  The emission properties of single quantum dots in planar microcavities are
studied experimentally and theoretically. Fivefold Enhanced spontaneous
emission outside the microcavity is found for dots in resonance with the cavity
mode, relative to detuned dots, while their radiative lifetime is only
marginally decreased. Using high power excitation we obtain the in-plane cavity
dispersion. Near field images of the emission show spatial distributions of
several microns for resonant dots, which decrease in size with the detuning
from resonance. These experimental findings are explained using a simple and
intuitive model.
