  We report on the radiative interaction of two single quantum dots (QDs) each
in a separate InP/GaInP-based microdisk cavity via resonant whispering gallery
modes. The investigations are based on ab initio coupled disk modes. We apply
optical spectroscopy involving a $4f$-setup, as well as mode-selective real
space imaging and photoluminescence mapping to discern single QDs coupled to a
resonant microdisk mode. Excitation of one disk of the double cavity structure
and detecting photoluminescene from the other yields proof of single photon
emission of a QD excited by incoherent energy transfer from one disk to the
other via a mode in the weak coupling regime. Finally, we present evidence of
photons emitted by a QD in one disk that are transferred to the other disk by a
resonant mode and are subsequently resonantly scattered by another QD.
