Radiation pattern of Erbium ions located inside a dielectric resonant
microcavity is investigated theoretically. We show that spontaneous em
ission of Erbium ions can be spatially controlled and enhanced in a di
rection normal to the structure. Investigation of the power emitted in
to the guided modes of the structure shows that this guided power must
be considered for an accurate design of the spontaneous emission cont
rol into planar microcavities.