  We report on the coherent optical response from an ensemble of (In,Ga)As
quantum dots (QDs) embedded in a planar Tamm-plasmon microcavity with a quality
factor of approx. 100. Significant enhancement of the light-matter interaction
is demonstrated under selective laser excitation of those quantum dots which
are in resonance with the cavity mode. The enhancement is manifested through
Rabi oscillations of the photon echo, demonstrating coherent control of
excitons with picosecond pulses at intensity levels more than an order of
magnitude smaller as compared with bare quantum dots. The decay of the photon
echo transients is weakly changed by the resonator indicating a small decrease
of the coherence time $T_2$ which we attribute to the interaction with the
electron plasma in the metal layer located close (40nm) to the QD layer.
Simultaneously we see a reduction of the population lifetime $T_1$, inferred
from the stimulated photon echo, due to an enhancement of the spontaneous
emission by a factor of 2, which is attributed to the Purcell effect, while
non-radiative processes are negligible as confirmed from time-resolved
photoluminescence.
