  We experimentally demonstrate control of the rate of spontaneous emission in
a tunable hybrid photonic system that consists of two canonical building blocks
for spontaneous emission control, an optical antenna and a mirror, each
providing a modification of the local density of optical states (LDOS).We
couple fluorophores to a plasmonic antenna to create a superemitter with an
enhanced decay rate. In a superemitter analog of the seminal Drexhage
experiment we probe the LDOS of a nanomechanically approached mirror. Due to
the electrodynamic interaction of the antenna with its own mirror image the
superemitter traces the inverse LDOS of the mirror, in stark contrast to a bare
source, whose decay rate is proportional to the mirror LDOS.
