Spontaneous emission of quantum dot systems in laterally structured microca
vities that exhibit photon confinement in all three directions has been stu
died by time-resolved photoluminescence spectroscopy. For on-resonance cond
itions, we find that the dot emission rate is increased substantially over
that of the unstructured planar cavity. For off-resonance conditions, we ar
e able to suppress the emission rate by an order of magnitude by using cavi
ties with metal coatings, which we attribute to the suppression of leaky op
tical modes in these structures.