[en] We studied the effect of planar microcavity eigenmodes on the optical excitation efficiency and the luminescence of emission centers (erbium ions) introduced in the active layer of the microcavity structure. We show experimentally that, if pumping conditions are chosen in order to excite the microcavity eigenmode, the emission intensity from erbium ions is enhanced by an order of magnitude compared to the case of pumping via excitation of photonic band states. The observed photoluminescence enhancement was theoretically and quantitatively estimated by analyzing the overlap integral between the distribution profiles of the electromagnetic fields inside the active layer of the microcavity