PHOTON STATISTICS OF FLUORESCENCE FROM A SINGLE 3-LEVEL ATOM

A sharp increase in the variance of the photon counting distribution for long collection times indicates an intermittent fluorescence signal, caused by (macroscopic) quantum jumps. Mandel's Q-parameter presents a convenient measure for the deviation of the actual statistics from that of a Poisson process. While the short time limit of Q(T) reflects the quantum statistical properties of individual emission events, the long time behaviour is dominated by the quasi-classical aspects of a random sequence of bright and dark periods. The typical signatures of quantum jumps, as they appear in the statistical description, can be visualized when comparing fluorescence from a two- and a three-level system. The classical aspects become obvious when comparison is made between the properties of a classical random telegraph signal and those of the quantum statistical calculation. © 1990 Springer-Verlag.