  We demonstrate the ability to control the spontaneous emission dynamics of
self-assembled quantum dots via the local density of optical modes in
2D-photonic crystals. We show that an incomplete 2D photonic bandgap is
sufficient to significantly lengthen the spontaneous emission lifetime
($>2\times$) over a wide bandwidth ($\Delta\lambda\geq40$ nm). For dots that
are both \textit{spectrally} and \textit{spatially} coupled to strongly
localized ($V_{mode}\sim1.5(\lambda/n)^{3}$), high $Q\sim2700$ optical modes,
we have directly measured a strong Purcell enhanced shortening of the emission
lifetime $\geq5.6\times$, limited only by our temporal resolution. Analysis of
the spectral dependence of the recombination dynamics shows a maximum lifetime
shortening of $19\pm4$. From the directly measured enhancement and suppression
we show that the single mode coupling efficiency for quantum dots in such
structures is at least $\beta=92%$ and is estimated to be as large as
$\sim97%$.
