  We investigate theoretically the photo absorbtion of the cluster of alkali
atoms embedded into a single mode quantum microcavity. We show that when the
energy of the giant plasmonic resonance lies close to the energy of the cavity
mode, the strong coupling between plasmon and cavity photon can occur, which is
characterized by mode anticrossing and observation of the doublet structure in
ptotoabsorbtion. The characteristic values of the Rabi splitting are expected
to be several orders of magnitude larger then those observed in single quantum
dot-cavity systems.
