given. For large separation of the lower levels we pro ve an interesting bunching property by the photons in the resonance fl uorescence near the dark resonance. We propose a realistic system for which these effects may be observed.