  The interaction of excitonic transitions with confined photonic modes enables
tests of quantum physics and design of efficient optoelectronic devices. Here
we study how key metrics such as Purcell factor, beta-factor and collection
efficiency are determined by the non-cavity modes which exist in real devices,
taking the well-studied micropillar cavity as an example. Samples with dots at
different positions in the cavity field allow us to quantify the effect of the
non-cavity modes and show that the zero-phonon line and the phonon-assisted
emission into the cavity mode HE11 is suppressed by positioning dots at the
field node.
