We report the experimental investigation of the optical properties of
porous silicon embedded in a planar microcavity structure in which bot
h the active layer and the two Bragg reflectors are fabricated by elec
trochemical processing of a p-type porous silicon wafer. By tuning the
cavity resonance energy around the maximum of the porous silicon emis
sion we have observed photoluminescence linewidths as narrow as 18-25
meV and an intensity enhancement of more than one order of magnitude.
The experimental results are clarified by theoretical calculations per
formed with the standard transfer-matrix approach in the framework of
a porous silicon quantum-box model.