A microcavity structure has been fabricated in which a polyimide layer with thickness on the order of the wavelength of light was sandwiched in between dielectric mirrors by using vacuum deposition polymerization (VDP). We deposited a 330-nm-thick polyimide layer through a polymerization reaction between two mutually reactive monomers evaporated onto a dielectric mirror consisting of TiO2/SiO2 multistacks. In the middle of the VDP process we deposited tris(8-hydroxyquinoline) aluminum (ALQ) so that a sublayer 30%-doped with ALQ was inserted within the polyimide layer. Upon the polyimide layer we coated a dielectric mirror consisting of Ta2O5/SiO2 multistacks. The mirrors were designed to have a broad high reflection band (stop band) with a reflectivity maximum of ∼90% at 530 nm. Fabrication of a microcavity was considered to be successful based on its optical properties. Within the stop band a sharp transmission band with a width of 8 nm appeared due to Fabry–Perot resonance. Correspondingly, ALQ photoluminescence became narrowed by the same width. We characterized the cavity resonance modes using a model considering penetration of the optical field into the dielectric layers. © 1999 American Vacuum Society.