Spontaneous emission from a planar microcavity below threshold and the wolf effect

Equivalence between a planar microcavity below threshold and a partially coherent primary source is pointed out for the first time. Spatial coherence properties of spontaneous emission from the planar microcavity are controllable by varying two cavity parameters of the cavity length and the mirror reflectivity. The spontaneous emission gives rise to the Wolf effect which is spectral changes induced by the spatial coherence. It is clearly shown from our theoretical analyses that the spectrum in the far field shifts toward higher frequencies than that on the emitting plane of the planar microcavity. In particular, the blue shift of the far-field spectrum takes a maximum value at the centre of the far-field plane and decreases gradually far away from the centre. Moreover, the blue shift increases with decreasing values of the two cavity parameters.