The spontaneous emission of a material can be controlled by placing it in a micron sized optical cavity. In this paper we assembled 8 hydroxyquinoline aluminum (Alq

3

) into porous silicon microcavities(PSMs) fabricated by pulsed electrochemical etching. The pulsed current etching is superior to DC etching in obtaining flat interfaces within the distributed Bragg reflectors because of its minor lateral etching. The measured peak reflectivity of the microcavities before the impregnation is 99.5%

and its full width at half maximum(FWHM)is Δλ=6 nm

and after impregnation Δλ=15nm. The spontaneous emission spectrum of the optically excited 8 hydroxyquinoline aluminum is drastically modified by micro cavity effects. Compared with the luminescence of a filled single P Si layer with the same thickness as the microcavity

and with an average of the porosity of the layers constituting the microcavity

the full width at half maximum of PL spectrum in a filled microcavity is drastically reduced from 85 nm to 15 nm

the peak emission intensity increased by one order.However

beside the resonant peak of PSMS

the weak side peaks origina ting from PS can be observed

because the reflectivity of the microcavities is decreased in this region. Random porous silicon dielectric multilayers are proposed as interesting materials for application as optical components. The use of random instead of periodic multilayers has the advantage of obtaining a wider stop band in Bragg reflectors with the same difference in the refractive indexes of the layers and in a higher finesse in Fabry Perot filters. In the case of Alq

3

being impregnated into random FP interference filter

the off resonant optical modes are highly depressed. The experimental results suggested that the porous silicon microcavities is a good encapsulated media for Alq

3

and Alq

3

emission properties was improved by the microcavities. This may make a new way for Alq

3

in application in electroluminescence.